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[albitz]

Had this misfire in gas for quite a while now (car runs fine on petrol).This would indicate a weakness in the HT circuit afaik so I changed the dispack a while back for one that was thought to be ok and certainly looked fine.When I took my old one out it was split and rusted so I was confident that was the problem.When I installed the replacement dispack the misfire was still there.
Yesterday I fitted another dispack which Im assured is a good one,and visably is in good condition. but the misfire is exactly the same.I was temped to change the HT leads at the same time,but didnt beause if the misfire had been cured I would have been curious if the problem had been the dispack or the leads. I guess the next step is to change the HT leads. I have a spare set which came off a car which was running fine,although that was just on petrol.
Question is,if I change the leads and the misfire is still present,what do I do next ?
I probably wont have a chance to investigate any further for several days as Im back at work from tonight,but its going to be bugging me in the meantime.
Tia for any suggestions.

[Kevin Wood]

Have you got a blocked LPG injector perhaps? Or injector pipe crushed / split?

Do you have the diag software for the LPG kit? If so, switch injectors back to petrol until you find the one that's misfiring then you have a clue as to where the problem is.

[albitz]

Have you got a blocked LPG injector perhaps? Or injector pipe crushed / split?

Do you have the diag software for the LPG kit? If so, switch injectors back to petrol until you find the one that's misfiring then you have a clue as to where the problem is.

Pipes look ok,reasonably sure none are kinked or crushed (had that one before),didnt check injectors tbh.I do have the software and interface but it doesnt seem to work now.Plug it into laptop and the blue light flashes once (iirc) and then nothing happens.
It was very useful for diagnosing problem last time I had trouble.I actually used it every time I drove the car to switch the relevant cylinder to petrol,until I discovered the crushed pipe.May have to replace it to try to solve this problem,if changing HT leads doesnt solve it.

[tunnie]

How old are the plugs? As we know LPG needs a stronger spark....

[tigers_gonads]

Best to change your plugs first Albs 
Cheapest and easiest option.
Use the old twin electrode ones for lpg.
More open flame front so better imo

[albitz]

Should have mentioned - new GM twins a couple of thousand miles ago.

[cem_devecioglu]

dont know what brand you use for lpg set but nowadays there are many faulty lpg injectors around..  you may need another known working one to try..

[symes]

have you fitted new inline lpg filter to injectors?could be gunked up-heavy ends?-only a guess though

[albitz]

New filter approx 10,000 miles ago.

[symes]

undo it and spray some carb cleaner into it + start it and rev it-that should clear it-did on mine

[albitz]

Update.
Changed HT leads today.Removed each LPG pipe(from solenoid to injectors) in turn and blew down them and resistance (or lack of it) seemed the same on all six,so assuming no blockage at injectors.Misfire just the same as it was.
Dont know where to go from here,apart from get hold of a working Stag interface and see if that throws anything up.

[albitz]

Dug out my interface and tried it,but it wont work.Lights flash until its plugged into laptop usb port and then they stop."no connection" message appears onscreen. So,Im stuck.

[RobG]

Dug out my interface and tried it,but it wont work.Lights flash until its plugged into laptop usb port and then they stop."no connection" message appears onscreen. So,Im stuck.

Can`t you get a replacement

[albitz]

I might have to,but at around £30 I would rather avoid it if possible.Particularily as Ive only used this one a few times and the damn thing stopped working after a few months.

[albitz]

Or could it be that the software I have installed is out of date and needs updating ? Havent a clue tbh.