Thread: Minimising effects of LPG backfiring

Will allowing the energy to dissipate easier stop the MAF becoming damaged in the event of a backfire?

Pssssssssssssst, just quietly, its probably best to find the cause of the backfire

Originally Posted by rovercare

Pssssssssssssst, just quietly, its probably best to find the cause of the backfire

Agreed, also just because the filter box lid doesnt explode doesnt mean the maf wont get damaged, it will be damaged way before it reaches the filter.

I think one of the causes of backfiring of LPG is a lean out of the mixture.

On mine it will back fire if I have the engine labouring at high revs with wide open throttle...

Happened the other day up a steep hill, foot flat for about 30 seconds and BANG! The only thing I can think that is causing it on mine is the valves are getting too hot and igniting the mixture? Or possibly a crossfire... Hmm....

Good idea...I have 3 backfire spring loaded covers - use a hole saw and stick them in - they close with spring pressure and move out allowing the gasses to escape. Most LP fitters will sell them to you.

Unfortunately backfires on EFI cars are common. When the spark is good it wont do it normally, but if you let the tank run to the point where its dry it will lean out when you accelerate hard and will backfire. The idea is to know your vehicle and know when she is (slowly) starting to run low on gas...they loose acceleration. As soon as that happens change to petrol and then go fill when you can with LPG...stick the boot in when she feels slugish because she is low on gas and get ready for BOOM.

Cheers

Thankfully I have a little red light that comes on to tell me when i'm running low Unfortunately I have run out of gas once, and my car is a LPG only engine so I always carry a hose that allows me to hook up a BBQ gas bottle up and run on that it smells just like a stove then hehe

Good stuff...my guage like most LPG guages no longer works well and even when new was hardly accurate...when working they show red when they still have 10 litres or so in them

Cheers

I had to replace an airflow meter a couple of years ago after one of my kids borrowed the truck.

The original post was about minimising the effects of backfire ..ie avoiding hoses being blown off. Not minimising backfiring.
The system was in place on my Disco when I bought it and when she backfires sometimes I need to replace the airfilter lid, sometimes it just re-seats itself.

As some of the other posts have stated, there are ways to minimise backfiring, but I haven't been able to completely eliminate it. Generally I don't experience much backfiring, maybe twice a year. I reckon it's a mix of technical stuff and driving technique. Got top notch spark leads and keep an eye on the air/gas mix. The IMPCO system tends to drift off setting, who knows why, maybe with the weather. When the Go pedal starts to feel a bit spongy, I lift the lid and give the mixture screw a tweek. Never needs more than 1/4 turn, usually just a small tweek. With the motor running, adjust one way, if the revs pick up leave it. If the revs drop go back the other direction, until the revs peak ..and Bob's yor Uncle. I need to do this maybe once a week ..maybe not for 3 weeks, it has a mind of its own. I'm not a mechanical engineer, but I do a lot of work on my trucks.

Here's how I understand the reason why my truck occasioanlly backfires. When driving on ULP the vehicle managment system leans and enriches the fuel mix as load on the motor demands. But, the old style gas system supplies the LPG into the manifold, bypassing the management system and the vehicle cannot reduce the supply of gas in an overpower situation. IE going downhill on engine brake. There's a build up of gas in the manifold and Bang! If I need to use the engine brake, off road usually, I switch over to ULP.
In town, I use the brakes.

I've had this truck for over 3 years. Half my k's are City (Sydney) and the rest out there. Mostly freeway getting to the good stuff.