Dual Fuel VS - Missfiring? on Petrol

[Wojzilla]

I've got a problem that has me totally lost.

A few months ago I had real problems starting the car on fuel and gas, turns out the fuel pump was dead.

I replaced the pump, put in new NGK plugs and leads... the car started ok on Gas not so well on Petrol and had a bad habit of backfiring, I tried reducing the gap on the plugs, that got rid of the backfire but it didnt help the petrol problem.

I have since replaced the NGKs with Bosch plugs.... twice, the first set i reduced the gap on to 0.9, the 2nd set left totally alone but the problem is still there.

When on petrol it idles roughly, when the accelerator is depressed it will almost conk out before revving up. On gas its fine, although im now getting ~300 km out of a 60 lt tank vs the 350 i was getting before.

I checked out the computer and its not reporting any faults, apart from putting some sort of wynn's fuel line cleaner in i have no idea what else to try.

 

[futronix]

try gapping them at 1.5mm if you havent already had them there... we had real issues with our duel fuel vs running crap on gas not so bad on petrol..... gapped them at 1.5mmm.. originally they were at 1.0mm... ran much better....

What NGK's did you have in there?

 

[Wojzilla]

try gapping them at 1.5mm if you havent already had them there... we had real issues with our duel fuel vs running crap on gas not so bad on petrol..... gapped them at 1.5mmm.. originally they were at 1.0mm... ran much better....

What NGK's did you have in there?

The NGKs were BPR6EFS-13, got BOSCH HR8DCX in there now at the standard 1.1mm.

Making the gap bigger does make some sense as i understand LPG requires a smaller gap as its not as conductive as petrol and Petrol needs a bigger gap so that there's a bigger spark as its not as flamable?
But wont increasing the gap be re-introducing my backfiring problems?

I've just checked the fuel lines, what kind of pressure should I be expecting on them?
When i put the car into ACC mode the pump fires up but the flow is a mere trickle, when it exits the lines in the engine bay it moves in an arc 10 cms long, i thought the pressure is meant to be much higher?

I also checked at the pump after the filter and before the filter, again really small arc.

 

[noah_73]

Forget about the Wynn's making any difference, remove the injectors and have them serviced if you want to make any difference to them.

 

[Wojzilla]

Should i be expecting more pressure on the fuel lines though?
From what i read it should be somewhere around 200-250 Kpa, i would have expected the stream to be more intense.

 

[Cooper6969]

I have just fixed a similar problem with my VS, it ended up being the gas relay was not turning the gas off when the switch was flicked to petrol so it was pumping both into the engine. Took it to an auto electrician cost like $50

 

[futronix]

the pressure should be significant.... we had a fuel line burst from the connector from the firewall to the rail while we were pressure testing the lines..... fuel sprayed everywhere and at a high pressure

 

[noah_73]

You need to carry out a fuel pressure test firstly but being a relatively new pump it should be ok, A 10cm squirt sounds ok to me. There is a good chance your injectors are going to be fairly dirty, this is what happens to all LPG powered vehicle when they aren't run on petrol for sometime. Other thing that inflicts problems is stale fuel.