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Joined: Apr 10 2018
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I'm getting a misfire on LPG but OK when I flick over to petrol.
I'm hopeful it's just the plugs struggling on gas but faring OK on the expensive stuff.
I'm assuming the leads are OK as she runs fine on petrol
BPR6ES plugs have done about 17k on gas, new ones coming next week, so will see how it goes.
Maybe the system is due a service - Simon install about 15 months ago, maybe a trip to Sunny Yorkshire is on the cards.
Had a quick spray round with leak detection fluid when engine was running - not a bubble in sight and no pong of gas in the car.

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Joined: Jul 12 2016
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Mine did this earlier in the year.

Found that one of the pipes from the LPG injector had come loose at the manifold end and one of the LPG injectors wasn't firing.

The loose pipe was found by disconnecting it from the injector end and blowing down it. If it's loose you'll be able to blow through it easily. Had to take the intake manifold off to reconnect it.

The injector not firing was going by disconnecting the pipes from the injectors one by one with the engine running on LPG. If the injector is firing you'll hearing kind of clicking rapidly. Of there's no noise it's not firing.

I'm not sure why my injector wasn't firing. I spent a good amount of time of the phone with Simon (he did my install too) and I swapped the electrical connectors around but the fault stayed in the same injector. I then took the injector block apart and moved various components to different locations but the fault still stayed on the same one. The stripped the injector block again and checked for blockages but there wasn't one.

Left it for a while and ran it on petrol and when I had time to look at it again if found it was suddenly working. No idea why.

I might have another chance to find the issue as my slight misfire has come back very recently!

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Joined: Dec 30 2015
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BPR6ES plugs after 17k on gas will be well knackered. I change mine every 10k miles whenever I do an oil and filter change. If the leads are more than a couple of years old, change them too.

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Joined: Apr 10 2018
Posts: 40

Thanks for the heads up on the plugs being well shot after 17k. luckily enough I have a set of new leads.
Will do the transplant next week

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Joined: Apr 10 2018
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Thanks, finger crossed it's plugs and leads.

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Joined: Dec 30 2015
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Hmm, mine have been in for... err. 19k? Then again, she did take a while to fire up all 8 after she'd been sitting for a few weeks.

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Joined: Nov 16 2016
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Is it a constant or intermittent misfire Hugh? Constant would point more to an LPG system problem, intermittent to ignition. Going straight from running OK to this sort of problem would point more to LPG, gradually getting worse point more to ignition (usually).
Any unusual noises such as popping when you switch to LPG?
No probs if you want to come see me... I'm busy but a problem with one of my conversions gets priority treatment ;-)

@RutlandRover Dave, did the pipe just come off or did it come off during your manifold removal lol?

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Joined: Jul 12 2016
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Lpgc wrote:

@RutlandRover Dave, did the pipe just come off or did it come off during your manifold removal lol?

I can't be 100% sure since it's not visible with the manifold on. When I disconnected it from the injector end and blew down it there was no resistance at all and when I took the manifold off it wasn't attached - but again, can't be 100% sure I didn't dislodge it fully during removal.

When I put it back on it felt looser than the others as I was able to rotate it etc without any effort at all. I've been meaning to check if there's alternative fittings to the spring type clips that are holding the pipes on at the moment. I'm not sure there's room for a regular type hose clip that can screwed tighter.

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Joined: Apr 10 2018
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The issue is intermittent, generally when I give a bit of acceleration. No popping noises, I'll do the plugs and leads and see how it goes.

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Joined: Nov 16 2016
Posts: 737

@RutlandRover Dave, there is room for a small type of wormdrive Jclip but they're fiddly and not usually necessary. The spring clips are good because they will self tighten if the rubber 'gives' a bit... Tighten a wormdrive clip to the extent the pipe won't come off even if the rubber gives a bit and eventually the pipe can snap at that point. There are other types of (tighter) spring clip but they're at least as fiddly as the small wormdrives. Or it is possible to fit the 'eared' spring clips I'll have fitted on yours but designed for 5mm id pipe rather than 6mm id pipe which makes them tighter.

@Hugh, that does point more to ignition but could also be a fuel trim or lambda (leading to fuel trim) issue.

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Joined: Jul 12 2016
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Lpgc wrote:

@RutlandRover Dave, there is room for a small type of wormdrive Jclip but they're fiddly and not usually necessary. The spring clips are good because they will self tighten if the rubber 'gives' a bit... Tighten a wormdrive clip to the extent the pipe won't come off even if the rubber gives a bit and eventually the pipe can snap at that point. There are other types of (tighter) spring clip but they're at least as fiddly as the small wormdrives. Or it is possible to fit the 'eared' spring clips I'll have fitted on yours but designed for 5mm id pipe rather than 6mm id pipe which makes them tighter.

I do like the eared spring clips you've used. They're nice and quick to fit and remove with just a pair of pliers!

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Joined: Nov 16 2016
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On some model vehicles I convert I put the pipe onto the spud (manifold nozzle), cut the ears off, apply loctite to the spud threads and pass the pipe through a narrow gap before screwing into the tapped hole I made on the manifold by turning the pipe to hand tighten (hence the loctite). The gap is so narrow, space around the position of the fitted spud so restricted and access to the spud so restricted that no other type of pipe to spud fixing mechanism would allow the same (besides perhaps some sort of glue which I wouldn't want to use) or even allow position/tightening of whatever it was I'd use instead to fix the pipe to the spud. With the lugs cut off the spring clips are very tight on the pipe and don't increase the overall diameter by more than a few thou, basically left with a couple of tight bands around the pipe with no protrusions.

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Joined: Apr 10 2018
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Changed the plugs - hell of a difference - all sorted.
Seems 17k is spark plug lIfespan on LPG.

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Joined: Dec 30 2015
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A nice simple one. Plugs are so cheap, my local factors charge £1.99 each for BPR6ES so at £16 a time, there's no reason not to do them regularly.

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Joined: Nov 16 2016
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hugh wrote:

Changed the plugs - hell of a difference - all sorted.
Seems 17k is spark plug lIfespan on LPG.

Good!

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Joined: Jul 12 2016
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Hmm, I might start there with mine then!

Mine does seem to be a little bit intermittent. It seems happier when cold and gets lumpier as it warms up.

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Joined: Dec 30 2015
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Running on LPG needs a better spark than on petrol and plugs seem to not last as long either. That's why I change mine every 10,000. For me that's £32 a year so no big deal. Yours won't take the BPR6ES plugs as it needs the others with the smaller hex, but as the actual electrodes are the same, I would think the same would apply.

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Joined: Dec 29 2015
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BPR6ES plugs after 17k on gas will be well knackered

What actually happens to them? I had mine out for a look at the weekend and they looked okay, electrodes not worn, gaps okay. I think they've been in for about 20k so I guess they're well knackered!

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Normally the outer electrode gets very thin and there's a gap you could drive a bus through. I think you gapped yours down when fitting them, maybe that has made the difference?