LPG gremlins...

[procrastination inc]

Looks like my disco has acquired a new electrical fault.

I won't be able to look at it til morning but hoped I might be able to get a few ideas where to look before I start.

Symptoms:

Ran to work on LPG.
would not restart on gas when I finished work, started on petrol, would not switch to gas on highway.

Tank IS full :P

[roverfj1200]

If it is a new tank the filter may be blocked..

[procrastination inc]

New tank of fuel, but the system was installed a year and a half ago.

LPG runs filters?

[procrastination inc]

filter in the solenoid on the tank?

[procrastination inc]

that could be it.

The filler is in the TOP of the bumper. When I bought the car it had no cap and the check valve in the filler leaks (probably dust) so it bleeds everything between the filler and the tank.

If the previous owner ran it like this for a while the tank might be full of guff :(

[loanrangie]

that could be it.

The filler is in the TOP of the bumper. When I bought the car it had no cap and the check valve in the filler leaks (probably dust) so it bleeds everything between the filler and the tank.

If the previous owner ran it like this for a while the tank might be full of guff :(

There should be a 1 way valve in the tank so it shouldnt rely on the filler line holding pressure. The are mesh filters in the lockoffs so if the tank has internal rust it could block the inlet.

[LandyAndy]

This happened on my Ser3.
Turned out to be faulty wiring on the LPG cut-off switch.(the one that senses the engine is running via ignition pulse)
The led on the switch wasnt lighting to show the switch was open.
Goodluck
Andrew

[roverfj1200]

This happened on my Ser3.
Turned out to be faulty wiring on the LPG cut-off switch.(the one that senses the engine is running via ignition pulse)
The led on the switch wasnt lighting to show the switch was open.
Goodluck
Andrew

see if the LED lights when you crank the engine..

Filter should be on the soleniod on the vapouriser

[procrastination inc]

Turned out to be faulty wiring on the LPG cut-off switch.(the one that senses the engine is running via ignition pulse).


Mine has a little box under the dash near the fuses that I think is meant to start on petrol and switch to gas over Idle speed. All the little lights switch as expected.

I'll pull my meter out and start hunting in the morning.

need to drive to Melbourne tomorrow, not doing that on a 30lt petrol tank...

[rovercare]

Check your water? convertor freezing??:D

[procrastination inc]

Check your water? convertor freezing??...

Yep, all hot and wet


Met that problem on a couple of fork lifts. Usually they start ok, then freeze up.

My disco not starting on gas.

[skidmark77]

might be just one of the gas lock offs not working
sounds like it

[GrahamH]

I'd agree with the others that it's most likely the gas shut-off solenoids which are starving the converter of liquid. To fail suddenly like this suggests a blocked filter is less likely - but not impossible.

There is a solenoid valve on the tank and one on the converter as you've noticed. Both are (usually) energised from a safety relay which is supplied from the ignition circuit via the LPG/petrol changeover switch and this has a control circuit which usually picks up pulses from one of the HT leads to tell the relay that the engine is turning over and needs gas. It usually operates for about 5 to 10 seconds at key switch-on to allow the engine to crank but if it doesn't fire and continue to make spark the control decides the engine is stopped and stops supplying gas for obvious reasons.


The HT lead pulses are often supplied to the safety relay by wrapping a few turns of the control lead around one of the HT leads - check that this hasn't fallen off. The relay usually has an LED on it which lights when it turns the solenoids on - get someone to crank the vehicle while you observe the LED (it's usually under the bonnet). If it doesn't light and sense HT pulses, and the wire is in the right place, I'd replace the relay - it must have some semi-conductors in it to do the job so it's vulnerable.

Don't crank the vehicle more than a couple of times without it starting if the relay LED is on, as it will probably be filling the air intake and plenum chamber with gas and you could get a backfire if you don't let the gas dissipate (you risk blowing the lid off your air-cleaner at best, killing your Mass Airflow Meter at worst). I've had a few backfires early on which have stretched the clamps on my air-cleaner but the MAF survived (it's intake side gauze didn't though).

Good luck - I'll be interested to see the final diagnosis.

[procrastination inc]

Thanks for your input guys.

I started by cracking the line at the solenoid before the converter. Some residual pressure there so a safe bet that the valve and filter at the tank are ok.

Checked the coil here and on the converter for continuity, both good.

Checked the fuses. All good.

Checked the plugs at the switch and safety cutoff. Look ok.

So I hooked up my meter to the cutoff solenoid under the bonnet to check for volts and switched the meter to peak hold.

Switch to gas, turn the key and the bugger starts:confused:

I hate fixing stuff and not knowing what was wrong in the first place. You're always left waiting for the other shoe to drop :mad:

[GrahamH]

That's bad luck - now you know your car is one of the walking wounded. Your fault-finding strategy was eminently sensible - my best advice now is to keep a multi-meter in car for when it fails again (which it will, and it will, of course happen at a most inconvenient moment!).

It sounds possible that one of the spade connectors is not properly crimped onto a wire somewhere or one has been crimped onto the insulation and partly penetrated the insulation which has been OK until now. You could go through all the connectors and re-crimp them but there's not much else you can do.

Best of luck - I'll be waiting for the end of the story but it could be a while coming.

[procrastination inc]

I'd actually like a sequential injection system.

Seriously considering taking it to Deacon and getting all but the tanks ripped out and have them start again. Just need to look at the bucks

[procrastination inc]

mongrel *&%$ bustard %^*$ car!

won't run on gas as I head off to Melb (300km away!)

now, if I unplug the ignition safety box and re plug it in, it'll start and run for the preset 2 sec on start up then it cuts the relay to the gas solenoids.

on restart it cuts immediately.

the voltage signal from the ignition coil to the safety box is good.

bypass the box?

[procrastination inc]

Think I found it.

What I thought was the coil signal was the ignition on signal.

no coil signal.

Traced to a quality twist and sticky tape joint:mad:

really expected better from the installer if this system

[procrastination inc]

Fixed, I think

I had to recheck a few of my assumptions.

When it ran this morning, it was only because it has a petrol start function that seems to take a while to reboot

When I checked the cut off solenoid before the converter, I checked that it had power and had continuity and I heard it click, BUT I didn't check that it actually switched the gas... It didn't.

Disassembled the valve, filter clear, I can blow through the ports when it's energised, the only thing I can spot is a little magnet in the bottom of the housing covered in crud.

Clean it up, put it back together. It works.

maybe I blew some guff out of the valve?

Anyway, time to hit the highway

[procrastination inc]

wish me luck:o

[TheLowRanger]

Been having similar problems with my LPG setup recently. It usually works but occasionly won't. I got told by the installer that it was probably one of the solenoids on the converter. There is a solonoid at the gas line , but on my converter the wiring from here also runs to a second solenoid located on the underside of the converter. This has a blue/purple plastic cover and to test whether they are turning on and off just run a wire from the battery to the + side of the solenoids. They should click. The blue one on mine wasn't working. Apparently they can get contaminated with oil and if they do they won't switch. To remove this involves taking a plastic cap off the bottom of the blue plastic cover and sliding the cover off. You then need to remove the solenoid with a 19mm spanner. From memory there is a spring and a pin inside that you must make sure comes out with it. Once removed just pull the bits apart and give the whole lot a good spray with some carby cleaner - including spraying up inside the converter - to make sure there is no oil left in there. I did this a couple of weeks ago but didn't have the carby cleaner so just cleaned it with a rag. I have only had problems a couple of times since and think that there may still be some oil contamination because I couldn't clean out the converter properly. I now have the carby cleaner and am just waiting for some time to clean it up properly. Hopefully this may give you some more options to try.

[procrastination inc]

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:eek:

My wife thinks this car is possessed and has dubbed it Diablo :twisted: 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:bangin:

I refuse to be beaten:)

[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?

[rovercare]

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:)

[GrahamH]

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).

[procrastination inc]

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?

[djam1]

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

[DeeJay]

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

[p38arover]

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.

[GrahamH]

Good Point Deejay. In fact your problem, Procrastination, might even be the safety solenoid valve at the converter, but but not jamming closed as you postulated, but perhaps not sealing properly, allowing the converter to de-pressurise the line from the tank by allowing gas to leak into the mixer when the vehicle is stopped. Is there a smell of gas around the air intake a few minutes after stopping perhaps?

To test this theory out, you could leave the vehicle standing for a while (perhaps an hour or so) and then carefully crack the gland nut on the tank side of the solenoid valve at the converter to see if any gas escapes - if it does it's held pressure and I'm wrong. Need I stress the word Carefully?!! And check it for leaks with soapy water after re-tightening it with pressure in the line, of course.

If I'm right the cure would be to replace the entire solenoid valve and shouldn't be expensive. And you'd owe me a beer of course.

[procrastination inc]

graham may be on to it.

the line between the cut off solenoid and the convertor is depressurised when I have this fault. This will create a bigger differential pressure across the cut off valve spool like I have noticed. I will check the pressure just after I stop to see if this is normal.

Still, why is it only an issue at higher ambient temperatures?

[procrastination inc]

Pulled the guts out of the solenoid in the convertor.

Quite a bit of crud in there with one obvious lump right on the seat.

Cleaned, reassembled and started engine.

Shut down and checked for pressure between the convertor and cut off. Heaps.

I'll check it again before I start it in the morning to see if it is holding.

Now, What sort of beer would you like graham?

[GrahamH]

It's a tough choice choice - I'm partial to James Boag but being in SA I'm also fond of Coopers Pale .

Glad to hear that you might have just "knocked the b@st@rd off" at last (to borrow the words of a famous Kiwi). Hope you really have nailed it and your vehicle is reliable again.
:twobeers:

[procrastination inc]

I'm planning on visiting the mother in law in Port Noarlunga in the next few months. Maybe we could settle the debt at a pub then ? :)

[GrahamH]

What an absolutely excellent idea! PM me and we can set it up! And then my Disco can buy your Disco a beer as well.

[DeeJay]

Still, why is it only an issue at higher ambient temperatures?

The higher temp may be tipping the gas up to a higher pressure and creating a leak that won't be there at lower temps.

David

[DeeJay]

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

If you stand next to the bowser and it is just ticking over, let the gun go and listen to the bowser. After approx 30 sec you should hear a definite " click". Thats the excess flow valve resetting, then you can start again. The trouble with the LPG guns is that they have a flat valve and it lifts vertically which you cant get to open slowly.
Thanks for the thanks:)
David