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Old 10-19-2017, 09:13 PM
1968ls2fisher 1968ls2fisher is offline
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Default Engine will fire than shut off

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.
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Old 10-19-2017, 10:07 PM
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GregWeld GregWeld is offline
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Originally Posted by 1968ls2fisher View Post
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.
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Old 10-20-2017, 05:46 AM
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TomM TomM is offline
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Have you had the VATS removed from the PCM? Sounds like this might be a contributing factor.....

T
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Old 10-20-2017, 06:47 AM
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cpd004 cpd004 is offline
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Could be that your fuel relay only has 12v at crank and not at both crank and run.
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Old 10-20-2017, 11:21 AM
1968ls2fisher 1968ls2fisher is offline
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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.
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Old 10-20-2017, 11:21 AM
68EFIvert 68EFIvert is offline
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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.
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Old 10-20-2017, 11:22 AM
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GregWeld GregWeld is offline
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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......
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Old 10-20-2017, 12:37 PM
1968ls2fisher 1968ls2fisher is offline
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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.
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Old 10-20-2017, 01:11 PM
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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,
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Old 10-21-2017, 09:27 PM
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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.
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