[BrawnE]

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.

 

[Jeremy R.]

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.

 

[RedP85]

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..

 

[BrawnE]

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.

 

[BrawnE]

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?

 

[RedP85]

Hot start: Almost started in the first 0.5sec.. like the check valve fuel line kept the pressure. Then as the pressure died, crank empty no fuel..

Hot Fuel pump sticking? and working properly when cold?

just an idea, not surethat it is the issue..

 

[82TURBOSUPRA]

Check fuel pressure regulator, heat soak maybe reducing the fuel pressure on restart after it sits for several minutes.

 

[Flyin' Hawaiian]

I agree with the above comments, sure sounds like fuel starvation. Easy to test if it is, when it won't start, spray a small amount of starter fluid into the intake, easiest way to do this is to pull this hose off of that big bolt on the side of the intake manifold and shoot a small amount inside then pop the vacuum hose back on:

Jump in and if it starts, its not electrical---at least not as far as spark and timing goes.

From your video, its acting as if the fuel pressure has dropped off after sitting and the pump is not getting enough fuel back up to the injectors. Of course, this could be all sorts of things, like a bad fuel pump, or a plugged fuel filter, or the regulator has failed or is failing to maintain pressure. Another thing you can try is to jump the fuel pump test connector (check the tsrm for instructions and connector placement) and listen for the pressure to build up, the fuel pump should be heard running then slow down once it gets to the proper ~43psi of pressure. If you don't hear it running, go back to the tank and see if you can hear it running inside the tank.

 

[BrawnE]

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!

 

[Flyin' Hawaiian]

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.

 

[BrawnE]

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.

 

[BrawnE]

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.

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)

 

[RedP85]

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.

 

[BrawnE]

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.

 

[Flyin' Hawaiian]

Sorry about the confusion, I was thinking of what I have mine set at for the 1UZFE engine, that one requires around 42-43psi, but the 5mge should be at 33-38psi as per the manual:

You're find if its within that range and 27-31psi at idle.

EDIT:
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.

 

[BrawnE]

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

 

[BrawnE]

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.

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.

After removing the upper portion of the manifold, the pesky fuel filter finally poked its head out to say hello.

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?

 

[BrawnE]

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 .

• 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...

 

[Flyin' Hawaiian]

If you have fuel in the cylinders and it still won't start, it has to be spark related. I'd pull all 6 plugs and crank to clear the cylinders out from excess fuel, then while the plugs are out, check each one for spark, as well as check each lead with a good spark plug to make sure none of them are damaged.

If you feel the plugs are fouled, change the spark plugs out since they aren't terribly expensive to replace and try starting it again.

If still no start and you have verified a good, solid spark from each lead and every plug, go back and re-stab the distributor properly with engine at 0ºTDC according to the manual.

If you are NOT getting a solid spark at all, or its a really weak spark, go back and check all the ground wires that attach to the intake. Its a bunch of brown wires and is sort of hidden near the underside around the throttle body.

 

[BrawnE]

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.