LPG switches

[scrambler]

My "new" 110 County has LPG installed. Switches are a 3 way toggle, which seems to activate either the tank valve or the petrol fuel pump, with the middle position being "off." There's also a push-pull cable control to be "in" for LPG and "out" for petrol.

What does the cable do?

And why, with petrol in the tank and the controls all at the "petrol" positions, won't it run on petrol?

Steve

[loanrangie]

Ok, the switch sends power either to the lpg controller or to the fuel pump/ fuel lockoff depending on the fuel selected, i take it you have a holley or similar carb and an impco lpg setup ? The cable is to open the diaphram on the mixer for when running on petrol to allow more airflow to the carby, i didnt fit one to mine as a V8 has enough vacum to run with it closed. Sounds like it hasnt run on petrol for a while, check that your pump is running and that the petrol lockoff opens when petrol is selected.

[scrambler]

I think I'm discovering some of the problem - 1/2 of what you say is greek to me. Judging from the fuel pump noise and the smell of the stuff, the pump is working. What and where is the petrol cutoff? The motor has standard carbs. LPG system is branded Landi-Hartog.

I'd say you're right about not running on petrol for a while.

[loanrangie]

Since you have standard carbs (twin strombergs) the cable wont be connected, check the oil level in the top of each carb, top up if needed and try to start it again, the lockoff will be in the fuel line somewhere between the carbs and the fuel filter - i'm not familiar with county engine bays but on a rangie of the same era there is a filter mounted to the left inner guard.

[scrambler]

Got the car started with LPG, then flicked switch to petrol. Changeover seemed to occur - running a little smoother for a moment then started to run very rough and put out black smoke/particulate like an old Diesel. Flick back to LPG and it died. Tried it 3 times - exactly the same response. Didn't seem to improve no matter how long I ran on petrol.

I need to tidy to up for roadworthy and the LPG tank's on empty. I can bring petrol home in a jerry, but LPG's a bit harder to get in the tank! Was hoping to run on petrol until ready for Safety Certificate.

Do I have oil in my petrol lines? Is something else going on? Is gas really this much trouble? I might have been better cooking up biodiesel! Do I need to clean the system somehow? There's not a sniff of smoke on LPG.

Steve

[George130]

Could be very old fuel. Try some fresh petrol and see what happens.

[scrambler]

The petrol was basically empty - I put 10l in the tank and I'd be surprised if there was more than 1-2l there before, if that. I guess I might be picking up crud off the bottom of the tank? I also use E10 - but I can't imagine that amout of ethanol would make that much difference. Still, I might give it a go. Another thing - should I use a higher or lower octane petrol?

[Ralf_the_RR]

Mine occasionally has the same symtoms.

If I don't run on petrol for a long time, the float bowl level gets stuffed up.
I think the needle & seat fail to seal, and there is too much fuel in the bowl.
This makes it run very very rich, hence the smoke.

My fix for this is too switch it petrol the night before I want to run it, and leave it pressurised. It then runs faultlessly.

If I need to run on petrol without doing the above, I constantly switch from petrol to off to petrol to off to petrol etc etc.
It's painful but it does run.

By the way, to switch from petrol to gas, you have to go through the off position, and run it out of fuel, then switch to gas.
Going from gas to petrol, you can switch staright to petrol.

[LRCounty]

This push-pull cable...have you tried leaving it IN and then running petrol?
I nearly bought a County with a similar setup to what you describe...except the way it was explained to me for this particular car was that you pulled the cable OUT to run LPG, because that lifted the needles in the Strombergs, so that they didn't wear out. The needles are centred usually with the flow of fuel, but on LPG they fall against the side of the jet and wear with the up and down movement. Lifting them when running LPG stops this from occurring.
On the test run, I flicked to petrol while cruising at 80km/h, but forgot to push the cable IN, and it flooded and died.

[Ralf_the_RR]

Ah yes, the lifting of the pistons.

Yep, that will be the problem.

Doesn't matter on gas, as the piston will rise and fall with vacuum, but doesn't effect gas flow.
On petrol, the rise and fall of the piston raises and lowers the needle which controls the mixture.
With the piston raised, it's on full rich, hence the smoke and poor running.

Good call LRCounty.

[scrambler]

Thanks for the assistance Harry and LRCounty. Using a combination of pulling the cable right out (it's well labelled with this conversion, LRCounty) and flicking the fuel pump on and off I can get it to almost behave itself, but every time the pump is left on, the engine floods. So I'm guessing that the main problem is the floats. I'll wait a bit to see if using petrol frees them up (as you were suggesting happens with Ralph, Harry) otherwise I guess I'll have a crash course in carbies ahead of me. I can get it to start with petrol now, by only running the fuel pump for a short while before turning it off and starting. So at least I'll be able to get it to a petrol station for gas when the time comes.

Thanks again for the help - if/when it all works 100% I'll post and let you know.