Apologies for the thread necromancy, but I've been having the same problem with an LPG converted Jag I recently bought and found a solution. Hopefully this may help any poor soul who comes across this page in the future searching for an answer.

My 2003 XJ6 started exhibiting the same symptoms after the corroded fuel filler neck was replaced. The new filler neck was missing a nipple to connect a narrow gauge rubber pipe that appeared to have no function. After investigation, my mechanic was unable to work out what the pipe was for, so he stoppered the end and made it safe. This was when the stalling and stuttering started. It would start OK on petrol and run fine on LPG, but if switched back to petrol it would start stuttering and eventually stall at idle, and run like a complete dog higher up the rev range. It was as though the petrol pressure was dropping, which, when connected to a diagnostic computer, was exactly what was happening: a straight, linear drop until it cut out.

A quick call to K Mugglestone & Co and we had the answer. What it turned out to be was a fuel return pipe had been plumbed in as part of the LPG system - this pipe allowed the fuel pump to keep operating (and keep the ECU happy) but return the petrol back to the tank via a pipe connected to the fuel filler pipe when it was running on LPG. Once the new nipple and return pipe were attached and the ECU reset (disconnect both terminals from the battery, hold together for 30 seconds, leave disconnected to 30 mins, then reattach to battery) everything was running fine. Just took the car for a long run, first on petrol then on LPG, for the ECU to relearn all the fuel settings.

So, a very big to Neil at K Mugglestone for taking the time to help! A small token of appreciation is winging its way to you now

Caveat: apparently, there is an alternative fitting that does not require the retro-fitted fuel return pipe and does it all electronically, but I don't know how that works or how it would be fixed if the same problem occurs.

 

Hi,

Problems seems to be known but I have always no solution!

Jaguar XJ 350/358 Fuel Pressure Issues | JagShops.com

Any idea please?

 

impianti GPL e metano per l'autotrazione Petrol Pressure Emulator

PRESSURE EMULATORS - Various emulators PRESSURE EMULATORS : AEB Alternative Fuel Electronics

 

Fault codes are


P0191: fuel rail pressure sensor A circuit range/performance

P0430: catalyst system efficiency below threshold bank 2

 

The first code suggests the LPG conversion has not changed the returnless system to one with a fuel return so not a suitable conversion.

 

Ok so which solution do you advice please?

Fuel pressure sensor emulator?

Benzindrucksimulator?

 

Seems to me that the solution lays in refitting the nipple and fuel return pipe that may have been taken off when installing the LPG system (krakead post above).
Did you check it or ask your LPG mechanics to do so?

 

Hi Serge,

Sure, I was just studying this thread tonight:

LPG DIY install - Page 2

"You may also have a problem with the petrol rail pressure getting too high (then on gas) which will result in 'limp home mode' but until its up and running you will not find out, mines fine but some models not. This is because the jaguar does not have a petrol return to the tank, so it changes the speed of the petrol pump to pressure the rail, so then on gas the pressure goes up/pump slows down and ecu may see this as a fault. But mine ok!
If you do have this problem fit a emulator or a petrol return to the tank."


"Also had to remove the fuel emulator and fit a fuel return as the jaguar like to see the fuel pressure change and with a emulator its set. So with a fuel return which has small valve to hold back the pressure the jag can still adjust it so happy. I got the fuel return kit from Tinley tech"


I've sent en email to Tinley Tech Limited Autogas conversion equipment and hope they have a fuel return kit for my XJ 4.2 NA.

Best regards
Chris

 

System Upgrades

(last one)

 

A fuel pressure sensor emulator (Benzindrucksimulator) was tried in my XJR but did not work.
So there was a pressure regulator installed with a gasoline return pipe.
P0430: Make sure to take care of every issue with LPG or gasoline - air mixture before you replace the catalyst, otherwise the new catalyst will be damaged soon.
Do a reset after any change of the LPG installation before driving.
Avoid any acceleration testing on gasoline as a too fat mixture could harm the new catalyst.
Remember the engine control module has only one ignition map that must be used for both LPG and gasoline.
In a Jaguar ECM there is no alternate map that can be switched to when on LPG.

Good luck

 

I've order this return pipe, wait and see!

 

Someone adviced me to fit a return line with a control solenoid to switch it on when on LPG, you will have to fit a resrtiction in the return line, 0.8mm seems to work well on Jag.
Either rout return to filler neck, or drill tank, cut a thread an screw in a fitting , seal it with Araldite.

I've order this kit, http://www.tinleytech.co.uk/acatalog...es.html#SID=25
(last one Petrol Return Kit Ref: HPET-RETURN)

Do you mean it's not a complete kit with the restricition ever made?

 

Some news, my lpg specialist has fit tinleytech return kit but issue is always on.

We have put off and on battery but orange check engine light reappears ans it gives same issues:

Impossible to Run on lpg engine stops after 4 minutes*

Lack of power on lpg between 2000-2500 rpm*

Any other idea please?*

Have you a scheme of return kit instal and 0.8mm solenoid?

Cheers
Chris