fuel pressure
#1
Guest
Posts: n/a
fuel pressure
here's my problem, my 2000xkr with 85k on it, used to start every time on the third crank.
now it starts on the sixth crank or the second time i turn the key.
i thought it might be a dirty fuel filter, so i changed it.
i thought it might be old spark plugs, so i changed them.
i thought diry maf sensor, so i cleaned it.
i thought my after market air filter might be it, so i put the stock air box and filter back on.
nothing worked it still takes more cranks to start than just two months ago.
so now i thought fuel pressure, and this is confussing.
car sits longer than 6hr's fuel rails have no pressure.
turn key to start position, i hear humming, but no pressure inthe rails.
start the car i get 40 psi inthe rails.
turn car off and it slowly bleeds down to zero pressure.
my big question is......why don't i have pressure in the rails with the kwy in the start position??????
i did all this with the proper guage on the engine.
shouldn't the rails be charged with pressure when the key is in the start position, just before
the engine cranks.
all intellegent answer's welcome.
thanks!!!!
now it starts on the sixth crank or the second time i turn the key.
i thought it might be a dirty fuel filter, so i changed it.
i thought it might be old spark plugs, so i changed them.
i thought diry maf sensor, so i cleaned it.
i thought my after market air filter might be it, so i put the stock air box and filter back on.
nothing worked it still takes more cranks to start than just two months ago.
so now i thought fuel pressure, and this is confussing.
car sits longer than 6hr's fuel rails have no pressure.
turn key to start position, i hear humming, but no pressure inthe rails.
start the car i get 40 psi inthe rails.
turn car off and it slowly bleeds down to zero pressure.
my big question is......why don't i have pressure in the rails with the kwy in the start position??????
i did all this with the proper guage on the engine.
shouldn't the rails be charged with pressure when the key is in the start position, just before
the engine cranks.
all intellegent answer's welcome.
thanks!!!!
#2
#4
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
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
#5
Guest
Posts: n/a
two fuel pumps?????
i was told that by the dealer, but it seemed funny.
could any one tell me where these two pumps are and which one is primary.
i still don't understand why the fuel rail is not charged with the key in start postion.
can anyone clarify that for me.
external leaks or leaky injectors i don't think is the problem, the fuel rail takes hours to bleed off, and i don't small gas anywhere.
i thought is was the check valve in the fule pump was bleeding off over time, but after thinking about that it sound normal from a safety point of view.
so i'm back to no fuel rail pressure with the key in start.
please i need more info to solve this.
oh yea a check engine light came on and a reduced performance light as well.
the deal turned off the check engine light and it hasn't come back on. the reduced performance light went off by it's self. the check engine light code said both banks were running rich, that's what made me think maf sensor.
but that clean now and she still takes more to start than normal.
thank again for the help.
carl
i was told that by the dealer, but it seemed funny.
could any one tell me where these two pumps are and which one is primary.
i still don't understand why the fuel rail is not charged with the key in start postion.
can anyone clarify that for me.
external leaks or leaky injectors i don't think is the problem, the fuel rail takes hours to bleed off, and i don't small gas anywhere.
i thought is was the check valve in the fule pump was bleeding off over time, but after thinking about that it sound normal from a safety point of view.
so i'm back to no fuel rail pressure with the key in start.
please i need more info to solve this.
oh yea a check engine light came on and a reduced performance light as well.
the deal turned off the check engine light and it hasn't come back on. the reduced performance light went off by it's self. the check engine light code said both banks were running rich, that's what made me think maf sensor.
but that clean now and she still takes more to start than normal.
thank again for the help.
carl
#6
#7
Same issue
two fuel pumps?????
i was told that by the dealer, but it seemed funny.
could any one tell me where these two pumps are and which one is primary.
i still don't understand why the fuel rail is not charged with the key in start postion.
can anyone clarify that for me.
external leaks or leaky injectors i don't think is the problem, the fuel rail takes hours to bleed off, and i don't small gas anywhere.
i thought is was the check valve in the fule pump was bleeding off over time, but after thinking about that it sound normal from a safety point of view.
so i'm back to no fuel rail pressure with the key in start.
please i need more info to solve this.
oh yea a check engine light came on and a reduced performance light as well.
the deal turned off the check engine light and it hasn't come back on. the reduced performance light went off by it's self. the check engine light code said both banks were running rich, that's what made me think maf sensor.
but that clean now and she still takes more to start than normal.
thank again for the help.
carl
i was told that by the dealer, but it seemed funny.
could any one tell me where these two pumps are and which one is primary.
i still don't understand why the fuel rail is not charged with the key in start postion.
can anyone clarify that for me.
external leaks or leaky injectors i don't think is the problem, the fuel rail takes hours to bleed off, and i don't small gas anywhere.
i thought is was the check valve in the fule pump was bleeding off over time, but after thinking about that it sound normal from a safety point of view.
so i'm back to no fuel rail pressure with the key in start.
please i need more info to solve this.
oh yea a check engine light came on and a reduced performance light as well.
the deal turned off the check engine light and it hasn't come back on. the reduced performance light went off by it's self. the check engine light code said both banks were running rich, that's what made me think maf sensor.
but that clean now and she still takes more to start than normal.
thank again for the help.
carl
How do you fix it?
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#8
#9
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
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
Last edited by ghurtado74; 12-02-2018 at 05:59 PM.
#10
#11
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
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
#12
#13
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.
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.
#14
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?
#15
Join Date: Jan 2018
Location: on the road in NE Oklahoma
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#16
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.
#17
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