Car turns over, runs for about half a second, then shuts off

[Alexander Cummings]

^^^ this. Below about 400 rpm the ignition module provides the ignition and injection signals - and the initial running at starting. Above that rpm the control is passed to the engine management system. So, if the security conditions aren’t met, it will stall.

The car does have a different barrel. I had to unlock the car with the key fob prior to starting the car with another key. My mechanic put that key into the key fob so I didn’t have to hit unlock anymore. But could that still be causing issues?

 

[Immortality]

Bridging out a relay basically means pulling the relay out of the base and "hot wiring" it with a piece of wire.

This is your basic relay outlay.

So after you have pulled out the relay you get a piece of wire and shove on end in location 30 and the other end in location 87 which should supply 12 volts directly to the fuel pump and let it run continuously.

If you have a multimeter, put on current mode and use the probes to bride the relay then you can also measure pump current draw.

My toolbox has a few wires in it with spade terminals at each end which are perfect for jobs like this.

 

[Immortality]

The car does have a different barrel. I had to unlock the car with the key fob prior to starting the car with another key. My mechanic put that key into the key fob so I didn’t have to hit unlock anymore. But could that still be causing issues?

Is the security light still flashing?

In theory, if the Vats security is still on then it shouldn't crank.

 

[chrisp]

The car does have a different barrel. I had to unlock the car with the key fob prior to starting the car with another key. My mechanic put that key into the key fob so I didn’t have to hit unlock anymore. But could that still be causing issues?

I’m not sure to be honest. But you have two strong leads - security system, fuel pump.

Like any forum advice, we’re diagnosing and offering suggestions from afar. You’re the one who has access to the car and can do some checks to work out if any if the suggestions are on the right track.

 

[BlackVXGTS]

Is the security light still flashing?

In theory, if the Vats security is still on then it shouldn't crank.

Not quite correct, view the Theft Deterrent excerpt below from the Holden VR/VS Service Manual:

Operation
When the ignition switch is turned to the on position, the engine management ECM/PCM will request from the BCM permission to start. If the BCM has received the correct security code from the remote coded key, then it will respond by enabling the start relay and giving the ECM/PCM permission to start (this allows the ECM/PCM to enable fuel system control).

If the correct security code is not detected by the BCM within two seconds of the ignition being turned on, the BCM will then monitor for Radio Frequency (RF) signal output from the remote coded key doors button. If the BCM receives the correct RF signal output from the remote coded key, it will then enable the start relay and give the engine management ECM/PCM permission to start. This feature allows engine starting should there be a malfunction with the remote coded key reader assembly.

Should the BCM not receive any communication from the engine management ECM/PCM with the ignition switched on, the BCM will enable the start relay after a one second delay. The engine will crank, but will not start as the engine management ECM/PCM has not enabled fuel system control (no fuel is injected).

NOTE: It is very important that the remote coded key reader is aligned correctly with the ignition lock assembly, or misalignment with the remote coded key contact may occur resulting in intermittent or no engine cranking or starting.

 

[Alexander Cummings]

ANSWER:

Thanks for the replies everyone. Was great help. My fuel cap was broken so it wasn’t sealed. Car was also left outside. Meaning when it rained water was getting into the fuel tank so the car was trying to run on water and fuel mixed.