VK on LPG

[85_Calais]

Hey,

My VK (3.3 litre, fuel injected) just recently has been making this popping sound and then stalling suddenly when under load on LPG (a little dangerous when a school run mum in a 4WD paying no attention is tailgating!). It's definitely not loud enough to be a full-on backfire, but I'm pretty sure when the LPG conversion was done 3000km ago they put something on there to suppress backfiring to prevent damage to the EFI system. Does this sound right?

It also has significantly less power at low revs than normal. Just wondering what the causes would be...air filter...spark plugs...leads, all the above or anything else?

Cheers,

Tim.

[Paiste402]

check ur spark mate. My LPG wont start at the moment, just backfires and makes popping noises. So i did ye olde screwdriver in the lead trick and the spark was yellow.

Im gettn a new coil cause of this but u may have a weak spark, maybe even a dead pot or 2 who knows. But def check out the spark, a good one for LPG'ers like us.

[blownba]

Check the resistance of your spark plug leads with a multimeter. Take them all off the plugs and take the dissy cap off and measure from the plug end and then the corresponding post in the cap. There should be around 7000ohms per foot resistance with stockleads. If you have open circuit or a dead lead the meter will not change reading. This will cause a poping on acceleration.
I would be looking at running a set of LPG compatible leads anyway if you are on gas. Bosch leads are good, I use ICE leads and they work the best IMO.
Also I advise fitting a set of LPG spark plugs. They will be a heat range colder and close the gap up to at least 1.1 mm ( I believe stock is 1.3 if I am not mistaken) this will lower the firing voltage in the system lowering the chance of backfire.

And worst case is that you have a slightly burnt valve and this will cause the same problem. But will be misfiring at idle too if it was a valve.

[85_Calais]

I got it fixed...all it needed was a tune up, so was pretty happy with that.