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Engine turns but will not start

Tiny
IR472
  • MEMBER
  • 1995 CHEVROLET 1500
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 200,000 MILES
Truck running fine and went to turn around to park and noticed a small noise and that it had lost a little power when reversing then going forward maybe drove like 30 feet after and parked. I did not hear any other noise and turned it off. I tried to start it back and it failed since then.

Went through the initial checklist compression, fuel, and spark and it all check outs. Spark is there and the fuel pump is turning on and the injectors are spraying even added extra fuel in the TB and it did not start.

I put a new ICM hoping it would help but it did not.

I had previously changed the ignition switch about a year ago when it did something similar. (The dash lights turn on when I turn the key to prime the pump so I don't think its the switch again).

could it be an ignition coil?
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Friday, June 21st, 2019 AT 10:14 AM

13 Replies

Tiny
ASEMASTER6371
  • MECHANIC
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Good afternoon,

What was the compression?

If you have spark and fuel pressure, did you check the actual pressure, then it is not a module or ignition switch.

https://www.2carpros.com/articles/car-cranks-but-wont-start

Roy
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Friday, June 21st, 2019 AT 12:18 PM
Tiny
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Update: adding some more information.

I got a better crank after letting it sit overnight, so at a certain point it is getting flooded with fuel from trying it.

Also, I unplugged the connector from the computer to the ignition control module and it started up but was pretty weak and shut off after a couple seconds. I tried it again plugged and unplugged ICM and the truck started up with it unplugged for a few seconds.
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Friday, June 21st, 2019 AT 12:21 PM
Tiny
ASEMASTER6371
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Does not make any sense if you unplugged the module. It would have no spark and will not run.

Roy
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Friday, June 21st, 2019 AT 12:35 PM
Tiny
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The ICM has two connections one to the computer and one to the ignition coil. From what I understand the spark should not be affected by unplugging the ecm connector.

Does that mean anything aside knowing that the icm is working?
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Friday, June 21st, 2019 AT 12:50 PM
Tiny
ASEMASTER6371
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I know how the ICM works. Yes, it is effected by unplugging the ECM.

You very well may have a bad ECM. Common on the OBD1 series. That is the only thing that makes sense here.

Roy
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Friday, June 21st, 2019 AT 1:00 PM
Tiny
IR472
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Thanks for your help so far. I will start looking at fuses/relays first then wiring as far as I can follow to see if that could be making the ecm not work properly.
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Friday, June 21st, 2019 AT 5:28 PM
Tiny
ASEMASTER6371
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Diagram for you of the ECM.

Roy
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Friday, June 21st, 2019 AT 5:36 PM
Tiny
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Update: Truck still wont start on its own, but it will start if I give it some gas as it turns.
Idle is very weak it almost turns off but it'll maintain when I step it on the gas it reacts on time. There is a code but I am lacking an OBD1 and the old paper clip trick isn't working.
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Monday, June 24th, 2019 AT 6:07 PM
Tiny
ASEMASTER6371
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Okay, from your description, it sounds like the ECM has failed. It controls the injectors and could also be the reason you cannot get it to communicate.

Roy

Replacement of the Electronic Control Module (ECM) consists of a service controller, without a PROM (CAL-PAK).

If the diagnostic procedures require the ECM to be replaced, the ECM, PROM (CAL-PAK) should be checked for the correct part number. If they are correct, remove the PROM (CAL-PA K) and install them in the service controller. The service controller will not contain a PROM (CAL-PAK).

IMPORTANT: When replacing a production ECM with a service controller, transfer the broadcast DTC and production ECM part number to the controller label. Do not record information on the access cover.

NOTE: The ignition must be "OFF, " when disconnecting or reconnecting the ECM connector, to prevent internal damage to the ECM.

NOTE: To prevent possible Electrostatic Discharge damage to the ECM, Do Not touch the connector pins or soldered components on the circuit board.

REMOVE OR DISCONNECT
1. Negative battery cable.
2. Glove box panel.
3. Mounting brackets and/or retainers.
4. PCM from tray.
5. PCM harness connectors.
6. Access cover and PROM (CAL-PAK).

INSTALL OR CONNECT
1. PROM (CAL-PAK) and access cover on new PCM.
2. Mounting brackets and module(s).
3. PCM into tray until clips lock.
4. PCM harness connectors.
5. Glove box panel.
6. Negative battery cable.
7. Perform functional check.
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Tuesday, June 25th, 2019 AT 2:35 AM
Tiny
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I did run a fuel pressure test and got 11 psi going to the injectors. It looks like the pump checks out and will start looking at the ECM.
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Wednesday, June 26th, 2019 AT 7:35 PM
Tiny
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Okay.

Roy
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Wednesday, June 26th, 2019 AT 9:49 PM
Tiny
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Late Update:
The ECM was the problem. Bought a used one off of ebay and swapped in the prom chip and the truck feels as good as new. It might have fixed up some other issues also, it feels like it is shifting a lot smoother.

Symptoms:
-Crank but no start (fuel, spark, and compression checked out).
-Eventually started by stepping on the gas while cranking.
-Low idle under under 500 RPM.
-Engine would rev but once I let off it would die out or almost die out the return to the 500 RPM.
-Noticeable loss of power when taking off from a stop.
-Check Engine light was ON but would not show the code.

Hope this helps anyone who is going thru the same thing.
Thanks for the help asemaster.
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Friday, July 19th, 2019 AT 4:20 PM
Tiny
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Sounds like the idle air control on the throttle body. A common failure for all those symptoms.

Roy
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Friday, July 19th, 2019 AT 4:44 PM

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