'98 K-3500 with 454 wont start, has spark and fuel pressure.

[Blue66]

Hi

I purchased non running 1998 Chevy Crew Cab 4x4 with a 454 and 4L80E. I bought it as a non running truck that was driven into storage last winter and would not start this spring. It has 60psi fuel pressure, and will start and run on a shot of either, so I'm assuming the injectors are not pulsing. I have had lots of experience with TBI engines but not as much with the vortech. All fuses and wiring looks ok.
Any help is appreciated.

Thanks

-John

 

[VorTecxas]

Did you check where the injector harness plugs into the main harness? If everything is hooked up then you may have a dead PCM

 

[Blue66]

Yes, all wiring and connections look fine. What triggers the injectors to fire, cam sensor? Could it be a bad cam sensor then?

 

[Osiris94ej]

Passlock?

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[Blue66]

Update, this morning while cranking and watching the fuel pressure gauge, 1 or 2 of the injectors are pulsing. I determined this by listening to the engine fire each time the fuel pressure gauge drops for a second. Still starts using a shot of either but quickly runs out. So one or two cylinders are firing but not sure which ones. Will try and use a 12V test light to see. Does the upper plenum have to come off to test the injectors?

 

[96Z71ECSB]

I would start by checking fuses. Particularly the F.I. fuse (ECM1 at under hood fuse panel). I usually check all fuses under hood and under dash before moving on.
Then I would move on to fuel delivery.
If it starts on ether, then spark/sensors should be fine.

 

[VorTecxas]

Does the upper plenum have to come off to test the injectors?

Yes, there's no other way to get to them. You can test the harness without removing it, though. The plug is behind the intake, towards the driver side. Might be hard to get to with your voltmeter but you won't have to remove the intake. Might have burned out the injector harness. If it checks out then I'd move to the injectors themselves. They may also just be gummed up. Always a good idea to check for power though, obviously.

If the truck has stock injectors, you should go ahead and replace them and the FPR. The factory ones tend to leak down badly and just generally go bad. I have 26lb Boschs for a '98 LS1 in mine, but that's going to be too much for a stock setup. The later LS1s used 21 or 24lb injectors I believe, and you can find remanufactured sets for pretty cheap. They'll fit and the stock tune will run them, factory ones are 19lb, but the way the L29 is set up it can take up to 24lb before needing to be tuned.

 

[VorTecxas]

I would start by checking fuses. Particularly the F.I. fuse (ECM1 at under hood fuse panel). I usually check all fuses under hood and under dash before moving on.
Then I would move on to fuel delivery.
If it starts on ether, then spark/sensors should be fine.

I was messing with mine the other day wiring in my fans and accidentally blew my ECM-1 fuse while the truck was running (didn't know I had). It continued running fine, but when I killed it and went to restart it would fire up for a couple seconds and then die. If I toed the throttle it would stay running, but would immediately die when I let off. Finally found the fuse was blown, replaced it and it was fine. With that said, yes, that fuse would keep it from starting on its own, but not from running entirely. Agreed that checking fuses and relays is part of the first stage of diag, though.

 

[Blue66]

I was messing with mine the other day wiring in my fans and accidentally blew my ECM-1 fuse while the truck was running (didn't know I had). It continued running fine, but when I killed it and went to restart it would fire up for a couple seconds and then die. If I toed the throttle it would stay running, but would immediately die when I let off. Finally found the fuse was blown, replaced it and it was fine. With that said, yes, that fuse would keep it from starting on its own, but not from running entirely. Agreed that checking fuses and relays is part of the first stage of diag, though.

Yes, I checked all fueses right away and they all look good. I can run the truck by trickling gas fed from a 1/4" from a 1 gallon can, through the air intake, and it runs good. but even when warmed up, it is still firing 1 or 2 injectors. I was hoping running it would unclog them if that was the case, but no change. I appreciate the advice about the stock injectors, and am going to go the Bosch route as long as I have it apart. Still have not pulled the plenum to test the injector wiring, but i will test it at the plug tommorow. I see the plug has ten contacts in it?

Thanks

-John

 

[VorTecxas]

I believe it has ten, yes. It comes from the same spot in the main harness as the coil plug.