Hi,


Last owner said that Jaguar Specialist diagnostis reports a fuel pressure fault which may or may not be due to the LPG conversion.



It runs perfectly on lpg but poor on petrol.



What do you think about it?

 

I have a fuel pressure issue, which meant the car would start, but then appear to have the symptoms of running out of fuel, and the engine dying.

I need to push gas to 2000RPM and wait 3 minutes that it permut in lpg to run perfectly.

On petrol car can't accelerate, RPM become low and low and it stops so it's impossible to drive it.

 

If the petrol side is not used much, the fuel pump could deteriorate, but who knows, you have a modified car, so it is very hard to work out what is going wrong via the internet. Get the car to a Jaguar specialist to check out the petrol fuel supply side. The pump is designed to run continuously and supply fuel to engine demand, there is no fuel return to the tank from the fuel rail.

 

long time ago, I read, that fuel pumps on jags are not operating constant.. there's some regulation. for lpg you have to simulate some regulation to make the ecm stay happy.
Maybe the lpg-conversion made some modifikation to the fuelpump-input of the ecm...

 

It is not difficult t o measure fuel pressure.

I would get a second opinion.

 

I think so but I have to wait that it permuts on lpg before driving as it's impossible to drive on petrol, impossibility to accelerate, the RPM is decreasing and stop the engine...


I accelerate at parking mode to 1500-2000 RPM for 3 minutes and when it goes on lpg I can drive.


So it seems to be a problem of pump.


The problem is that it was running perfectly on lpg but now I can't reach more than 3000RPM if not it cuts the power with big trouble.


What do you think about it?

 

Hi Christophe !

That sounds like the control unit of your car switched to emergency mode which allows to limp home.
I had to install a pressure regulator for gasoline fuel in my XJR to assure the control unit that the injectors are not clogged up when driving on LPG.
Some important questions regarding your problem :
- Which car model do you own ?
- What kind of gas equipment was installed into your car ?
- How is your control unit fooled that gasoline pressure at the rail is not far too high when on gas ?
- How is the pressure sensor of the gasoline fuel pump(s) fooled when on gas ?
- Does the dashboard display any error message ?
- If it does not, why doesn't it ?

Cheers

 

As Nebelfuerst mentioned the gasoline fuel pumps of X350s are regulated load dependent through a current range between 8 and 12 Volt.
Actual there is no LPG gas equipment available that uses such a pump, what can lead to the additional problem of not enough LPG gas pressure at high load.
Because of that I needed a vacuum controlled pressure regulator for my XJRs ICOM gas equipment, which they call "bigfoot".

Please check your gas equipment configuration concerning this matter.

Cheers

 

To make it worse, the ECM tries to do necessary adjustments to carburetion when on LPG gas, which leads to faulty fuel-air mixtures when switching back to regular gasoline.
The Denso controller does not realize that a complete different hardware is operating the engine when switching from gasoline to gas and vice versa. That could lead to all kinds of confusion and multiple adverse effects which never occur during regular tests, so maybe for some cases no error messages exist.
During the installation of the ICOM JTG into my car I experienced the same as Christophe did: The engine ran well on gas and badly on gasoline.
This effect made several ECM software updates (flash) necessary.

After flashing the ECM and reseting the engine operating map the alternatives are:
- Never drive on gas again
- Do not drive on gas until the injection systems of gas and gasoline do act very similarly.

The second possibility could require:
- Installation of a LPG gas pump that is able to vary pressure or the installation of an intake manifold vacuum controlled LPG pressure regulator that raises pressure at high loads
- Installation of a pressure regulator for gasoline that keeps the fuel pressure on a constant level when driving on gas and maybe when driving on gasoline as well
- Check, comparison and optimization of the engine operating maps for gasoline and gas (that is tuning)
- Avoid to drive on gasoline and never drive fast on gasoline

Christophe, it seems to me that the gas equipment installation on your car is still unfinished.
My odyssey took me almost 2 years, so please stay patient.
I could recommend an engineer (Kraft in Lippstadt) but he is resident in Germany.
If anyone is interested I will post some pics.
Christophe, nice talking to you. At least I am not alone.

Good luck


gasoline pressure regulator
https://www.jaguarforums.com/forum/m...r-57-24521.jpg
______________________


intake manifold vacuum controlled LPG pressure regulator
https://www.jaguarforums.com/forum/m...r-12-24518.jpg
______________________________________________

 

Thanks for your help.


It's a 3.5 V8 with stag2 lpg conversion.


The problem is only on petrol so I think for pressure regulator.


When I start engine, I'm obliged to accelerate on 2000RPM for 3 minutes until it permuts on lpg, if not the engine RPM decrease less than 800RPM and it stops like a die... If I try to accelerate to avoid the stop it makes like a "clong" noise as if it was impossible to put more petrol.


I've ever tried to return on petrol on highway when engine is in good temperature, and it's impossible to accelerate, the speed decrease like a fuel pump problem...


At the moment I can drive the car as I've found a possibility to avoid petrol run but if I had not lpg I couldn't drive!




Have you OEM pressure regulator number to find one on eBay.de or eBay.co.uk please?


Best regards/Viele danke
Mfg,
Chris

 

Maybe the problem is more complicated than we realize.
The problem is on petrol, yes, but as I see it, the cause is on LPG.
On installing gas equipment, many workshops failed in this duty and Jaguars are known to be difficult.
If you are not a specialized engineer or very experienced there is no reasonable chance to succeed.
Do you think the previous owner sold the car because of the failed gas equipment installation ?
If you think so, maybe you should choose the first alternative, let someone flash the ECM and reset the engine operating map to manufacturing standard and never drive on gas again.
Otherwise, if you find an stag2 authorized workshop who already successfully installed a stag2 into a Jaguar X350 V8 and you can afford to spend some grand you should go for it.
Please search and ask at the gas forums for that.
Sorry, I could just help you if your gas equipment was ICOM JTG and your engine AJ34S.
My XJR is actually at the workshop for air suspension issues so actually I cannot make a pic of the fuel pressure regulator.

Can anyone else help, please ?

Kind regards

 

The car has ever been reinitialized by a Jaguar garage but the issue reapears.

Lpg specialist said car had no problem on lpg.

 

Please have a look at this engine operating map.
A similar map is stored in the ECM of your X350 and its values get adjusted every time your car is driven.



It seems that the LPG gas equipment messes it up every time you drive on gas.
__________________________________________________ ____________

To reset the engine operating map it is not sufficient to disconnect the battery.
Your catalytic convertors could suffer from rich mixture, have them checked on occasion.

Please perform the following as a test:

1. Drive on gasoline exclusively for some days after a flash of the ECM. Your Jaguar should be without any problems if the ECM flash was done properly and every component of the gasoline injection system is in working order.
2. After that, drive on LPG for some time and watch the problem reappear when you switch back to gasoline.

Now you proved that LPG is the cause of the problem.

Please carefully read and understand what I wrote in my previous posts. If any questions arise, don't hesitate to ask.
Your LPG specialist is literally right saying "car had no problem on lpg".
But the LPG installer is responsible for the adverse effects on gasoline operation too.

Your aim should be to switch from LPG to gasoline and from gasoline to LPG without getting in trouble.
Therefore driving your car on LPG must generate an engine operating map which could be used on gasoline as well and vice versa.
To achieve that, the injection systems of gas and gasoline must act very similarly.
That does not seem to be the case here.

Kind regards

 

Here is a Dutch workshop recommendation out of a different thread:
https://www.jaguarforums.com/forum/p...e4/#post498116

BS-AutoTune - Home

This workshop (Ulrich Kraft, Lippstadt, Germany) cured my XJR:
59557 Autogaszentrum Lippstadt - Postleitzahlengebiet 5 - Umrüster - Autogas-Boerse.de

The only gas equipment I know which runs fine as it is in a X350 V8 is Prins VSI:
Prins Autogassystemen BV

index - Go-lpg
seems to work with ROMANO gas equipment:
HOME

Chris, where do you live ?

 

Hi,

A UK Jag specialist said that "they don’t have regulators on the car only the fuel pressure sensor. Price is £47.71 and postage is £15.99."

Is it true?

Thanks

 

Yes it's true, regulators are not used anymore by Jaguar, for the X350 they used a system similar to Ford Lincoln by Denso.
Installing a fuel pressure regulator is a deep intrusion in the carburetion. As compensation the ECM will prolong the injection time at high loads.
Before changing the origin Jaguar injection system I would prefer to tune the gas equipment with a LPG gas pump that is able to vary pressure (as Jaguar fuel pumps do) or the installation of an intake manifold vacuum controlled LPG pressure regulator that raises pressure at high loads.
If there a stag2 controller exists, maybe someone can reprogram it or adjust its engine operating map.
Most important is to analyse which values are given by the sensors to the ECM when on LPG and to anticipate how the ECM will change the gasoline engine operating map according to that.
After that you may decide what do to.
As Nebelfuerst stated above, "for lpg you have to simulate some regulation to make the ecm stay happy".

I hope stag2 can provide something.

Kind regards

 

Chris, could you please have a look at the two PDFs of Dennis posted by H20boy ?
https://www.jaguarforums.com/forum/x...85/#post669785
There is explained what the ECM essentially does concerning fuel-air mixture.
BTW, does your stag2 equipment have a control module of its own or does it use Jaguars ECM to calculate injection times like ICOM does ?

 

Hi Christophe, how are you and did you find a solution ?

 

Not again, I've bought fuel filter and fuel pressure regulator but I ave no time to go to garage.

Thank you so much.

 

By the way do U live near Sutton Coldfield, West Midlands?

Or do you know a specialist near it who could inspect ans check a car for me?

I'd like to buy a LHD RR vogue but needs to be checked.

Cheers,
Chris