LPG switchover problem

[willste01]

Hello All,

Long shot but I am at a loss with it. Took a trip to Oban with my boat with my LPG converted Chrysler and I ran out of LPG and it cut out. Half a tank of Petrol in there but it just wont switch back over to Petrol. AA dude was not able to help but checked over the engine and said there is no fault with the car itself it seems it just wont switch back over to Petrol.

Anyone any ideas what might be stopping it from doing this I have tried everything checked every fuse i can find even tried removing the ECU of the LPG in hope it would fault and go back to petrol.

If anyone has any advise or even a way to disable it completely and get it back to petrol I would be extremely grateful.

Cheers,

Steve.

[Gilbertd]

What sort of LPG system? Singlepoint, multipoint? What sort of car? Modern Chrysler or old school Yank job?

[willste01]

Hello,

Thanks for the response. It is multipoint. Not sure of what kind of system I can take a pic of it when I get home if that will help.

Its an old Chrysler grand voyager.

[LPGC]

Yes please, post pics.

[Brian_H]

You should find that pulling the lpg fuse from the battery feed (should be an inline fuse connector on a wire) should disable the lpg system and allow petrol operation. Pulling the ecu won't do that, as it breaks the petrol circuit completely.

Worst case to fix it where it is and get it back home on petrol, find where the petrol injector wires have been cut and joined to the lpg loom, and return them to their original connection (match the coloured wires) and leave the lpg wires disconnected.

Simon might have some other ideas once you post the pics.

[willste01]

Hello,

Very sorry for the late reply I was away working and had no time to get any pictures.

Managed to take a couple

Forum will only allow me to add 3 pictures so I uploaded the other 3.

I removed the fuse as advised but there was no difference the engine still would not start.

https://imgur.com/a/SAEoEog

[Brian_H]

Looks like its an ESGI system - at least the map sensor you can see in the middle pic is ESGI.

If you want to get it running so you can move it, given pulling the fuse doesn't seem to be helping I'd suggest your best bet is to either reconnect the petrol injector wire breaks back to how they were prior to lpg being installed (they will be soldered most likely on one side and fed back into the lpg loom, its a case of locating the wires that relate to the car, cut the wires from the join to the lpg loom, and rejoin them to the matching wire on the car loom. That should be enough to get you running on petrol again, just make sure you have the loose ends taped up, and I'd pull the lpg system fuse as well to be on the safe side. That at least would get it mobile again, or leave you in a state where it should run on petrol (long as nothing else has failed - petrol pump for example can fail if its run with too little fuel in the tank, as it gets too hot and will burn out - on petrol operation the petrol cools the pump, and the pump would stop when it ran out as the engine stopped. On lpg the engine keeps running, so the pump will as well). Was the half tank of petrol in there when it cut out, or did you put it in to try and get it going again, and if so how much was in the tank?

I'd give a try with diagnostics onto the lpg ecu if you can - You need to verify what system it is first if you don't already have a lead. Might be easier to take it to an installer and explain whats happened. But it might be best first to reconnect the petrol wiring and check it is really an lpg problem, not something else.

You should be able to post further pictures in another reply if you have any that you think are helpful?

[willste01]

Brian,

Thanks very much for the advice. First time I have had an LPG so have no clue about them at all. It had a full tank of petrol when it cut out as I was heading off up to Oban and wanted to have plenty fuel for when the LPG ran out (didn't quite work out like that! Made it to Oban but ran out of gas and cut out AA charged me a 100 quid to sign up then 300 quid to tow me and the car and boat home lol! Damn thing only cost me £500 was tempted to leave it there.) The AA dude point blank refused to do anything with it being LPG but he did connect it up to the his diagnostic machine and said there were no faults relating to the car on the petrol side.

I will try and locate these petrol injector wires (couldn't seem to see them last time i looked!) as it was only bought as a cheap way to move my boat for a year, so I am not too fussed about the LPG system functioning and would be happy with it just running on petrol, definitely would rather not spend any more money on the thing haha.

Will also have a look and see if there's anything relating to what type of system it is. Again thanks for your advice its much appreciated (Mrs is starting to whine that its been sat in the drive months now )

[LPGC]

Said it won't run on petrol... Just to be clear - If you turn the ignition on can you switch between gas and petrol modes using the switch or is the switch dead/un-responsive? You can attempt to start on gas by holding the switch button in while cranking the engine, if you do that does the engine run (or try to run)?

You said AA guy was unhelpful so I wonder what tests if any he did... He should have at least checked for fuel and sparks and since these engines are very basic, if you've got fuel and sparks there's not much else to prevent them running provided major components aren't completely buggered! I've owned plenty of the same model car but I don't quite remember if there is a fuel rail pressure test / bleed valve... I seem to remember there being one on the front bank petrol rail. If there is a valve just depress the centre of it in like deflating a tyre valve and see if any petrol squirts out, if not the fuel pump isn't running or is broken, broken fuel pumps are a common fault. Even if there isn't a valve you could cut the petrol feed pipe which as I remember is on the UK drivers side of this engine (obviously rejoin it properly after!).

It would never even try to run with the LPG ECU disconnected. It would be unheard of for the LPG ECU to be broke to the extent that it didn't connect at least most of the petrol injectors back to the petrol ECU, so it should at least try to fire up when you crank it if the problem is anything LPG related... so it's most likely car not LPG related. If the LPG system was working you'd have used all the LPG before running on petrol, are you sure you ran out of both LPG and petrol or could something else on the car have gone wrong such as the crank sensor (rear side of bellhousing on these motors), TPS (on throttle body), map sensor (on manifold near throttle body), coil pack (drivers side of engine)? It should still run with a broken TPS and the coil pack is actually 3 coils in one so even if that were broken it should still run on 4 cylinders unless it's common positive feed was broken. An installer might have connected to the coil's common positive feed wire (to get ignition on signal) and will have broken into one of the coil's other 3 wires (to get rpm signal).

Looks pretty clean under the bonnet except for the bit of oil around the bottom of the rocker cover.. Haven't been pressure washing under there, especially not near the LPG ECU, have you lol?

Do your own checks for sparks first, then fuel.

Simon

[willste01]

Simon,

Thanks for taking the time to reply. I was not aware I could switch it between the two the guy I bought from only told me it was automatic and would go to petrol when gas ran out. It has a little button down by the handbrake I tried changing this between the two lights it has but it made no difference.

The AA guy hooked it up to the ecu and ran diagnostic tests and said it passed for everything. What he did I am not certain of as I just let him get on with it. He said the fuel pump was working as he could here it when the ignition was on. He did say that he was sure these things had a solenoid valve that switched between LPG and Petrol and it was probably stuck and that was causing the problem but I was not sure he was giving me accurate information.

I will have a look for the fuel rail pressure test / bleed valve when I get home from work.

It never ran out of Petrol, still had a full tank. We reached Oban with one bar on the LPG gauge and the guys wanted to charge their phones so I left the car idling over while they were sat charging. The car then made a noise like dipped revs and a few minutes later the engine just died. From then on it would not start just turned over and I just assumed the gas had ran out and failed to switch over to petrol as I had no other explanation for it. Normally it would make like 5 beeps then automatically go to petrol but i have never had it run out while the engine was idle not sure that would make any difference.

It was a pretty clean motor I bought it from an older guy who had been holding onto it for years and it was well looked after but no definitely have not cleaned anything under the hood lol.

[Brian_H]

Simon,

Thanks for taking the time to reply. I was not aware I could switch it between the two the guy I bought from only told me it was automatic and would go to petrol when gas ran out. It has a little button down by the handbrake I tried changing this between the two lights it has but it made no difference.

The AA guy hooked it up to the ecu and ran diagnostic tests and said it passed for everything. What he did I am not certain of as I just let him get on with it. He said the fuel pump was working as he could here it when the ignition was on. He did say that he was sure these things had a solenoid valve that switched between LPG and Petrol and it was probably stuck and that was causing the problem but I was not sure he was giving me accurate information.

I will have a look for the fuel rail pressure test / bleed valve when I get home from work.

It never ran out of Petrol, still had a full tank. We reached Oban with one bar on the LPG gauge and the guys wanted to charge their phones so I left the car idling over while they were sat charging. The car then made a noise like dipped revs and a few minutes later the engine just died. From then on it would not start just turned over and I just assumed the gas had ran out and failed to switch over to petrol as I had no other explanation for it. Normally it would make like 5 beeps then automatically go to petrol but i have never had it run out while the engine was idle not sure that would make any difference.

It was a pretty clean motor I bought it from an older guy who had been holding onto it for years and it was well looked after but no definitely have not cleaned anything under the hood lol.

Doesn't quite work like that on a sequential system (which the photos show you have as the red blocks are your injectors), There are shutoff solenoids for the lpg, but these just shut off the supply for the front end, they don't do anything with the petrol.

What hes described is a bit more true of a single point system, a sequential system will start on petrol, then switch to gas when it meets the conditions set on the ecu (combination of coolant temperature and rpm mostly).

You will find your joins to the wires by following the wires from the silver box to see where they go - there will be a few that run to the vapouriser, some that run to the tank (might be the same sets that run to the vapouriser) one running to the battery, a wire running to the drivers panel, the rest will join the cars own wiring.

You might find it easier to fix it than to try and remove the kit anyway.

[LPGC]

Try this (copied from what I said above)... You can attempt to start on gas by holding the switch button in while cranking the engine, if you do that does the engine run (or try to run)?

Can you hear the petrol pump running? You might need someone to turn the ignition on and perhaps crank the engine for a second while you listen near the petrol tank.

Another common issue on these (now old) cars is broken engine ECU but they don't usually just suddenly fail, when failing they start to give occasional misfires which gets increasingly worse. Even this is a fairly easy fix... you fit a different engine ECU, but you can't just fit the ECU you also need the ignition key and ignition barrel surround as a matching set. You don't need to mess with the ignition barrel itself (you can still use your existing ignition key), because you don't fit the new barrel surround to the barrel but just hide the surround under the dash somewhere with the key that came part of the set taped to it. You lose the coded key immobiliser so someone could then just hotwire it but nobody would know that unless you told them. Anyway - the misfires in this case are caused by loss of sparks, if you've got sparks (and fuel) it should run. But this was worth mentioning in case you were to realise it did seem to start misfiring etc before it finally wouldn't run.

[willste01]

Try this (copied from what I said above)... You can attempt to start on gas by holding the switch button in while cranking the engine, if you do that does the engine run (or try to run)?

Can you hear the petrol pump running? You might need someone to turn the ignition on and perhaps crank the engine for a second while you listen near the petrol tank.

Another common issue on these (now old) cars is broken engine ECU but they don't usually just suddenly fail, when failing they start to give occasional misfires which gets increasingly worse. Even this is a fairly easy fix... you fit a different engine ECU, but you can't just fit the ECU you also need the ignition key and ignition barrel surround as a matching set. You don't need to mess with the ignition barrel itself (you can still use your existing ignition key), because you don't fit the new barrel surround to the barrel but just hide the surround under the dash somewhere with the key that came part of the set taped to it. You lose the coded key immobiliser so someone could then just hotwire it but nobody would know that unless you told them. Anyway - the misfires in this case are caused by loss of sparks, if you've got sparks (and fuel) it should run. But this was worth mentioning in case you were to realise it did seem to start misfiring etc before it finally wouldn't run.

Hello,

Thanks for reply. Tried it tonight the button as attached has 2 modes one the lights are off one the lights are on. No difference holding the button. Starter motor just ticking over not any attempt to fire at all. I can hear the pump running that was the first thing the AA guy looked for. I finish work for 2 weeks after tomorrow so will see if I can try rewiring these injector wires back up. Did not have any issues with misfiring it ran sweet as a nut all the way from Dundee to Oban.

The revs did dip a few times before it cut out but other than that nothing.

Thanks again for all your advice.

[Brian_H]

Also - if the OP does want a relatively easy test to do, then pulling a spark plug lead off and checking if there is any sign of a spark would be a simple test to see if the ecu fix Simon detailed above would help any. If there is no spark, its pointless trying to reconnect the petrol injectors as it still won't work in that state. a pair of pliers with well insulated handles probably a good idea if your not used to messing with that sort of thing as it can give you quite a poke otherwise.