WA
12884 posts
It's a factory fitted gas conversion, late 2006 vz wagon.
while on petrol with gas conversion hooked up, there is a very small signal to #3 petrol injector, which fails to fire. (haven't measured it with meter, but logic light just glimmers faintly, whereas on the other injectors it's bright).
If the gas conversion wiring to the petrol injectors is disconnected and the original plug connected straight into the manifold socket, it works fine.
I suspected the gas computer, but just to be sure I've checked continuity in the gas conversion wiring from petrol injectors back to gas computer, with some strange results.
I was expecting 6 direct connections between both plug and socket to the plug into the gas computer. Checked the plug first and only found 5 direct connections, I then checked the socket still expecting 6 direct connections, the extra connection revealing the faulty connection on the plug. BUT!!! I could only find 4 direct connections.
So has anybody got a wiring diagram of the gas conversion?
I'm especially looking for the pin numbering of plugs and sockets between gas converter and the petrol injectors.
Any theories as to what's actually happening would also be appreciated.
WA
12884 posts
Well I guess it was a long shot, that somebody here has a gas conversion wiring diagram, but I'm bumping it up just in case somebody has, and missed this the first time round.
WA
15849 posts
Is there anything on the net? I know stupid question but I would have thought that it would be a common thing.
Have you tried any Holden dealers if it was factory fitted.
WA
15102 posts
I know nothing about the wiring of either an LPG system or a VZ commodore, but I suspect that the wiring for the injectors is connected to the LPG system so that it can keep the injectors from firing when the LPG system takes over.
I am guessing that this means it only needs to isolate the power (or ground) to the injectors, in order to disable them, so it shouldn't need to have all injectors wired back. Well, not individually at least, but with a common power or ground.
I don't really understand the way all this is wired up from your description, but are you able to swap the wiring from one injector to another? Does the fault follow the injector or the wiring? (Even in a sequential petrol system, injecting early or late shouldn't matter, as older systems do this anyway)
Can you do the basics, disconnect the loom from the LPG computer, connect one end of a multimeter, and trace through this missing/faulty connection to see if it is intact?
WA
4642 posts
The fact that it is only #3 injector which is not working would indicate that they are switching off all six injectors individually by way of a six pole relay or maybe a six channel solid state switch. I don't know what the wiring for it is but if the common return from the injectors is via the engine frame then they would not be able to switch the common ground and would therefore have to do it the way they have, i.e., switch each injector individually.
In any case, given the symptoms, it sounds like the relay contact or switch circuit for injector #3 is not working, or the wiring to or from the relay is clagged for that injector only. I would say the 'in to out' of each injector driver should be straight though in petrol mode and open circuit in gas mode.
If you have a cable tracer you can buzz it through. If it's just a simple six pole relay you could do this with an ohm meter.
I don't have any circuit for it so all this is only assuming they have done the most probable. Sometimes they don't.
WA
12884 posts
Thanks for the replies guys.
Doggie, I can't find anything on the net.
FormulaNova,
Apparently there needs to be a small signal to the petrol injectors when using gas, otherwise the main computer will go into fault mode. This is possibly the small signal we're seeing on #3 and why I suspected the LPG black box, (it's probably a solid state switch not a relay).
So there appear to be 1 wire for each injector, going to and from the gas conversion computer. This is done by unplugging the original plug and socket at the rear of the manifold, and plugging in them into the in/out plug and socket of the conversion. So it's possible to unplug them at the manifold and the LPG box and meter between them for continuity. And doing this came up with the strange result of 5 connections on one and 4 on the other
Yes, you can swap anything around you like, fault stays on #3
Pweedas, the most probable assumption is always getting me into trouble!
My next line of attack ( if I can't get a wiring diag or info about it) is to remove the manifold and check the wiring between injectors and the manifold plug, (I know that works fine) and see what number pin #3 injector is on. I suspect it will coincide with a pin on the conversion plug and socket where there is no continuity. If this is so I have a good chance of fixing it myself.
B
WA
12884 posts
OK guys relax, the nice people at IMPCO have emailed me the wiring diagrams, part of the mystery is plug "B" that I hadn't noticed.
Now if everybody keeps their fingers crossed I may be able to find what is wrong with the thing.
WA
12884 posts
Yoyo gave me a hand this arvo, and there is continuity thru the loom for #3 petrol injector. Just plugged the manifold conversion plug and socket together and measured thru them from the plug into the gas computer.
This indicates the problem is in the computer. I've had a think about it and I think the next step, is to check into the computer from the manifold plug and socket, if a difference is obvious between #3 and the others, without ignition on, then I may be able to fix it.
I checked on the price of a new computer but the local autogas people only had an old price list that said $875 +freight, + fitting. They're going to check tomorrow to see how much it's changed.
QLD
12365 posts
Best way to fix any problem with a Commodore is to pour petrol inside it and light it.
WA
12884 posts
Hey, fixed it!!!!!!!
The reason for the earlier confusion is a well hidden plug on the bottom of the unit with ccts 5 and 6 in.
I made a mistake the other day, good job I rechecked. Ccts 1, 2 4 where 5ohms, cct3 was 5k ohms, I didn't notice the difference!.
So traced the 5k ohms to the emulator, also conveniently hidden behind the air cleaner, was a badly soldered dry joint, just had to resolder it and put it all back together again.
Cisco, the reason I prefer my commodore over a falcon wagon, is the split seat set up. With the holden the wider split seat is behind the front passenger seat. This allows 4 boards 4 sails and 3 booms inside the wagon with room for a passenger behind the driver, plus all the stuff necessary for a 2 people, windsurfing 5 week holiday.
