I have a 99 XJR, 41K, Black/Black and live in the St. Louis Missouri area. I am currently in process of replacing both fuel pumps and was wondering if anyone had investigated replacing (or have replaced) the internal pumps with external ones utilizing the existing relays, wiring, etc. I have read some posts regarding this issue on newer models that use a single fuel line and more complex computerization to monitor fuel temperature, pressure and pump speed. However, I have not found anything on the duel line models. Any help or suggestions would be appreciated. Thanks.
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1999/XJR/41K miles

 

that's an interesting idea - well worth pursuing. I've not heard of any developments in this area though. Keep us in the loop with possible components used.

 

Was thinking exactly the same thing for my XKR 4.0. I've just replaced both pumps, put it all back together and found one pump isn't working. Grrr!

My ideas were to re-route the fuel lines so the so-called "quick-disconnect" couplings are behind the tank to make it easier to remove, or to relocate the pumps. My main concern with exterior pumps is the temperature - I've heard that they run in the fuel to keep them cool and prevent cavitation of the fuel inside the pump.

This was a major issue on injected TR6's, that would stop working on hot days. Some people dreamed up elaborate water-cooling schemes to keep them cool. It might just be possible to air cool the pump(s) with a cool air feed from the wheel arch and a heat-sink.

Later cars (4.2L) only had one pump, so it must also be possible to use a single high-pressure racing pump to cut down on parts.

My last thought was to fit a removable plate in the back of the tank, with a gasket, so that the pumps could be easily accessed without having to remove the tank. This could be custom fabricated with pipes, mounting points for the pump, etc. as well.

Unfortunately I've seen no-one else discuss this topic, despite the obvious weak-point of the original design. I guess not many people have scrambled around on their own garage floor trying to undo those blasted quick-release couplings!

Nglshmn
2001 XKR Convertible
San Diego, CA

 

It is true that pumps designed for in-tank mounting depend on the fuel bath for cooling and lubrication. However, pumps designed for external mounting have no such requirement, or the requirement is met by the fuel inside a larger pump housing.

Lots of people .. or at least lots of owners who happen to be on JF have done the pumps.

The use of an external pump has been mentioned privately at least once.

What is the layout of the lines within the tank?

Is it filter sock -> pump outlet -> hose -> loop -> outlet?

In other words, does the top hose loop 180 degrees towards the inside of the quick disconnect at the bottom of the tank?

External pumps don't like to siphon fuel up, they like a gravity feed on the inlet side to keep prime.

As far as the wiring goes, there are only the power feeds to the pumps and the ECM does not even know if those feeds are live as the ECM only monitors the control circuit on the fuel pump relays and not the power circuit itself. You can cut the pump feed circuit completely and the ECM would not complain as long as the relays are still in the sockets.

The pressure sensor for the evap will still work because the atmospheric pressure conditions will remain the same, you are just pumping from somewhere further down the fuel line.

Your wiring should be 12# or better.

 

I have completed the installation of the two new pumps on my 99 XJR. The car starts and drives well but I have not had the time to check if both pumps are working by removing fuses or relays. I used Fuel Injection Corporation pumps which are an exact fit and no modification of any type was required. The procedure, as noted by many, is time consuming and aggravating.
I can’t give up on the idea of re-engineering the fuel pump design so it would be relatively easy to replace a bad pump or pumps. My initial thinking was to place one external pump or perhaps two external pumps where the fuel filter is currently mounted. The one external would probably be a racing pump from Summit or two external pumps from Fuel Injection Corporation if they make an external equivalent. Fuel Injection Corporation could probably tell you what fuel flow requirements would be needed by you model or someone else on the forum may know. Then, the decision between two or one pump would have to be made. One would probably be less expensive and easier to mount but two would provide some redundancy depending on the order of failure. Also, an external racing pump, for instance, may not be as prone to failure…I don’t really know. Hopefully, these pump(s) would have simple barb and hose w/clamp connections on both ends and could be placed where the fuel filter is now mounted with only slight modifications to the existing fuel line. These pump(s) would be down-stream from the tank and allow gravity feed of fuel (as noted previously) and only the electrical connections would have to be routed to the pump from the trunk. This would keep the basic engineering of gas tank, fuses, relays, etc. in place. However, the pumps and hoses currently in the tank would act as a block to fuel flow and would have to be removed which is not a problem if they have failed. The gasoline tank would then be a “dumb” tank of the old days but the evaporation flange and ascending unit would still function as normal (as noted previously). There would not be any “strainers” and contaminates in the tank may be a problem. I was thinking that a small in-line filter next to the pumps may work but I am not sure if there is enough space to use one. As far as the existing fuel filter, I was definitely planning a small in-line filter somewhere between the new pump and the engine. Hopefully this could also be mounted for easy replacement and possibly hidden so the car appeared un-altered.
I am not sure how your XKR is designed, but on my XJR I have found an approach to the removal of the “quick release” couplings in the tank which might be of help to you (if you have to replace the one pump that is not working). With this approach, I can get my fingers on both hands up to the lines to attach the Lisle (white in color) low profile disconnection device. Also, I made a tool to help in releasing the lines from the tank using the Lisle disconnect device. My problem was that I could not push the disconnecting device deep enough into the connection to release the lines and pull the lines out at the same time. This tool is used in conjunction with the Lisle disconnect device and is easy to make and does not require a band saw or Dremel tool, etc. Once I used the tool with the Lisle disconnection device the lines came out in a few seconds. Prior to this I had spent over an hour trying to remove them with no success. If you would like more details let me know.

 

Hi,
It is such a difficult job to even get at the fuel tank quick disconnects that should my pump fail while I own the car, then I will be using the cutout method as shown. It was not my idea but to me it seems a whole lot better than lying on my back with 2 tons of car above me, I do not have a 4 post lift. The original poster used a wet blanket over the tank and made the cut with a dremel type tool and fiberglass cutting disks. Getting at and changing the pump/pumps is a whole lot easier this way, the cutout can be put back in place with screws or pop rivits.

 

Yes, changes to the fuel system are in order. I just lost both pumps in the middle of no where. We had a hell of a time getting the tank out because of the fuel lines. No room for tools or big hands.
Due to lack of parts we replaced the pumps with a hi output performance pump for a camaro. It did let the car run but with a lack of fuel problem.
I replaced it with 2 used pumps, one of them failed in less than a mile. With only one OEM pump it was hard to get it back to the shop. The system must require alot of fuel to operate properly.
I replaced both with new ones. The car still doesn't run as it should. Any time I get aggresive with the throttle it runs lean or completely out of fuel.
I am looking for an alternitive fueling system. An external pump would fit on the frame rail. relocate the filter ahead of the pump. I would think to put a klunk in fuel tank going to the well.
Does any one have the pressure and GPM or GPH specs for the factory pumps or system requirements?
Thanks,
David

 

Check your fuel filter. There is no reason that the car will not get sufficient fuel for highway cruise on one pump. The second pump is for high demand when the engine is above 3500 rpm.

 

I replaced the filter after the camero pump was installed and had fuel supply issues. It made no difference at that time. The filter that was removed was back flowed at my shop and was really clean. I didn't cut it open.