3.9 disco missfire on lpg ?

hi all,
i have a 1997 3.9 discovery running with a tartarini ? single pont lpg system, last week the disco started to miss fire very badly and was way down on power and wouldnt rev and eventually wouldnt run, i switched over to petrol and eventually it strarted and run but quite rough. i got it home changed the plugs and cleaned out the gas ring ( quite black) and the wee servo that supplies the gas to the ring (also quite black).

i drove a bout for 30 or 40 miles on petrol and established that it was going ok on petrol. no miss fire smooth idle and plenty of power. i filled it with gas tonight and after about 10 miles the missfire reappeared but left as soon as i switched over to petrol.

i have never serviced the vaporiser and i can see no filter.safe to say it hasnr been serviced for the last 6/7 years. would a clean out of the vapouriser help this issue or am i overlooking something. ??

could anybody show me a link on how to clean/service a vapouriser or explane the procedure?

cheers gary

Mine started to do this when the cooling system went south and I discovered a crack in the block.

Don't want to panic you that was just my experience, but it meant that the liquid wasn't getting vapourised properly and at one point I had the LPG hoses and vapouriser iced up, mind you that was when it finally failed.

Check you have sufficient coolant, and it is circulating properly. Does the system switch in ok? I also had the solenoid valve on the tank slowly fail, to the point where eventually the system would try to switch to LPG but then went back to petrol as it couldn't sense any pressure from the tank.

I would imagine it has a filter somewhere, normally where the pipe comes into the vapouriser and then one potentially in the line from the vapouriser to the valve/mixer ring.

You could also check your plugs, when were they last changed? This is the start point really, as LPG will need a good spark.


Jon

Hi There,
Yes first thing to establish is if the vapouriser is getting a supply of hot water or not.

The vapouriser (as its name suggests) changes the liquid fuel to a vapour ready for the engine to burn however this is a very cold process so if the vapouriser is not heated it will simply freeze.

The single point systems work really well on these engines so don't be tempted to move away from the system you have.

Can I ask if you have upgraded your ignition system at all?

If the vapouriser is not freezing and feel warm also then it could be a fuel problem caused be either a faulty lambda (you will need to see if the LPG box is wired to the original lambdas or its own, or it could be the stepper motor not functioning correctly) You can rule these two parts out by placing a straight connector in place of the stepper motor with a adjuster in it and set the adjuster at about 1/2 to 3.4 wound out.

Hope that's of some help.

Could be an LPG issue - weak mixture.
But. Before you go meddling -
LPG will find weakness in your ignition system like nothing else.
How old are your leads, cap etc,.
I only say this, cos it's happened a few times to me.
All is well on petrol, but the odd misfire starts on LPG.
I find that carbon leads don't last too long - typically 4 years.
Changed mine back in 2010, when she started misfiring when I was doing a lot of heavy towing of bricks.
Changed cap and leads - all good.
Watch out for the cheapo sh1tpart cap and rotor arm - was left on hard shoulder at 2.00 am due to a rotor arm coming apart.