Won't run on gas

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morticiaskeeper · #1 Post by **morticiaskeeper** » Fri Feb 17, 2006 5:28 pm

VW 2.0 ADY engine, single point lpg system. One wet morning last week, it was a bit rough running on gas, then had a backfire, saved by the valve on the airbox. this morning, wet & cold, I couldn't keep it running on gas, so went about a mile on petrol before switching over. Everything was ok until pulling away from lights, lots of misfires then a backfire. Tonight, couldn't keep it running on gas, warmed it up on petrol but struggled to run on gas, very misfiry, wouldn't dare put any load on it. Feathering the throttle on petrol, a slight lumpiness, normal if you had a carb, but not quite right for injection. I'm thinking an HT problem, the whole ht system is at least 2 years old. Will start with dizzy cap & rotor then move onto plugs (any idea of a gap?). Am I thinking along the right lines? Paul

classicswede · #2 Post by **classicswede** » Fri Feb 17, 2006 8:55 pm

Yep do all the electrics plugs leads points cap and rotor. Gap the pluge to 25 thou

morticiaskeeper · #3 Post by **morticiaskeeper** » Sat Feb 18, 2006 2:48 pm

Changed the plugs, leads, dizzy cap & rotor - still the same. The Dizzy cap & rotor were wrecked, so I mst be getting a better spark now. The Lektron Coregas controller is showing a green light. IF i can get it lumpily idling on gas, switching to petrol sends the revs up to 1800 for a while before settling back down to idle.

bigtrevster · #4 Post by **bigtrevster** » Sat Feb 18, 2006 3:04 pm

along with all my problems when i flick to petrol my jeep also does the same,jumps over 2000 revs tho...also does it on start up.

morticiaskeeper · #5 Post by **morticiaskeeper** » Sat Feb 18, 2006 3:46 pm

Just been out for a tweak, richened up the Lektron solenoid mixture until it idled smoothly, then drove on gas with no problems. Thinking about it, there is a bit more induction roar especially on a loaded throttle, the air box is ok, so it must be the inlet tract somewhere. Need to find an Exhaust Gas Analyser now.

bigtrevster · #6 Post by **bigtrevster** » Sat Feb 18, 2006 3:51 pm

when on gas the induction on my jeep is pretty loud now,i think im running to rich reading threw the forum,how do i lean it out??sometimes when idleing on gas the revs get rally low and pumping the gas has no effect....it just dies.i did think this gas malarky would be good but tbh im pi$$ed off

jack · #8 Post by **jack** » Sat Mar 18, 2006 6:50 am

Bob, have and old vehicle as well,1976 Bedford, changed the dizzy from points to a Bosch HEI electronic dizzy, made a lot of differences, gives a good spark in the full rev range, and LPG needs a good spark, try it and see, got mine from the car wreckers, quite cheap including the coil as well,as you need to change the coil to suit the dizzy

go_lpg · #9 Post by **go_lpg** » Sat Mar 18, 2006 11:35 pm

It is likely that you froze the vaporiser on that cold wet morning, resulting in the backfire. The backfire may well have caused some damage to the vaporiser in the first instance, putting it out of tune at least. Secondly, the backfire may well have blown off a pipe or broken a joint of some kind resulting in too much air being inducted and the mixer being at least partially defeated in its purpose, causing weak LPG mixture which would, in turn, result in more backfiring. For further info, see 'Hints for LPG motoring' on our website. The best advice that anyone can give anyone on LPG use is to ALWAYS run up to temp. on petrol before switching to gas, especilly on damp mornings, not neccesarily cold ones either (Water makes ICE, cold temps do not if there is no water around). Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

morticiaskeeper · #10 Post by **morticiaskeeper** » Sun Mar 19, 2006 9:11 am

Thanks Steve It seems to be working ok now, changed the whole ht system and richened up the mixture on the co re gas system until the LED's indicated correct mixture. I've just got the VAG COM diagnostic system so set the laptop up to log the lambda output on a run and everything seems fine. I suspect the Vap (Zavoli) is out of tune, but I haven't managed to find out any info on which screw does what, so I've left it alone for the moment. Paul