VX V6 won't start.

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VX V6 won't start.

Postby Dave001 » Mon Jul 18, 2016 9:15 pm

Hey everyone,
Got an annoying VX here at the moment, and I have no idea where to look next.
Car was driving along on the highway, and just died, from the description given by the owner, I suspected a dead fuel pump, which wasn't the case.

It's a VX V6 ecotech manual, won't start, cranks, occasionally fires, sounds like the timing is incorrect. Done a compression test, found a couple of cylinders where low, we had another VX V6 manual that run sweet that was being scrapped, so we decided to just pull that complete motor, box, ECU, wiring, BCM and steering column out, and fitted it all into the original VX.

Still does exactly the same thing. I suspected a problem with the BCM to ECU wiring, so disabled VATS on the ECU, still no go.

So to recap, engine has correct fuel pressure, injectors pulse, ignition has good spark, has tested 12v at the injector rail, has tested 12v at the DFI module, no codes are logged, except for code 12 (10 10 1 2), engine was running in the car we pulled it out of, so the problem has to be somewhere in the vehicle before the three engine harness plugs (YE110, YE111, YE112). I've attempted to test all the wires to these plugs, but the wiring diagrams I have only account for about 55% of the wires in that part of the loom.

So the time has come to ask for help. :) Anyone run into a problem like this before? Any suggestions on where to look next?

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Re: VX V6 won't start.

Postby MAGP » Tue Jul 19, 2016 9:53 am

Dave001 wrote:So to recap, engine has correct fuel pressure, injectors pulse, ignition has good spark, ...snip
If you hadn't said you changed the engine etc over I would have said you've got good fuel pressure, spark, injector pulses, but do you have fuel coming out of the injectors? I had that happen to me once and, like you, I did the same thing thinking fuel was getting in but it wasn't. I found out by spraying "startyabastard" into it and it started and run while I kept spraying.

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Re: VX V6 won't start.

Postby pman92 » Tue Jul 19, 2016 10:46 am

You only need 4 things right for it to run:
-fuel pressure
-injector pulse
-spark
-compression

Check the fuel pressure with a gauge, is it correct? This eliminates fuel pump, filter, regulator, electrical fault relating to pump etc.
Injector pulse. Connect an injector plug to a led test lift or noid light. If it flashes under cranking then the injectors are opening. This eliminates ECU fault, electrical fault relating to ECU, sensor fault etc. even if there is a sensor fault it will still run but maybe run rough.
Spark. Check it at the spark plug end off the lead, make sure it jumps a 20mm gap. Eliminates coils, DFI module, electrical fault etc. check leads are routed to the correct cylinders!
Compression, do a quick compression check, quickest way to make sure the engine is mechanically good.

I almost guarantee it will be something simple and when you find it will make perfect sense. Go back to basics and make sure the 4 above things are right, in that order, before moving onto the next thing.
VR-VY Holden BCM Simulator: LINK
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Re: VX V6 won't start.

Postby kojab » Tue Jul 19, 2016 10:56 am

Maybe someone put diesel fuel in the tank.

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Re: VX V6 won't start.

Postby Charlescrown » Tue Jul 19, 2016 11:09 am

Don't suppose it's constipated? Pull out the O2 sensors and see if it goes.

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Re: VX V6 won't start.

Postby MAGP » Tue Jul 19, 2016 3:34 pm

pman92 wrote:You only need 4 things right for it to run:
-fuel pressure
-injector pulse
-spark
-compression
Not quite correct. You can have all the fuel pressure in the world but if your injectors aren't letting fuel through you wont get combustion. The fuel needs to be getting into the cylinder in large enough quantities for stable combustion. Yes I know I'm probably being picky but I've been caught with this assumption myself.

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Re: VX V6 won't start.

Postby pman92 » Tue Jul 19, 2016 3:46 pm

I guess your correct. If all them 4 things are good the only 2 possibilitys are blocked exhaust or all injectors are blocked.
In the real world it's unlikely all 6 injectors would fail at the same time, you would have a misfire on 1 or maybe 2 cylinders that did fail.
Blocked exhaust is a real possibility, would probably start and run fine for 1 second then begin running rough and then stalling within a second or 2.
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Re: VX V6 won't start.

Postby Charlescrown » Tue Jul 19, 2016 4:13 pm

I had one car that refused to even kick. You would just crank and crank and after a lot of testing I decided to drop the exhaust of and bingo. I found the guts of the cat lodged well and truly inside the tailpipe.

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Re: VX V6 won't start.

Postby MAGP » Tue Jul 19, 2016 4:56 pm

I hadn't considered blocked exhaust but yeah that's a possibility as well.

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Re: VX V6 won't start.

Postby Dave001 » Tue Jul 19, 2016 6:15 pm

I hadn't even considered a blocked exhaust, I completely overlooked the basics, and went searching for something more complex. I just phoned my mate and he's going to try and get it onto the hoist tomorrow and drop the exhaust.

Definitely not bad fuel, or a fuel blockage, fuel pressures been tested with a gauge, all within spec, and the engine was running in one car, removed bolted into the other car, and wouldn't run. Probably should have mentioned that it wouldn't run on Aerostart either.

A blocked exhaust fits the symptoms, I truly feel like an idiot for not coming to that conclusion on my own.
Thanks for the replies everyone, I'll post back with the results.
Thanks again.

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