VZ SS - cranks for a while before starting, mainly after being driven and parked

[Evil66]

Hi Guys,

Got a problem with my L76 6L VZ SS not starting easily after being driven a bit earlier (say 1/2hr to 1 1/2 hrs earlier). Sometimes it will start after a bit of cranking, other times it times out on the autocrank feature and I have to crank it again before it will fire. Noticed the other day when it does eventually start that it blows a bit of black smoke (fuel). If I leave it until the next day it will start first kick. Car also has a very minor miss at idle but not that noticeabl and it drives fine from idle to redline.

Things I have done so far:

New plugs
New plug leads
Ultrasonic clean injectors and refit
New fuel filter
Swap a known good coil onto each cylinder and start car.
Test fuel pressure (fine at 58psi)
Plugged into EFI live - not showing any fault codes at all.

Has anyone ever had this sort of issue or got any ideas on what it might be?

Thanks

 

[st3r3otyp3]

O2 sensors, or fuel pressure regulator would be what I`d be looking at next.

 

[99notout]

Do you have access to a Tech 2? If so check the injectors with a lead down test. I would guess one or more isn't holding pressure and leaking into the cylinder.

 

[Evil66]

Was considering the O2 sensors but seeing as the car runs so well otherwise and has no fuel consumption issues I didn't think they would cause starting issues?

Does the car have a fuel pressure regulator, I thought this was built into the fuel pump on the later model stuff, fuel pressure tested well with a gauge and held it at 58psi.

Jut literally had the injectors cleaned and tested on a bench and all good.

A friend has suggested the coolant temp sensor, can anyone confirm if the same sensor in the side of the head on passengers side gives the signal to the gauge and computer to control fuel mixture and fans? If so the temperatures that come up in the engineering mode seem pretty spot on with the thermostat temperature and conditions.