VS 5 litre V8 - Urgent help needed!

[Drewie]

Need some expert advice for a good friend of mine, he has a 5 litre VS V8 Commodore, some time back it developed a problem that it would stall intermittently and refuse to restart, or some mornings would not start at all, but if he tried a few hours later it would somtimes restart fine, other times not, very unpredictable, well he has changed the following items and each time he has thought he has solved the problem it has reoccurred.
This is the list of components that have been changed:
New coil, new distributor, plugs & leads, tried another ignition module, cleaned the throttle body, new fuel pump, he has noticed the tacho becomes a bit erratic as it stalls, when he has changed a component it seems fine for a while then bingo it fails again. He had an auto elect check it out and he diagnosed the coil, that failed to fix it. It is not throwing any fault codes, it just cuts out then refuses to restart. All the connections have been checked and appear to be ok, main earth from the motor has been cleaned up.
Has any one got any thoughts on what to check? Have run out of ideas on what to check next.

[vrcalais5ltr]

a bit more info on what it is actually doing would help. i.e is it still cranking over when it dies, is the fuel pump still building up pressure when keys turned, is it still getting spark so on so forth. that info will help find the fix allot quicker

[5.0L UTE]

I had a similar problem turned out one of my injectors was leaking causing it to flood. Car stalled and wouldn't start. Couple of hours later it would start (sometimes).

[greenfoam]

I was going to say the dizzy but since you've replaced that and almost everything else It's really got to be a leaky injector or 3 but then that wouldn't stall it whiel driving soooooo I think you had multiple problems but now probably only have leaking injectors

[hako]

A longshot is the ignition switch badly worn which can give intermittent operation although usually by turning the key again it will make contact. (unless the contacts are overheating).

[westerlybreeze]

TPS (throttle position switch) faulty?
Usually accredited for engine stalling and sometimes hard to start (needing to "floor it")

[VrWagz1]

I would say maybe TPS too but that would throw up an error i would thing. Fuel filter been replaced with the pump yeah if not then change it too, it could be blocked up.

When you say the tacho bounces it seems like it is definatly an electrcal fault but it seems you have replaced everything everything.

But as #2 posts asks. Need more info. Once it is stalled whats missing??? Spark, fuel, injector pulse, has the immobiliser light stopped blinking ect... We can be a bit more specific with answers then.

[Not_An_Abba_Fan]

It could be the hall effect sensor. When you say the dizzy has been replaced, was it a known working one or a s/h one from a wrecker or a brand new one?

[coolngroovy]

If it was a red 6 or a 308, i would suggest rechecking the dizzy earth.
I'm not sure if the VS dizzy has the earth or not, but i have struck the exact same issue in other cars.