V6 refusing to fire - help please

[Lowrider Dave]

Cavalier V6.
Immobiliser deactivated.
Normally fires at the turn of a key. Recently not started for nearly 2 months, after a few turns it did and idled fine. (see video: https://vimeo.com/156162301)

Went to start it today and it just turned and turned without firing. Battery is strong as it keeps on turning without fading. Checked all connections and spark plug leads, checked fuses, nothing obviously amiss - can hear a small clonk from behind me which I presume to be the fuel pump.

Any suggestions please?

[humbucker]

Didn't you have this problem a few weeks ago?
Does the EML light come on when you're trying to fire the engine? If not, give the driver's kick panel a boot.
Is there fuel in the car?
I'd also say battery in key fob, but not if the immobiliser is inactive. That said, if the EML isn't showing, then the immobiliser may well be up and running.

[Lowrider Dave]

EML is on. Immobiliser was by passed but rest remains, just works off key now. Worked fine in January and last weekend.
Half tank in car.
It's on the verge of firing but just won't.
This is doing my head in...I'm on the verge of selling it too.

[James McGrath]

Very strange.

Not really my field but I would check the fuel pump and possibly the ECU.

[colin1]

Fuel getting to the front of the car?
Sticky injectors?

Any unnoticed induction leaks or holes/trunking not refitted properly?

Is it distributor or DIS? Quick look at the dizzie posts and rotor arm if it's the former.

Cam cover gasket(s) for oil leaks into the plug recesses.

[Lowrider Dave]

WIll check fuel pump but everything else seems to be working okay. I will dig out my spare DIS and try that.

[Lowrider Dave]

Checked fuel pump as far as I could, seems okay.
Tried different car battery - still the same.
Tried different DIS pack - still the same.
Tried without connector on DIS pack - still the same. Therefore problem must be before DIS pack?

[colin1]

If you have a method of checking for spark (those bright orange spark plug testers spring to mind) and there's no spark, it might be reasonable to suspect that the LT module has given up the ghost. Thing is, I don't think that they go intermittently, the second they die - they're dead; I say this because you have previously started it in January and again after that.

Did you disconnect the fuel hose under the bonnet and crank it into a rag? If no fuel's getting to the inlet then disconnection of the DIS will make little difference. If fuel is delivered into the rag, I'd still be inclined to go with sticky injectors (long stands are no friend of healthy fuel injection), if no spark (there's other ways of checking it eg getting an HT lead to spark to the block [be careful]) I'd look at the LT module.

[Lowrider Dave]

Sorry Colin, What's an LT?

[colin1]

Sorry Colin, What's an LT?

Sorry Dave
the LT module is the low tension module, usually located on the same bracket as the coil, underneath it with a harness leading to the distributor/DIS. It provides the means of collapsing the field between the electrodes of the plug, the greater the rate of collapse, the fatter the spark.

These don't go that often but they do go, the two that I know of (one was mine on an Astra Mk II) they didn't fade away, they just died and that was that.

HT lead to the block should confirm whether this is still kicking, after that, I'd have the fuel hose off and crank it into a rag.

[Lowrider Dave]

Swapped over the fuel relay, just in case, but that wasn't it.
Undid the fuel lines by the fuel rail and fuel spurted out, so fuel is getting there.
This narrows it down to spark.

I'm unaware if the V6 has a low tension module, it just seems to have the DIS pack which has one plug - which connects to the main wiring - it's a far old weight and about the size of a magazine tub.

I need to test spark but I need another pair of hands to help me to this and I also need to do the paperclip test.

[Lowrider Dave]

Paperclip test came back with 31 - but that's because it's not running.

[Cavalier342]

Starting to sound like the coil pack then mate. They ain't cheap though.

Shame I can't pop down to help... Two brains might have made a light meal out of troubleshooting it.

[humbucker]

I have a genuine GM (Bosch) V6 coil pack here, brand new and unused. I'll happily sell it to you. I bought it for my own V6 as a spare, handy to have in my arsenal of parts etc. The Y32SE in my MV6 runs a different ignition setup, so the Cavalier part is available for you to take advantage of if you're interested. Let me know.

[Lowrider Dave]

Tried different DIS pack - still the same.

Done already, bought a year or so earlier when had earlier problems.

[colin1]

Dave
low tension module - here's one I made earlier

http://www.ebay.co.uk/itm/Vauxhall-Cava ... 2122979914

[colin1]

...This narrows it down to spark...

Quite possibly but don't rule out sticky injectors just yet

...I need to test spark but I need another pair of hands to help me to this and I also need to do the paperclip test.

If you can find a suitably sized screwdriver that will wedge in the end of the HT lead and lie it across the block, you may be able to reach in through the open driver's window and crank it while watching for spark, or even just gaffer tape the peeled-back HT lead to the block.

[Lowrider Dave]

low tension module - here's one I made earlier

Well, I'll be! I wonder where that is hiding in the engine bay!

[colin1]

low tension module - here's one I made earlier

Well, I'll be! I wonder where that is hiding in the engine bay!

Typically
it will be mounted on the same aluminium bracket that the coil is mounted on but then, I'm assuming that the coil set up for the V6 is the same as the four-pots. I can't imagine it being that dissimilar - in or around the coil mounting on the near-side wing, wouldn't make much sense to mount it any distance away from there

[colin1]

For example
these look like they've been drilled (and spaced) to be bolted down under the coil on the n/s wing

http://www.ebay.co.uk/itm/IGNITION-CONT ... SwJkJWkorJ

[Lowrider Dave]

Okay thanks. After work I'll have a look around again. It looks vaguely familiar yet I cannot remember where I've seen it...

[Lowrider Dave]

Thanks to Colin's suggestions I went hunting after work and found the LT module - hidden under the PAS fluid bottle and washer bottle! V6 engine bay is cramped to say the least so I had to remove PAS and battery to get at it. It was holding on by one bolt and looks like this:







Don't know if this is excess expansion tank fluid dried on it or what, but it looks a bit knackered. Looks like I'm in for a £50 secondhand ebay job then... sigh!

[Cavalier342]

Born in the USA.. It was Born in the USA....

[colin1]

Dave
do you have access to a known good unit before you go shelling out on a new one?
Even just borrow one off a mate?

That unit doesn't look to be in great shape, if it's only holding on by one bolt then its heatsinking activities may have become compromised which could lead to the intermittent symptoms you've been seeing. As you say, the detritus could have come from the bits and pieces that it's hiding under although I suppose that's what could be causing it to fail as well.

Some tips:
clean the alu bracket, wire brush it if you can.
clean the mounting point on the wing, wire brush that if you can.
that stuff you see goo-ing out from under the module, that is highly likely to be heatsink compound, try and source some fresh to apply for when you put it back together; LT modules are pretty busy items and they get warm - an LT module sinking onto heatsink compound sinking onto a clean bracket sinking onto a clean wing will help significantly.

I'm reasonably optimistic that we've found your problem

[Lowrider Dave]

Thanks Colin, with your help I think we've found the weak link. I can't think of anyone locally at the moment who may have one I can try but I'm away on business all week so cannot look at the car until next weekend at the earliest. Will try to arrange to borrow one during the week.