Hi Guys,

I have just bought a 1994 XG falcon ute auto that had duel fuel fitted in 1994. It has 305000kms but drives a lot like new and handles impressively.

I bought it in Victoria and live in NSW, so i need a blue slip. The tank hasn't been tested since new according to the plate on the tank so it seems i'm up for that (i don't know how it passed RWC's?).

Where i'm stuck is it runs great on petrol but not on lpg. I've just read through relevant articles in the fordmods archives but still have questions. It has an OMVL R90e converter and a box under the dash that presumably controls what happens.

- The car won't start when the switch is on lpg.
- If i start on petrol then switch to lpg, the guage lights up and an orange light flashes under the symbol 'G', but the red light under the petrol bowser doesn't go off (?). The car idles no differently. I can gently raise the revs to say 1200rpm and it runs fine, but over that it stalls. Maybe it's just running on petrol.
- If i start on petrol and raise the revs to say 3000rpm then switch to lpg, the revs drop and it runs poorly but stays at say 2000rpm. No real power though.

When switching at idle between petrol and lpg i can't hear any sound coming from either of the shut-off's. When switching with the revs up i can't hear anything either, but engine and exhaust noise makes it hard to tell. I tried to test voltage to one of them but blew a fuse under the dash, which stopped the petrol/lpg switch from functioning. I still don't see how that happenned.

The car is running cool so i will replace the thermostat soon, but i've never noticed the converter feeling cold.

After shutdown a small amount of coolant leaks from the coolant hose elbow that fits into the converter, and some air leaks too, but i don't imagine this would affect performance. Releasing the radiator cap stops this from happening. I don't see how to fix this without dismantling the converter.

Any ideas, comments, suggestions?


PS: I used to own a 350chev on straight gas with an impco converter and gas carby. In comparison i don't understand how the falcon's fuel is metered. There is what could be a metering device mounted in the low pressure line from the converter to the air inlet tract, is that what does the job?

I've made some progress. I hadn't used my multimeter for some time and had put the leads in the wrong ports. I have now identified that the shut offs are working.

- When i switch to LPG at idle and then raise the revs, the shut offs release not far above idle. But as i mentioned before, the car then stalls.

- When the engine is revved to say 4000rpm then switched to LPG, the revs reduce to say 3500rpm. It's rough though.

A friend is theorising that the petrol is not being switched off and at high revs the engine can in some measure accomodate the extra fuel. I don't as yet know how to determine if the petrol is being switched off or not.

I notice that some original looking wiring that is connected to injectors and related looking stuff goes to the LPG black box. There are about 12 to 15 wires in total going to the black box.

Any help would be appreciated.

I'm not learning much about LPG from the internet, or elsewhere.

I'm now thinking that inlet vacuum controls the lpg flow from the converter. So the thing in the low pressure lpg line does something else, maybe prevent backfires?

I have been told by Elgas that i should be fine to remove and refit the tank. He said sealing compound is not used nor are there o-rings or seals, just a copper/brass (i think) flange setup. Mine has separate inlet and outlet valves which is common and now costs $130 to test (multi-valves cost $300 to test).

I had the chance to quickly take some pictures at night of my engine bay but seem to need to host them somewhere else and don't have anywhere else at the moment.

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some lpg photos are now in my user photo gallery

Something good to know . . .

When an LPG tank is tested the date and tester identity etc is put on the tank. The original plate for my tank had a special place on it for this to be marked when it occurred, but nothing was marked. I didn't know the history of the vehicle. The ford dealer i am getting a blue slip from told me i had to get it tested as the tank is more than 10 years old. I drained a full tank of gas and removed the tank only to find an aluminium plate with retest info stuck in the bottom of the tank portal (valve area). Bugger. An Elgas staffer tells me the dealer should have checked for this, he mentioned the retest plate on his own car is in this location.

Hey there.

Ive done a few installs in my time.
When running on GAS there is a relay to cut the positave power to the injector rail so your injectors dont fire and if you have a good gas system also the fuel pump so it does not burn out.

If you can revv the car up and switch to LPG and while the engine is dropping revs unplug all your fuel injectors. If fuel is flooding the engine then this will cut the fuel supply and the engine will run happily on LPG.

Then you simply need to address the Eletrical and LPG Control Modules looking for a fault. unfortunatly its not simple and there is no way to "download" lpg modules. The only LPG system with a true fuel computer is the IMPCO system that ford uses as a factory option and also comes in after market. IMPCO systems are the coolest around. There regulators dont use vacume balance ect. and the ecu for it can actually change lpg mix rates based on HEGO sensor data.

You may find your car wont start on LPG as most new gas systems start on fuel untill the engine is hot then turn over to LPG. gas is a prick to start in the cold and in most cases the regulator freezes up before the engine heats up causing stalling.

Also check your service valve on the tank isnt partially closed.

If all else fails, Take it to a gas mechanic it will be a cheeper fix and quicker.

Thats a Italian Regulator with a AEC Controller.
It looks at HEGO data and also there should be a relay neer there firewall somewhere thats tapped into the Injector wiring. it re-directs the injector pulses to the AEC Module, Then as it looks at that it opens and closes that valve in the GAS Vapour line between the Mixer Plate and the Regulator to help keep fueling inline with what your EFI is looking for.

If the module lets you sit the switch in the middle position then you can force start LPG with the injectors disconnected.

I used to LPG start my EB when the fuel pump passed away between getting it fixed.
However some models of that controller do not support it.

- If i start on petrol then switch to lpg, the guage lights up and an orange light flashes under the symbol 'G', but the red light under the petrol bowser doesn't go off (?). The car idles no differently. I can gently raise the revs to say 1200rpm and it runs fine, but over that it stalls. Maybe it's just running on petrol.

Thats the FUEL to GAS Changeover RPM Speed for the Controller.


- If i start on petrol and raise the revs to say 3000rpm then switch to lpg, the revs drop and it runs poorly but stays at say 2000rpm. No real power though.

Possable LPG and or Fuel Flooding.

When switching at idle between petrol and lpg i can't hear any sound coming from either of the shut-off's. When switching with the revs up i can't hear anything either, but engine and exhaust noise makes it hard to tell.

Most LPG systems do not change over at idle.

Hi Garsiph,

I've had a few days away from the computer. Thanks for your input, i hadn't really made any progress on this.


Okay, i think i will be able to try this.



Yes, okay. (I was having pinging problem with my old holden one-tonner and someone told me to punch out the thermostat, i did and about one kay into my drive to work the next day the converter froze).



Checked.



Yes, i'm thinking i'll try what i can over the next week and if it's not fixed come January i'll go to an LPG mechanic. Even if i go to a mechanic the information is all good to know, especially in remote areas. Plus it functions as a tutorial for other forumgoers.



Okay, a google search tells me HEGA stands for "heated exhaust gas-oxygen sensor". I take it this is the sensor at the end of the exhaust manifold. I can confirm that this is connected to the LPG system.

You mention a control valve between the "mixer plate" and "regulator". Is this the thing with four wires (from memory) attached that is located in the low pressure LPG line between the regulator (converter) and the air inlet? Does this mean the LPG is metered by both vacuum and the valve, or just the valve?

The low pressure LPG line seems to just plumb into the air inlet duct, though perhaps there is something inside that i can't see which might function as a "mixer plate"?



When you say "module" do you mean the dashboard mounted guage/switch? That only has two positions.




Thankfully my car runs well on petrol.



Thanks for confirmation.



Okay, that narrows it down.

Ill follow this up after x-mas. next 3 days are gonna be busy and I need to find some resources.

Did you try getting somone to pull the fuelinjectors power off while running on lpg ?

That 4 wire valve betwene the intake and mixer opens and closes in steps to fine tune the lpg mix based on HEGO data

No prob.


Done. First i removed the fine wire stays from the injector electrical wire plugs. Then i started the car on petrol and set up a throttle stick to maintain about 2200rpm. I waited till the engine reached normal temperature.

I then switched to LPG and the revs dropped to a constant speed of about 1200rpm, running roughly. I removed the injector electrical wires and the engine did not change.

I switched the engine back to petrol and it stopped, confirming that the injectors had been neutered.

So i conclude that the engine was in fact running on LPG, and therefore that LPG is being supplied. It also seems that the injectors are being turned off by the LPG control module as per normal. (?)


I think you said the next step is to troubleshoot the LPG control module.

Perhaps i should point out that i haven't as yet touched the converter adjustment bolts. I read through the sticky about how to tune LPG, but one part in particular about decomissioning part of the engine's ECU is currently beyond my ability. Nor do i know the condition of the converter internals.

I wondered for a moment if the timing could be retarded to the point where it runs poorly on LPG but still runs okay on petrol, but that doesn't seem likely (to me) given how well it runs on petrol and it seems fuel efficient.

Thats all good news.

Pretty much check that the mixer plate is okay and not cloged with s**t. Also check the atmospheric balance pipes for ants and spiders living in there causing a blockage.
if non found the converter is probberly shagged. just get somone to replace and re tune the lpg.

your lpg system wont require any stuffing around with the ecu.

Does that mean checking where the LPG enters the air inlet? I'll have a look.


Is that the small hose between the airbox and the converter? I'll have a look.


So you don't think the problem could just be bad tuning? Should i dismantle the converter to check it's internals?


Okay.

Yes Yes and No.
Replace Converters there only about 100 - 200 Bucks.

I located the mixer plate in the inlet tract, it was covered in a black greasy substance. Hot soapy water didn't affect it, so not seeing any potentially vulnerable components i swished it in petrol and reinstalled.


I checked the balance pipe, it was free flowing to my lungs and what i could see was clean.

I tested the engine on LPG again and it was the same.



Okay, but . . .

. . . my first impression was there was likely to be something wrong because it is obviously so far from proper running. Then i discovered that the handbrake did absolutely nothing even when pulled all the way, and all that was required to fix it was heaps of adjustment . . .

. . . the blue slip man on the other hand said the handle doesn't come out all the way and the front cable is probably stuffed and quoted $60 for a new cable and $60 for labour . . . he is also my nearest LPG mechanic and didn't find the retest plate (quoted $310 drive-in drive-out to get tested) and quoted $350 for a new converter . . .

. . . for that and other reasons i'm not keen on using him and therefore have to travel about 140kms to utilise another LPG mechanic. If i am confident the converter needs replacement i can get the car fixed quicker and in one trip rather than two. And if it turns out i can save $100 by getting a converter myself and fitting it, i would prefer to do that, fitting looks easy, but it would still need professional tuning.

I trust your judgment but am left wondering if the metering valve or its control signals could be the problem and should be checked?