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I have a '93 4Runner 3.0L V6 4x4 with an auto transmission and she is refusing to start. A little background.
Since the time I have gotten this truck (nov 2019) it has always run rich. I can always smell gas when it is running. Been planning on replacing the oxygen sensor and making my way through the emission system but now this starting issue has taken priority. Don't know if this is relevant but I am pretty sure someone who owned it before me cut out the Catalytic converter and put in a straight pipe.
If I drive the truck til it is warm and then I turn it off and say go into the store and come back out to start it, it will idle SUPER low and sometimes even shut off when I shift into reverse. It is all good once I get moving again, no issues if I am just idling at a light or anything after I get going that first time. I have a feeling this is all related to the same thing going on here...
The last time I drove it, I was driving at about 35 and everything was going fine. All the sudden, with no change in throttle by me, the transmission shifted and the RPMs began shooting up over 3k and holding for a second or two and then it dropped back down to ~2k. I parked it at my friend house after that drive and since then it has not started
When I attempt to start it is rotating the crankshaft
I have installed a fuel pressure gauge on the banjo bolt on the cold start injector and I can see that fuel pressure good so that ruled out the fuel pump
I have tested spark plugs 1 and 3 and both have good spark (I tested those 2 by pulling them out of the chamber and holding them to the intake manifold). I am planning on pulling the others out as well but I have a feeling this is not the problem
I tested the circuit opening relay and there was not continuity between B and Fc but I don't think this is preventing the truck from starting...
I took out the cold start injector to test it and it is spraying fuel fine. When I pulled it out it was covered in gunk tho... maybe relevant? See the image attached
I pulled the codes from the engine and got a 41 code which I found is the TPS sensor.
I took off the TPS and tested it according to a procedure I found here ( http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml ) and it seems fine to me. There may be a slight low resistance reading on Test # 1 (VTA - E2) but I have a feeling that this wouldn't prevent the truck from starting
I Ohmed out the Air Flow Meter as detailed in my Haynes manual and everything checked out there.
I tested the #2 injector for resistance and it was within spec. I want to avoid doing all the effort to get to the fuel rail so I haven't checked the others but I have a hard time believing that the injectors just went out randomly...
After all of this, my thoughts are it has to either be an electrical issue leading to airflow issues or the timing belt. The timing belt was changed less than 20k miles ago so I have a hard time believing that it just took a dump on me this early... On the electrical side I have heard that the crank position sensor can cause problems? Anyone know where this is located? My stupid Haynes manual doesn't talk much about it.... Also I have heard the MAF may cause problems like this?
Something I would love to know is everything required electrically to start. This way I can check each sensor and try to debug it one by one. Any kind of sensor bypassing tips or tricks would be super helpful too. I welcome any and all ideas I am starting to run out of them myself...
Thanks!
P.S. if anyone has an FSM for the 2nd gen 4runner or the 93 one specifically that would be much appreciated.
Last edited by austinmfox; 04-02-2020 at 06:26 PM.
First, the pedantics. You don't have a MAF (Mass Air Flow meter), you have a VAF (volume air flow meter). Different technology. You don't have a "crank position sensor," the crank position (used by the ECM to fire the plugs) is inferred by the coils in the Distributor. (More modern cars need a crank position sensor to detect misfires; your ECM can't do that.)
1. Jumper B+ to FP in the diagnostic connector. With key-on, you should hear the fuel pump (and your gauge should show 38-44psi). Will it start now? If it does, you have a problem in the VAF-COR circuit (the key starts the pump in STArt, the VAF keeps the pump running when the engine pulls air. This checks all of that.)
2. Use a compression gauge on each cylinder. Since you have spark, you don't have a broken timing belt. It's possible, but very rare, for the belt to "jump time." If that happened, your compression will be low. This also checks for a lot of other things you want to know.
3. Put your timing light on each plug lead, and crank. If the light flashes, the plug is firing. Now check the ignition timing. My guess your timing is way off.
4. Spray just a touch of starting fluid into the intake. Does it run for a few seconds? Your ignition is okay, your fuel system is letting you down.
First, the pedantics. You don't have a MAF (Mass Air Flow meter), you have a VAF (volume air flow meter). Different technology. You don't have a "crank position sensor," the crank position (used by the ECM to fire the plugs) is inferred by the coils in the Distributor. (More modern cars need a crank position sensor to detect misfires; your ECM can't do that.)
1. Jumper B+ to FP in the diagnostic connector. With key-on, you should hear the fuel pump (and your gauge should show 38-44psi). Will it start now? If it does, you have a problem in the VAF-COR circuit (the key starts the pump in STArt, the VAF keeps the pump running when the engine pulls air. This checks all of that.)
2. Use a compression gauge on each cylinder. Since you have spark, you don't have a broken timing belt. It's possible, but very rare, for the belt to "jump time." If that happened, your compression will be low. This also checks for a lot of other things you want to know.
3. Put your timing light on each plug lead, and crank. If the light flashes, the plug is firing. Now check the ignition timing. My guess your timing is way off.
4. Spray just a touch of starting fluid into the intake. Does it run for a few seconds? Your ignition is okay, your fuel system is letting you down.
Hello thank you for helping me out!
Thanks for the info on the VAFM and the crank position sensor that is super helpful. It sounds like these coils that sense the distributor position could potentially be an issue...
As far as the steps go...
1) I have jumped B+ to FP and seen good PSI on the fuel line. Still will not start tho.. I just replaced my circuit opening relay which did not help.
2) I will get a compression gauge and try this.
3) I am starting to suspect timing as well. I plan on checking the spark at each plug today. Why would the timing just go out all of the sudden? Would that be a sign of failure in the crank sensing elements you mentioned in the distributor? Can I turn the distributor to advance/slow timing to see if it will start? Am I right in thinking that if moving the distributor around makes no difference then there is likely something wrong in the distributor?
4) I will get some starter fluid and try this as well. Since my cold start injector is spraying well do you think that this proves that the fuel system is okay?
My battery is starting to die so I just put a charger on it. (was down at 12V and sounding pretty weak on the cranks) Hopefully later today I will have some more juice to work with...
Last edited by austinmfox; 04-03-2020 at 09:28 AM.
Jumpering B+ to FP bypasses the COR; so if bypassing makes no difference, your problem wasn't the COR (how much did that thing cost?) The point is that your tests might only have detected fuel pressure with the key to start; you want the fuel pressure to stay up after it fires.
Your timing may have been off only far enough to make it barely run, then something (like everything else) happened to push it over the edge. You won't know until you check it.
Of course, your timing could be correct and something else is wrong. So turning the distributor wouldn't make any difference, but it would tell you nothing about the distributor.
If it's cold enough, you should get fuel spraying through the CSI. But if your CSI is stuck open, it would flood out and the engine would not start. You could pull the CSI out of the plenum, disconnect the electrical connector, then turn the key to start (or, jumper FP to B+). If it sprays then, your CSI is stuck open.
There are lots of things that can cause a no-start. Guessing is fun, but won't advance your inquiry. Do the standard tests (e.g., timing, fuel pressure, spark) in order.
Jumpering B+ to FP bypasses the COR; so if bypassing makes no difference, your problem wasn't the COR (how much did that thing cost?) The point is that your tests might only have detected fuel pressure with the key to start; you want the fuel pressure to stay up after it fires.
Your timing may have been off only far enough to make it barely run, then something (like everything else) happened to push it over the edge. You won't know until you check it.
Of course, your timing could be correct and something else is wrong. So turning the distributor wouldn't make any difference, but it would tell you nothing about the distributor.
If it's cold enough, you should get fuel spraying through the CSI. But if your CSI is stuck open, it would flood out and the engine would not start. You could pull the CSI out of the plenum, disconnect the electrical connector, then turn the key to start (or, jumper FP to B+). If it sprays then, your CSI is stuck open.
There are lots of things that can cause a no-start. Guessing is fun, but won't advance your inquiry. Do the standard tests (e.g., timing, fuel pressure, spark) in order.
COR was only 30 bucks. I figured since it didn't test within spec I may as well replace it.
How can I check timing without the engine running? Try to line up the mark on the pulley with -10 and see if the rotor is at the 1 cylinder spot?
I will also check to see if the CSI is stuck open as you described. It is quite cold here now so it will definitely be spraying
Thanks again for your quick reply I really appreciate it. Time to dig in.
The runner is still not wanting to start at all and I cannot determine what is wrong.
I have tried a few things over the past week or so and still have made no progress.
-Replaced fuel filter
-Checked timing by moving to TDC and verifying that the rotor was on the #1 location when the timing mark was at 0 on the crankshaft pulley. I suppose the only way the timing would be off is if the distributor was firing on the exhaust stroke. Not sure how this could happen unless the issue is in the ECM or something... The image below shows the rotor position with the timing mark at 0.
-Tried to start with starter fluid. I sprayed starter fluid into the intake and no change was observed at all when cranking
-There is fuel pressure when I am cranking at ~44PSI
-I have verified that there is spark on all 6 plug wires with a timing light
-Still getting a 41 error code (TPS) - I have a new TPS on the way but I feel like this isn't the reason the car isn't starting
My next move is to check compression in the cylinders. Assuming the compression is okay, what should I be checking next? I am kind of lost...
-Since the starter fluid did not help, my problem is not fuel correct?
-Could the engine be flooded? I have had the cold start injector plugged in for most of my starting attempts and I know it is spraying out fuel. I have observed fluid coming out of the air intake that looks pretty brown and dirty...
-Could this be an ECM issue? Would the ECM possibly not be sending the right signal at the right time due to some input change that occurred? Can I probe the ECM to check if anything is wrong?
Update... It was my timing. My timing belt had slipped nearly 5 teeth off. Just fired her up yesterday. I am super stoked. Only thing is I sheared one of the intake plenum studs off when torquing on. It's always something.
I shouldn't have assumed that the timing belt was good even though it was changed less than 20k miles ago. I guess somebody did something wrong with the install...
04-02-2020, 06:24 PM
'93 4Runner V6 Not Starting
