Thread: LPG misfire

The only thing that I will say is that quite often, LPG fitters don't move the PCV hose when installing the LPG. Ideally the PCV port should be moved from the plenum chamber inlet, to somewhere between the LPG mixer ring and the air-cleaner. You should also make sure the flame trap is clean and working.

When the engine is new you don't get any ignition flame bypassing the rings, as the engine gets older you can get flame into the crank-case and this flame runs along the PCV tube back to the inlet. If there is LPG in the plenum you get ignition of the LPG in the plenum often blowing apart the air cleaner box.

On my 4.6 you can see the blanked original PCV port (in-line with the orange oil filler cap), to it's right the LPG mixer ring on the plenum and (following the green line to) the moved PCV port to the RHS of the LPG mixer.

The LPG fitter did move that hose and plumbed it into the engine side of the AFM housing by tapping a new hole.
However I just recently blocked that off and have vented my engine to an oil catch can.
I wanted to see how much is coming out and so far it is bugger all.

Give your plugs a check/clean.
Also,under cover of dark with the mojo running use a spray bottle mister and spray the leads lightly,it will show any leakage of spark from the leads or dizzy cap.
Goodluck
Andrew

Originally Posted by Utemad

I'm going to get hold of a genuine rotor button just in case it is ....... So long as it isn't a crazy price.

Yep ... It will be a crazy price .....

Try to borrow one if you can

Sounds to me that your HT leads are crossed somewhere. It is a known phenomenon that L.P.G. will reveal any slight electrical issues, and will get worse as it warms up..

CAUTION: Failure to route the leads correctly, as shown, can cause cross firing between cylinders five and seven, as can be seen by the firing order 18436572. When cylinder 5 is at T.D.C. on the power stroke, cylinder 7 is at 90 degree before T.D.C. on the compression stroke ready for ignition. If the plug leads for these two cylinders are routed parallel in adjacent clips, HT current to number 5 plug will also be induced in number 7 causing combustion of the mixture in number 7 cylinder to occur 90 degrees B.T.D.C. and again at T.D.C. It is for this reason that the correct clipping of the plug leads is observe to avoid the possibility of severe damage to the engine.

(Quote from Land Rover Discovery Workshop Manual)


I don't have a scanner, so I cant upload the lead arrangement as shown in the book, but perhaps someone on here has the resources to post up a pic?

Hope that helps,


Ben

My leads aren't run the best. But they never have been and never caused a problem before. I'll sort them out though when I check their resistance.

I'll play with it again tonight.

What do people use to separate their leads?
My lead separator thingys are all broken (be careful when you remove your tappet covers!) and didn't fit these bigger leads anyway.

Would covering them in split tube where they touch be effective isolation?
No doubt the heat would destroy the tubing eventually.

The spray bottle mist will show you where you where your leads are breaking down.If nothing shows at idle,set the revs at 2000rpm and try again.
WORKS A TREAT
Andrew