Still problems with Zafira

[neilw]

My wife is still having trouble with her Zafira. It starts OK on gas, and runs around town on gas, and it will run OK on dual carriageway on gas.

Once it is hot (say 2-3 miles) it starts switching to petrol. It always misfires when it switches,but its not clear if the misfire (like little jerk) causes the change or follows it. It doesn't jerk if you switch from gas to petrol with the switch. She thinks it may be made worse by bumpy roads, but I'm not sure if that's just the jerking giving that impression.

It always switches back OK.

The regulator has been serviced, I have cleaned the 'aluminium can' filter before the injectors (it was clean anyway) and I have cleaned out the solenoid valve (which was badly gunked up).

I'm wondering if something like a knock sensor is over sensitive?

Any ideas?

Neil

[pjpj]

Have you checked for any fault codes stored on the main ECU and on the LPG ECU separately?

You can probably do the pedal test for the petrol ECU and I'll PM you instructions on reading the LPG ECU.

It could be crank or cam sensor issues or 58x module or connections or injectors.

Best of luck.

[rossko]

In your previous thread
http://lpgforum.co.uk/viewtopic.php?f=28&t=12150
you described some very odd pressures, but didn't give any more details?

[neilw]

Hello having trouble finding the grey wire.Any suggestions please

[LPGC]

Loads of things this could be...

Everything pjpj said plus a few more I'll mention

When the reducer is hot the gas density is lower - if the pressure is marginal and ECU trims are at max then a lean lambda for 4 seconds would cause the switch back.

The lambda probe

EGR valve (if fitted)

Coil pack, plugs, ignition related

The petrol ECU could have a coil pack driver issue that's highlighted more running on gas - vauxhall ECUs do break

I have a few factory fit ECU's and emulator packs here

Simon

[neilw]

Thanks Simon,

I'm having endless problems getting the forum to accept my posts. I'm trying to find the legendary grey wire to get teh LPG ECU codes but it isn't behind the switch or in the relay box by the battery. Any ideas where to look?

Thanks

neil

[LPGC]

I've never bothered with the grey wire.

These systems are easily diagnosed using a multimeter while driving. Connect multimeter to lambda output and watch voltage flick. If it stays around 1 volt too long or 0 volt too long it will switch back to petrol. Too long is about 4 seconds. If zero volts, unscrew the allen socket on the reducer, if 1 volt screw allen socket in. Adjust a little at a time - a quarter turn.

Anything much else wrong and they're hardly worth fixing in terms of parts costs - It takes only a broken reducer or a broken ECU or 2 broken injectors on one of these to render the system uneconomical to repair and better off replaced with an aftermarket system.

Simon