Resolved : 3100 issues

[datman7890]

Well I bought a 96 corsica with a 3100 in it. The motor was overheated and had a cracked block. So I got a deal on a 3100 from a 96 lumina. Dropped it in and hooked everything up. Problem is it will not start. Tested ICM and tried a spare. Getting spark though. Tested fuel pressure. Showed 43psi although could not test while cranking. (could be a problem) Changed 7x crank sensor and cam sensor anyhow. Tried a different known good map sensor. And stuck the volt meter on the tps. Everything is good and still will not run. Although it did run one time. Had a slight miss which was more then likely because I had the UIM gasket screwed up from being in a hurry. The entire motor has new gaskets. Show 160psi across the board on the cylinders.

PCM possibly?

The car did sit for 2 years. I added 10 gallons of fresh gas and left the air box disconnected to rule out any nest.

[bszopi]

Are the plug wires in the proper locations? When you say it doesn't start, what exactly does it do? It sounds like it's cranking, but just not turning over.

[datman7890]

Yes the plug wires are on correct. Have looked over it many times thinking that myself. It is cranking over just will not start. Other then that one time. Also forgot to add it is like the ignition timing is off some how. The engine fights the starter alot, like the timing is very retarded. Once in awhile it will pop or backfire through the intake. I know the push rods are in correct order. And I think compression backs up that statement.

Any ideas?? need this thing going. Will the car run without a MAF sensor?

[bszopi]

Yes, the car will run without the MAF, although not ideal. It still has a MAP that the computer can use. It still sounds to me like the spark plug wires are in the wrong spots....



Since you said you already changed out the 7x crank sensor, you may want to inspect the wire going from the crank sensor to the ICM. Any kind of knick in the wire will potential cause a loss of signal to the ICM.

[datman7890]

On the SFI engine aren't the coil packs the other way around. Starting with 5 and ending with 1? I will check that wire for nicks. Although I am getting a consistent spark.

[bszopi]

Here is a view of the coil packs and the ICM, showing the connectors.

[datman7890]

Yea so if you flip that photo 180º then that would be correct. That's how my wires are. This is the SFI engine with the coils mounted on top of the engine over the rear head. Did all 3.1 engines come with the same tone ring on the crank?? As in all have the same 7 notch ring? This thing really fights the starter, surprised the nose has not broke off yet actually. Going to try a pcm from a 96 lumina tomorrow to see if it works. Same computer. I am completely out of ideas. About time for a scope.

[Superdave]

#1 cyl is next to the alternator (rear, passenger side), if you are standing infront of the car and looking at the engine bszopi's picture is correct.


If it's fighting the starter that's a good indication that the plug wires are on wrong.

[datman7890]

going by what the picture says and the arrow pointing forward then yes it is correct. I know they are on right. Cyl 1 is by the firewall.. blower motor.. and all the way to the passenger side. coil pack order from left to right standing in by the front the car starts with cyl 5 and ends with cyl 1. I know it is not the plug wires. It has to be something with the computer getting the wrong information. or sending out incorrect info.

Back to the crank trigger idea.. Would they be the same?

[bszopi]

All crank triggers are the same until you get to the 3500 (and maybe a 3400 out of an Equinox).

Just for shits and giggles, try swapping the wires around. Its not like its going to hurt anything...

[datman7890]

I can try, but the coil packs are numbered. Still factory coils mounted on the ICM. Same order on both sets. Would low fuel pressure upon cranking keep it from running. Say the fuel filter clogged up bad from sitting.

[1meanz]

check the cat... would keep it from starting, make it fight to start, and pop through the intake also. unbolt the dp and try it.

[datman7890]

check the cat... would keep it from starting, make it fight to start, and pop through the intake also. unbolt the dp and try it.

That was also on my mind alot. Seemed like the muffler might be clogged when I did get it started. Will try that.

[datman7890]

Alright well I am about 1 day away from just burning this thing to the ground.

Who as experienced a bad computer and what did it do? I checked the wire from the 7x sensor to the ICM. All looks good continuity checks out great no breaks will bending it around or anything. Disconnected the exhaust from the manifold and still does the same thing. Also have the air box apart to eliminate that. I know the plug wires are correct. I double checked and compared to a 3400 today just for shits. Compression is 155-160 in all cylinders.. can't be a pushrod in the wrong spot. Would assume it would bend a valve if they were or be way off in compression. If I hold the pedal to the floor though I can hear popping through the intake. I have no idea what is going on. If I disconnect the relay running the fuel pump it will start and run for like 10 seconds, and smoothly. Then upon reconnecting it after some cranking will start again for about 10 seconds. No amount of messing with the throttle will keep it running though. Also will not stay running on ether without the pump running so it has to be ignition related. Its like the computer is sending false signal.

I really need a scanner.
Can I just toss another computer of the same number in and try to start it?? or does it have to be flashed to my car?

Thanks for the help guys.

[datman7890]

I have not replaced the crank sensor behind the crank pulley. Thinking it does not need that sensor. Does the computer need this sensor for the engine to run? From my understanding only the rear sensor needs to work to make it run.