Trouble starting when warm

Fuel + Spark = running engine provided the timing is good and the spark is hot. For kicks and giggles do you have a coil pack you can try? I am curious if the coil is throwing weak spark once hot? This is a strange one to say the least.

I probally still have my stock coil pack laying around somewhere. Right now I have the screaming deamon coil pack and a nice set of Liveware plug wires on it. I had thought about this but since the coil pack gets hot while the motor is running and the car runs good once it starts logic says it's not the coil pack.

However at this point I'm willing to try anything.

I really appricate the input. Keep the questions coming if you can.

Spray some carb cleaner in the intake then crank it to see if it starts. Unplug the MAF and try it.

Trouble starting when warm (or hot)

I have experience the same problem. The car was 1992 5 speed. When driving at operating temperatures for no other reason it "died". When (3 + hours) the car cooled off it would start and drive as if nothing happened. Until the next time. Sometimes the car was fine for a couple days. Sometimes couple weeks. I won't tell you how much I spent on tows back to the house. I checked fuel pressures, IRCM, Emergency Fuel Shut-OFF Switch, Fuses, spark plugs, wires, ignition pack and fuel pump to tank harness. All checked good. I also changed the DIS, Crank/Cam sensors and the ignition switch. In my case it turn out to be the DIS electrical harness. I inspected and discovered electrical lead "breaks" with exposed wiring at both ends of DIS connectors. The harness itself was "brittle" at the Cam sensor connector again with exposed wiring. Just to make sure I re-installed the "suspect" harness and the problem happen again when the car was hot. Installed the replacement harness and the problem has not returned.

sam jones said:

I have experience the same problem. The car was 1992 5 speed. When driving at operating temperatures for no other reason it "died". When (3 + hours) the car cooled off it would start and drive as if nothing happened. Until the next time. Sometimes the car was fine for a couple days. Sometimes couple weeks. I won't tell you how much I spent on tows back to the house. I checked fuel pressures, IRCM, Emergency Fuel Shut-OFF Switch, Fuses, spark plugs, wires, ignition pack and fuel pump to tank harness. All checked good. I also changed the DIS, Crank/Cam sensors and the ignition switch. In my case it turn out to be the DIS electrical harness. I inspected and discovered electrical lead "breaks" with exposed wiring at both ends of DIS connectors. The harness itself was "brittle" at the Cam sensor connector again with exposed wiring. Just to make sure I re-installed the "suspect" harness and the problem happen again when the car was hot. Installed the replacement harness and the problem has not returned.

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This is also a good idea. I like the thought process

Did you try turning up the fuel pressure and seeing if that makes a difference?

I haven't tried the carb cleaner yet. I'll have to get some.

I've tried unhooking the maf when I have the problem and it dosen't make any difference.

I've also borrowed a set of noid lights. I'll try them today to make sure the injectors are getting a signal.

My problem is like Sam's however the car has never once shut off while I was driving it.

In fact it runs great. While taking it for a ride yesterday and guy in what looked like about 92 cougar 5.0 wanted some action at a light so I gave him a car off the line, spun my tires all the way through 1st gear and then drove past him at about 50-60 mph with a big damn grin in my face the entire time.

Tony8470 said:

Did you try turning up the fuel pressure and seeing if that makes a difference?

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I have not.

Does anyone know what the fuel pressure should be? I thought the 36-38 range at startup sounded normal but I could be wrong.

Oh and just for extra info it does have the 255lph hi pressure pump in the tank and 60 pound injectors.

JasonMiller94SC said:

I probally still have my stock coil pack laying around somewhere. Right now I have the screaming deamon coil pack and a nice set of Liveware plug wires on it. I had thought about this but since the coil pack gets hot while the motor is running and the car runs good once it starts logic says it's not the coil pack.

However at this point I'm willing to try anything.

I really appricate the input. Keep the questions coming if you can.

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When its hot and wont start try cranking it with the gas pedal held at WOT
Never mind i see that you have tried that

JasonMiller94SC said:

I have not.

Does anyone know what the fuel pressure should be? I thought the 36-38 range at startup sounded normal but I could be wrong.

Oh and just for extra info it does have the 255lph hi pressure pump in the tank and 60 pound injectors.

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I think 40 is stock but 36-38 wont keep it from firing

JasonMiller94SC said:

Yea I did check it while running so I'll double check it while hot. Borrowed a set of noid lights from a friend today so I can check to make sure the injectors are getting a signal. I'll check the fuel pressure at the same time.

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what did the noid lights tell you?

JasonMiller94SC said:

Yea it's chipped. But, it's been running the same program it was dyno tuned on for 5 years.

I'd have to take it somewhere to have the program looked at since I don't have any tuning software and the closest tuning place to me can't do anything with the SC computer code I'd have to make a road trip somewere to get it looked and and I might not make it back if it won't start.

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Long Shots


I wonder if something is going on with the connector the ECM dose get warm try removing and reconnecting the chip a couple of times to clean off the contacts

As a trouble shooting aid when experiencing the no start condition remove the chip and try to start it without it It will run like crap and be hog rich but that will prove wether its in the tune or chip hardware or not.

I saw that you have tried the WOT trick how long did you crank it wile holding WOT? When you hold it WOT it turns the injectors off. If you’re flooded it can take 15-30 sec of cranking with the pedal held firmly to the floor to clear the cylinders and dry off the plugs before you get a sputter pop and start.

Another thing to do is during the no start condition pull a plug and see if its wet or dry

Is the car smoking at all dose the exhaust smell sweet?

Ok, took it for a very short drive today cause I was low on gas but when I got back it started right back up the first try. So thinking maybe I didn't drive it far enough I went and got a gallon of gas out of the garrage and put it in and then took it for the usual 5 mile drive.

Now when I got back this time It fired right back up. I let it run for a a min then shut it off for 30 seconds. Tried again and got a couple spudders but no start. Waited 15 seconds then tried agian and it started right up.

I repeated this a few times and it would eather start or it would spudder then on the very next try it would start. I think I started it a total of 4 times only having tried starting it a total of 7 tries.

So I have no idea what changed as I didn't do anything differnet than yesteray when we tried 7 times in a row to start it with no luck.

I could honestly live with the car taking 2 tries to start if it will keep doing that.

To verify:

So the actual problem is lack of starting when hot. It always starts when cold. Often fails to start when hot, but sometimes it will.

Times when it doesn't start, the starter motor is spinning the engine, but the engine doesn't start. Upshift light is not flashing during cranking.

If you have a fuel pressure gauge, and it sounds like you do. I'd run the motor, get it hot, park it and monitor fuel pressure at the rail over time.

My #1 WAG is this. Something in the fuel system is allowing the engine to flood with fuel. Either a bad fuel pressure regulator (leaking by the manifold pressure vac line... check it for any fuel) or problem injectors. Check the plugs.

My #2 WAG is that the interface at the J3 port on the EEC has corroded and the chip is no longer making good contact. This poor quality connection leads to improper fueling at startup. The quality of the connection is made worse with the heat. Pull down the ecu, use a flash light and a magnifying glass and take a hard look at the connector on the J3 port. Clean the port, and the connector on the chip. Do this very carefully.

No start when hot, when all mechanical pieces are working points to either control system issues, or fuel fouling. Issues with leaking injectors or FPR will be more likely to occur during a specific window after running. Too soon, not enough fuel has leaked to cause a significant issue. Too far off, all the fuel has leaked and has already evaporated.

It's now getting better.

Let it cool for a couple hours and went out fired it right up and drove it 3 miles to the store. Came out 20 min later and it fired right up. The last time I drove it to the same store it almost left me sitting there but after a half dozen tries it started.

I did watch the fuel pressure after I had it running and when running at idle I was at 40 psi.

I shut off the motor and sat there and BS'ed with my buddy for 5 min and it might have dropped 1psi, if that.

Funny thing is when it dosen't start it really dosent' matter how long it sits. I can drive it then turn it off for 30 seconds and it won't start. I can come back 10 min later and still not start. 2 hours later, fires right up. Or like yesterday I drove it and then shut it off and it started right back up. Let it run for 30 seconds then tried 7 more times to start it and never did fire.

I don't know what has changed but this is the best day of driving it I've had in a long long time. of the 15 starts I've done with it all day long I'd say it started on the first or second try all day long. Last week I would have said of the 15 tries it started once and that would have been when cold.

So now I'm kinda at the point where I'm dissapointed that it's starting up every time cause I can't troubleshoot it. But then again I'm happy it's starting. Talk about mixed emotions.

Mike8675309 said:

My #2 WAG is that the interface at the J3 port on the EEC has corroded and the chip is no longer making good contact. This poor quality connection leads to improper fueling at startup. The quality of the connection is made worse with the heat. Pull down the ecu, use a flash light and a magnifying glass and take a hard look at the connector on the J3 port. Clean the port, and the connector on the chip. Do this very carefully.

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O.k... then WAG #2 is my predicted winner.

or WAG #3... check and make sure all the grounds are good.

I'll keep you updated the next time it fails to start. Started it twice today with no problems. So weird.

JasonMiller94SC said:

I'll keep you updated the next time it fails to start. Started it twice today with no problems. So weird.

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its a dirty connector, disconnect the battery pull your pass kick panel to get at the ecm remove the chip and reinstall it a couple of times this will clean off the contacts see if that dosent clear up your problem

I have been following this thread for a while due to my 93 5-speed having the EXACT same issue and after checking my connections and my sensors, I finally fixed it when I put another computer in the car. Now it fires up EVERY TIME

I did put the old one back in and it went right back to the same old problem.... I'm not saying it is your problem but it did fix mine and my symptom was just as you described to the T!

Good luck

Thanks for the input. It's been starting to drive me crazy. I'm going to take Motohead's advice and clean the contacts between the computer and the chip. If that dosent' seem to fix it I'll swap the computer out of the other 94SC and see if the problem follows the computer. I'd do it today but it's already 85 degrees out on it's way up to 100. Not a good day to lay inside the car removing the computer. Besides, the other SC is the only car we have with working AC should we need to go somewhere.