Extreme fuel restriction from the fuel pump causes the car to die out immediately after starting. The engine starts strong after waiting 10-15 mins than immediately starts to chug and starves out after 15-20 seconds. Confirmed low pressure (starts at 50~ psi and drops to 5psi) with computer and physical fuel pressure gauge. At the same time, the fuel pump checks out as working fine. I have completed my due diligence related to fuel pressure regulator and throttle position sensors, grounds… pretty much tried everything to run down the issue other than pulling the fuel pump; until today.

Today I decided that it was time to ignore the computer and go old school and address the issue as I would any other normal car with these symptoms. I removed the rear seat and pulled the passenger side fuel pump. Disassembled it to remove the pump element and to evaluate the filters (2) and the pump for restrictions or obvious signs of wear. It appears to be original equipment, or replaced by agency as it has the heat shrink fuel connections intact. What I did discover is that the one way check valve appears to be restricting fuel flow, in the extreme. I can barely blow through the valve, and when I put about 120psi of air pressure through it the valve sings like a plugged horn.

So, my question is this:
Is it normal for the fuel pump to have to overcome so much restriction to feed the fuel rail?… I am guessing no. And does anyone know of an aftermarket check valve that can be installed to replace what appears to be an obvious mechanical fuel system fault on this vehicle. My thinking is that I would rather keep the OEM pump and assembly as long as possible $$$ and replace what I am going to guess is a 10-20 dollar check valve.

 

Those check valves are necessary and are designed to prevent fuel pressure drop along the entire fuel line from tank to engine.

They are prone to failing. Usually they fail open taking excessive cranking to get the fuel rail pressurized.

Shocked to hear it failed closed but with Jaguar I'm not surprised.

They do NOT sell these separately.

I may have one or two laying around in my parts bin as I stripped 2 fuel pump assemblies and I'm known to keep everything... lol

Feel free to send me a PM.

 

Anyone used one of these?
10mm 3/8" Fuel Non Return One Way Check Valve Petrol Diesel Aluminium Alloy
https://a.co/d/hSkDvlv

 

i used that ebay one on an old audi that had a bad new fuel pump module. kind of works just make sure your hose is tight

might as well slap a $9.99 ebay pump motor while you’re in there

 

FYI, it is possible to put an aftermarket check valve into the existing fuel pump assembly.

 

Nice!!!!

Just throw some fuel injection band clamps on each end for safe measure.... let us know how it goes.

 

So this did not work. The one way valve will not support the pressure generated in the system.

 

then bypass and it just rely on the check valve in the pump

it’s only like 55psi i don’t see why it would just blow out

 

Oddly if that were the case, than it should have still held pressure, but the new fuel pump did not hold the pressure at all. I just assumed that the fuel pump did not have a check valve and that is why the additional oem check valve was used.

Note the construction of the oem valve as well. There is a pressure relief function built into it…. That would suggest to me that the pump is designed to NOT hold the pressure. Thoughts?

 

It is possible the OEM valve has a pressure relief (bypass) function integrated to protect the downstream fuel system from excessive pressure, just in case the fuel pump control system (FPS or rear electronics module) happened to develop a fault and inadvertently "overdrive" the fuel pump. Also prohibits excessive fuel line pressure building when fuel expands with " under hood heat soak" that would otherwise cause potential over pressure errors on a recently run and parked car.

May be somewhat relevant.......My 2005 X-Type's fuel pump is only driven by a supply relay, as the 2.1 V6 variant doesn't have a fuel pressure sensor in the injector manifold, nor a fuel pump control module, which makes that engine fuel system different from the 2.5 and 3.0 powered variants.
It has no fuel return line either, so fuel pressure is simply governed by a pressure regulator valve in the fuel sender assembly (sorry never took any photos of that pump assembly when I was replacing the faulty tank fuel level sender unit a year ago), but I imagine it possibly has a similar check/relief valve incorporated in the fuel sender assembly.

Only thing I can suggest is if you can monitor the fuel pump drive voltage (it will be pulse width modulated drive but still measurable with a normal DC multi-meter) to see if the drive voltage applied to the fuel pump is being increased as you see the fuel line pressure drop.
If the fuel pressure sensor and rear electronics module are working normally, you should see the supply voltage increasing as the control systems try to compensate.
If that is occurring, you are hunting a mechanical delivery issue not a control one.

I am curious with your picture of the whole assembly.....you have a fuel line coming from the pump unit, coupled to a three way "valve" assembly which has one pipe that goes to your check valve. That leaves the third outlet with nothing connected. Have your disconnected a pipe from that outlet during your removal process, or is that outlet just open ended?
If it has not pipe that connects to it, the that might be the relief valve outlet port.

 

The other port is connected to the left hand side of the fuel tank.

 

Hi Bluefish001,

That makes sense.....haven't had to go into my XJ8 tank yet (I am not really in a hurry to either at this stage).....and simply couldn't recall if my X-Type assembly had a similar port configuration.

If you have a variable 0-12 volt DC bench power supply, you could just separately power up the pump motor to check your output flow through to the inline filter or up to the fuel rail making an appropriate disconnection and collecting the output.
I certainly know the pump motor brushes wear out and then pump motors become intermittent, which can drive us crazy hunting occasional fuel starvation issues no matter what model of car.
When I have tested any DC motors (early printer/plotter axis motors, turntable and tapedeck motors etc.), I found it useful to bench run them and dial the voltage down to see if the motor remains smooth or starts to divulge weak/dead spots. Also you can see if the current draw fluctuates at low RPM indicating a bad commutator or perhaps a winding with an issue.

 

Thank you for the insight. It does appear to be an odd confluence of issues. Will let you know what I find.

 

update: I have decided to stop messing with this and attempting to find a cheap solution to this fuel pressure problem. Purchased a new fuel pump assembly. In the interest of helping others, I have some antidotal findings.

1. removing the fuel pump assembly on the xj8 could not be easier.
2. do not pull/remove the fuel lines that are heat shrunk to the fittings on the assembly unless you have the tools to replace them with the same type of fuel lines.
3. fuel hose will not survive being immersed in the tank.
4. the one way valve is more sophisticated than it would appear at first glance.
5. aftermarket one way valves must be high pressure rated… aka it must be able to hold 55-90psi of fuel pressure. Ideally it should allow back flow if the pressure exceeds that amount and reset itself. I found no aftermarket that accomplished this. All aftermarket, sold at racing retail, are strictly one way valves.
6. it is Techinical possible to add a one way valve outside of the tank. You might be able to add it near the fuel filter… but issue #5 still is relevant and unexplored. If an over pressure situation occurs that over pressure has to go somewhere. The weakest link is the fuel rail o-rings or the injectors themselves leaking into the intake manifold both are very bad situations that can result in toasting your vehicle if it is not caught immediately .
7. cheap one way valves should only be used on lawnmowers.
8. You absolutely need to open up both sides of the tank! Even if you only have the xj8 with one fuel pump the other side assembly has the fuel lines that quick disconnect inside the tank making it possible to easily remove the fuel pump assembly.
   
9. when removing the assembly from the tank, Take a moment to remove the float arm before attempting to pull it out of the tank. It is easy to do with a pick and it will save you damaging the fuel level sensor.
10. you do not have to drain the tank. Obviously it would be a more pleasant experience if you did and you have the added advantage of cleaning the bottom… but it is not required.
    
11. I noticed that the electrical block/connector that is located inside the vehicle next to the fuel tank access port that runs to the grommet that carries the wires to the fuel pump was badly corroded. It looked fine on a passive inspection, but when I disconnected it was green inside. Appears to be water incursion. I removed the connection and soldered each wire. Over 20 wires to solder and heat shrink, but it is a definite fix and eliminated that item as a variable now an in the future.
12. it is remarkably easy to pull the fuel rail on this vehicle to manually service/clean/and test the injectors. Less than 8 screws/nuts and the rail lifts right out. My injectors benefited from the cleaning and I now know that they are all dispersing fuel optimally.
13. replace the injector o-rings if you pull them. Do not assume they will work because they look ok. I did just that and 4 of the 8 injectors leaked. The good news is it is very obvious to see the leak. The bad news is you will not be able to source OEM o-rings at your parts store. However Fel-Pro has generic o-rings that work just fine although way to expensive for what they are in my opinion.
14. the fuel regulator is an easy item to replace… and in my case is not the cause of my fuel issue.
15. replacing the fuel pump in the assembly was also very easy…. But make sure that your one way valve is working properly aka, not restricting the fuel flow to the fuel rail (as in my case) or letting fuel back flow into the tank which apparently is more common of an issue…. Test it before you invest in a pump as the valve is not sold separately and will require that you replace the assembly.

I am now 100% certain that I have a Circuit grounding out somewhere between the ECM and the fuel pressure regulator that I have been unable to trace because of my lack of experience with this type of electrical system. But following the diagnostic that is in the manual keeps bring me back to the circuit grounding out issue. ohms are too high or too low.

 

Where did you buy the fuel pump and how expensive was it?

 

ONER New Electric Fuel Pump & Install Kit Fit Multiple Models Replaces E8229 E2068 E8213 EFP382A

4.1 out of 5 stars
| $19.98$19.98

 

So apparently the SCP bus is shorted to battery. Any idea of a strategy to track down the short?

 

look at the wiring diagram then start unplugging things