VT V6 Starts every few hours then no spark

[chrisp]

I suspect that the fault is in the ignition system. Have a look at this very detailled (read long and involved) test procedure http://easyautodiagnostics.com/gm/3.8L/ignition-module-and-crank-sensor-test-1

It'll probably take ages to do, but at least it should help to find the problem.

 

[lout]

tech 2 wont work if bridging 5 and 6 doesnt work
unless your sparky is exceptional i wouldnt get my hopes up
you sound pretty switched on so have a read of these posts and see if you have an intermittent version of same fault
https://forums.justcommodores.com.au/threads/no-spark-in-my-vt.264190/#post-2893434
https://forums.justcommodores.com.au/threads/vx-dreaded-serv-error-_.261820/
https://forums.justcommodores.com.a...1-auto-v6-all-warning-lights-flashing.242876/
and as i mentioned before need to know if you have serv error when fault occurs
and in the last post use the dash diagnostic function and check the dash trouble codes

 

[delcowizzid]

Bcm has no effect on spark what so ever it's purely ignition switch to fuse and relay by battery to dfi injectors.no idea why you can't flash codes

 

[2O4TS]

tech 2 wont work if bridging 5 and 6 doesnt work
unless your sparky is exceptional i wouldnt get my hopes up
you sound pretty switched on so have a read of these posts and see if you have an intermittent version of same fault
https://forums.justcommodores.com.au/threads/no-spark-in-my-vt.264190/#post-2893434
https://forums.justcommodores.com.au/threads/vx-dreaded-serv-error-_.261820/
https://forums.justcommodores.com.a...1-auto-v6-all-warning-lights-flashing.242876/
and as i mentioned before need to know if you have serv error when fault occurs
and in the last post use the dash diagnostic function and check the dash trouble codes

Cheers Lout. I'm gonna follow yours and delcowizzid's advice. Again, could be a while re-posting Other things also need my attention. Absolutely appreciate your assistance. FYI, my family owned mechanical repair shops throughout my formative years. With 4 full time mechanics and two apprentices already we were fully stocked with wrenchmen. Although I worked there I was involved with day to day running of the business but stuff rubs off and I was car mad as a young fella but drifted away from it when I became more 'mature'. TBH, if the Holden dealership hadn't screwed me when I first bought this car I would have barely touched it. With a little help from here I've maintained, repaired and upgraded it myself ever since but it's a very different animal to the carburetted, dizzy and coil sparked cars I worked on day and night as a lad.

Bcm has no effect on spark what so ever it's purely ignition switch to fuse and relay by battery to dfi injectors.no idea why you can't flash codes

Thanks delcowizzid. I was (incorrectly) thinking if the immobiliser was dodgy it might have been the issue but of course when I think clearly (a lot on my mind ATM) the immobiliser stops it from cranking. I've tried bridging 5 & 6 on a few separate occasions because I've walked away and then doubted myself that I'd done it properly. I mean I can count, I have a plug diagram from pcmhacking. I dismounted the ALDL socket to check the wiring into the back of the ALDL socket on Friday and it's as per the diagram.

But you know what... it takes seconds so I'll do it again regardless.

I thank you too for your assistance. I highly doubt i'll be the last time I pick your brain. Expect to see me on pcmhacking in the not too distant future as once this is sorted then I'll be going ahead with my A2A'd L67 to recon L36 top swap and the required tuning for which I'll be using (TheOne's?) ALDL cable and EEPROM, all of which I have read about (including the basic and advanced tuning of Delco ECU's section) multiple times already. Hopefully I've already educated myself enough there to not have any issues but we'll see. Cheers again.

 

[2O4TS]

I suspect that the fault is in the ignition system. Have a look at this very detailled (read long and involved) test procedure http://easyautodiagnostics.com/gm/3.8L/ignition-module-and-crank-sensor-test-1

It'll probably take ages to do, but at least it should help to find the problem.

Thanks. I'll have a read at my first opportunity.

Sometimes the way that seems the longest and most difficult at first glance can workout to be quicker and simpler in the long run than attempting short cuts.

 

[delcowizzid]

I had trouble flashing codes on mine when my airbag module shorted out and tied up the aldl bus but everything went nuts fan on etc.check engine light is run by the bcm but if it comes on at key on it should work

 

[devilly]

sorry I was wrong. sounds more electrical problems going on then fuel. when mine did this it turned out to be 2 things one was the wiring to connector to bcm had come loose.i could pull the wirers out of the connector . I had to get another connector and resoldering it in. other was the ring on the key barrel so I think it's just going through every thing and checking things oh and the one that got me was it turned out to be the start relay under the hood getting hot and cutting out. just adding a few more ideas to try

 

[2O4TS]

Just an update.

Many thanks to @chrisp for the diagnostic article.

Seems like it's the crank angle sensor. I ran through the tests systematically when I had time. Couldn't do them all in the same session unfortunately. Nonetheless prior to doing the 3x CKP test as outlined in the link chrisp sent to me and having tested for power to the Ignition Control Module and sufficient earths etc, all signs were pointing to the CAS or (CKP, CranKPosition sensor as per the article) as everything else checked out fine.

I finally did the 3xCKP test this afternoon using the 12v LED method as per the article and received no signal.

The CAS in my car is non-genuine and about 2 years old. When the initial testing was pointing to the CAS I ordered a genuine Delphi replacement and the 3x CKP/CAS test seems to have confirmed that this is the issue. Will update further after I receive and install the replacement CAS, hopefully in about 4 or 5 days.

TBH, I wan't expecting this issue initially as my understanding was the CAS tended to fail when the vehicle was hot. We all know the 'pour cold water' trick and I have previously replaced the CAS on other vehicles with exactly this issue using the cold water test myself. Add to that the the fact I replaced the original CAS to avoid break down issues, it just wasn't on my list of possible issues.

I'll also add that the car was occasionally missing under load before it broke down completely so this may also be the issue when people are have a 'breaking down under load' issue they are having difficulty troubleshooting. An oscilloscope would be a very useful tool while on a dyno for determining this. I used to have these available to me before my folks retired.

 

[2O4TS]

*Fixed*

I received the new crank angle sensor yesterday and went about fitting it this afternoon.

Started first go.

Now I get to diagnose the engine noise it started making just after I got it home. I think the 'new' motor might be going in just in time.

Thanks again to everyone who assisted.

 

[darren nic]

I suspect that the fault is in the ignition system. Have a look at this very detailled (read long and involved) test procedure http://easyautodiagnostics.com/gm/3.8L/ignition-module-and-crank-sensor-test-1

It'll probably take ages to do, but at least it should help to find the problem.

JUST REPACED MY ''DFI'' PLATE..with a new ''american'' built one...runs fine after trying 4 ''old'' ones..and changing..''CAS'' its your ''dfi''100%