5.3 won't start, ideas?

[OKGMC4]

Just got to this point and no go. It's an 01 all stock, stand alone harness from a dealer in TX, and an ECM reflashed for street rod use from SpareECM on ebay. The fuel pump powers on but when I crank it doesn't seem to get spark at the plug wires and my noid light shows no pulse at the injectors. I checked and I do have power to the ECM. I've got to be missing something and not sure what? Any ideas appreciated.

[usmcchevy]

Did you check both the constant power and the key on power to the ECU? I somehow blew the constant power fuse during my install.

[ls1nova71]

Originally Posted by OKGMC4

Just got to this point and no go. It's an 01 all stock, stand alone harness from a dealer in TX, and an ECM reflashed for street rod use from SpareECM on ebay. The fuel pump powers on but when I crank it doesn't seem to get spark at the plug wires and my noid light shows no pulse at the injectors. I checked and I do have power to the ECM. I've got to be missing something and not sure what? Any ideas appreciated.

If you have power to the coils and injectors, check your grounds, make sure they're all in place and tight on clean bare metal.

Also make sure that you have power WHILE CRANKING, certain wires on some ignition switches will have power, but loose power while cranking.

[OKGMC4]

Don't have a switch yet, just holding the pink wire and the solenoid wire to the battery to see if it will start. Done this in the past with an LT1 and my brother in laws LS7 and it worked to fire up the engine. I do have 12v at the coils, the injectors, and the crank sensor, and swapped in another crank sensor and no change. The plugs for the PCM show to have good power and ground (I went by a pinout chart) The check engine light comes on as it should. I don't have the brake switch wire hooked up but shouldn't need it just to start. I've heard that if it were a VATS problem it should at least try to start, then die. Not sure about the tune but I don't know anyone with a 99-02 5.3 truck that I could try the ECM in. Sarting to feel frustrated and out of options. Probably need a scanner but don't know which one would do any good. Don't want to waste money on a bad scan tool. Surely I'm not the only person to have seen this?

[OKGMC4]

Just borrowed an AutoXRay scanner and worse news -- "vehicle not communicating with scanner." I double checked all my battery and ignition power wires in the ECM plug and all the ecm ground wires and they are all good, plus I checked for continuity between the serial data wire and the aldl connector and it's good as well. I can't think of any reason why this thing won't fire or talk to a scanner other than a bad ECM. Is that right?

[harnalien]

Originally Posted by ls1nova71

If you have power to the coils and injectors, check your grounds, make sure they're all in place and tight on clean bare metal.

Also make sure that you have power WHILE CRANKING, certain wires on some ignition switches will have power, but loose power while cranking.

I read this two days ago, but didn't catch it. That's what my problem was. I was losing power during cranking! Got it fired up early this afternoon!!
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[Clyde65]

Harnalien, did you get your truck on the road yet?

[harnalien]

Originally Posted by Clyde65

Harnalien, did you get your truck on the road yet?

Not yet, just got it started today! It's been an eventful few months, so I've only been able to work on it here and there. Hopefully I'll be rolling by this weekend. Gotta put the tranny cable on and clean up. This thing sounds like a BEAST!!!
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[OKGMC4]

Sent my ECM off to the guy who sold it to / programmed it for me. He said there was a catastrophic failure. It wouldn't talk to the software in his laptop either. Asked me if I rewired the harness myself and I told him no, I used a harness from a guy in Texas who goes by techrods on ebay. The ecm guy says they are good harnesses, he was afraid I did it myself and crossed some wires. Anyhow, he's setting up a new computer and shipping it back to me under the 1 year warranty so if I'm lucky I may still be able to hear this thing run this week!

[BR3W CITY]

Catastrophic failure of an ecm isn't the most common, unless something happend somewhere down the line. I've seen an ecm fry/fail when a battery died during uploading a tune, although never just had one "go bad". I've had "code gremlins" on other gm's so I wouldn't rule it out.

[OKGMC4]

I got the ecm today and plugged it in and it fired off almost immediately. I won't run for more than 3-6 seconds and sometimes it sounds good and sometimes it sounds rough. The engine hasn't run in 4 or 5 years so I'm thinking clogged injectors maybe. I'm just tickled that it works and that the ecm was the problem. I've got some more trouble shooting to do...

[OKGMC4]

Spent a lot of time cleaning gooey clogged injectors and it runs GREAT! Starts right up, louder than hell with no exhaust. My neighbors hate me now...

[BR3W CITY]

mine too, that just means your doing it right!