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Hunting Engine

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Range Rover Blues:

--- Quote from: "Guardian." ---MINE IS SET UP TO RUN ON GAS, ITS A 3.9 BLOCK, BUT WITH MY OLD CARBS, THIS RUNS MINT ON GA BUT IDLES VERY SLOW AND CAN PINK A BIT ON PETROL, YOU CAN NOT HAVE IT RUNNING PERFECT ON BOTH, UNLESS YOU BUY ONE OF THOSE ELECTRONIC BOXES TO CHANGE THE SETTINGS WHEN YOU SWITCH BETWEEN FUEL.
IM GUESSIUNG YOURS IS THE SAME, SET TO RUN 100% ON GAS.
--- End quote ---


My LSE runs on a multi point system, it's about as good as you'll get an engine to run on dual fuels.

The ideal C:R for LPG is around 12.5:1, so it's not just the static advance but the whole advance curve that's wrong for LPG if not the whole engine.  Probably one of the reasons we get worse economy on LPG even though it burns hotter :?
I'm told that in the 'states it's common to have a dual-mapped ignition for LPG.

Megajolt anyone?

Coastcard:
What Mr. Blues says. On Injection engine it is normally the injectors that are disabled so the pump runs and in the process cools the injectors. It would appear that you are compounding the problem by letting the injectors run dry and still firing them all the time with no fuel.

Having said this, if it has always done it, you can try to adjust the idle CO (bypass) on the AFM (hex screw). Screwing anti-clockwise should lean it up. As a base point, start at 2.5 turns out from fully home (having measured how many turns in it was originally, so you can go back if it makes no difference).

A third option is the old favourite, the coolant temperature sensor?

Dave Rogers:
Cheers all, food for thought anyway, will check the injector dc feed. will add to the relay set up.

Odd thing is, on sunday, it didn't play up at all until much later on........

Confusing!

Rossko:
This'll be the flapper type ECU system then .  My guess is it'll never idle quite right unless you set the base idle speed correctly, at the plenum as you say.  The reason why it won't then idle on gas is that the flapper AFM needs a little gizmo to prop the flap open a bit.

If yer too skinflint to buy a proper switch it shouldn't be too demanding to make one  :wink: it only needs to be open a few mm.    On the homemade switch side, you have rigged it so it will shut off gas if the engine stalls?  This is in important safety featue of commercial switches.

cheers, Ross K

Range Rover Blues:
Actually that's a good point, on SU carbs and flapper EFis system you need to iliminate the variable vent or VAF flap when running on LPG, both to protect it from damage and to stop it messing up the mixture.

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