Outer Limits 4x4 Board

I am running an IMPCO gas system on the '89 Maverick and its always been reliable but the other day it wouldnt start on Gas so I started on petrol. If I switch to gas while driving it has plenty of power but if you come to a stop it just stalls. Same if driving at say 80km and depress clutch it will drop to zero revs and when you lift the clutch again it will power up again. Figure the gas must be getting through as it runs fine, plenty of power to overtake. If you let it stall at an intersection you cant start it on gas must switch back to petrol. Bloody dangerous as you can imagine. Any ideas.

There is an "idle" adjustment on the mixer or on the line going to the carby.

My guess is the "idle" mixture for the gas needs to be increased.

It's a little screw usually on the pipe going from mixer to carby/engine.

Worth 30 seconds of your time, chances are that will fix it.

Thanks foad but I tried turning that a couple of turns both clockwise and anti clockwise and it made no difference. It just suddenly stopped working from driving home perfect one day and karked it the next so wouldn't think it would be an adjustment, more like something broken.

on mine i have a handle that you pull out when you run on petrol on the left hand side of the steering column under the dash switches. when it is pulled out and run on gas the same symptoms occur. this handle is attached to the carby which allows a greater amount of air into the carby via a cable, supposed to make petrol run better and less rich, but when running on gas, the car cracks the shits.

does this make sense? its hard to explain sorry. let us know if you have one of these. someone else might be able to pitch in about this.

hottiemonster wrote:on mine i have a handle that you pull out when you run on petrol on the left hand side of the steering column under the dash switches. when it is pulled out and run on gas the same symptoms occur. this handle is attached to the carby which allows a greater amount of air into the carby via a cable, supposed to make petrol run better and less rich, but when running on gas, the car cracks the shits.

does this make sense? its hard to explain sorry. let us know if you have one of these. someone else might be able to pitch in about this.

choke?

hottiemonster wrote:on mine i have a handle that you pull out when you run on petrol on the left hand side of the steering column under the dash switches. when it is pulled out and run on gas the same symptoms occur. this handle is attached to the carby which allows a greater amount of air into the carby via a cable, supposed to make petrol run better and less rich, but when running on gas, the car cracks the shits.

does this make sense? its hard to explain sorry. let us know if you have one of these. someone else might be able to pitch in about this.

The one on mine is vacuum operated. But it basically does the samething as far as letting more air in the carb when swithced to petrol.

No handles under my dash, Ive had the thing since new in '89 and its got an auto choke, runs sweet one petrol. A mate had suggested he thinks there are 2 setups in the converter one for running and one for idle, does this sound right, if the idle one is dead that may be the problem.

with mine, with gas you never have it pulled out. but petrol you have it pulled out all the time.

hottiemonster wrote:with mine, with gas you never have it pulled out. but petrol you have it pulled out all the time.

If it's the choke, that's cause gas doesnt need to atomised for the engine to fire when its cold.

I still don't understand what that handle/lever thing is, if it's not the choke.

there is a little pin in the middle of the converter, that controls the gas flow, they can get gum on them form the gas and stick, it usually goes away when it heats up though, i would be checking for air leaks first, use a little aerostart, and spray around, if the revs go up there will be a leak there, gas systems cant handle air leaks

I will remove the converter tomorrow night and see if I can see this little pin that may be stuck. thanks for the advice.

I will try and be a little more intelligent than the bloke in todays herald sun (page 5) who ruptured his gas line while removing th tray but couldnt turn it off at the tank. So he knew it was leaking gas and went inside for a coffee with his mate. The gas found a pilot light under the house, destroyed the vehicle and $400,000 house destroyed. He blames LPG not his own stupidity.

The choke style handle hottie is refuring to is a cable attached to the 300A impco mixer, it manualy lifts the gas diaphram assembly off the opening into the carby adaptor so air passes unrestricted into the petrol carby.
Without this lever pulled the engine needs to develope vacuum before the gas diaphram will lift , allowing better air flow for petrol.

Also for your problem, check to see if the mixer and adaptors are sealed correctly (no air leaks around Carby to Adaptor / Adaptor to Mixer.
If there is air leaks while Cranking , Engine vacuum escapes through leaks and doesnot draw gas via the Converter and while runing when engine revs drop Gas to Air ratio chages and leans out to the point it cannot sustain combustion.
When you are belting down the hwy or the revs are high enough the engine vacuum is enough to draw gas to keep the car running.

I had this problem many times over the years with a duel fuel V8 40 series, the mixer hanging from the side of the carby would come loose in the bush after rough roads or tracks and the momment i would slow down to a stop the truck would die and no start untill i tightened everything back up.
I also run silicon between all the machined surfaces of the mating parts.
Then braced the alloy extention piece that was common on gas cars at the time.

Cheers Grant hope this helps.

Thanks for that Grant the symptoms are the same for sure so when I pull it out tonight I will check all the seals etc as you suggest.

you seem to know much more about the specific details Grant.

my gas on my 88gq kept cutting out, wouldnt idle and backfired alot, i swapped the mixerr from my dads statesman onto my car and the gas was working, i put in a new diaphram and got my carbie reco'd at the same time and was working well but still cut out and that turned out to be an electrical problem with the gas switch. this was a 300A impco system if i remember correctly

Hey Red Mav
When you said that you had heaps of power on gas,would that be the same amount of power that you`d have on Petrol?
If so how is the economy?
Reason being that i have a TorqueGas setup on mine and it is like have a 4 cylinder in it.I have got an IMPCO mixer and converter that i can use but have been told that it will not be any better than the system i already have.

Its fixed now and the prize for suggestions goes to Grant, who picked leaking air in the mixer. Stripped it all down and resealed now its OK.

CB0569 your question on power, mine runs just as well on Gas as Petrol. When towing an 18' 6" caravan there is no noticeable difference in power. When in the bush I prefer to run it on Gas as its more responsive and much easier to run over on Gas. Economy, (there is no such thing with a 4x4) its all just fuel consumption, I get 350km to 380 max out of 110 litres useable gas.

Red_MAv wrote:Its fixed now and the prize for suggestions goes to Grant, who picked leaking air in the mixer. Stripped it all down and resealed now its OK.

CB0569 your question on power, mine runs just as well on Gas as Petrol. When towing an 18' 6" caravan there is no noticeable difference in power. When in the bush I prefer to run it on Gas as its more responsive and much easier to run over on Gas. Economy, (there is no such thing with a 4x4) its all just fuel consumption, I get 350km to 380 max out of 110 litres useable gas.

As soon as i read your Post i knew what the problem would be.
i have had duel fuel fourwheel drives for years, and had just about every possible problem with them.
Pleased to be able to help you

Cheers Grant.

Forums such as this are a great way to resolve annoying problems. Helpful fellow 4x4'ers are always ready to offer advice and its always appreciated. In most cases someones had the problem before and there is no point reinventing the wheel. Thanks to Grant for his diagnosis and all the others who offered suggestions as well.