Extended crank when warm or hot on crate GM L31

[Schurkey]

No it’s 25 on the spark tester… not sure what the units are. I think it’s meaning kV. Anyways… it translates to about .65 inches gap between electrode and cathode of the tester. Sorry for the confusion…

Some HEI-equipped vehicles had spark plug gaps at .080.

Keep in mind that .080 at 8:1 compression would be require way more voltage than at atmospheric pressure--although I don't know how adding some fuel to the air might change the ionization.

The HEI tester I like has a much larger gap than .065.

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The whole point of this testing is to catch an ignition (or fuel pressure) problem when the vehicle won't start. Testing it when it will start tells you nothing.

If this is really random--have you considered an ignition-switch problem? Intermittent contact inside the switch, providing power to some things, but--perhaps--not the ignition coil, or not the ECM?

 

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Some HEI-equipped vehicles had spark plug gaps at .080.

Keep in mind that .080 at 8:1 compression would be require way more voltage than at atmospheric pressure--although I don't know how adding some fuel to the air might change the ionization.

The HEI tester I like has a much larger gap than .065.

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The whole point of this testing is to catch an ignition (or fuel pressure) problem when the vehicle won't start. Testing it when it will start tells you nothing.

If this is really random--have you considered an ignition-switch problem? Intermittent contact inside the switch, providing power to some things, but--perhaps--not the ignition coil, or not the ECM?

Good thought on the ignition switch. I’ve thought of that but haven’t devised a good way to test it.

My tester gap is .65in. Not .065. It’s the tester of this style

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The problem is I don’t know if it’ll do the extended crank until I turn it over, and once I release the key to hook up a test of whatever if always starts first try on the second cycle of the key. Test or no test. So I never trust that I’m running the test when it is pulling an extended crank. If that makes sense.

 

[Schurkey]

Funny thing is that I have one of those spark testers. I've never used it...yet.

My bad on the decimal error.

 

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Funny thing is that I have one of those spark testers. I've never used it...yet.

My bad on the decimal error.

See I have that one and one of the standard blinking ones. I tried both. And of course the blinking one doesn’t show the “quality” of spark… but they both seemed just fine.

 

[HopHead357]

Was this issue ever resolved? I am having the exact same issue with my new GM L31 Crate engine with a newly installed Delphi MFI injector set up in my 1999 ECSB.

I just stumbled across the thread, so I haven't gone through all the tests you have yet.

 

[HopHead357]

Was this issue ever resolved? I am having the exact same issue with my new GM L31 Crate engine with a newly installed Delphi MFI injector set up in my 1999 ECSB.

I just stumbled across the thread, so I haven't gone through all the tests you have yet.

For anyone else who has this issue, I think I have figured out the solution. At least in my case.

I was using the original coolant temperature sensor and replaced it with a new one. This is the sensor in the intake that sends temperature to the computer, not the one in the side of the head which sends the temp to the gauge. When this is not working properly, the computer will think the engine is at the wrong temperature and sends the wrong mount of fuel which is causing it to have a hard time starting.

Changed this out about a week ago and have put about 300 miles on the engine since and have not experienced the issue again. In fact, the engine seems to be running better in general, but that could just be in my head.

 

[HotWheelsBurban]

For anyone else who has this issue, I think I have figured out the solution. At least in my case.

I was using the original coolant temperature sensor and replaced it with a new one. This is the sensor in the intake that sends temperature to the computer, not the one in the side of the head which sends the temp to the gauge. When this is not working properly, the computer will think the engine is at the wrong temperature and send the wrong mount of fuel causing it to have a hard time starting.

Changed this out about a week ago and have put about 300 miles on the engine since and have not experienced the issue since. In fact, the engine seems to be running better in general, but that could just be in my head.

If the fuel amounts are more aligned properly because of the new sensor giving correct information to the PCM...it probably is running better!

 

[Fragment]

For anyone else who has this issue, I think I have figured out the solution. At least in my case.

I was using the original coolant temperature sensor and replaced it with a new one. This is the sensor in the intake that sends temperature to the computer, not the one in the side of the head which sends the temp to the gauge. When this is not working properly, the computer will think the engine is at the wrong temperature and sends the wrong mount of fuel which is causing it to have a hard time starting.

Changed this out about a week ago and have put about 300 miles on the engine since and have not experienced the issue again. In fact, the engine seems to be running better in general, but that could just be in my head.

Unfortunately I am still having this issue with this truck. I have tried three different coolant sensors.

 

[Schurkey]

Unfortunately I am still having this issue with this truck. I have tried three different coolant sensors.

Stop replacing parts. Start TESTING parts.

Connect a scan tool, find out what the computer is receiving for temperature input.

 

[SAATR]

Unfortunately I am still having this issue with this truck. I have tried three different coolant sensors.

Have you swapped the ECM yet? You mention it in your first post, but never confirmed that you had tried replacing the ECM.