. . . only intelligent answers? Leaves a lot of us out.

The XKR has two fuel pumps. Sounds like an issue with the primary pump or the wiring harness. The harness has a history.

 

lol

 

I just went through this exact scenario on my other car (1995 Corvette). The symptoms were that it took slightly longer to start than "normal". I hooked up a pressure gauge to the schrader valve on the fuel rails and noticed that when I turned the key (but did not start) the pressure would crank up to 40+ psi but then drop to zero after a few seconds. Once started, the car would run fine but when turning off, the pressure in the rail would quickly drop to zero.

A slow drop in pressure would indicate something like leaky injectors but a quick drop would indicate something like a failing fuel pressure regulator or fuel pump. In my case, it was the fuel pump and replacing it solved the problem.

So the first place to start would be to hook up a pressure gauge and see what is happening.

Doug

 

I was under the impression that with fuel injected cars, turning the key to start (but not actually cranking) should charge up the fuel rails. It seems that this would be necessary!

Doug

 

How do you fix it?

 

+1 and I believe it does (or should!) do that.

 

Hello, same issue.
turn key to start position, i hear humming from throttle body.
the fuel rail is not charged with the key in start position.
check engine light code said both banks were running rich.
Negative fuel trim both bank.
Rough idle.
CB00JAGUAR, How do you fix it?

Maf?
O2 sensor?
Fuel pressure regulator valve?
Leak injector? uneven.

thanks

 

Read OBD sensor etc values and hope for clues.

 

First thank the help and apologize for my English translated by google.

I put in background.

Jaguar xk8 2001 aj27.

A long story. When I bought the car It had cracked the block and cylinder heads and put pressure in the coolant circuit. But aceptable compression 140 psi in all cylinder.

then Swaped engine from scrap yard.
Now, coolant it is ok. No pressure at all. No over heating. but
I did compression test first. The new short block has low compressión in general about 120 psi. but cylinder 7: 100 psi and cylinder 8: 110 psi.. Then I put oil and pressure raise 220 psi. Result: worn ring.
i did leak down test too. Result valve close perfect. Only Noise coming from oil cap. So worn ring confirmed.

But i thing no enough to misfire. I belive misfire consecuence of pretty negative fuel trim. i know a misfire drive to a positive trim as raw fuel and more oxygen to read by the sensor.


Symptom:
- Low compressión cylinder
- Very negative fuel trim both bank. -25% bank 1 - 12% bank 2 in close loop.
- Misfire cylinder 7 , 8. (P0307 , P0308)

I did pressure fuel test gauge.
Fuel pressure rail regulator it is ok. No leak through vacum line. No injectors leak. Fuel pump ok 42 psi in crank possition key (no start) 20 minutes and hold rail pressure.

To rule out the problem, unpluged all O2 sensor looking for open loop.

crank/ start the car and the following happens:

Now it is assumed that the mixture only depends on the maf and still gives very rich because it stinks of gasoline. May be due misfire. I don´t know.
But MAF works fine and respond ok to variation idle to WOT.

8 injector are brand new.
8 ignition coil brand new too.

i am thinking clogged cat.

I'm going crazy and I do not feel like getting the engine back (mayor surgery), I'd like to find the fault before.

sorry for the book

regards

 

Gerard- check for oil in the spark plug wells. May be a leaking cam cover gasket.

Also, would be good idea to start new post for your problem, it will get more attention.

 

As far as fuel pump operation goes - from SERVICE TRAINING COURSE 881
V6 / V8 ENGINE MANAGEMENT

Fuel pump operation, section 6.5
• The fuel pump is switched by the ECM via the fuel
pump relay.
• When the ignition is switched on (position II), the
ECM switches on the fuel pump after a delay of 0.1
second.
• If the ignition switch remains in position II without
moving the key to crank (position III), the ECM will
switch off the pump after a maximum of 2 seconds.
• When the ignition switch is moved to crank (position
III), the fuel pump is activated and operates continuously
while the engine is running.
• If the engine stops with the ignition on (position II),
the ECM will switch OFF the pump after two seconds.

XKR has 2 fuel pumps to deliver enough fuel at higher revs due to the extra power over Xk8
From same source, section 12.8
Supercharged EMS Components
Fuel Pumps
Two fuel pumps are used to provide adequate fuel flow during high engine loads. Both pumps are operated by the
ECM via relays. Operation of fuel pump 1 is identical to the normally aspirated single fuel pump. Diagnostic monitoring
for the N/A single fuel pump remains unchanged. The other warnings and default action differs for the SC
pump 1. Fuel pump 2 is switched by the ECM as determined by engine operating conditions.

For the XKR, if primary pump goes bad (they all go bad, often almost at the same time), then if the ECU can detect it then it will switch to using the secondary after a few tries. Several threads on the forum about checking if both pumps are working, such as disabling each in turn (e.g. pull fuse) and see if the car still starts.
If you are on your original pumps, then certainly they could be going bad....but is seems you are getting good pressure.
You could check to see if both pumps are good. Other than that, likely need more clues/throwing more codes before narrowing down the possible causes, or start shooting in the dark....
The pumps are in the tank - plenty of threads on how to replace - no fun to do if you have a convertible....a bit easier with coupe.

 

My 2004 XKR fuel pressure hits low to mid 50's at key on goes up a couple points at start, at heavier acceleration goes higher in the low 60's settles in at idol 52/53...this was read electronically from a code reader. It holds about full pressure for several minutes then starts to drop. I thought it interesting when I turned the engine off then lost the connection from code reader as it lost power, then turned the key back on for power to the reader, it was off long enough the fuel pump kicked back on and the pressure went to 70. Then dropped back to low 50s. Repeated key on pressure is low 50's. Does this sound Normal?

 

do you have a lot of idle time on your hands ?

My take:
if the car runs as it should, then don’t go looking for trouble. It will find you soon enough anyway.



Z

 

It runs great. Usually starts fine. Every once in a while it cranks longer than it should. I've had 2 and neither one started like my American cars, Corvette, Cadillac, pontiac. You'd think by 2004 you could just hit the key and instant start, but nope.

 

A