I'm getting error code P0193. The symptoms are interesting. Approximately half the time, there is no fuel present when I turn the ignition. Initial fuel pressure on startup is 60 psi. The engine then runs pretty smoothly, but the fuel pressure almost immediately climbs to 100 psi at the fuel rail schrader valve, where it stays at all times thereafter, except immediately after after revving. After letting off the accelerator, the pressure drops to 60 psi.

I suspect the fuel pump(s), as the car sat for 8 years without being started, but not sure that a failing pump would produce HIGH fuel pressure, as low pressure tends to be the far more common symptom. I know I can swap out the pumps for about $20 a piece, but I'd prefer not to throw parts at the problem before asking whether anyone has a better idea.

Thoughts?

 

the fuel pump is pulse width modulated , controlled by the fuel pressure regulator and the RECModule .
often the regs fail
you may want to try checking the vacuume line on &/or testing/replacing the fuel pressure reg, possibly - Part #: AJ87977.

 

I just replaced the regulator, it had broken while I was redoing all the wiring. Could it be anything else?

 

you mean the frp sensor?


if you didn’t use motorcraft or genuine jaguar you will have problems

 

Hey another Lincoln LS guy?? I had one too!

I had the same code and here is my thread on the repair on my 2005 S Type R.
Fuel Pressure Regulator

You did get the correct part number from Datsport up thread.
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Thank you for the suggestions. I have a new Ford OEM part on its way, I'm hoping this resolves the problem. I'll keep you posted.

 

Did you check the vacuum line to the reg as I mentioned,
before ordering parts ? It’s always worth checking. .
Good luck regardless .

 

I did. Before getting the part, I checked the vacuum hose return to the throttle body. It was cracked and brittle, so I replaced it. That did not resolve the problem. However, the new Ford OEM part seems to have done the trick. Thank you to everyone for your help!

 

I did. Before getting the part, I checked the vacuum hose return to the throttle body. It was cracked and brittle, so I replaced it. That did not resolve the problem. However, the new Ford OEM part seems to have done the trick. Thank you to everyone for your help!

 

I have looked for the fuel pressure regulator in the electrical guide for 2004 and it doesn't show up anywhere. It does show in the regular manual. I was wondering how it was wired. Any idea why it's not shown?
Also I didn't see a fuel pressure sensor. Thought there was one. I get zero fuel pressure readout off the data link so I was thinking the fuel pump/regulator was bad. (cranks, no start). I've reset the inertia switch also (once that was tripped). Car sat for the winter- maybe the pump froze up.

 

Hook a mechanical gauge to the Schrader test port so you know if there is any fuel pressure and what it reads.
All 4.2L engines have the FPR mounted on the LH (Drivers side in the US) rear of the engine. If you follow my link posted above the pictures posted will show you where it is. Note the strange problem I had as the first sensor I purchased was made wrong and would not bolt to the engine.

Note I did post under Tbird6 and Clubairth1 user names which causes some confusion.
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Which vehicle and engine? 2004 XJ8 as in your signature?

IIRC, the regulator and sensor are a single unit. The unit doesn't actually do much in the way of regulating. Description here, courtesy of Jaguar. You didn't mention which model, so I picked the V6 in the S-Type. Other models should be similar:

"The Injection Pressure (IP) Sensor, also known as a fuel rail pressure sensor, is mounted to the end of the fuel rail (for fuel pressure sensing) and has an intake manifold vacuum line port to compensate for changes in manifold vacuum. The IP Sensor is a 3-wire pressure transducer with one side of a diaphragm in contact with the pressurized fuel and the other side connected to manifold vacuum. The differential between rail pressure and manifold pressure is calculated by the ECM to control rail pressure. The ECM uses this information to demand a specific fuel flow rate from the fuel pump..."

See page 5-8 here:

http://www.jagrepair.com/images/Trai...ve%2006_06.pdf


Also note the unit is called the IP sensor, for Injection Pressure. It's in the wiring diagrams if you search "IP sensor".

 

Thanks for the info and document. I see what's going on now. I have an '04 XJ8. I probably have a bad sensor causing the fuel pump to not go on at all. There is no click or anything coming from the rear when I turn the key on. If the pump was bad I'd probably hear the relay clicking. And I'd probably get a code if the pump was not pumping when it is supposed to. But then again I should be seeing a pressure reading if the sensor is showing pressure already, shutting off the pump. I think I'll look for the fuel pump relay and bypass it to see if the pump turns on. Gut feel is the pump is bad. It's about time. Last year this happened once but I came back when it was warmer and it worked fine.

Bob

 

Once it got warmer the fuel pump started working. Works fine now. Turned on the key and pump buzzed for a couple seconds and built pressure. Repeating, it just buzzed for a split second, so it holds pressure. No way to manually turn on pump because it takes a PWM signal (pulse width modulation). The relay had voltage, which is all I could check. Pump simply did not work when cold. I only drive it in summer anyway.