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84 not starting after a long/hard drive + occasional/random strange idle (fuel problem?)

1087 Views 33 Replies 5 Participants Last post by  RedP85
Picked up my AT 84 L-Type on November 28th 2022 and have been on the road to going from fair condition to good condition ever since. I am happy and proud of the progress I have made so far, but the last couple of weeks have been puzzling. Here is the situation...

After acquiring the vehicle, checking it for safety and doing a full service I managed to get it to run well and even pass CA smog. After cleaning the EGR system and replacing the thermostat with an OEM one from Toyota I even managed to get the check engine light to stay off! I began driving the car for a few errands weekly, still using my other vehicle for most long days or long drives. One day after a 1.5 hour drive I parked, came back 20 mins later to start it again and no start. Cranks fine, smells like gas in engine bay, but will not start. I used my other vehicle instead, came back after a few hours and tried to start the Supra again. It started up a little limp but then it ran great after a few seconds.

After research I learned it might be the infamous "heat soak" issue; an electrical, fuel or air related problem. I started testing potential culprits.
  1. Battery passed, main grounds are good and secure
  2. Plugs, inline spark tester passed all six
  3. The air flow meter passed resistance and physical inspection beneath cap
  4. Main relays 1 & 2 passed
  5. Circuit opening relay passed
  6. Solenoid resistor passed
  7. Start injector time switch passed
  8. Water temp sensor passed
  9. Ignition coil passed
EDITED* I figured out how to test the coil after a closer look at the wiring coming from the bottom I found the brown wire and ID'd the proper terminal. [I went to go test the ignition coil and could not find the positive (brown) terminal as described in the TSRM. Mine appears to only have a negative (black) terminal. Where is the positive terminal located?]

Distributor rotor, cap and cap O-ring are new OEM from Toyota directly. Plugs are new NGKs installed in December. Wires are new 10mm OMLs installed in January. The problem persists with these new parts and with the old parts that the car came with.

This problem does not seem to occur if the engine is only off for a minute or two. Said differently, if I take the car out for a long drive and shut it off for less than 2 minutes or so and then try to start it again it fires right up. But if I let it sit for 10 or more minutes it will not start and only fill the air with the scent of gas. No gas leaks on the ground or on anything that I can see. The scent appears strongest near the EFI housing.

I have not yet tested fuel pressure and compression as I do not think I have a low-pressure condition or a compression issue since it smells like gas and when it runs it runs great. However I am considering it could be a fuel line over-pressured issue so I may do this test soon.

The other thing happening, and this might need to be its own thread but I am concerned it is related so I wanted to include it, is what I am calling an occasional "strange squealing idle" for lack of better knowledge of what it is. Engine starts but immediately begins making an unbearable squealing and grinding sound while in P. Then when I move the shifter to R, it stops and starts idling fine. I can even drive the car in reverse with no issues or strange sounds. Moving the shifter to N or D kills the engine. Moving it back to P RESTARTS THE ENGINE!?!?!? Yea... it restarts the engine then goes right back into the strange squealing sounds until I put it into R again. When this happened I had to do a lap around my block in reverse just to get the car back in my driveway... I got a video of this happening because it was just so weird. Showing the video to some mechanics they said it might be the neutral safety switch going out. This issue has only happened twice so far but to make it weirder, the second time it happened it was D that would function instead of R like it was in the first time. Could this be an ECU problem?

Any advice on how to proceed with identifying what is causing this/these problem(s) is a greatly appreciated as I am hoping to approach this strategically to save time/money.
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Shorted wiring? Allot of the wiring on these has become brittle over the decades. Check the wiring closet to the engine first and work your way around the engine compartment.
Totally possible. I have checked most of the grounds but have not fully gone through all the wiring or checked at the ecu. Thanks for the strategy around the engine compartment, I will print out the EWD pages that show the routing in the compartment and start checking things off the list one by one to not miss any.

My first Supra developped a similar problem long ago. I never found the source, and finally had to recycle the car.
But out of your potential culprits, engine sensors (Temp and CSITS) were my suspect items, as they easilly could suffer heat soak, and put ECU in an out-of-bound state..
I noticed many (on this forum and others) recommended an overhaul of the cooling system for heat soak. That can be an expensive endeavor for a 'maybe' fix. At what point is it acceptable to the community to just drop a 2J and MT in? That's what I should be working on.
Tested for shorts and ground faults in both static and dynamic tests. Still haven't found anything that is failing and could be causing this. But during my testing I set up the camera to get some video of what it is doing. Does anyone know what this unpleasant screech that occurs after attempting to start the car when hot for the first time?
Glad to hear it sounds fuel starvation related. That's something I should be able to pinpoint with just a few tests. I have a inline fuel pressure test gauge around somewhere. Wondering if I should pull the injectors and have them cleaned and tested since I don't know when they were last serviced. If I do that I might as well drop the tank and take a gander at the pump while I am waiting on them. I will run some tests first but if I get to the point I want to service the injectors what are the recommended vendors?

Don't judge me, I have had a fuel filter for the car since December and still have not replaced it because I have adult sized hands... I will find a way to do this.

Will report back soon. Thanks friends!
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Personally, I like RC Injectors for cleaning, have been using them for decades now and always get back nice, clean injectors, a full report of before and after flow rate and spray patterns, and they replace all the screens and rubber seals/o rings with new parts.

Its always a good idea to get injectors cleaned at least every 150-200k, mainly just to make sure they aren't running lean or dripping. I'm always surprised how many of my injectors are reported as low flow rates and poor spray patterns!

As for the pressure gauge, that should tell you what you need to know instantly.
Thanks! They aren't that far from me and sometimes I drive by their city. I will have to give them a call and see if maybe I can save on shipping. As far as the ones in the car I just don't know if they have ever been done in 38 years and 145k miles which makes me very curious to how they would test.
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Removed the throttle body and surrounding hoses to test fuel pressure since my gauge kit did not come with an adapter to connect to the outlet on the fuel rail, so I had to get to the one going into the cold start injector.

I got up to step (m) from FI-46 of the TSRM. Results from step (l) were about 33-34 PSI (see image below). At the low end of the 33-38 PSI recommended range out of the TSRM, but still technically passing. I kept the fuel pump on for a couple minutes just to make sure I did not see any spikes or drops. It was steady.

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I stopped here because I wanted to ask about the service wire to be disconnected from the service connector in step (m) page FI-46. In the TSRM it look like it is on or near the regulator. Which connector is it and can I proceed on with the tests including starting the engine with the throttle body just sitting on the engine as below? Or do I need to do some reassembly first? (second pic is with fuel pump off, still held around 13 PSI)

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the fuel pump should be heard running then slow down once it gets to the proper ~43psi of pressure.
Going back through a few things I noticed you said ~43psi. Am I failing at 33psi despite the TSRM saying 33-38psi? Or is ~43psi the expected pressure before the regulator? Cheers!

Engine will not be running with the AFM not metering flow. Yes you can force the pump to run, but ECU needs to read AFM opening to trigger injectors.
... well, that is what I think.
Thank you! After cleaning the area and swapping the filter I plan to reassemble the TB and intake to do this test.
Forgot to mention, these tests should be done with a fully-charged battery. If your battery is weak, your pressure may be lower than it normally would be with a good battery.
No problem! I checked my battery before testing, it was 12.4v. That's around 75% full according to Century batteries. I will borrow a battery charger so I can be sure this is not part of the problem before I retest. Thanks for all the pointers
I found a few more potential culprits as I make my way deeper into the fuel system.

First was the ground wire to the cold start injector connector. See below, it was cut.
Motor vehicle Electrical wiring Gas Coil Auto part

Then I noticed it was re-wired at some point and instead of using a proper splice they just twisted the wire together and wrapped it in electrical tape. Not very cash money of them... At least the ground side had a splice... But looking closer the wire they used does not look like auto wire to me so I will be replacing it.
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After removing the upper portion of the manifold, the pesky fuel filter finally poked its head out to say hello.
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I have been replacing all of the hoses and found several that were completely clogged up with dirt, grease and carbon buildup. I am surprised the engine would run as well as it did with all the clogs I found. Also been cleaning all contacts and inspecting for shorts/ground faults as I go.

Injectors and fuel filter this weekend. Wish me luck.

Do you think I could have fixed the issue by clearing the clogs or repairing this wire?
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Decided to reassemble the manifold without pulling the injectors. I did get the fuel filter replaced and three clogged hoses replaced. I restored the edge of the aluminum manifold and made new gaskets. After getting it all back together, now it wont start at all :confused:.

  • I checked for spark
  • Double checked spark plug wire order
  • Jumped the fuel pump and listened to it fill the fuel rail
  • Pulled timing cover and verified timing belt is still aligned at TDC
  • Put starting fluid in the manifold and tried cranking
  • Pulled a spark plug, smells like gas, some fouling present but not terrible
  • Checked the throttle body and intake for potential vac leaks, it looks tight (especially since I replaced an old cracked rubber coupling this weekend)
  • Tried reinstalling the distributor at 0 degrees instead of at 10 degrees

The engine has stumbled a couple of times like it wants to start but still has not. Looks like I have made one step forward and two back...
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I'd pull all 6 plugs and crank to clear the cylinders out from excess fuel
Does it matter if I crank by hand or with starter to get the fuel out? Thanks Hawaiian!

Good idea on checking the grounds. I know the wires you are talking about, I believe I got them attached but will verify.
So the ground wires Hawaiian mentioned did not pass my inspection. Although they appeared secured at first I was able to slide the grounds around with my fingernail. No bueno. Got them attached properly. But now I am concerned because power was going through something without it being properly grounded. What can I do to check for possible damage caused by my failure to ground these properly the first time?

Cleared the cylinders of fuel using Jocelyn's method above, while moving the intake piping to get to the plugs I found a hose clamp starting to strip so I will replace that before it becomes a vacuum leak. Picking up an extra set of plugs today along with a loaner battery charger to juice it up before trying to start it again. I hope I didn't fry something :/
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There ya go! Remove that fuse and crank, should clear cylinders quickly.
I did not physically see any fuel come out of the cylinders when I cranked but I smelled a little bit afterwards. Removing the EFI fuse seems to eliminate spark. Is that supposed to happen? After reinstalling the fuse I was able to test for spark. I put new NGK plugs in just in case, they test good.
Removed the timing belt cover and verified that skipping hasn't occurred.
Re-stabbed the distributor (with new o-ring), made sure camshaft hole was visible through the oil fill hole at TDC. I made sure the drill marks were aligned. After stabbing I found the only way to get the signal rotor to align with the pickup coil was to rotate the distributor all the way counterclockwise, till it bottoms out against the set screw for it. Does that sound right?
Carefully installed the wires and double checked all the little stuff. Still no start.. Here is a video of the sound of failure while cranking.
1984 Toyota Celica Supra 5MGE Automatic no start after rebuilding EFI manifold
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Also, leaving the bolt out of the distributor will allow you to rotate it much further than its supposed to just to see if you can get it to fire up in a different position.
First suggestion here worked! It fired up with the flange and bolt hole pretty far off. Much past where I could test with the set bolt in place.
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This makes sense that it was timing. It's like I just need one more click on the rotor clockwise to line it up. I gave that a shot and used 10 btdc to test. Still can't get the tip of the signal rotor to align with the pickup coil while also getting the flange in a spot with bolt hole access.
Below is the closest I could get it at the 10btdc position. When stabbed with the markings aligned at 0 TDC. The fact I cant get this align must be the issue.
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Well that's good news! So, pop it back out, rotate it one tooth at a time, then re-stab it until you have it sitting about midway in the slot with the bolt. That way you can rotate the timing forward or backwards without having to go past the bolt hole.

You're almost there, just a little bit of fine tuning now!
ITS ALIVE!!!! Thank you Hawaiian and Jocelyn for sticking with me! Turns out I did just need one more tooth clockwise before the distributor stab! Went for a drive last night and tested to see if I had problems starting again if I turn it off for 15 minutes and nope! Fired right up! With the limited testing I have done so far the car starts up every time!!! I am stoked!
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Update: After over 25 tests the car started every time I turned the key, even after drives that would normally not start! It is idling weird now though. RPMs seem to bounce at a tempo between 600-800 RPM. I am thinking I may have adjusted the ISCV on accident or something. That'll be the next thing to troubleshoot.
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