I swapped a 94 LT1 in my 93 and I tried to start it today. It cranks, but won't start. (before, it didn't even crank, so I had to change the wiring harness)
I know the ECM and harness worked fine on the old motor and I know everything is connected.
I'm pretty sure the fuel pump is providing fuel since I cranked it with the fuel lines disconnected the first time and I could see the fuel coming out of the lines.... plus, you can hear it prime every time you turn the key.

While cranking, the check gages light stays on. I know I connected all grounds and everything else, so I have no idea why it stays on.

Also, there are some traces of a lame installed aftermarket alarm on the car. I disconnected two wires before the swap... what appears to be a ground and a positive for something. I could find a remote start box, but no alarm brain. Could this have something to do with my problem?

Any other ideas?
Thanks.

 

Give us some more details. ie.
Was the 94 running before or fresh built?
Are you using the 94 PCM and not the 93?
Have you checked spark and compression?

 

I bought the 94 engine used. (The previous owner had it in his garage for a while (2-3 years?) and supposedly he heard it run before pulled out of the car.
Since I said ECM, I'm using the 93 ECM and harness.

How do I check for spark? Pull a plug and wire and crank?

 

that should work. a friend of mine installed his opti wrong when he rebuilt his motor and it still sparked but the timing was so far off it wouldnt fire so there being timing is not always gonna mean it will fire.

 

just pull the # 1 wire stick a screw driver in the boot and get it close to the header/manafold and have a trusted friend crank it fo you

If there is spark, i would then check the fuel pressure, then injectors and so on

 

Spark probably isn't your problem. I'll bet your problem is fuel. I guarantee the guy that set the engine aside didn't clean out the fuel rails. The fuel went stale and clogged up the rails.

BTW, high energy ignitions don't like low resistance to ground. If you want to check spark, use a spark plug and plug it on to a plug wire. Leave the plug in the head and use another plug. Lay it on the engine and have someone crank it. Once you see spark from several/all plugs, try squirting fuel directly in the throttle body with blades held slightly open. Then try to crank it. When it starts up and then shuts off, you know you have a fuel problem.

Next check fuel pressure and be sure it comes up for a few seconds with the key on but engine off. If the pressure comes up and the fuel squirt test showed the car starts and then shuts off right away, I suggest you clean the fuel rails and injectors. It will have to come off the engine to do so.

I would suggest you get a 94 or later PCM since the 93 engine used batch fired injectors. Since they fired more than once per 4 stroke cycle. I think (I admit I don't know) I think they may have been lower flow injectors in the "93". You will now be telling "94" injectors designed to fire sequentially to now fire in batches. This may or may not be a problem. But better safe than sorry.

 

I think he posted another thread where he got it running. Problem was clogged injectors.