1989 GTA, 5.7L, 36,000 miles.

The car will start up beautifully when cold. Idles and drives like a dream. But when it's warmed up to operating temp, it won't start. The starter making the ruh, ruh, ruh, ruh sound like it should, but it doesn't actually start the car. The oil pressure gauge seems to stay down near or on zero when this happens. Although I've never really payed attention where the oil pressure is when it starts normally.

I doubt it's the starter getting heat soaked because I have stock L98 manifolds. And it's never had trouble starting up when it's 95° outside and I've been driving around doing errands. On the other hand, it's the original starter.

The fuel pump does make the 2 second sound when putting the key in RUN before trying to start. Fuel pressure at the regulator is 40 psi. Pulling a spark plug wire boot off the plug, I can see spark travelling from the boot to the plug when cranking.

The car will start with starter fluid sprayed into the throttle body. And it stays running just fine. I actually drove it home from an emissions test that way last week. (Drove for 15 minutes to warm it up. Parked it at their shop off. They started it, drove into their bay. Shut it off. Did the inspection. Start it and run it on the emissions dyno. Shut it off....I go to drive it home. It wouldn't start. Thus the starter fluid came out and it fired up.

I got stuck in a mall parking lot about 2 weeks ago in the middle of the afternoon. Went inside and came out 10 minutes later. Wouldn't start. Waited for 3 hours. Still wouldn't start. Got it towed. It started the next day after taking it off the tow truck.

I've scanned it and no codes come up (aside from code 12)

In 2007 it got cap/rotor, new sparkplugs, new fuel filter. Spark plug wires are TPIS wires that have been on the car since 1990.

It's the original fuel pump in there. It has been making the occasional humming noise from the back end. Usually while moderately accelerating at 30-45 mph. Even when the tank is full. Could it be the fuel pump starting to die? Would this cause a no warm start? The car has half a tank of gas in it at the moment.

New battery and alternator a few months back. Battery was at 12.5 volts while engine off. Not dropping below 11 volts while cranking.

Base timing is set at 6°. I've tried both a PCMForLess chip as well as my old Hypertech chip. Makes no difference in regards to the no warm start. Car isn't overheating at all. Runs at 180°.

 

do you have fuel pressure when it doesnt start? I would get a gauge on there and see what its doing before you toss a fuel pump in it.

 

Yes. 40 psi while cranking the engine.

 

Can we say your question boils down to:

''Why do my fuel injectors NOT fire while in the CRANK mode when the engine is HOT?''

 

That would make sense. Oh goodie. Taking the SuperRam off to get at the injectors....Then again, it's still probably easier than dealing with a fuel pump.

 

Well we can modify this a bit and ask:

''Why does the ECM NOT fire the injectors in the CRANK mode when the engine is HOT?''

If you know you have 40 PSI when in the CRANK mode when the engine is HOT then there apparently is no problem with fuel pressure at that time.

Now surely someone out there knows the difference in how the ECM is supposed to operate in the CRANK mode vs the RUN mode. The injectors do fire and the ECM does fire them in the RUN mode when the engine is HOT or COLD, and in the CRANK mode only when the engine is COLD.

 

Maybe you can run this test for me:

Turn the air conditioner off and the vent fan off so that you can hear the fuel pump motor during this test.

When you have the car hot enough that you will most likely have a problem starting it, turn it off. Wait a few seconds. Then turn the ignition key to the 'RUN' position and listen for the fuel pump to run the entire two second period. When the fuel pump stops, try cranking the engine to start it. If it does not start (thus you are experiencing the problem at hand) then let the key fall back to the RUN position BUT listen to see if the fuel pump continues to run for an additional two seconds.

I would expect that if you can hear the fuel pump run for an additional two seconds after the key reverts to the RUN position then the ECM is telling us that it knew it was in the CRANK mode and it energized the fuel pump relay. If you do not hear the pump run for an additional two seconds then maybe the ECM did not detect it was supposed to be in the CRANK mode, thus it thought it was still in the RUN mode and thus it did NOT trigger the fuel pump relay and did NOT fire the injectors. If that is true then maybe, for whatever reason, when the engine is HOT the ECM is not seeing the signal telling it that the engine is being CRANKED and thus it does not place itself in the CRANK mode.

 

i will bet you that if you have gm mutec injectors that they are bad. ohm check them hot. If they ohm out under 10 thay are gubatch.. call FIC and get some Bosch. If they ohm ok. check the ICM.

 

What's an ICM?

 

I'll take a look and see if I can measure the injectors tomorrow. I'm pretty sure the back injectors are covered by the SuperRam though.

I do have the original injectors in there.

I put the fuel pressure gauge on there today. Engine running = 38 psi vac. line on (idle), 45 psi vac. line unplugged....Gave the throttle a little blip with the vac line on and the psi seems to dip a bit. Around 35 psi. Kind of bounced back and forth between 35 and 38 psi. I couldn't really rev it much higher than about 2500 RPM due to neighbours.

Shutting the car off, the psi went to 42 psi and stayed there. I went inside for 40 minutes and when I came out it was sitting on 38 psi. Not moving. So it doesn't appear to be dropping pressure while it's shut off.

 

''ICM'' ... probably stands for ''Ignition Control Module''

The puzzle is that everything appears to be working FINE in the RUN mode when it is HOT or COLD (no problems and is repeatable). Which means ignition coil, Distributor (H.E.I) Module, Distributor, Injectors, Spark plugs, etc.

I would crawl under the car and make sure that all of the wires attaching to the starter are in => good shape (good insulation, clean,etc.) <= and the connections are => clean and tight <=. I believe one of those will be purple/white and is used to tell the ECM when it should be in CRANK mode. If you eliminate a possible problem with those wires and wire connections we can eliminate that concern completely. And it is simple and cheap to do.

 

I've looked at the youtube videos from John at FIC. Good info. They seem to have a good rep among TGO members as well. I do have the stock injectors from when the car was new.

I checked the ohms on the two injectors on the driver side front. They're the only ones I can see. With the SR and the AIR box on the passenger side, all the rest are hidden.

Cold start (93°F outside ambient)

Injector #1 is 2.5 ohms engine off. Starting the engine, it bounces between 20 and 70 ohms.

Injector #3 is 1.9 ohms engine off. Starting the engine, it bounces between 30 and 85 ohms. Sometimes jumping to 115 ohms or so.

Aren't injectors supposed to stay around 12-15 ohms? I didn't do a warmed up engine check. (forgot)

 

I think what irocuroc meant was to get the injectors hot by running the car to the point where you think it would not start properly (your problem condition), then shut the car off, pull the wires off the injectors and measure the resistance. In other words, the plugs are 'physically hot' not 'electrically hot'.

I hope you get a chance to check the integrity of the wires at the starter as mentioned above.

 

Well a minor update I guess. It's not the starter. Cleaned the fuel injectors. Hooked up an injector noid light and it blinks dimly while trying to start the car.

Have tried unplugging the MAF and the TPS. Won't start with either of those unplugged. Put a new AC Delco ICM in there. No difference.

I'm wondering if it could be my chip or the ECM. Would be an easy fix. I suppose it's still possible the original injectors just aren't up to snuff. But leaving the car off for half an hour with the fuel pressure gauge connected, the psi doesn't drop.

 

Well it looks like the problem is solved. Turned out when I ohm checked the injectors, I wound up checking the ohms in the clips that attach to the injector rather than the injectors themselves.

.....Boy do I feel stupid. No wonder I had bizarre readings above.

Anyways, after testing the injectors, I got the following ohm readings. 17, 11, 12, 9 ohms. Those were at the 4 injectors that were visible with the SuperRam on the car. So the injectors are definitely shot. They're supposed to be 16-17 ohms.

I phoned up FIC and ordered a set of their Bosch III injectors for the car. Talked to John there for probably 10 minutes. Asked him what the truth was on increasing the psi from 43 to say 47-50 psi and getting more horsepower (the old TPIS insider hints tip). He said with the old multec injectors back in the late 80's/early 90's, that helped a bit with the atomization. Whereas with the new Bosch, they have such a good spray pattern right from 35-140 psi, that there isn't really any benefit to be gained by cranking up the psi.

So I'll be sticking with 43 psi once it's all put back together.