Can anyone point me in the direction of a new fuel pressure reg for the N/A 4.2 engine 04 X350 model

When I search all I can find is fuel pressure sensor and its a small black box with a hose fitting

 

Is there a regulator? There is a releif valve on the fuel pump but I don't see any mention of a regulator. The pressure is managed by the releif valve and the speed of the pump.

I think?

 

Correct, the 4.2 is what they call a non return style system.

The ECU varies the speed of the pump to control pressure based on the sensor mounted to the injector rail. The little black box is (basically) the regulator.

 

Why are you inquiring doc?

(I'm only asking because it's gotten cold in the single digits here, and my xj8 does not want to start, lots and lots of cranking; I've been doing some research and the pump relief valve is suspect. It will restart fine once warm, and once the weather is warmer; but cold takes 4-5 series of turning the engine over and over).

 

Its had this strange cranking habit since I bought the car

When hot sometimes not every time it will crank and crank then all of a sudden it will catch fart and fluff then the idle will smooth out

This morning I must have jinxed it because it did it when cold first start of the day

Then all day its been starting fine but its been very wet and humid up here

I have seen that little square sensor thing for sale just wanted to know what it did and if these cars had a fuel pressure reg like the XJR6 did

I might just replace it see what it does there are no codes and the ******* is running perfect except for the odd starting problem

It's like a cat that's got stage fright it only hesitates when someone is looking (LOL)

 

A few X350 owners in the UK had problems with hot starting; long cranking before it fires, seems that the issues were resolved with an ECU reflash (which may not be an option for you?)

 

doc,

A few random thoughts that haven't been mentioned by others:

1. A leaking fuel injector could cause rapid loss of pressure in the fuel rail at shutdown, allowing the remaining fuel in the rail to vaporize, causing classic vapor lock.

2. If your engine coolant temperature sensor (ECT) has drifted in value, or there's corrosion on the electrical connector or a problem with the wiring, the ECM may think the engine is cold even when it's hot and apply cold-start fuel enrichment, which could cause hot start issues, especially if your air filter is a little past its prime or your MAFS needs to be cleaned.

How long since your last tune up (plugs, fuel & air filter, clean the MAFS, check for oil in the spark plug wells, etc.)?

If you're still on the original CKPS and CMPS it might be worth replacing those preemptively. They're inexpensive (at least here in the U.S.), and when they begin to fail they can cause hard-to-diagnose starting problems.

Please keep us informed.

Don

 

She has done less than 10,000 k,s on everything

Map and maf sensor's plugs oil & filter transmission full flush and service coolant full flush and header tank modified diff oil changed new 200 cell cats new O2 sensors x4 and a remap to compensate for the high flow cats and K&N panel it did it before I did all the work

I had actually forgotten about the problem till the other day when I tried starting it after some running around and thought this thing isn't going to start

That's when I thought need to ask the forum brains trust


I think what Cam is saying sounds right as my X350 is a private import into Australia and is a 2003 XJ8
the Aussie ones only came out in 04 same as the USA got the X350 in 04 as well

 

My fuel pressure regulator if that is the right part is what is leaking

Can this be replaced? How can I relieve the fuel pressure so when I wiggle it off it doesn't spray gasoline everywhere like it just did one me.

 

Hi kellyfontes,

In order to answer your question with any specificity we will need to know the year, model and engine of your Jaguar. It's a good idea to add this to your signature line so it appears in all your posts.

To answer your second question, the typical procedure for relieving the fuel pressure prior to performing any repair on the fuel system is to remove the fuel pump relay, then start the engine and let it run until it dies. If the engine won't start at all after cranking for a few seconds the fuel pressure is usually sufficiently relieved.

Cheers,

Don

 

Don, After any repairs are made to a depressurized system (fuel filter) is there any special procedure at start-up or to "repressurize" the system?

 

Hi Dan,

Before you start the engine for the first time, you can turn the key to position II (ON) but do not crank the engine. This will cause the fuel pump to run briefly to prime the system. If you think your fuel lines are very empty, you can repeat the priming burst two or three times. That will usually fill and pressurize the system to avoid excessive cranking of the engine.

Cheers,

Don

 

It sounded like a dying fuel pump to me. Try hook up to a n OBII reader that provides live view of fuel pressure. Better yet, a reader specific to Jaguar to determine engine error codes.

 

After a few days removed from trying to sort out my no start issue i revisited the car and started going through the ground connections and fuses again. Curiously I found a 5A (not blown) fuse in the front box for the fuel pump instead of a 10A. While I had every other denomination of fuse, I didn't have a 10A so I'll get one tomorrow. I'm curious what impact the weaker fuse would have since it has been that way for the 3.5 years I've owned the car.

 

Other than it might blow (but hasn't) and I suppose might not seat properly, no impact.

 

As JagV8 states, The wrong lower amp rating of a fuse won't cause any issues unless the draw from the equipment connected to it goes over the amp rating causing it to blow. Fitting a higher rated fuse than is specified could cause a problem if something connected to that fuse draws too much amps due to a fault as this can be a fire hazard as the fuse will not blow when it should.

 

If you do decide to replace your Fuel Rail Pressure Sensor, might be worth taking a look at this post (courtesy Datsports):

https://www.jaguarforums.com/forum/s...6/#post1702366

I replaced mine with a Ford part...No problems.....

 

Black Beauty is back on the road and I want to thank all the great minds that helped me out. I will say this is a car that gets different nicknames at different points in the diagnosis/repair cycle. An some of those names aren't fit for this forum.
My issue started with what seemed like fuel starvation then restricted performance then no firing. I changed a fuel filter as an easy first step and figured it needed it anyway. After reading a lot of posts about tracking down the power supply and making sure the pump was energized (it was), I purchased a pump (ouch). Before installing I went through the ground points, checked every fuse again (there was a 5 amp fuse in place of the designed 10 amp fuse for the fuel pump), cleaned and greased every electrical connection I could see before removing the pump. I said what the hell and tried to start it and it ran fine with no fuel issues. I returned the pump!
So, I'm not sure which connection or fuse contact made the difference.

 

X350 series use a “fuel pressure sensor” as the computer adjusts the fuel pump to regulate fuel pressure. Older Jags used a mechanical version. (Possibly with a diaphragm). BTW, you don’t have to buy one from a Jaguar dealer. I believe this is the same unit used on the same year Lincoln LS with a 4.2 L V8.

Why? These were the years jaguar was owned by Ford. As a matter fact even now that they are owned by Tata there are still many ford part numbers on newer jaguars.