BAD IDEA, Not using petrol will quickly cause the petrol system to fail. You need to use it and you need to keep at least 1/4 tank of fresh fuel. Or next time you need it, it won't work and will cost $$$$ to get fixed.

I agree with SV-Valiant.

My AU runs flawlessly on both fuels. same economy on petrol as it had before the conversion And as it seems excellent economy on LPG. No flat spots hesitations or problems at all.
LPG will make less power as it contains less energy and runs at leaner AFRs.

People that can't get it right either have the wrong parts fitted or can't tune.

I realise this topic seems to have been abandoned a while ago, but here are my two cents after having to research a similar issue:

If you are having LPG issues after about 100km driving, consider the following parts:

Inlet manifold. Make sure its tight and that it has a good gasket fitted. That will cause icing issues.

Vacuum tube from the Inlet Manifold to the MAP sensor on the driver-side firewall. Check that it hasn't blown off or is leaking

Check your converter fluid.

Check you have an LPG thermostat fitted properly.

Those should cover most common issues beyond the usual bleeding/flushing advice.

I have realised that cranking start on lpg takes longer on AU Falcon (dual fuel). Noticed that if I turn on the battery and then start, it starts a bit better even then cranking time is still higher than usual.
Any Idea how to make it better without screwing up anything?

check/fix the following...

1) Breather Hose - there's a hose that runs from the back of the LPG converter to the air box (make sure its connected & make sure there are NO hole's in the hose).

2) ICS - A dirty/fowled Idle Control Solenoid will produce a stalling effect on most falcons. Remove & clean thoroughly with throttle body cleaner.

3) Thermostat - The LPG converter needs hot water to turn the gas into liquid.

4) Spark Plug Gaps. The spark plug gaps need to be around 0.9mm apart for correct LPG combustion.

5) Leads - Faulty/Old leads won't carry enough electricity to the spark plug to discharge the correct amount of spark.

6) Intake system - Make sure there are NO air leaks on the intake system. Too much air will cause backfiring of the LPG system & more than likely blow the system up. EF owners i suggest converting to EL/AU intake system. You only need the piping from the throttle body to the air box lid. You can still keep the same air box & lid.

These are what i have found to be of concern when dealing with LPG issue's. If all these items above are in good working order then your LPG system should be 100% OK.

A faulty coil pack is also usually the cause of issue's however this will be felt in both LPG & petrol modes.

If anyone else care's to add to this list please do so.

Check the lock off. Sometmes they loosen up and when driving around they rattle tight and loose. From the heat, the seal between the lock off and converter if it's installed on there can increase and decrease.

It might not be it but just another thing to cross off the list.

Check the spark plug gap. I had this issue for long time as well. Even though different things may have been wrong on your system. But I guess its a good idea to check with spark plug gaps (ideally 0.9 mm)

+1 for that idea. definitely this is a good chance. Also the lock of valve on the gas tank might get stuck as well. My sister's EF tickford factory gas had this issue. We changed everything & i mean everything under the hood & the problem still persisted. It was the valve getting stuck which the solenoid opens & closes. For some reason a little bit of CRC fixed it all up.

Spark plugs wont make it stall like that. Gap is important but you wont run and then stall just because of gaps

Hey Guys,

Im new to the forum!! Ive got a 97 EL on duel fuel and having the same troubles of stalling or almost stalling on hard braking. The issue only happens when on GAS not petrol.

Any ideas??

Ben

If there is only black, smoke on petrol its unburnt fuel and your map sensor vacuum hose has probably come unplugged from either the manifold or the map sensor itself. ( on the cars firewall behind the intake manifold.) That wouldn't be affecting your gas running though.. perhaps you need a new or re-co converter, but if it was me I'd get it running perfectly on petrol first and then fix the gas so you can eliminate non LPG related faults.

Last edited by frankieh on Fri Jul 01, 2011 6:41 pm, edited 3 times in total.

check/fix the following...

1) Breather Hose - there's a hose that runs from the back of the LPG converter to the air box (make sure its connected & make sure there are NO hole's in the hose).

2) ICS - A dirty/fowled Idle Control Solenoid will produce a stalling effect on most falcons. Remove & clean thoroughly with throttle body cleaner.

3) Thermostat - The LPG converter needs hot water to turn the gas into liquid.

4) Spark Plug Gaps. The spark plug gaps need to be around 0.9mm apart for correct LPG combustion.

5) Leads - Faulty/Old leads won't carry enough electricity to the spark plug to discharge the correct amount of spark.

6) Intake system - Make sure there are NO air leaks on the intake system. Too much air will cause backfiring of the LPG system & more than likely blow the system up. EF owners i suggest converting to EL/AU intake system. You only need the piping from the throttle body to the air box lid. You can still keep the same air box & lid.

These are what i have found to be of concern when dealing with LPG issue's. If all these items above are in good working order then your LPG system should be 100% OK.

A faulty coil pack is also usually the cause of issue's however this will be felt in both LPG & petrol modes.

The EL's ECU controls fine tuning of the timing.. so unless the base timing is way out it will tidy it up for you all by self... put the car in diag mode (put a female blade terminal over top and bottom far left terminals of the diag block in the fuse box.) and then check your timing after letting it idle for a few minutes (over 2 at least) on the front of the engine with a timing light.. if they match up and your ECU has no issues, it will handle the rest for you.. putting the timing light on while the ECU is not in diag mode will not work as the ECU will have moved the timing itself and it won't line up.

Yeh mate, also check the lockoff like mentioned before. If your system is ages old too, your converter may need a little bit of overhauling