Hard to start VS V8

[vombil]

I have a 97 VS V8 which takes 2-3 turns of the key to fire when stone cold. No problem starting warm and drives perfectly once it's running.
I've cleaned the throttle body and IAC and also put a different ECU in it.
Interestingly you cannot hear the fuel pump priming when you turn the ignition.

I know it's a long shot but any takers? My gut tells me there's an issue with auto choke or TPS or something in the throttle body. It was 'hunting' too prior to me cleaning the throttle body.
I've had a commy give starting issues when it had fouled plugs. I suppose I should check them but yeah, it does not miss when it's running so I didn't bother looking.

TIA

 

[VS 5.0]

Interestingly you cannot hear the fuel pump priming when you turn the ignition.

Is this with every attemped start, whether hot or cold, or only when it won't start.

When it won't start, is it cranking and not firing or nothing at all ?

 

[someguy360]

If your not hearing the pump prime, I suspect you probably have an intermittently faulty pump, maybe it's triggered by sitting for long periods.

 

[Immortality]

Check the fuel pump relay.

The fuel pump is supplied power via the oil pressure switch, this is a safety feature in case of an accident so when the engine shuts off/stalls the fuel pump stops. For the VS the fuel pump relay is a 2 way relay. In it's normal off position the relay supplies power to the pump via the oil pressure switch, when you first turn on the ignition the PCM will energise the relay and power the pump bypassing the oil pressure switch. See the attached wiring diagram.

 

[BlackVXGTS]

Any error codes set? - refer to attached link. How long since the spark plugs were changed? Easier for the spark to bridge the plug gap on a hot engine, which may explain why hot starts are OK. Could also be a faulty coolant temperature sensor.

https://forums.justcommodores.com.au/threads/checking-error-codes-vr-vs-revised.22307/

 

[lowandslow]

My VQ 5L would take ages to start when cold 95% of the time. Was a dud ecu temp sender. (there are 2 next to each other under the TB)

 

[vombil]

If your not hearing the pump prime, I suspect you probably have an intermittently faulty pump, maybe it's triggered by sitting for long periods.

yeah i think this is worth looking at. i might pull the fuel line off and hit ignition. that should tell me pretty quickly

 

[vombil]

My VQ 5L would take ages to start when cold 95% of the time. Was a dud ecu temp sender. (there are 2 next to each other under the TB)

yeah a mate of mine suggested this might be the case. will looking into it

 

[vombil]

Any error codes set? - refer to attached link. How long since the spark plugs were changed? Easier for the spark to bridge the plug gap on a hot engine, which may explain why hot starts are OK. Could also be a faulty coolant temperature sensor.

https://forums.justcommodores.com.au/threads/checking-error-codes-vr-vs-revised.22307/

checked plugs today and they are all very clean and look fairly new. bit moist like over fueling but not dirty. no codes at all!

 

[vombil]

Is this with every attemped start, whether hot or cold, or only when it won't start.

When it won't start, is it cranking and not firing or nothing at all ?

only issue on first start mate then it's OK for the rest of the day. next morning when stone cold its a pig. cranks and has spark just won't run. im not sitting there cranking the hell out of it. should fire immediately, if not then i turn key back and hit it again for a couple seconds. second or third key stroke and it's running nicely.
it used to hunt and stall and **** before I cleaned IAC and throttle. it goes like a cut snake. one of those freak motors. no cam, no diff gears, no exhaust. just a freakish donk. it would chew up any stock roller motor 5L i've ever owned