X-100 fuel pump(s) and preemptive care strategies
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X-100 fuel pump(s) and pre-emptive care strategies
Given the surgery needed to replace the fuel pump, or pumps as the case may be, are there any strategies or habits that one can employ to extend the fuel pump’s life span ?
All the ideas I’ve heard may be helpful, but to what degree they are helpful or relevant, that is something that’s just guesswork to me.
some of these are no-brainers , but how much they impact the fuel pump longevity, I just don’t know:
1) keeping the fuel filter clean by replacing often. How often is often ?
2) keeping the fuel tank full as possible, especially in the summertime. The idea being to have the extra fuel keep the pump cooler.
3) drive the car often. I’ve heard anecdotal stories, here and elsewhere, that fuel pump will suffer if left unused too long. How long is too long ? That said, the 4.0 XKR’s have a 2nd pump that doesn’t get used unless a high demand is placed on the engine. So I try to get the rpm and acceleration in the needed range often in order to activate the 2nd pump.
But I don’t really know the exact parameters necessary to activate the 2nd pump. Can anyone chime in with this information ? Would be nice to know for certain .
4) Use a reputable fuel treatment occasionally, like the Chevron Techron
those are the only ideas I’ve heard of, any confirmations or disputing those would be interesting to read.
And there are sure to be some ideas not listed too….
Z
All the ideas I’ve heard may be helpful, but to what degree they are helpful or relevant, that is something that’s just guesswork to me.
some of these are no-brainers , but how much they impact the fuel pump longevity, I just don’t know:
1) keeping the fuel filter clean by replacing often. How often is often ?
2) keeping the fuel tank full as possible, especially in the summertime. The idea being to have the extra fuel keep the pump cooler.
3) drive the car often. I’ve heard anecdotal stories, here and elsewhere, that fuel pump will suffer if left unused too long. How long is too long ? That said, the 4.0 XKR’s have a 2nd pump that doesn’t get used unless a high demand is placed on the engine. So I try to get the rpm and acceleration in the needed range often in order to activate the 2nd pump.
But I don’t really know the exact parameters necessary to activate the 2nd pump. Can anyone chime in with this information ? Would be nice to know for certain .
4) Use a reputable fuel treatment occasionally, like the Chevron Techron
those are the only ideas I’ve heard of, any confirmations or disputing those would be interesting to read.
And there are sure to be some ideas not listed too….
Z
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If you really want to exercise the second fuel pump, this is how to do it, either as an occasional test, or as a permanent modification:-
Full thread here if any 4.0 XKR owners haven't seen it (and BTW this only applies to 4.0 XKR owners, the XK8 and 4.2 cars are different):-
https://www.jaguarforums.com/forum/x...el-pump-85882/
The normal operating roles of the two pumps as documented by Avos are as follows:
initial fuel rail priming - secondary pump
running - primary pump
heavy demand - primary pump + secondary pump
Another way to test is to use make a jumper lead consisting of a male spade connector, a foot of 14 or 16 gauge wire and an alligator clip. Connect the alligator clip to the battery power stud in the fuse box and insert the spade into the relay connection leading to each of the fuel pumps in turn. The pump should be heard spinning. The jumper lead can then be stored in the trunk in the event that it is needed in an emergency to jumper the circuit. Testing this way avoids having "restricted performance" lights due to the ECM detecting a missing relay as a bad relay.
If a car is usually not in high demand mode, the secondary pump can suffer from lack of use as it only comes on long enough to prime the fuel rail. If the fuel system is in good shape, the pump will get very little exercise. Given the effects of ethanol, this is something to be avoided. If a secondary pump has been pickling for some time, it can fail within a few miles of being pressed into service after the primary has failed.
On my own car, I added a small control box a few weeks ago to be able to balance the fuel pump usage. This was posted in the X308 section at the time. It is two SPDT toggle switches potted with epoxy in a used tic-tac box attached to the fusebox with double sided tape. The taps were made in the trunk harness close to the entry to the fusebox.
The switches control the primary circuits on the two fuel pump relays and allow selection of the fuel pump to be controlled by each relay. This way, the roles of the pumps can be reversed to even out usage patterns, or both pumps can be forced to either relay. This modification has to be top quality because if it is not reliable, a failure can strand the car just as easily as failed pumps.
Once the system is in place, it is probably sufficient to do a role reversal at perhaps each change in the four seasons. Make the change with the ignition off so that the ECM does not see a "missing" relay during the change. If the jumper cable described above is also in the trunk, it would only take a couple of more minutes to verify that both pumps are still spinning.
initial fuel rail priming - secondary pump
running - primary pump
heavy demand - primary pump + secondary pump
Another way to test is to use make a jumper lead consisting of a male spade connector, a foot of 14 or 16 gauge wire and an alligator clip. Connect the alligator clip to the battery power stud in the fuse box and insert the spade into the relay connection leading to each of the fuel pumps in turn. The pump should be heard spinning. The jumper lead can then be stored in the trunk in the event that it is needed in an emergency to jumper the circuit. Testing this way avoids having "restricted performance" lights due to the ECM detecting a missing relay as a bad relay.
If a car is usually not in high demand mode, the secondary pump can suffer from lack of use as it only comes on long enough to prime the fuel rail. If the fuel system is in good shape, the pump will get very little exercise. Given the effects of ethanol, this is something to be avoided. If a secondary pump has been pickling for some time, it can fail within a few miles of being pressed into service after the primary has failed.
On my own car, I added a small control box a few weeks ago to be able to balance the fuel pump usage. This was posted in the X308 section at the time. It is two SPDT toggle switches potted with epoxy in a used tic-tac box attached to the fusebox with double sided tape. The taps were made in the trunk harness close to the entry to the fusebox.
The switches control the primary circuits on the two fuel pump relays and allow selection of the fuel pump to be controlled by each relay. This way, the roles of the pumps can be reversed to even out usage patterns, or both pumps can be forced to either relay. This modification has to be top quality because if it is not reliable, a failure can strand the car just as easily as failed pumps.
Once the system is in place, it is probably sufficient to do a role reversal at perhaps each change in the four seasons. Make the change with the ignition off so that the ECM does not see a "missing" relay during the change. If the jumper cable described above is also in the trunk, it would only take a couple of more minutes to verify that both pumps are still spinning.
https://www.jaguarforums.com/forum/x...el-pump-85882/
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More seriously: can you work the wiring of the pumps so primary and secondary are, in effect, swapped? And do that every oil change or whatever.
To my knowledge, the secondary pump becomes primary if the primary fails and the car does not start after a number of attempts. Maybe disconnect the primary pump once in a while so the secondary gets some attention.
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“…..More seriously: can you work the wiring of the pumps so primary and secondary are, in effect, swapped? And do that every oil change or whatever.
To my knowledge, the secondary pump becomes primary if the primary fails and the car does not start after a number of attempts. Maybe disconnect the primary pump once in a while so the secondary gets some attention.
To my knowledge, the secondary pump becomes primary if the primary fails and the car does not start after a number of attempts. Maybe disconnect the primary pump once in a while so the secondary gets some attention.
but I’d have to see some photos and drawings of that type of arrangement before I’d feel comfortable doing it.
I could just manually disable the primary jump for a while, but while that’s something in my comfort zone, it would leave me without a 2nd pump for those addictive bursts of acceleration.
So I’ll just keep on with the manufacturer’s method of #2 pump activation for now. At least until a simple way of reversing the pumps is demonstrated.
I would still like to hear about any thing that can be done to baby the fuel pumps along. Mine are the originals, and who knows how much life is left in them.
PS: anyone have some factory documentation showing when exactly the #2 turns on ??
Z
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After nearly 11 years of ownership, I continue to believe that the best way to keep these XK8 / XKR fuel pumps alive and kicking is to take the car out for some strenuous exercise on a regular basis. My wife's 2006 XK8 was her daily driver from early February 2012 until late October 2018. It has been just a toy since then, but I take it out for at least a 25-mile back roads-and-highways romp a couple of times per week all year long. The owners who report the most fuel pump failures here on the forum have always been the ones who store their cars away for months or years, then attempt to bring the car out of hibernation and quickly learn that their fuel pump died during that long period of inactivity....
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Z
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Ive often wondered about the possibility of adding an external in line performance fuel pump instead of replacing the factory pumps.im guessing fuel would still flow through the old pumps even if they're locked up. Obviously unless the screens are clogged up.
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the stock pumps are junk and always lock up with lack of use. put a quality part in or a $9.99 ebay special and forget about it
ask the db7 guys how many pumps they have seize up.
if you can’t hear #2 priming go cut a hole in the shelf and solve the problem before you get stuck.
ask the db7 guys how many pumps they have seize up.
if you can’t hear #2 priming go cut a hole in the shelf and solve the problem before you get stuck.
Last edited by xalty; Jan 22, 2023 at 12:00 PM.
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For 4.2 cars I would say a super important thing is to keep an eye on the fuel pressure reading coming from the sensor on the rail. A sensor that is bad or under-reporting will have a direct influence on how hard the pump is working.
I recently had a sensor fail and it failed to 30psi. (as low as 15.9psi) Pump was running full blast whenever the car was running for how long I don't know. More than that, the pumps in the 4.2 SC cars (at least) are super robust heavy pumps (I don't know how that translates in to voltage or amperage draw) and running full blast I would say that the power draw and heat are more significant than the average fuel pump. Jus say'n... Could be a thing?
I recently had a sensor fail and it failed to 30psi. (as low as 15.9psi) Pump was running full blast whenever the car was running for how long I don't know. More than that, the pumps in the 4.2 SC cars (at least) are super robust heavy pumps (I don't know how that translates in to voltage or amperage draw) and running full blast I would say that the power draw and heat are more significant than the average fuel pump. Jus say'n... Could be a thing?
Last edited by JayJagJay; Feb 23, 2025 at 06:04 PM.
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Interesting thread, because I just replaced both fuel pumps on my 2002 XKR two days ago. My primary pump was working fine, but the secondary was dead . The advice I'm going to take is within every tank of fuel, just really get down on it to open it up and use that secondary pump. Also, I try to fill it with non-ethanol premium as much as possible.
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Interesting thread, because I just replaced both fuel pumps on my 2002 XKR two days ago. My primary pump was working fine, but the secondary was dead . The advice I'm going to take is within every tank of fuel, just really get down on it to open it up and use that secondary pump. Also, I try to fill it with non-ethanol premium as much as possible.
What method did you use to replace both pumps? Which pumps did you get?
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I made the access hole and replaced both of them through there. And I ordered the pumps through SNG Barratt. I'm not sure exactly what brand they are, but hopefully coming from there, they are of a good quality. I've historically ordered my parts from there, and they have been very good.
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