LPG Backfire Issue - Solution

[DVS_DANNY]

Hi all, my VS V6 continues to backfire whilst Running on LPG when i have simply forgotten to change down a gear for say, going up a hill or overtaking, or catching that amber light... when normally the engine produces enough torque to not require that gear change... i'm afraid to lend my car to anyone, in case it happens to them, and Fcuk its embarrassing! plus its a pain in the bum, and i would like to once and for all, gather all the experts together to find a definitive solution to this problem...

I have replaced my leads with LPG 8.0 MM leads
I have replaced the spark plugs
I have replaced the coil pack with one known to be working perfectly on another Holden running on LPG
I have enriched the mixture,
I have replace the air-box with a pod filter to prevent Air-box Explosions
I have replace the THE LPG Tank,
I Have replaced the lines,
I have Checked and replaced vacuum lines
I have checked the exhaust for leaks.
I have checked and cleaned from pod filter to the E.F.I and cleaned the plenum chamber and checked for leaks.
I have done damn near everything else i have been told to do, and still it backfires and blows the darn intake pipe off and sometimes the clamps, which get lost on the road...


is there a better position for the return hose to sit? i'm buggered if i know how anyone runs them on LPG without this issue... and like i said, it would be nice to find a solution to this issue, so anyone else out there with this issue with a V6 Ecotec can perhaps not have as much of a **** of a time like i have.

If you have the solution, please for the love of H.O.L.D.E.N, share that wealth of information with the rest of us...

Signed
Brain Snap

 

[lowandslow]

What LPG system are you running?

Sounds like it's leaning out and going pop. Have you had an AFR gauge on it to check?

 

[Jxfwsf]

Taken it to an lpg specialist to get it tuned? Could be an issue with the converter which would show up.
Could be intake manifold gasket, could be leaky injector orings, leak/split in the intake pipe, dodgy valve..... you've replaced the obvious causes (and some)
How does it behave on petrol?

Depending on the system:
Does it rely on the tps and/or o2 sensor? (any fault codes stored in the ecu?)
Is there more than 1 adjustment on it, sense, mixture/s?

 

[Tonner Matt]

Did you fit the right spark plugs ?
For LPG you need to use a plug that is 1 heat range colder to allow for the increased heat in the combustion chamber.
Instead of fitting a BPR6EFS-15 did you fit a BPR7EFS-15. I can't remember if they are the correct part numbers or not, but used them as an example.
Another handy trick is to reduce the plug gap by 0.1mm increments. NGK advised me to do this.

LPG is cheap to run on but can be an absolute prick to deal with when it starts to play up. I hated the stuff when I was working on Forklifts, gimme a diesel or petrol machine anyday.
As suggested I would take it to a specialist if I could not get it sorted, after all they work on these systems for a living.

 

[EYY]

Replace the coils with new ones. Make sure there are no vacuum leaks.

Post pics of the lpg system under the bonnet.

 

[Vince89]

Hello Brain Snap
I went through a lot of FIXES to stop my VR Commodore to back firing. NO luck.

One day the car stop running all together
The mechanic replaced the CRANKSHAFT POSITION SENSOR and the back firing stopped. It's been over a year now!!

Have a look in the manual. The sensor is located behind the crankshaft balancer.
POUR water onto it after car has back fired- to cool it.
If it's the sensor the car will run normally. A RAA man showed me this trick.

good luck. I hope this is the problem for car too.
Vince 89.

 

[CCCMikey]

I've had direct injection LPG for 7-8 years now and never once had a backfire. I think from what I've read the direct injection systems rarely do.

For plugs I'm using BPR7EFS-15 (not 5 as suggested above) so if you're going to change plugs double check whether the number goes up or down for cooler running plugs.

 

[EYY]

Yeah I've had lpg injection for a while now and no hint of backfiring at all. No more destroyed intake pipes, MAFs and airboxes, better power, economy and reliability too. Will also make the engjne last longer because the AFR's are always right.

With ngk, the higher the number the cooler the plug. You don't need to run cooler plugs or plugs with a smaller gap but it can help especially with a mixer system where the mixtures are rarely spot on or the ignition system isn't in the best condition

 

[strgas]

non resistor type plugs for LPG mixer systems NGK BP6EFS - 1.0mm , have used these plugs in many V6 conversion over the years ,
vacuum leaks from split hoses or injector o-rings poor manifold gaskets worm valve stems incorrectly plumbed hose and breathers poor electrical connections have been some of the common problems over the years .

 

[pete d]

hi dany my friend had a had the same problem with vr com replaced everything electrical still backfired pulled inlet manifold off to fix leak then noticed some of the injectors were wet he hadnt been using petrol before he pulled manifold off so presumed they were leaking which they were he replaced the injectors and no more backfires we presume that the injectors that were leaking had made the mixture to rich to ignite and that was causing backfire worth thinking about anyway