weird gas switching

[dj_steve]

hello all, new here.
i have just bought a 2003 vauxhall vectra dualfuel which does run on gas but likes to swap over to petrol usually when i slow down and/or accelerate.it does not do so every time but probably 90% of time. i can flick the lpg switch and it will switch back most of the time. the car is factory fit lpg koltec gsi system i believe but the lpg switch in cabin does not flash or anything it just lights up wen switch is in lpg position.. i know someone has had switch out in past and im not certain its wired correctly. any ideas what might be fault. have run cleaner through injectors already and filter is brand new

[kbs]

Suggest visiting pjpj's page.

homepage.ntlworld.com/paul.joyce53/bin/

This excellent site will help you ID the system you have, then it will tell you how to read error codes from the LPG system (no tools or software required).

If error codes don't make sense to you, post them here.

[dj_steve]

yes ive read that hence knowing its a koltec gsi system, i cant read fault codes as the light in the lpg switch does not appear to work how it should (the light just comes on when switch is in the lpg position but from what i have read it should flash during switchover etc)

[kbs]

So what does the LED do when you ask the system to report its faults codes?

Any clues from the Vx pedal trick?

Wiring diagram for 2003 type is also on pjpj page of you want to check how your switch is/should be connected.

If your wiring is the later type (shouldn't be in 2003) then I have the diagram if needed.

[dj_steve]

the switch does absolutely nothing. just stays lit or unlit depending on if itsin lpg or petrol. ill go take a look for wiring now

no engine error codes stored as i have obd dongle

[Brian_H]

Theres a vacuum connection on the reducer, when the reducer diaphragms start to fail you will get gas coming out of that port into the air intake system. That seems a common cause of the switching back to petrol on these and is easy to check for (stick end of the hose into water and see if bubbles appear).

If its switching to lpg I'd suspect you won't have any error codes coming up from the lpg side. You probably aren't seeing the flashing as its switching almost straight away - its more likely to take longer when the engine is completely cold.

[dj_steve]

where is the reducer on this system as i only know where vaporiser is. and it does run on lpg for fair bit of time, only seems to swap over if i slow down to idle or accelerate, almost like their is not enough pressure, also the fuel guage only goes up very very slowly.

the switch has not worked correctly since i got the car and did notlight up at all until i moved the connections about and plugged back in the third cable which was not attached

[mat_fenwick]

Vaporiser and reducer are different names for the same thing.

[dj_steve]

ahh ok, its my first lpg car so still getting used to all the terms, will the reducer run without vac pipe connected just to test the idea ?

[Brian_H]

Yes it will but idle may be poor. Reason i'm suggesting it is it matches the symptoms I had.

[dj_steve]

to be honest their does seem to be a very faint smell of gas in the engine bay but its hard to pinpoint as its really faint. would lack of pressure cause the switch back also ? as surely if it was a vacum pipe leak it would switch back quite regular whereas this car can work for quite some time on gas sat at constant speeds like on motorway etc, but it only seems to fluctuate on idle/accell/deaccell really. will pull the vac pipe off and have a drive later though, im assuming i need to plug the pipe also

[Brian_H]

That suggests to me that you need to start looking at the vapouriser. Its an easy thing to test . You don't need to plug it as you won't be driving while doing it.

Lack of pressure should cause it to swap as it will think its empty.

It's not a case of the pipe leaking that's the issue. It's that your getting fuel leaking into the inlet that shouldn't be there.

[Brian_H]

It will be worse at lower speed as your getting more percentage extra fuel causing the mixture to Be more inconsistent/rich

[dj_steve]

so if it is leaking fuel through into said pipe i should be able to smell it without much trouble im assuming

[rich r]

The fuel gauge does move very slowly on the Vectra, whether on petrol or LPG. After switching manually, it'd take mine up to 15 minutes to move to the correct level. So I wouldn't worry about that.

[Brian_H]

Possibly yes. You may be able to see it. Depending how bad it is

[dj_steve]

fuel guage i aint too worried about, yeah i think i need to refurb the vaporiser, took the vac pipe off the rear of throttle body (could not reach the one on vaporiser easily, and just ran the engine for a min or so and the smell of gas was really strong more than it has been at any other point, so i would suspect that it could be on its way out, ill have to buy the refurb kit next week.

[Brian_H]

If you can see the vapouriser have a look what the heads on the bolts are (torx or cross head). The cross head ones i found have a nasty habit of not wanting to come undone and rounding off, so before taking it apart see if you can find some replacements (m5 thread,5X40mm length,7X16mm length and 2 45mm length if memory serves me correctly). The refurb instructions do list lengths but not very clearly (you have to read though and look for it).

I found the torx ones would come undone without major problems.

[dj_steve]

ok got a replacement vaporiser that im going to be fitting today hopefully, is their any major pitfalls i need to worry about when removing/refitting

[Brian_H]

Its fairly straightforward as you have probably found already as long as you can get to it. Be careful when disconnecting the gas line as there can be some gas in the supply pipe (loosen it and let the pressure relieve itself).

Also do it outside away from drains/pits etc.