Engine will fire than shut off

[1968ls2fisher]

What's up guys I have a ls2/t56 magnum swap I'm finishing up. I have the motor installed and most of the wire connected. I'm running a reworked stock harness. With 2 12v ignition wires 1 12v constant wire. I'm getting the 12v ignition from the fuse panel under the dash. And the 12v constant im gettingstraight from battery. The engine fires for few seconds and than dies. Any suggestions on what it might be and things I can check on. Thanks.

[GregWeld]

What's up guys I have a ls2/t56 magnum swap I'm finishing up. I have the motor installed and most of the wire connected. I'm running a reworked stock harness. With 2 12v ignition wires 1 12v constant wire. I'm getting the 12v ignition from the fuse panel under the dash. And the 12v constant im gettingstraight from battery. The engine fires for few seconds and than dies. Any suggestions on what it might be and things I can check on. Thanks.

Does it have FUEL??

You might be getting cold start fuel and then nothing more....

To check this -- try having someone spray some starting fluid at the intake when it fires off.... if it keeps running - it's a fuel issue - if not - you have electrical issues.

[TomM]

Have you had the VATS removed from the PCM? Sounds like this might be a contributing factor.....

T

[cpd004]

Could be that your fuel relay only has 12v at crank and not at both crank and run.

[1968ls2fisher]

I know that there's fuel at ignition. I can hear the fuel pump turn on. After crank not sure if there is still fuel. And the Vats should have been removed. Going to check fuel relay later today. Thanks guys.

[68EFIvert]

Have you had the VATS removed from the PCM? Sounds like this might be a contributing factor.....

T

Mine did the same thing and it was the VATS.

[GregWeld]

I know that there's fuel at ignition. I can hear the fuel pump turn on. After crank not sure if there is still fuel. And the Vats should have been removed. Going to check fuel relay later today. Thanks guys.



Should just be able to check the fuel pressure gauge......

[1968ls2fisher]

I don't have a fuel pressure gauge yet just ordered one for the fuel rails. I'm going to call the guy who did my harness and ecu work. To make sure he got rid of the vats.

[TomM]

I don't have a fuel pressure gauge yet just ordered one for the fuel rails. I'm going to call the guy who did my harness and ecu work. To make sure he got rid of the vats.

Ask him when he deleted VATS did he do a "write entire" or just a "write calibration'.....If he did a "write calibration" it may not have taken...I have had this happen to me before, he needs to do the "write entire" on re-flash....


T,

[PTAddict]

What PCM are you using? With most of the later model PCMs, you have to disable both VATS and "Starter Fault Checks" or you will get exactly the behavior you're describing.

[Z06vette]

Agree with all the above on the VATS, and turn off anything Start enable/disable related, write entire. I also have needed to disable the the clutch switch, which is in a different table if using HP tuners.

[BLO BY U - TA]

I'd put a fuel pressure gauge on it first...

You could have low pressure from the pump, just enough to prime then it runs out...