Often not able to run LPG switching from petrol

[SiNH]

My problem has been progressively getting worse.

I have a 1993 TB42 Dual fuel.

I used to be able to crank the engine and start the truck with half a turn of the ignition. This had been the norm for ages.

Then it used to take an extra crank to get the engine started.

It then started to take several attempts, about 4 cranks to start the engine.

Now often I am not able to start the truck on gas at all, have to switch it over to petrol and give it 2 cranks and the engine would start.

I have been leaving it like this for several months now, start the car on petrol and drive off and flick it over to lpg while on the move and it would kick over on lpg almost instantly. This method had been working fine for a while until now.

Now I start the truck on petrol and drive, and flick it over to lpg while the truck is in gear and rolling waiting for the lpg to kick in ( this used to take 1 second for the truck to run on gas as long as it was rolling ).

Now I could be rolling down a hill at 50km/h and run the petrol out of the carby before switching over to lpg and it could come to a complete stop and the engine still not fire, I would have to switch it over to petrol again just before coming to a complete stop to be able to drive again, this can last up to 30seconds and still NOTHING.

I would drive along to find another long stretch of road and try again and usually to the result, after rolling with nothing for 30seconds or so I have to revert back to petrol.

I would then find another long stretch of road for a 3rd attempt, its a hit and miss affair, on the 3rd attempt it could kick over to lpg and work fine after rolling for about 20seconds or it could come to a dead stop so at this time I flick it over to petrol and finish off the journey on petrol.

2 days ago I was able to get it running on lpg, once on lpg there was no issues at all, however for the first time it played up, at night it was really cold about 4degrees outside but I was able to start the car up on lpg anyways so I was driving on lpg for about 5mins then all of a sudden the engine stalls for no reason and I had come to a dead stop. Tried to start it again on lpg but no success after about 4 cranks which totalled about 1minute so I flicked it over to petrol and cranked it twice and the engine started and I drove home.

I know I will eventually be able to run it on lpg again, but I fear I would have to be on a freeway travelling at 110km/h to have enough road for the lpg system to kick in.

It scared me because once I am able to run it on lpg it used to run flawlessly, never once had the engine cut out/stall before until now.

My Impco300a system is over 9.5 years though so its old but I need to know what needs replacing.

Help Please

[TassieTroll]

There's a Solinoid which controls the fuel cut out and LPG delivery system, I can't remember what it's called but it should be located on the front of the Carbie/Intake Manifold. I would bet that this is the issue and needs replacing.

Take it to a LPG Specialist.

[bowtie landie]

More than likely the converter will need replacing. It has probably filled with a black ooze that is the by-product of LPG changing state (from liquid to gas). The vapour hose from the converter to the mixer should probably be replaced also.

Get a LPG specialist to do the job though as it will need to be leak tested & tuned.

Peter K.

[V8Patrol]

Impco 300A's rarely fawkup


few things to check however..........

1/
the converter diaphram may well be worn out & the convertor itself may be full of wax , this is a simple strip down and wash the wax out and replace the rubber.
Most likey cause of ya problem/issue !

2/
the electrical safety switch (CARMCONTROL)......... the one on the firewall, bypass it and test the LPG system, if it works then dump it and fit a new one.
It reads from the coil and only allows the LPG side of things to work if the engine is running ( IE: it senses spark pulses ), it has SFA to do with the petrol side of things.
High chance and equal favourite for "problem solved"

3/
Check ya hot water supply hoses to the converter, in older cars the corrosion buildup can cause a blockage in both the hose and converter and therefore the system will freeze up or wont be at the 'proper opperating temp'
This doesnt sound like your issue tho


4/
rare but none the less it happens.......
check for a tank sub compartment leak..... there will be heaps of dead blowflies in the sub compartment if there is one !
The LPG freezes in the line and restricts flow dramitaclly.
A tight bend right at the tank connection can also be a contributor of this problem.

Again I dont belive this is ya problem.

Kingy

[PGS 4WD]

Thats all good, I've also seen a case or two where there is a small leak after the tank lock off while, your on petrol the gas leaks away, when the tank lock off opens the rush of gas causes the excess flow valve to operate, it takes a little time for the small internal bleed to allow the line pressure to equalize to tank pressure. Same thing can happen when you run the car right out of gas, when you fill it and try to run on LPG, the car wont run due to the line pressure being very low compared to the tank and the excess flow valve operates.
Joel