Thread: LPG gremlins...

Well, I went out to the car after my last post to head off.

Started the car and checked under the bonnet to make sure all was OK. It wasn't. The fitting to the cut off solenoid was leaking a bit. It was all tight so I pulled it apart to check the sealing faces. sitting in the hose and just across the sealing face was what looked like a film of hardened thread sealant. Maybe this was blocking the port to the solenoid before and we were only running now because I'd disturbed it earlier

Popped a brake hose leaving melbourne

My wife thinks this car is possessed and has dubbed it Diablo My daughter found a little plastic skull ring in the back from the previous owners. and has hung it from the rear view mirror with the little disco ball she put there last week. The car also had a "Proud to be Wiccan" sticker on the back when I bought it pentagram and all...

I am thinking of taking it to the priest to be exorcised

I refuse to be beaten

The bugger did it again.

I'm a bit concerned that the restricted gas flow when this happens will lean out the mix and stuff my motor.

What are the chances of that?

Originally Posted by procrastination inc

The bugger did it again.

I'm a bit concerned that the restricted gas flow when this happens will lean out the mix and stuff my motor.

What are the chances of that?

Practically nil

My understanding is that running lean on LPG is not a problem for the engine - unlike petrol where a lean mixture can cause overheating. With LPG, my understanding is that running rich puts more fuel in the cylinder which equals bigger bang which causes overheating.

However running lean on LPG can lead to backfires which are not good for your Mass AirFlow meter (MAF). You'll soon know if you've got backfire problems! One very important check with an LPG V8 in my opinion is to run the engine with the bonnet up in the dark and check for cross firing between HT leads. Keep HT leads scrupulously clean, use good quality thick insulation silicon leads and route them carefully to ensure good separation as much as possible.

It does sound as though it would be worth checking all the wiring associated with the LPG control system for poor joints in your car, and if it's been in place a while, and replace the solenoids for the safety cut-offs.

I also find that the converter needs a refurbishment kit (new diaphragm and seals) about every 18 to 24 months. The diaphragm becomes stiff and coated with wax and the (presumably) neoprene seals in the valves inside become deformed. The converter runs but the engine doesn't run as well as it should. It's usually about a $50 job for the parts - you should really get it done by a registered gas installer of course ('nuff said).

still haven't nailed this

it seems to be a problem with the cut off solenoid before the convertor. When the weather is hot 32+ and the car has sat for a bit. it won't run on LPG.

Disconnecting the outlet of this solenoid an switching on the system produces no flow.

Manually actuating the solenoid produces no flow.

If I depressurise the line before the cut off valve it works fine, until it sits and heat soaks again.

it seems to me that the line pressure between the tank and the valve goes up as the fuel in the line gets to ambient temp. This forces the solenoid spool closed with more force than the coil can apply to open it.

The earth to the coil is good. Voltage to coil is good. 11W coil measuring 9ohms, good. new filter in the valve, swapped out the coil and spool mechanisim from another valve. Still have the same symptoms.

stumped

Should it have a more powerful coil?

Procrastination inc
Im not saying this is the answer but I find if the mixture is slightly rich and the temps are high the car wont run and its all frustrating.
I find that if I lean the mixture off 1/4 to 1/2 a turn things will go back to normal.
I havent read everything that you have posted but have found that as temps increase gas gets fussy.
I actually find that I need to run it slightly lean at idle to get it to run in high temps (48 degrees plus).
Have you checked the wire that goes fron the safety cutout to the ignition I personally put it on the coil lead as it has more activity, some experts prefer it on an individual plug wire.
I have found in the past that if the safety pick up is long in the tooth (more than 2 years old) they can be trouble and they are only $30 to replace.
Hope this helps

I've been in the lpg industry for 20 + years now.
Every gas tank is fitted with an excess flow valve internally. The idea of this is that if a fuel line ruptures the valve will snap shut as it "senses" the extra rush of fuel, thereby containing the leakage. There is a very minor bypass to equalize the pressure if its a false alarm. It will reset if the pressure equalises in the fuel line to that of the tank.
My guess is that you have a very minor leak between the tank solenoid and the engine solenoid. When you switch on the ignition the tank solenoid opens up and the fuel rushes down this "empty" line and is sometimes enough to trip the internal tank excess flow valve. As said, it will equalize and open up after about 30 sec but that could be tricky if the inbuilt safety devices shut down the solenoids if there is no ignition or engine firing up.
BTW this happens at bowsers at servo's, usually when people reef open a lpg nozzle on a bone dry tank. They usually end up walking to the operator complaining that they have put 10cents in for a minute and the operator clears it and says try again. They get back to the car and its OK.
What they have done is two things.
1/, Put some back pressure in the tank ( the 10c worth)
2/. Waited the 30 sec for it to reset
David

Originally Posted by DeeJay

They usually end up walking to the operator complaining that they have put 10cents in for a minute and the operator clears it and says try again. They get back to the car and its OK.
What they have done is two things.
1/, Put some back pressure in the tank ( the 10c worth)
2/. Waited the 30 sec for it to reset
David

Ahh. Been there, done that. Now I know what to do. Thanks David.