7,4 vprtec 0411 swap no start

Gentlemen, first time poster. I attempted to use the search function but couldnt find anything that really helped me. I have a PCM that was programmed by Jeff at Lextech, and i am getting the crank but no start. I have double checked pins that seem to pertain to fuel and ignition and it seems correct. I can prime the fuel system and fire the injectors via my tech II. I can read all the sensors with the scanner as well. It will crank and crank and maybe fire on a cylinder or two and die. engine ran perfectly this morning on the black box before the swap. I have also shorted the fifth connector , if that even does anything. i noticed that the scanner dies when cranking over, but i assume thats the system drawing too much power to keep the scanner alive through the OBDii. or is that a sign the PCM isnt maintaining power through the crank cycle? Sorry if i missed the thread and this has been discussed ad nauseam.

I just went through each pin again and all seemed correct.

At the moment, I can't remember a specific post on the '0411 upgrade.

Maybe the '0411 is faulty?

Attached is the '0411 schematics I've used to build new stand-alone '0411 harness for 96 - 99 Vortec 5.7 & 7.4 engines.


dave w

Quote:

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Originally Posted by dave w

At the moment, I can't remember a specific post on the '0411 upgrade.

Maybe the '0411 is faulty?

Attached is the '0411 schematics I've used to build new stand-alone '0411 harness for 96 - 99 Vortec 5.7 & 7.4 engines.


dave w

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Hi Dave,

Thanks for those schematics. I went over them and have noticed a few discrepancies between what they say and what my pinout sheet says. This is for a 7.4 vortec, maybe there are differences?

CKP
spread sheet says C1-2 is not used, Diagrams shows that as CKP 12v reference. I have CKP signal in C1 12 and CKP sensor low reference in C1 28. Correct spots as per the diagram, different names though.

CMP
Diagram shows C2 39 as 12v reference, my spreadsheet shows not used. C1 73 and spreadsheet agree for sensor signal. C2 61 and spreadsheet agree on CMP low reference.

IC
Ignition coil locations agree on spread sheet and diagram with C2 26

Update: Unplugging the MAF works. MAF reference pin is in the correct spot. However i get no response from the sensor with key on engine off. Bad MAF? it was just working that morning.

My schematics are for a 2002 Express Van 5.7 Liter. I've used the schematics to build new Stand-Alone harness for both the Vortec 5.7 and Vortec 7.4 (1996 - 1999).

The sensor part # information below is from RockAuto: Same sensor part numbers, same wiring. There might be more than one source in the '0411 for 12 volts and sensor reference. There is only one place the sensor signal can be wired to. Check the sensor connector wiring, by unplugging the connector from the sensor ... Key On / Engine Off measure the pin voltages on the unplugged connectors.

The MAF will send a signal Key On / Engine Off if you have air flowing through it, like a blast of compressed air. Caution, do not BLAST compressed air next to the MAF, about 6" away from the MAF is safe.

dave w

2002 Express Van 5.7
CKP – SMP PC123
CMP - BECK/ARNLEY 1800750


1998 C2500 7.4
CKP – SMP PC123
CMP - BECK/ARNLEY 1800750

Quote:

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Originally Posted by dave w

My schematics are for a 2002 Express Van 5.7 Liter. I've used the schematics to build new Stand-Alone harness for both the Vortec 5.7 and Vortec 7.4 (1996 - 1999).

The sensor part # information below is from RockAuto: Same sensor part numbers, same wiring. There might be more than one source in the '0411 for 12 volts and sensor reference. There is only one place the sensor signal can be wired to. Check the sensor connector wiring, by unplugging the connector from the sensor ... Key On / Engine Off measure the pin voltages on the unplugged connectors.

The MAF will send a signal Key On / Engine Off if you have air flowing through it, like a blast of compressed air. Caution, do not BLAST compressed air next to the MAF, about 6" away from the MAF is safe.

dave w

2002 Express Van 5.7
CKP – SMP PC123
CMP - BECK/ARNLEY 1800750


1998 C2500 7.4
CKP – SMP PC123
CMP - BECK/ARNLEY 1800750

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I can get it to fire up with the MAF unplugged. So I dont think CMP/CPK sensors are bad or mispinned. I'll check voltage later tonight when it cools off. I'll also visually inspect the maf to see if its dirty. I find it hard to believe the MAF is dead as it worked 8 hours earlier

Update: MAF connector gets 12v with key on. Connector also has a good ground. Connector is showing 5v reference. There is continuity between reference line at connector and C2 31. So....bad MAF? Could the PCM have a fault in the tune?

It's interesting the engine runs without the MAF plugged in. So, I'm wanting to understand correctly, with the MAF plugged in the engine won't start?

lMAF sensors are the same part numbers, 2002 Vortec 5.7 liter and 1998 Vortec 7,4 liter.

The starter flash I use for the '0411 Vortec 7.4 liter conversion is a modified 2002 Express Van 5.7 liter flash. Basically a 5.7 liter flash with 7.4 fuel, air (displacement), & spark parameters.

dave w

Quote:

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Originally Posted by dave w

It's interesting the engine runs without the MAF plugged in. So, I'm wanting to understand correctly, with the MAF plugged in the engine won't start?

lMAF sensors are the same part numbers, 2002 Vortec 5.7 liter and 1998 Vortec 7,4 liter.

The starter flash I use for the '0411 Vortec 7.4 liter conversion is a modified 2002 Express Van 5.7 liter flash. Basically a 5.7 liter flash with 7.4 fuel, air (displacement), & spark parameters.

dave w

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Correct. It will run, and will pretty well with the MAF unplugged. The PCM was supposed to have been flashed accordingly by Jeff. So I dont know if the MAF is actually bad, bad tune parameters or what. But the pcm isnt showing any response from the MAF. It's not showing g/s or MAF frequency.

The MAF wire is in fact getting hot, so it is still receiving power and at least functioning.

I would inspect the '0411 pins for damage (bent or recessed into the pCM).

Possibly, a connector pin is damaged? It's rare, but possibly the connector pin lock isn't locking the pin.

The flash is likely OK.

It's possible the PCM is bad. The '0411 is known to have failures.

dave w

Quote:

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Originally Posted by dave w

I would inspect the '0411 pins for damage (bent or recessed into the pCM).

Possibly, a connector pin is damaged? It's rare, but possibly the connector pin lock isn't locking the pin.

The flash is likely OK.

It's possible the PCM is bad. The '0411 is known to have failures.

dave w

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It lives. I didnt di anything. I just fired it up to move it out of the garage and it lived. I have a feeling this is just a fluke though. Drove it around the block and wants to die at idle. But drives fine. I feel that may be a tuning issue through