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So this is me starting a new less convoluted thread to my previous 22re rebuild no start throwing codes thread that was extremely convoluted. Hopeful that's not breaking the rules but if we come to a solution here I plan to update that one as well for any future searches.
So here we go. I've just freshly rebuilt this 86 4runner with a 22re engine and w56 transmission and I've been having a hard starting problem. I already troubleshot the AFM, the Circuit Opening Relay, Getting spark, the coil is good, distributor is good, etc... and now I have verified low fuel pressure at the cold start injector using the LC Engineering banjo fitting and a gauge from the pressure tester kit I bought. I first tested the rail where the regulator screws on (using the Aisin fitting that came with my generic pressure tester kit) and was getting around 75psi without the regulator installed. I did see a slow drop in pressure over time, with the fuel pump off, which lead me to believe that one of my injectors might have been leaking, second thing that lead me to believe one of the injectors was leaking was the intermittent misfire I was getting and the smell of gas on the spark plug from cylinder number 2. Coincidentally that is the same injector that got dropped when I was installing them. I didn't notice damage to the injector but today when I pulled the injectors I saw the pintle cap was cracked pretty good on that injector although the pintle its self did not show any sign of being damaged at all. Last weekend I pulled 4 "new" injectors from an 85 Camry at the local pick n pull (50% off weekend meant they only cost me 18$ I figured even if they weren't the issue a new rebuild should have rebuilt injectors as well) and I rebuilt them with new micro screens o'rings and pintle caps earlier this week and today I installed them and ran the fuel pump to check for leaks, all seemed well until I went to start the truck and it hydrolocked. I pulled the EFI fuse, pulled the spark plugs and coil wire, covered the coil with plastic and then turned over the motor and it blew about a 1/2 gallon of gas out the spark plug holes. NO BUENO. So, thinking it was the "new to me" injectors leaking I pulled everything apart and rolled back to the old injectors. Once I got down to the rail I noticed the likely cause of the hydrolock problem, the return hose from the regulator was torn and wasn't taking excess fuel back into the tank DOH! so I fixed that and the truck started. for the record I ran it about 60 seconds and shut it down because it obviously needs an oil change after all that gas getting in there. Anyway to get back to the meat n potatoes of the issue, with the test gauge connected at the cold start injector banjo fitting I was only getting 28psi with the truck running which is about 10psi bellow spec.
So at least I finally have some definitive answers about my hard starting problem and it seems like the pump its self is capable of generating plenty of fuel pressure. Also another symptom to note is the truck fired up immediately from stone cold after I got the return line fixed and the old injectors back in probably because there was already fuel in the mix chamber from the flooding. So I'm thinking it's either my fuel pressure regulator alone or the regulator and the cold start injector having issues (or maybe my cold start time switch which is a little out of spec). That said, I verified the cold start injector fires using the test laid out in the FSM (connecting alligator clips to the injector from the battery and jumping the fuel pump to verify spray) so I guess I need to dig in to check continuity at the connector for the cold start injector next and then what are your thoughts on the low pressure issue? Am I on the right track to think this is probably the pressure regulator? Like I mentioned above when I bypassed the regulator and pressure tested at the fuel rail it was getting about 75psi pressure but it didn't hold at that pressure and slowly leaked down, would that be a symptom of something or would that just be natural since the system isn't designed to run at that high of pressure?
FYI for some more background info I don't have gas coming out of the vacuum line connected to the regulator I checked that as well and it was bone dry in the vacuum line (gas in the vacuum line is one sign of the regulator going bad, so I read), I also took the opportunity to bypass the VSV for the regulator and Im now just going straight vacuum from the intake to the regulator. I was driving the truck all week even though it was hard to start it would finally fire after about 10 seconds and after I bypassed that VSV the truck seemed a little more lively so maybe there was an issue at the VSV as well, not sure on that.
Any help would be appreciated.
- Brian
Last edited by outdoorjunky; 09-08-2018 at 08:32 PM.
the torn fuel return line didn't cause flooding in the cylinders; it should have leaked any fuel trying to return to the tank out to the "open air".
75 psi is a dubious reading; max possible should be 50-55 psi. 28 is a more reliable reading, and hints at your hard starting and misfire problem. pump is the likely culprit. however, test the pump and regulator to confirm. csi system is probably fine.
the torn fuel return line didn't cause flooding in the cylinders; it should have leaked any fuel trying to return to the tank out to the "open air".
75 psi is a dubious reading; max possible should be 50-55 psi. 28 is a more reliable reading, and hints at your hard starting and misfire problem. pump is the likely culprit. however, test the pump and regulator to confirm. csi system is probably fine.
Exactly how certain are you at what pressure the valve in the pump opens at, you have a gauge permanently mounted, go clamp off the return soft line and show us a picture please.
So I just went out to clamp the soft return line and the truck fired up immediately again. Secondly when I clamped the hose off it went from 29psi to over 90 psi and the truck almost stalled out.
Pics are in order from clamped, then normal operation, then 3 seconds after the engine was cut the pressure is already at zero psi.
Last edited by outdoorjunky; 09-09-2018 at 08:13 AM.
About the fuel return line I was mistaken to think it was pulling fuel back it’s pushing fuel back. So maybe the injectors I rebuilt from the junkyard weren’t good after all? I rolled back to my original injectors because I never had this flooding problem before changing them.
Yeah time for a new pressure regulator. Obviously the fuel pumps internal pressure relief valve holds pressure just fine.
Injectors firing at 90 (whoa good pressure) is delivering to much fuel. Iirc this maths out as "double the pressure quadruple the flow", in which case the pulse width would need cut to 1/4 duration and that switching circuit is not physically capable of that.
PS. I was asking Wally for his max fuel pressure with the return clamped. This tells the max pressure of the pump, when the relief valve starts to recirculate fuel inside the pump housing.
10-4 will replace the regulator and then address the misfire secondly, if the fuel pressure isn’t the cause of that which it might be based on what you just said.
Low idle fuel pressure can be caused by a leaky FPR, or a weak pump. Your pump hitting 90psi with the return line clamped suggests the pump is okay (but keep reading). The fuel pressure can also run low with TOO MUCH vacuum, but too much is hard to get (unlike too little) so it is most likely the regulator.
The fuel pump has an internal check valve that holds the pressure up in the rail for "a while." The spec is: remain above 21psi for 5 minutes. (There are specs on all of this; you don't have to guess.) Since yours drops way too quickly, you either have a weak check valve in the pump, or you're leaking the fuel somewhere else. One of those somewhere elses (assuming you don't have gasoline dripping on the ground) is the FPR.
You can diagnose the FPR with a hand-held vacuum pump (I'd recommend you do it for completeness), but if you are reporting your other tests accurately I'd say to go ahead and replace the FPR. RockAuto has them for $58 (I see you're familiar with salvage yards; I wouldn't waste time on a salvaged FPR.)
Low idle fuel pressure can be caused by a leaky FPR, or a weak pump. Your pump hitting 90psi with the return line clamped suggests the pump is okay (but keep reading). The fuel pressure can also run low with TOO MUCH vacuum, but too much is hard to get (unlike too little) so it is most likely the regulator.
The fuel pump has an internal check valve that holds the pressure up in the rail for "a while." The spec is: remain above 21psi for 5 minutes. (There are specs on all of this; you don't have to guess.) Since yours drops way too quickly, you either have a weak check valve in the pump, or you're leaking the fuel somewhere else. One of those somewhere elses (assuming you don't have gasoline dripping on the ground) is the FPR.
You can diagnose the FPR with a hand-held vacuum pump (I'd recommend you do it for completeness), but if you are reporting your other tests accurately I'd say to go ahead and replace the FPR. RockAuto has them for $58 (I see you're familiar with salvage yards; I wouldn't waste time on a salvaged FPR.)
thanks scope and yeah I am farmiliar with salvage yards and I could have pulled two or three regulators while I was there but it seemed like a part better purchased new. Probably should have had that philosophy with the injectors as well. I’ll probably send those 4 injectors out to have them gone through professionally and install them at a later date though. .
Whoa guys today the misfire totally stopped happening so I popped the hood to take a look at the pressure gauge I’ve still got temporarily installed and what the heck do I see? The fuel pressure at idle is up at 58psi and now 5 minutes after shutting off my engine the pressure is still holding at 38psi. Obviously I know 58psi is not good ... just wondering if this new symptom paints a different picture or are we still looking at probable fuel pressure regulator as the issue here? I’m going to get a hand vacuum tester on Friday to verify the regulator is bad for sure just wondering if a failing regulator would suddenly do a 180 degree flip and start giving too much fuel pressure? In the time it took me to put this message together the pressure has only leaked down 2 psi and is now sitting at 36psi.
Last edited by outdoorjunky; 09-12-2018 at 11:43 AM.
Huh well the mis isn’t totally gone but I’ve figured out the high readings. ... the backing plate in the gauge broke free and shifted so the needle was reading in the wrong place it looks like it’s time to remove it and get the normal banjo bolt back in place I’d say. False alarm. My bad
It’s the gauge that came with the generic Actron fuel pressure tester. actron fuel pressure tester Part number CP7838 that Scope recommended. The gauge was never intended for long term use I just figured I could get a week out of it while I come to the final diagnosis on this thing but I guess not.
So, seems like the regulator and something else is wrong in the fuel system chain. I replaced the regulator with the suggested part number Scope listed from rock auto and now when I jump the fuel pump it rises to around 38 psi (got a liquid filled Marshall instruments pressure gauge to replace the Jenky one I was using) then as soon as I pull the jumper the pressure bleeds off fast still. So I clamped off the fuel return soft line then ran the test again and pressure goes high like previous readings (85-90 psi) but when I pull the jumper from the diagnostic port for the pump the pressure drops only about 5psi then holds and then very slowly trickles down over a 5-10 minute period. The second I unclamped the fuel return line pressure bled off to zero again. Get this though ... while running the PSI is sitting around 30 and as throttle is applied it spikes to 38-40psi range. So wouldn’t that point to the pump being the issue as well ie: the weak check valve theory scope presented further up in the thread? Seems like the regulator was also problematic because in previous tests I didn’t get readings in the 38psi range with the regulator installed, now I do with the replacement in place. Also i did some crawling under the truck and I don’t see any noticeable fuel dripping anywhere between the tank and the fuel rail.
My hand held vacuum test pump kit should be here today so I can test vacuum and make sure My setup is not creating too much vacuum somehow.
Last edited by outdoorjunky; 09-15-2018 at 11:47 AM.
Got my vacuum test kit today and let me tell you I can’t believe I haven’t had one of these sooner. Valuable tool and I can also bleed haydrauloc systems like brakes and clutch without a second person.
I checked vacuum direct from the intake and it’s good at 21-22psi. I also took the liberty of testing all the components of the EGR system and they are working as try should and I also made sure my throttle is pulling vacuum on all ports.
So with that said my FPR is now operating within spec at 27-31psi idle and 33-38 psi with no vacuum on the regulator.
Pressure still drops pretty much immediately after the engine stops so the probably has got to be in the check valve on the pump since I don’t see eveidence of a fuel leak anywhere on the truck. I ordered a Denso replacement pump, strainer screen, and tank gasket which should arrive should by Tuesday. Hoping that’s it for this problem because other things need to be addressed.
I tracked down the source of the misfire this morning. O2 sensor was bad. Not throwing any code on the dash but the truck was smelling really rich and since I verified the EGR system is working fine I turned to the O2 sensor as the cause. Picked up a new Denso sensor for 30$ at napa popped it in and she’s running like a top with no more misfire. Love it!
the fuel pressure hard starting issue is officially resolved. I installed the Denso fuel pump this afternoon and the truck holds pressure to spec even after the engine is turned off and it started immediately an hour later when usually it would Be hard to start again after 5-10 minutes of sitting.
Now im also dealing with this dead misfire that’s only really present when the truck drops idle and starts to warm. It’s why I thought I fixed it by replacing the old o2 sensor but the next time I drove it was back. I decided to check timing and that’s when I noticed a mis on spark plug wire 1.... I checked all wires and they all had a mis intermittently so then I tested the pickup coil ... bad... replaced distributor still getting a mis. Tested the coil ... way bad ... it was reading high side of spec a few weeks ago now it’s reading 1.9-2.7 ohm depending on where the probe leads touch the poles on the primary coil. I ordered a new Toyota coil and it should be here tomorrow I hope or Monday. In the meantime I tested all wiring between the igniter and ECU also tested grounds around the engine bay using a power probe and tested voltages and resistance on ECU connections (back probing the pins) everything checks out so hopefully the issue is coil related but I’ve got a couple used part sources around town that have 053 igniters for around 100$ if need be.
Also Im getting some strange coolant temp readings on my gauge ... checked with two verified sender units and got same results ... under load up hills at hwy speeds she starts running hot, never over heating just running 75% in the white range ... engine has 1000 miles on it, brand new copper dual core radiator new dual stage thermostat and brand new Aisin fan clutch ... old fan clutch was not working so that needed replacing anyway. Could the misfire be causing high engine temps? I’m not losing a drop of coolant so I don’t think this is a head gasket issue. I tested the coolant temp sensor with leads attached and submerged in room temp water and ran it up to boiling and the resistance steadily dropped and was within spec the entire time (used a lab thermometer to verify temps and compared to the FSM curve graph) I know it wasn’t running hot like that before the misfire showed up but not sure If that’s anecdotal thinking or not? I really put my head to the FSM and went through all the testing I could... hopefully the coil is what the issue is.
Anyway obviously I talk way too much LOL 😂 but thanks guys for helping me figure out the fuel pump/pressure issue and for kicking me in the butt to get me troubleshooting this stuff properly. Much appreciated!
🍻
Last edited by outdoorjunky; 09-21-2018 at 06:13 PM.
09-08-2018, 08:30 PM
