Sport 4.2 supercharged stalling issue

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Biketeacherdave
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Sport 4.2 supercharged stalling issue

#1 Post by Biketeacherdave »

Hi all I was a member on this great site years ago but have lost my login details so back with a new name and clearly a new problem.
Iv been reading previous posts and using the search to no avail iv recently picked up a range rover sport 4.2 supercharged 2006 fitted with a brc lpg conversion it looks pretty neat with auto flash lube so seems to be good.

The previous owner never used the lpg in the 3 years he owned it so iv recently decided to recommission it, 1st thing was to part fill the tank and check for leaks...all good 2nd try it out and see what happens....well it smelled of gas, stalled out and then poured petrol out of the rotten fuel return line to the tank. Replaced said rubber hose with similar no more leaking petrol reattached 1 of the lpg injector pipes and gave it another go.

Well it switched over OK run ruff a bit then seems to work fine on lpg the issues come when it switches back to petrol it stalls out and throws up "fuel pressure low" codes and mil light. When running on gas it's great it's just the switching over that's doing my head in, it will also flutter and sometimes stall switching from petrol to lpg.

Now I know this ain't right and I can believe any installer would have sent it out like this the original install was done about 10 years ago.

Local lpg guy connected it up run a few tests and said it was all good the only thing he commented on was it was running a bit rich on lpg but he didn't want todo anything to it on this type of engine as it should be set rich......now that's new to me iv been running a range rover L322 4.4 m62 for years trouble free and you can switch over from 1 fuel to the other and you don't notice a thing.

I'm.sure it's a mapping issue so any pointers or suggestion would be great

Thanks again guys

Biketeacherdave
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Joined: Tue Jun 21, 2022 1:52 am

Re: Sport 4.2 supercharged stalling issue

#2 Post by Biketeacherdave »

Sport 4.2 supercharged stalling issue
by Biketeacherdave » Tue Jun 21, 2022 2:13 am

Hi all I was a member on this great site years ago but have lost my login details so back with a new name and clearly a new problem.
Iv been reading previous posts and using the search to no avail iv recently picked up a range rover sport 4.2 supercharged 2006 fitted with a brc lpg conversion it looks pretty neat with auto flash lube so seems to be good.

The previous owner never used the lpg in the 3 years he owned it so iv recently decided to recommission it, 1st thing was to part fill the tank and check for leaks...all good 2nd try it out and see what happens....well it smelled of gas, stalled out and then poured petrol out of the rotten fuel return line to the tank. Replaced said rubber hose with similar no more leaking petrol reattached 1 of the lpg injector pipes and gave it another go.

Well it switched over OK run ruff a bit then seems to work fine on lpg the issues come when it switches back to petrol it stalls out and throws up "fuel pressure low" codes and mil light. When running on gas it's great it's just the switching over that's doing my head in, it will also flutter and sometimes stall switching from petrol to lpg.

Now I know this ain't right and I can believe any installer would have sent it out like this the original install was done about 10 years ago.

Local lpg guy connected it up run a few tests and said it was all good the only thing he commented on was it was running a bit rich on lpg but he didn't want todo anything to it on this type of engine as it should be set rich......now that's new to me iv been running a range rover L322 4.4 m62 for years trouble free and you can switch over from 1 fuel to the other and you don't notice a thing.

I'm.sure it's a mapping issue so any pointers or suggestion would be great

Thanks again guys

Gilbertd
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Joined: Wed Apr 09, 2008 10:00 am
Location: Peterborough

Re: Sport 4.2 supercharged stalling issue

#3 Post by Gilbertd »

It certainly does sound like a mapping issue, or something to do with the petrol return, but others far more knowledgeable than me will be along soon. The supercharged uses the later Jag engine so has soft valve seats so does need flashlube but even with that, if it is run lean, will cause VSR. Compare that with the M62 engine, like most BMW engines, has much harder valve seats so it isn't a worry.
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LPGC
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Re: Sport 4.2 supercharged stalling issue

#4 Post by LPGC »

I'd be checking the petrol return first. There should be a nozzle in it to restrict the return flow rate (which you could have accidentally removed during replacing the return pipe?). If the return flows too much it could explain all of the symptoms you've listed (the low petrol pressure error, the running rich on LPG, the stalling during switching).

Loads of threads on supercharged rangerover problems on this forum.
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Biketeacherdave
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Re: Sport 4.2 supercharged stalling issue

#5 Post by Biketeacherdave »

Thanks for the replies guys, I swopped out the rotten return hose for same size internally and externally and found no nozzles any other restriction in the old hose which was leaking very badly.

I did have the same thought tho so maybe I need to put a reducer somewhere inline in the return hose ?

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Re: Sport 4.2 supercharged stalling issue

#6 Post by LPGC »

Be careful if you put any restriction in the return hose unless you know the return hose is specced for the (higher than usual) fuel injection pressure. I'll leave this line as it stands even though I've just realised (heh!) that you swopped the fuel return line so you'll know the spec of the return hose. But some/most installers used return hose supplied by LPG components suppliers as part of a 'fuel return kit' that is not fuel injection pressure rated and will balloon/burst if you put a restriction in it. I did have my doubts about how the Echo Arena car park fire got started...

In the old days installers used to fit a mig welding nozzle inline with the return pipe. Later fuel return kits had a similar nozzle fitted directly to the T that fits into the fuel delivery pipe between firewall and engine.

Simply read fuel pressure from OBD? You want it to be around the same when running on petrol (fuel return gizmos disabled) and running on LPG (enabled).
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Biketeacherdave
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Re: Sport 4.2 supercharged stalling issue

#7 Post by Biketeacherdave »

This is the spec of the hose I bought thought it good enuff at 20 bar
6mm 13mm 3.5mm 20 Bar 60 Bar
60 bar being the bursting pressure and 6mm being the ID. Iv looked and looked but I can find the fuel pressure on my ID 11 tool.

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Re: Sport 4.2 supercharged stalling issue

#8 Post by LPGC »

For sure 20 bar is more than good enough. A lot of suitable fuel pipe is rated at only 8 bar but good stuff.

Besides being rated for the pressure you also want it to be clamped securely at each end and some types (especially braided hoses) don't lend themselves well to secure fastening at the ends.

60 Bar... jees! As though that would be needed for fuel injection pressures lol. But some of the carb stuff will balloon at very low pressures.
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Biketeacherdave
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Joined: Tue Jun 21, 2022 1:52 am

Re: Sport 4.2 supercharged stalling issue

#9 Post by Biketeacherdave »

So the working pressure for my car is 48/50 psi or 3.35 ish bar. I will check with a gauge to confirm pressure when on petrol then running on lpg.

As you have kindly pointed out a reducer of some sort is required to maintain correct fuel pressure for the ecu to monitor. I understand the ecu varies the fuel pump speed to maintain fuel.presdure at different engine loads so a quick check at the shrader valve should point me in the right direction.

Many thanks Simon I have been reading a lot of your other fine posts if only you were local.i would just drop the car off and let you sort it for me.

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