Sorry about the length of this, but I wanted to explain the history of what has been found, attempted resolutions, and results. I sincerely appreciate your suggestions on additional items to check. I work on this as time is available and I am a year into it.

I have a fuel related problem with my

1991 Toyota Pickup
3.0 VZE 6 cyl engine (appr70k mi)
Automatic Transmission
Rear wheel drive (dually)
Toyota sold this vehicle as a cab and chassis, which Winnebago used for a Warrior RV / motorhome.



The engine never idled or ran rough prior to this problem occurring. When it ran, it seemed to run normal - until this matter arose, then died for not obvious reasons. The problem presented itself when as it was being driven It stalled for just a moment, then a few seconds later it completely died and would not restart for some time. We attempted a few things (among the list of items below), but nothing worked. After about 30 minutes (and several cranks), it finally started and I was able to make it to home about a mile away.

The next morning, I wanted to see if I could repeat the problem. It started with a little more cranking than norma, I made it to the end of our street (about Ľ mile) and it died again with same symptoms. After about an hour of letting it sit, it finally started again and I got back home. When I parked it at my home, it would not restart. I pulled the spark plug wires from cylinder 2, and one other, and found good spark to both. The exhaust had a smell of gas. I also that the oil had a strong smell of gas on the stick, and when draining it, found 2 or 3 quarts of gasoline mixed in the oil.

I directed my attention to the fuel system and components. Obviously something was allowing too much fuel into the system allowing it to flood the engine and reach the oil pan. I checked various items and components with the limited tools I had, and used some diagnostic shortcuts (found on here). But I did not find anything that was the obvious cause (fuel pressure regulator, fuel pump kicking on properly, etc). I decided to go ahead and replace the injectors as they probably had never been replaced, and it seemed to be the logical suspect of allowing too much fuel into the engine.

To reach the injectors, the plenum had to be removed (a time consuming job that makes me question Toyota’s engineering using this design and the endless hoses). Since the vehicle was several years old, the plenum removal allowed me access to items that probably had never been replaced, so I went ahead and changed the following items:

Fuel injectors (all six from Precision Injectors)
Plenum gasket
PCV valve and gasket
Spark plugs and wires
Fuel Pressure Pulsation Damper (BTW: I recommend to get OEM on this as the after market items are notorious for not having the ability torque up enough without breaking)

I also checked the function of the cold start injector and found that when the key was on and cranking, this injector opened up allow gas to flow out for a few seconds, then closing and stopping the flow.

After installing, it cranked right up after a few seconds and the engine idled/revved up/ran perfect with no indications of problems. I put a fuel pressure gage on the rail, drove the vehicle for a couple of miles, and found that it stayed around 40 psi. I allowed the engine to run at idle for about an hour to test it. Everything looked good, but then…

On Monday, I drove it to my work where I store it (about 20 miles) and about 1 mile from my house it stalled out for just a moment. It did not die and picked back, and from there it ran fine all the remaining 19 miles to my work. The following Friday, we were planning on using it for a short camping trip but I was very apprehensive about it, and decided to start it and allow it to idle for several minutes before leaving. After about 15 minutes, the engine died while idling. After trying to start it a few times, the engine made a “thud” sound and would not crank at all. This led me to believe that the starter had now failed. The oil again had a strong smell of gas which told me that our prior efforts may have been in vain,

I then started investigating further about this and found that excessive fuel flooding can lead to a hydrolock condition. Based on how the starter seem to “lock up”, I believed that this may have occurred but unsure what caused it since the injectors were essentially new. I removed the plugs and while someone watched, and the engine cranked over spraying fuel out of the cylinders. I think I was fortunate that the engine does not appear to be damaged since the hydrolock occurred during the starter cranking and did not put the same strain on the engine had it been traveling down the road. I cranked it over briefly a few times, and it turned over fine without any noticeable noises that would lead me to believe rod damage, etc.

I put the fuel pressure gage on the rail again. Without cranking using the key on, opening VAFM vane by hand, the pressure would reach the 40 psi, but within a few seconds, fall off to about 20 psi. I also removed the entire air intake box and found quite a bit of fuel in the bottom of the box.

NOTE: Before this multimeter and found that all readings across all the VAFM points were in spec, the fuel pump relay clicked, and the pump was buzzing. I then directed my efforts towards the fuel pump thinking that the pump was possibly failing causing spikes and drops in fuel pressure. Due to the location, I cut a hole in the floor under the dinette seat and was easily able to access the tank’s pump location and replaced the pump (OEM Denso) , filter bag, and went ahead and replaced the Fuel Pressure Regulator (fyi: found both pump and regulator on sale < $35 ea). Using the VAFM vane hack, found the fuel pressure initially reach normal pressure, then again fell quickly to appr. 20 psi – another gut punch.

So, if you are still with me, much thanks for hanging in. I know throwing parts (and money) at this is not the best solution, but I tried to only replace items that seemed to be the reasonable suspects contributing to the problem, or those that were still on the vehicle for over 30 years old and probably due for replacement.

I also believe that at the fuel injector, or CSI, key is on and the VAFM vane is open – based upon the pressure rising then falling quickly to 20psi with no fuel leaks found anywhere else (that I know could cause the pressure to fall).

With no other leaks found, the only means I know that gasoline can enter cylinders is through the injectors or the CSI in an open position. Therefore, my newest areas of concern are the following:

- Short in the injector wiring harness wires / circuit
- Cold start injector remaining open (possibly intermittent since tested ok before)
- ECU / ECM failure leaving the injector circuit open (unsure if possibly intermittent for this type of component)

The fact that there was gasoline found in the air intake box area would seem to favor the CSI open circuit, but I am not sure that the CSI being open 100% of the e could dump as much fuel as I am finding it the oil, etc. in such a short time.



-Could the pistons be throwing the excess fuel from the cylinders back through the intake plenum and then flowing down into the air intake box area?

-If the injectors are open at all times, how could the fuel initially reach pressure, then fall off?

-Is there something in the system that must allow the fuel to reach a pressure range at start up , then instructs the injectors to open (the ECM or some other component?).

-If so, then could that component be bad (i.e. receiving or sending incorrect information?).



I am not 100% of the order of the protocol the vehicle follows to start from being off to the other systems being aware of the engine running and providing operation adjustments or informationl.



Therefore, at this point, my next actions will are as follows:

- rebuild / replace the section of the wiring harness associated with the fuel injector
- ECU / ECM – I am hoping that this is not the cause. Despite using a similar part number for this device across other models, the one used for the motorhomes/RVs is generally believed to possibly unique operational characteristics on ECM apparently because is left Toyota as a Cab and Chassis, Automatic Transmission, and a 2x4 DRW drive. In other words, you can’t just grab one with the same major part number and have it work due to the secondary part number.

I am seeking any additional advice and expertise that you may be able to provide me regarding this situation. Is there anything that I should check, test, or diagnose that may be the source of the problem. I have literally wracked my brain about it, and nothing seems to be the proper solution.. Thank you in advance of any help.

 

what a bizzare problem, and really not good for the truck, i wouldn't drive it or run it with that much gas in the oil.

on my 22re the fuel pressure varies with vacuum, aka load on the engine etc., not sure what it looks like after extended idling because i don't idle engines, it destroys the catalytic converter... but yours is probably gone anyway from that fuel issue.

with fuel in the intake i'd be inclined to plug the fuel line to the csi, just eliminate it as a potential problem and see what happens... can't say how fuel would get into the air box on your 3.0, i've never worked on one.

 

Any update?

Edit: Thanks for the update.

 

Yes and no. Today I tried some additional diagnosis on the cause. Since this situation began, I have found fuel in the oil pan, fuel in the air box, and fuel hydrolocking the engine during starter cranks. As I do not know of any other source for fuel to these areas, I continue to keep my focus on the fuel injectors and/or the cold start injector (CSI). I have checked the CSI several times and each time it operated properly - and as such, give it a much lower probability as the source for the excessive fuel.

Today, my friend and I ran a few more checks on the engine and using a homemade noid light (a 194 light bulb with some gator clips leads). The #2 cylinder injector plug was the only readily accessible one, so I disconnected it from the injector, used a couple of pins to make extended and accessible contacts points for each of the two wire terminals within the injector plug going towards the harness. I attached the two gator clip to the two pins extending out from the #2 cylinder injector plug to the noid light, cranked the engine, and watch the light. i cranked the engine in a few short cycles and the light came on and flickered, but I think the flicker was caused by the engine's variations in speed from the cranking, but the light was on. When the cranking ended and the key still in the on position, the noid light remained on. I believe this identifies an electrical cause to the open injectors as the source. But what electrical source.
My suspects of the cause of the problem is now:
1. ECU is malfunctioning (i.e. injector driver) or
2. Injector wiring has a ground to short
If anyone has any other information that may cause the injectors to stay open, please advise.

After some additional research this afternoon, the cause of the noid staying lit (injector staying open dumping fuel) can be further identified by:a fairly simple method. With the ECU installed, if the noid remains on (no flicker/pulse) when cranking the engine and key in on position, remove the ECU and repeat cranking..
a. If the light stays on when cranking with the ECU removed - most likely a short to ground in the injector wiring circuit.
b. If the light goes off, most likely problem is with the ECU.
This seems like a logical means to isolate the cause of the open injectors.

I'm going to repeat the noid test Monday, both with and without ECU installed to hopefully reduce the possible causes by one more.

 

Latest update:

1. Ran through the majority of the ECM Pin Out procedure and did not find a single multi-meter measurement out of tolerance (according to the specs on the pin out routine).
2. Checked cold start injector function (upon cranking a small amount of fuel squirted out, then shut off), and resistance across CSI tabs (measured 3.3 which was within the 2 to 4 ohm spec).
3. Tested a noid light on the number 2 cylinder injector plug (front/forward most on driver side), AND
ECM (connected) from #10 to E01 and #20 to E02
The test was done by pushing a needle/pin throught the wires to make contact and connecting the NOID light probes to the two pins - (NOID light was "homemade" 12v bulb style)
At all three locations the result of the tests were identical:
KEY OFF: Noid light off
KEY ON POSITION: Noid light on and sold
KEY ON ENGINE RUNNING: Noid light on and flickering/flashing (it never went "out/off' entirely which I am assuming was because the frequency of the pulse was so fast that the light would not have time to completely discharge the wire's glow)

I also confirmed that there was continuity from various body ground locations (plenum, bolts, etc) to the #10 (white/red stripe) and #20(white) injector ground control wires.

From the information I have read this indicates either a bad ECU/Injector module circuit int he ECM
OR
Injector wiring harness short to ground

From further investigation, I am to understand that if you remove the ECM and obtain the same results as above then the problem is a SHORT TO GROUND condition. However, if the Noid light does not stay on, then the problem would be in the ECM/ECM injector module.

I removed the ECM from the connectors and repeated the above test and had the exact same results - thus leading me to believe that the problem IS a SHORT TO GROUND condition within the injector wiring circuit somewhere.

Is there any other possibility or component that may be causing the problems and providing the Noid light results? I do not want to have to remove the plenum to access the injectors and harness only to find it may have been something much less time consuming.
OR
Confirm that I have pretty much tracked the problem to the most likely (or only) cause and that a short to ground in the injector wiring is the most likely culprit?

And if there is a "typical" location that the short to ground would likely occur (in harness / under plenum / injector connector plugs / etc)?

Much thanks to anyone and everyone that can hopefully assist me in this frustrating issue. Thank you.

 

Latest Update:

NOTE: UNLESS NOTED, ALL TESTS WERE DONE WITH THE IGNITION IN THE OFF POSITION.

Based upon the multimeter (MM) readings with and without the ECM connected, it appeared that there was a short to ground (STG) in the injector wiring circuit. I built an new wiring harness section for the injectors from about 6” from the ECM plug back to the injectors and included new injector connectors. After installing, with the ECM, injectors, and battery disconnected, I found continuity on the ground wire (passenger side #10 white/red and drivers side #20 white) from the connectors back to the appropriate ECM plug pins (#10 and #20). No continuity was found either sides circuit by checking a ground on the connector to a ground point on the vehicle. I believed that the excess fuel/flooding problem would now be behind me. Based upon my prior MM readings, and internet research, the only cause to the flooding should have been a STG in the injector circuit OR a faulty ECM.

BTW: For whatever reason there appears to be slight differences in some model years in the injector circuit – one design (apparently more common) with the #10 and #20 injector wirings that are spliced together creating one circuit, AND one where the #10 and the #20 are NOT spliced together forming two separate circuits with each serving only three cylinders each (1/3/5 and 2/4/6). Based on MM readings mine is the later of the two with two separate circuits.



I then wanted to check a few more items before putting the plenum back on and putting on in the win column. I checked the EFI Main Relay – in spec. I check each injector’s ohms – all in spec. With the ECM, injectors, and battery disconnected I checked continuity from each injector connector (control ground side) to ground. All ground sides of the connector showed no continuity. Then I checked the hot/POS side of the injector connectors. THEY ALL SHOWED CONTINUITY TO GROUND! I was quite deflated from the MM results.


Still disconnected, I checked the continuity from POS to NEG battery terminal (bat disconnected) and found continuity here. The only silver lining was that based on the MM readings, the problems was most likely NOT the ground injector circuits.

Ok. So now we are checking out the wiring schematics and believe that a STG exists somewhere in the EFI/Ignition circuit (but not including the injector wiring). Again with the ECM, injectors, and battery disconnected, I put the MM probes on the POS and NEG bat terminals and found continuity. I then started pulling fuses, one at a time, from the passenger side box near the battery. Once I pulled the EFI Main Relay (round metal relay), the continuity ceased. We pulled the connectors from the igniter and coil with the same continuity results. While these connectors were off I checked the igniter and coil with the MM and found both to be within spec (hoping to remove them as possible culprits).

We then reinstalled the EFI Main Relay, connected the battery and the EFI clicked. The disconnected the battery and found STG continuity again between POS and NEG terminals (or any other engine compartment ground points) as before. We went to the driver’s kickpanel fuse box and did some MM readings. With the ignition switch fuse removed from that block (1) we checked continuity of both sides of the fuse blade receptical to engine compartment grounds for STG. We found continuity on one blade but not the other (I cannot remember if it was the top or bottom, but if anyone knows for sure, please let me know as this will give me an idea which directing the STG will be located). I’m relatively certain that there should not be any continuity to ground on either of these wires.


We believe that the STG could be either a component in the IG2 ignition circuit (not the ST1 starter side), or a STG in a wiring circuit somewhere. With the igniter and coil disconnected, I believe the only other components would be the ignition switch and/or distributor (and the wiring of course).

Now let me rewind back a few months ago. When the engine hydrolocked with just sitting at idle for 15 minutes, we pulled it into the garage. I had to have the ignition in a non-OFF position to steer. When I turned the ignition to the OFF position, I noticed that some of the dash lights were still on – even after I had removed the key from the ignition. I don’t remember how I got them to turn off, but disconnected the battery(ies). Please remember that this is and RV and has an isolator solenoid going back to the cabin battery. I thought the cause of this may have been an issue with the isolator solenoid allowing voltage from the cabin battery to go back to the engine compartment and somehow “bleed” into the circuit. I now believe that this was not possible, HOWEVER, this may have been my red flag that there is an issue with a faulty ignition switch.

After considering this, and some additional internet research, it appears that a shorted ignition switch (or other ignition circuit components) can allow either a ground to bleed into the injector circuits keeping them in an open position, or allow the some vehicle components to “think” it is still running and keep various circuit open (i.e. injectors) so that they stay in the open position even with the key off.

I cannot fully understand how either is possible, and trust me when I say I have been disappointed with the “I know exactly what the resolution is” internet forum experts. Regardless, I have added a lot more to my shade-tree mechanic experience, but I am tired of learning and would rather get back to enjoying my RV again.

As a reminder, this vehicle never failed to crank (except the one time hydrolock), had spark a the plugs (each time we checked it), and would always start and stop with the key (unless flooded – as far as we know). Therefore, my current suspect is the ignition switch – sad to say but a pain in a$$ component location for replacement, and a discontinued OEM part. Once we remove the dash component to get better access, we will run a few more MM tests and provide another update.

I thank everyone that has contacted me and provided some suggestions. I would now like to ask if anyone can provide me with a bit more of their experience – especially in the electrical side of auto repair: Can you help me with the following questions I have:

a. The exact route of the POS voltage path (my info only show the general circuit and components that are part of it, but they do not show the realistic and actual path (or flow) from the battery, then through the engine area, at some point to the cowl/ignition switch area, and then maybe back to engine, etc. or ECM, etc.

b. Are there any other components on the ignition circuit that I have not listed that I should check and how would you recommend that I test them and the circuit integrity (ie. with the battery, ECM, injectors, igniter, and coil all disconnected, or some other arrangement).

c. At the driver’s kick panel fuse box. The ignition fuse is a 7.5A in position C1 #9. Can you tell me where each of the blade receivers go to, or where they are in the ignition circuit’s “path”? This may help me in tracking down where the STG may be located in the circuit.

d. Do you think the flooding problem could be associated with a STG in the ignition circuit as others have suggested? I am surprised that after so many hours of research, I NEVER saw this possibility discussed – with most indicating a STG in the injector circuit or a faulty ground control or injector module of the ECM as the cause.

e. If a STG exists in the ignition circuit, why does my battery not seem to lose charge quickly (although I have not really had a change to check this with the RV being out of commission for a while now). However, if a STG exists, whether the key is in an ON or OFF position, how could it have enough ground voltage to keep the injectors open, but not causing a shorting out or burning wires, or other things generally associated when POS and NEG voltages contact each other?

f. Do you have any other suggestions on what or where the problem may be? Given that most of the fuel related components have been replaced, I am hoping that I have significantly reduced the potential culprits causing my flooding issues.

Again, a big thank you to everyone on here. Sorry about the length of these, but I’d rather let you know what we have done and the results of our tests and component replacements.

 

hello,

i am very novice with the 3VZE as i have just recently purchased a '94runner.

My suggestion would be to check the engine codes and post them. perhaps others have had similar codes and what sequence to troubleshoot??

also i have read in another older thread that if you hook up one of the 3 vacuum lines wrong it could cause the fuel in oil smell as one of those vacuum lines connects to the fuel regulator.



that thread also mentioned to check the egr vacuum modulator to make sure the filter is not clogged up.

 

duplicate

 

Thanks for the information. During the entire time that this problem has existed, the vehicle has never shown a Check Engine light. Using the control box jumper hack to have the CEL flash code numbers, it did not provide any codes either.

The vacuum hoses have never disconnected by myself prior to this problem, and when the vehicle would run, it ran great. I'll check these hose for cracks and connection, as well as the vacuum modulator filter. Thanks again.

 

Thank you so much for sharing.


 

UPDATE:

As a result of my wife's regular reminders that we have been without our RV (Toyota 3VZE one ton chassis with Winnebago Warrior cabin) for a little over two years now, I found a renewed determination to find the cause of the problem I originally described as the initiator of this forum post/thread. Giving a lot of thought that the engine getting far too much fuel, then leading to the vehicle stalling out (and hydrolocking on one occasion) and ultimately getting into the oil was the singular focus.

I reviewed all of my notes that I had made on the attempted resolutions and their results. After reading these notes again, the fact that we gas was found in the air box told me led me to focus on any hose/tube that carried fuel, AND any component that interacts with other fuel related components that may be allowing fuel to enter the plenum. NOTE: i had already ruled out the injectors - other than the possibility of an intermittent problem which would be very difficult to identify, diagnose and repair. The injector circuit multi-meter readings and noid light checks were correct and it did not seem possible that a faulty injector(s) could dump enough fuel into the cylinders and then be forced backwards through the valves, then through the plenum making it to the lower part of the air box which would require fighting and strong upstream flow of air from the throttle heading towards the cylinders - maybe possible but seemingly highly improbable.

I first confirmed the routes of all of the vacuum hose, fuel tubes/hoses, coolant hoses, etc. were correct. Then I considered any component that may have the ability to introduce fuel into the plenum / air box. Using this as my guide, I found narrowed the list to two items that could provide that would have the ability to dump fuel into both the cylinders and the air box. The items I focused on were:

1. Cold Start Injector (and CSI related components)
I had checked this item several times in the past by removing it from the plenum, and placing into a container and starting the vehicle. Each time it injected fuel for a moment and shut off. It also checked within spec for the ohms. Therefore, I originally did not believe the CSI to be the source of the excess fuel. NOTE: I had previously replaced the engine coolant temperature sensor located on the water manifold with other sensors in the rear of the engine compartment. It was relatively inexpensive and a easy install while the plenum was off
.
2. Cold Start Injector Timing Switch
I thought that if any of the various CSI components were sending faulty or bad intermittent info to the ECM, the ECM may have, in turn, caused the CSI to open allowing excess fuel into the plenum and causing the flooding issue(s)

3. Fuel Pressure Regulator
I had replaced this item during my last efforts to resolve this problem, but did not consider that the if newer one installed may could have had a ruptured diaphragm which would allow fuel to be vacuumed from the FPR through the vacuum valves and back into the plenum. It would be a relatively easy check once I put the plenum back and started the engine.

4. ECM/ECU
I had obtained an ECM for my vehicle some time ago, but never installed it since I originally though the injector wiring had a short to ground, OR some other component was failing. Due to the fact that my vehicle was built as a cab/chassis (1 ton frame / auto tranny) and then Winnebago putting an RV cabin on it limited the market availability of a suitable ECM.

I put a new OEM Cold Start Injector and OEM CSI Timing Switch while the plenum was off, and installed the ECM that I obtained some time ago, then changed the oil that had a lot of gas mixed in it (and in the air box) from the last time that I unsuccessfully attempted repairs/replacements of other items and tested those repairs by allowing the engine to run for several minutes - until it flooded and died. The engine cranked for 3 or 4 seconds, and started right up - despite several months of just sitting. When it started, it appeared to run fine, except there was quite a bit of smoke from the exhaust, but after a couple of minutes, the smoke from the exhaust ended.

While running the engine I pulled the vacuum hose off of the top of the FPR for about 10 minutes and saw no fuel come leaking from it nor from the vacuum hose. Therefore, I believe that the FPR and it's vacuum hose were NOT the source of the excess fuel.

Although the CSI and the CSI Timing Switch multi-meter readings were in the proper range I wanted to check the startup function of the CSI. I removed the CSI from the plenum and plugged the plenum hole and started the vehicle several times, but no fuel was release (most likely because it was 90 degrees here and higher than the threshold that would cause it to release). I continued to run the engine for several minutes with the CSI out and it never released any fuel.

Finally, I drove the vehicle about 10 miles and found no fuel in the air box, no gas in the oil, no stalling, no smoke from the exhaust, no gas odor from the exhaust, and to put it simply - the vehicle ran perfectly without any noticeable difference from how it ran prior to this excess fuel mystery. I will continue to drive it further each day over the next week and check all possible excess fuel accumulation locations. At the end of the week I also intend to start it up and let it simply idle for maybe an hour and see if any issues return.

At this point I am hesitantly optimistic that I have finally resolved my problem. The results today were the best that I have had after several months of repairs that were produced nothing more than emotional roller coasters rides. Sadly I cannot specifically identify the ultimate cause with 100% certainty, but I sincerely believe it was somewhere in the CSI components and/or the ECM. However, I do know that there may be some additional causes (i.e. CSI and/or ECM wiring issues or other items that may present themselves intermittently - fingers crossed).

I will provide another update in a few months after I can really put this vehicle in a longer term real road test. For now I am praying that the matter has finally been resolved after so many months and unsuccessful attempts. Thank you all for your help and I hope that this may be beneficial to someone else that may be having similar issues.

 

did you ever figure this out im having the same issue with my 93

 

Well, the truth is.... I'm not sure I "figured it out", however, it is up and running again like a champ and we have taken it on a few trips, the longest being 7 hours one way, and had ZERO problems with it. The primary problem was that despite all the efforts to diagnose and replace part after part, it continued to provide excessive fuel to the engine/cylinders. I replaced almost ever component in the fuel system and was quite defeated that my effort was for naught. When removing the plenum - again - I notice fuel sitting in the very bottom of the air box. This lead to investigating every single possible source of fuel that may enter the air box (even those that are very unlikely - but possible). I concentrated my focus on the Cold Start Injector circuit and components - which were:
Cold Start Injector
CSI Temperature Sensor
CSI Timing Switch / Sensor
ECM / ECU

We had checked the CSI several times before and removed it from our suspect list, as in every test we performed it came on and shot a small amount of fuel, then shut off - just like it was supposed to, but we did not consider the possiblility of any intermittent problems. I replaced the CSI, the temp sensor, the CSI timing switch, and the ECM/ECU. After installation, and sitting unstarted for over 1.5 years, I cranked it over and within 4 or 5 seconds, it started up and ran without any issue - and has been running fine every since.

So, the honest answer to your question is, "to the be of my knowledge, and based on what I have witnessed since that day, the vehicle is running properly and has not shown any sign of excessive fuel to the engine". However, I cannot honestly tell you which of the final components that I replaced was the problem - but we are very happy to be able to enjoy it once again.

I'll be happy to give you any advice that I can, as I have literally become a shadetree mechanic when it comes to the fuel system of the 3VZE engine. Can you tell me what exactly is happening to your vehicle? Repeated flooding / fuel in oil / etc? Something else? The real problem that I encountered was that there are numerous reasons a vehicle wont' start, and several reasons that an engine will flood. However, I did not have a significant amount of diagnositic equipment, nor experience, and everyone I have asked has scratched their head, or provide advice - but did not end up being the cause.

Best wishes and I hope you are able to get back up and going, and my offer for any assistance that I can provide remains open.

 

I was in a similar rabbit hole with my old 4Runner, and like you, I kept chasing electrical gremlins and replacing parts while the real issue was actually....wait for it...a component combination failure. Essentially a drift in specs across multiple sensors that together tricked the ECM into extended cold-start mode? The coolant temp sensor reading slightly low plus a tired CSI timer switch with delayed cutoff plus an aging ECU struggling to process the signal cleanly. Alone, each passed a multimeter test. Together, they created a perfect storm of flooding. Such a system wide degradation can throw off calibration. Glad your rig is back on the road. Keep us posted on the long-term results!

 

Upon getting my vehicle running again, I wondered if the problem could have been some combination of component failures (or intermittent issues of multiple items). Every component checked out within the proper ranges.
- CSI turned on and off (but just a short tern test and only at startup with no further monitoring of it's activity)
- CSI timer switch multimeter readings - passed
- Coolant temp sensor multimeter measurement - passed
- ECM/ECU - multimeter measurement on every FSM test (pinout) - passed

All of the tests were done in a "static" mode There may have been a problem with a component, or a combination of the components, that would remain disguised until the proper conditions created the flooding problems - and as such were never found in our attempted FSM test procedures.

I am quite relieved that we were able to get it back up and running - at least for now. Thanks for the information regarding the cause(s) behind your flooding issue. Best wishes.

 

im haviig the same problem you have been dealing with, good spark, and compression, vehicle starts and runs for a half a second and dies. Spark plugs soaked in fuel, and oil saturated with fuel. I have determined its not the CSI due to it still flooding with it disconnect. And I figured that if the CSI was bad it would be less of a not running issue and more of a rich run with rough idle. I have also determined the ecu is switching the ground for the injectors and looks good according to a multimeter.

 

Can you tell me what type of vehicle, model and year, and engine type.
My vehicle was a 91 Pickup, 3VZE 6 cyl, 1 ton chassis with an RV. Any info I can provide will be limited to my experience with that engine type.

When you say the CSI was disconnected, how was it disconnected? Was the electrical connector removed from the CSI on the plenum, or the fuel supply to the CSI closed/blocked in some manner?

And,have you or anyone done any maintenance or work on the vehicle shortly before your issues began - especially any work that may have required the removal or disconnecting any hoses, vacuum hoses or others?

I'll get back you tomorrow with more info.

Finally, check out the recent reply from the person that found that his similar problem was more or less a stack up of multiple items in the CSI circuit that were drifting out of tolerance, leading to his problem. After scratching my head for over two years, this may be the source of my issues as well since every other troubleshooting effort did not resolve it.

 

Please remember, I am not a trained mechanic at all, and any advice I may provide may not provide the answer you are seeking, however, I will do my very best to describe what I tried and suggest areas to investigate. Also, I am not sure of your personal mechanic experience, so I do not wish to over or under describe anything here. It has been over two years since I started having these issues, with so many efforts to resolve, so my memory on everything we tried, tested, evaluated, etc. may not represent everything (but I’m trying to note the ones I can remember and may have higher priority).
I am hopeful that if anything I am attempting to describe is less than complete, or incorrect, that other persons with more knowledge or better information on this site are willing to provide corrections as needed.

I guess my first question would be what kind of vehicle and engine are you having the issues with?

Mine is a 1991 Pickup (one ton chassis RV) with a 3VZE engine, so my advice and descriptions will be limited to this engine type.

The fuel system operation.
The number lines that carry and/or feed fuel to the engine compartment, and the intended end points where fuel may enter into engine area (as opposed to a leak on the outside of the engine or on the ground) are actually not very numerous. I think the highest priority is to find which point (or points) is the source of the excess fuel. Once this is determined, then on to perhaps the more difficult part – WHY and WHERE it is coming from that location.

A few things I could recommend that may assist in diagnosis if you can get it started for a short period of time.

- Do not run the engine with fuel saturated oil (I would guess I had to change mine 6 to 8 times throughout my ordeal). Change the oil and only run the engine for short periods as you diagnose and work on it.

- have you checked/tested the fuel pressure (usually there is a place where you can connect to the fuel rail for testing)? If not holding pressure for some period of time after turning engine off, injectors may be stuck open. If pressure is too high, then maybe pump or FPR may be part of the problem.

- Trace the entire length of the fuel return hose coming out of the FPR to make sure it is transporting fuel back the the tank. When engine is started and fuel pressure is at normal pressure, remove the hose from the fuel pressure regulator and see if there is fuel coming out of it.



To the best of my understanding, fuel can enter into the engine area via these items.

1. Fuel Injectors
Fuel is pumped from the tank and is pressurized throughout the fuel delivery side of the system, then comes to the fuel rail, and awaits the injectors opening to spray into the cylinder.
Potential Problems :

a. Injectors remaining open (from mechanical failure of injector, or a hort to ground in the injector wiring circuit_

b. ECU related problem, false sensor information, or inaccurate processing of that information



2. Cold Start Injector
The CSI supply hose connects to the fuel rail and bring fuel to the CSI which gives a shot of fuel to the air intake as an engine "kickstarter" for colder temps.
Potential Problems:

a. Injector remaining open (from mechanical or electrical causes)

b. Other sensors (coolant temp sensor, CSI timer switch, other???) that provide info for the CSI operations (usually via the ECU/ECM) may be giving incorrect information, thereby causing the CIS to open / stay open

c. ECU/ECM problem or misinterpreting info from other sensors causing CSI to stay open, or possibly a faulty CSI circuit within the ECU/ECM.

d. Some combination of components (as the person that relied earlier) that may individually test within spec, or near their limits, in combination with each other leading to this issue.

e. And, lastly one that I could not confirm, but an issue with the wiring of the CSI, the sensors associated with its operation, and/or to and from the ECU/ECM ???


3. Fuel Pressure Regulator (FPR) (or perhaps the EVAP or EGR systems )
The 3VZE’s fuel pressure regulator is usually located on the fuel rail and easy to see. Through some voodoo magic it uses a vacuum (created by the plenum’s air intake) and an internal diaphragm to regulate the fuel intake system’s pressure (around 38 to 40 psi) by allowing fuel to pass into the fuel return line, which routes it back to the fuel tank.

Potential Problems:

Let me say that this would not seem to be a possible source for the fuel into the engine, but given the right conditions, it can result in fuel quickly pouring into the plenum by following two conditions:
a. This seems the least likely since on my vehicle:

1. the fuel return hose/tube that is connected to the FPR and then to a the tube that routes in and out of the vacuum hose group, and returns excess fuel from the FPR to the gas tank, and

2. One of the many vacuum hoses that run across the front of my 3VZE engine,



are slightly different sizes. However, IF the hoses were removed at some point, and then accidentally reinstalled incorrectly, the fuel coming out of the FPR (that should be returned to fuel tank) is now connected to a vacuum hose, and being pulled by vacuum to dump into the plenum. I have been told of possible similar issues within the EVAP and EGR (maybe legendary myths), but again it would seem that the cause of these would be related to incorrectly installed hoses.



b. A similar condition, but one where all the hoses ARE connected properly would be if the internal diaphragm of the FPR developed a leak/split/rupture and allowed fuel to pass through it, then the result would be the same – vacuum pulls the fuel through the vacuum hoses and dumps into the plenum. Please refer to the photo of the vacuum hoses routing at the bottom of this.



It is possible that there could be some other condition(s) that is causing the excess fuel / flooding of your engine. You said that you could get yours to start for short moment, but then it would die. Once mine died out from the flooding, it would not start until sitting for long periods of time (I guess allowing the fuel to seep down to the oil pan or just evaporate somehow.



Did you happen to see if there was fuel in the bottom of your air box? If so, I personally think that the problem is with your CSI or fuel coming though the vacuum system. Why? Because the amount of air flowing out of the plenum into the cylinders appears to have enough flow to prevent any excess fuel that may have gotten into the cylinders to literally flow backwards through the plenum and landing in the fuel box. I did not see fuel in the box until we let the engine run at idle for about 15 minutes and it died – flooded again. But in those 15 minutes, approximately 2 additional quarts of fuel made its way to the oil pan, and a small amount to the bottom of the air box. Where could so much EXCESS fuel have been able to get into the engine / oil pan in 15 minutes of idling?

Since we had already put a new FPR in it, we focused our efforts on the CSI (despite multiple successful tests starting the engine with squirts of fuel and multimeter confirmations of sensors within range. Everything, including a complete test of each of the ECU/ECM pins (using the FSM) was outweighed by the circumstantial evidence from replacing all of those in-spec components resulting in the vehicle running like a champ now up. Maybe it was just luck, but whatever it was, I am again one happy camper (literally).

Good luck – I know it is a very frustrating ordeal because there seems to be no end to the possibilities – and I have scoured the internet searching for answers.




Lesson of the day – do not always believe that a static test with a multimeter is conclusive proof of correctly operational device.

 

93 4runner with a 91 3vze that has been rebuilt entirely by me about 8 months ago and has ran flawlessly until recently. I have determined its not the CSI circuit by unplugging and hose clamping the line to keep fuel pressure away from the CSI issue persists. I have ordered a ECU it should be here next week ill keep you updated on what happens.

 

Good luck with your ongoing efforts to identify and repair your vehicle. And please do let me know what was the source of the problem once you have discovered it. Best wishes.