vz commodore cranks and almost starts, then dies

[BAW]

So I've gone through just about all the threads out there, and nothing has solved my problem yet.
Before I call in the 'professionals' was hoping someone here would have the solution.
Ive included as much detail as I can, but skip to the bottom for the short version

History:
Used the car (05 VZ exec) regularly, using it last on a sunday.
Did not touch the car again until the next friday, when I moved if a few metres out of the way.
Didnt use again till the next tuesday, I started it up and put it in reverse and it died (I cant be certain it actually started, it sounded like it was borderline, and as I grabbed the shifter it all died)
Since then I have not been able to start the car.
It cranks on the verge of firing, sounds like its almost there, but never starts.

I never heard the fuel pump priming, and there was no pressure in the fuel rail.
So I replaced the fuel pump and fuel filter.
Now when I turn the key to 'on' sometimes the fuel pump primes, but most of the time it doesnt. There is also pressure in the fuel rail now.
I cannot find what conditions decide if the fuel pump will prime or not, but it primes probably less than 1 in 20 attempts (if it primes, the fuel pump relay clicks, otherwise the relay is silent).
Playing with the relay, I can get the fuel pump to pump continually by bridging the fuse. This leads me to think that the problem is not the pump, nor the wiring from the relay to the pump.
Makes me think it is something electrical, to do with controlling when the relay is activated (hopefully not ECU-related).
However, when I crank the engine, after a second or two, the fuel pump comes on (everytime) but only as the engine gives up cranking, then the pump turns off.

Also replaced the oil pressure sensor/switch, as that was overdue to be replaced,and I have heard it is linked in with the fuel pump circuit.
The rubber elbow from near the throttle body to the EVAP/purge line was also cracked, so I replaced that too.

When I turn the key, I get a low fuel message (i think the new fuel pump is not calibrated properly yet, but it has about 15-18 L in the tank)
Occasionally, and randomly, I will get a service vehicle soon message too.

Since the problem started, the engine has never run, not even for a few seconds. Gets to the point of almost starting (sounds like its about to start, or is starting), then gives up cranking and goes silent. Does the same thing whether I flick the key to start, or hold the key to start.

Battery has been checked, and swapped for a known working one out another commodore, but same result.

Spark plugs or injectors crossed my mind, but its unlikely these would all fail at once, so suddenly. (or is there a program in the computer that shuts it all down if it senses a problem with one)

Also, I have no problem with the immobilisation (red lock light goes away once key is in), and all the fuses and relays I have checked and swapped, theyre all fine.

Any help or suggestions would be much appreciated before I fork out some serious cash for call-out fees and the run-around from different mechanics and auto-electricians.
Thanks.

Short version:
car cranks but wont start
fuel pump and filter replaced
fuel pump now primes sometimes
when cranking, fuel pump comes on as engine sounds like its about to start, but then everything shuts down

 

[XioiX1983]

Could be the key, it requires contact with the metal knob and the ring around ignition. Try a another key

 

[BAW]

well, im happy to say i think its been solved (fingers crossed)
after 10 days of reading threads and trying different solutions, the answer comes 30mins after i posted this thread.
but anyways, might as well post it, it might help someone in the future.
even if its only a temporary fix, it may still help you move the car somewhere more convenient.
these threads can be invaluable when you have nothing else.

what ended up working was bridging the starter relay so the starter didnt give up after 6 seconds.
a 15 second-or-so bridge of the starter relay got the engine to start, and now starts first time, every time.

any guesses as to what the problem was? blockage? air-lock?

anyways, if anyone comes across a similar problem its worth a shot.

Could be the key, it requires contact with the metal knob and the ring around ignition. Try a another key

thanks for the suggestion, that was one thing i tried earlier on, but it didnt work
also apparently if the problem is the key, you wont see the anti-theft lock light disappear on the dash.

 

[BAW]

I should also add that the intermittent fuel pump priming doesnt seem to be an issue, it was a red herring.
It still primes randomly (compared to the VY which will prime first time on every new key insertion), but even though my vz is random (either computer-controlled, time or pressure dependent), it doesnt seem to affect the car now.
Once the engine starts, pump goes and works fine.

 

[99notout]

Thanks for posting the reply, it will help someone in the future for sure. Any chance you could show the relay, location and how to short it etc?? Thanks again.

 

[Benboy]

What you have described is a common problem. What can happen is the fuel system floods - caused by starting the engine and running for only a few seconds (particularly in cold conditions) which doesn't enable all of the sensors to send correct and appropriate information to the ECU (Engine Control Unit). FIX: Disconnect battery for a few minutes to enable ALL settings to be erased from ECU. If possible, connect a jump start battery to yours and then, without depressing accelerator, commence starting procedure. Sometime it can take minutes before the engine starts. When it does, be prepared for some very rough running and heaps of black sooty (smelly) stuff from the exhaust. Once running leave to idle for a few minutes before removing jump start battery. (Why the jump start ? Unless your battery is 100% you will not be able to start the engine).

 

[BAW]

thanks for the info Benboy, your diagnosis seems probable, however Im not sure your tips would have helped in my case.
1. Battery had been removed for recharging, so theoretically all errors should have been reset.
2. When trying with jump-starting, it was a no go. No battery ticking or starter motor sound. Cables were hooked up right, and donor car was running, so not sure why my car had 'locked out' any form of jumpstart.
3. You mention the 'starting procedure' can take minutes. what is this? do you mean holding the key down, or just keep turning it repeatedly? Either way I couldnt get the engine/starter to turn over for more than 5 seconds before conking out.
4. after getting it going by bridging the starter relay, it ran fine. no coughing or black smoke at all.

i also tried out the old fuel pump before chucking it. it didnt sound too flash, but then I dont know what they're meant to sound like outside of the tank.
so whether the fuel pump was part of the problem is still unknown.

 

[Benboy]

What happens is that the engine becomes flooded with fuel. The sensors are unable to immediately reset to resolve the problem. The only way is to repeatedly crank the engine (hence the suggestion of a jumper battery to assist) until it begins to fire. Once that happens you have to keep cranking until the engine fires and continues running. As stated previously, be prepared for a load of black smelly exhaust emission - owing to the flooded condition of the engine. Hope it helps, cannot make the procedure any clearer.

The steps are based on my experience guided by an Auto Club Mechanic who had experienced the problem several times.

The first time he heard of it related to a VZ that Holden had on display at Elizabeth for a Press Meeting. They started it to move it a couple of metres and then shut the engine down. As it was cold weather the sensors did not get time to adjust to the various temperatures and they caused flooding when an attempt was made to re-start. Disconnecting the battery can cause the ECU and or Sensors to re-set enabling an opportunity to start the engine. Holden people were also apparently 'perplexed and confused' in regard to the situation. Something that they had never previously experienced with the Alloytec.

 

[bcw61]

What happens is that the engine becomes flooded with fuel. The sensors are unable to immediately reset to resolve the problem. The only way is to repeatedly crank the engine (hence the suggestion of a jumper battery to assist) until it begins to fire. Once that happens you have to keep cranking until the engine fires and continues running. As stated previously, be prepared for a load of black smelly exhaust emission - owing to the flooded condition of the engine. Hope it helps, cannot make the procedure any clearer.

The steps are based on my experience guided by an Auto Club Mechanic who had experienced the problem several times.

The first time he heard of it related to a VZ that Holden had on display at Elizabeth for a Press Meeting. They started it to move it a couple of metres and then shut the engine down. As it was cold weather the sensors did not get time to adjust to the various temperatures and they caused flooding when an attempt was made to re-start. Disconnecting the battery can cause the ECU and or Sensors to re-set enabling an opportunity to start the engine. Holden people were also apparently 'perplexed and confused' in regard to the situation. Something that they had never previously experienced with the Alloytec.

If the VZ ECU has an 'unloader' function similar to the VN ECU, starting a flooded engine can be achieved by holding the accelerator fully open. This should command the ECU to enter a 'clear flood' mode, by deactivating the fuel injectors, allowing excess fuel to be cleared more quickly during cranking. It might also save the battery and starter motor from excessive use as well.

It is similar to the unloader function for a flooded condition in old carburetor equipped engines; in that it is achieved by holding the accelerator fully open during cranking.

 

[Jasevb72]

You blokes are life savers!!!

I had this exact situation happen to my VZ last night / this morning. I was tearing my hair out... then found this thread.
I combined the ideas of disconnecting the battery (once the battery was disconnected I turned the ignition on, to allow 'battery' and 'ignition' circuits within the ECU to clear - BUT, I made sure to turn the ignition off before reconnecting the battery), connecting a jump starter to the battery, and bridging out the start relay to allow for longer cranking. It took a few go's, but the car finally started, cleared the crap out the exhaust, and then ran normally.

Thanks for the info... awesome.
Cheers.