Hi Guys,
Just had the usual twin pump failure and left stranded and having managed to get the car home decided to investigate the issue.
Having accessed the fuel tank in-situ, in the boot and through the rear parcel shelf speaker, I tested the wiring to the pumps and found the pumps "open circuit". I set about removing the pumps.

After removing the two pumps I decided to investigate one of the pumps and found that the actual pump had failed as a result of over heating and melting.

The attached picture shows that the blue plastic sleeve round the armature had melted between the magnets inside the housing.

The brushes in the top of the motor had got stuck due to the plastic melting.

As the pump cycles, it draws fuel through the bottom inlet and passes through the pump housing and through to the outlet and into the fuel line, this must act as a form of coolant for the pump.

Unfortunately, as the magnets have a void between them, the blue plastic around the armature melts and fills this void and in doing so prevents the armature from spinning, ending in failure.

After replacing the pumps the car is purring again...

 

Not a pleasant experience, being left on the side of the road. I've been told that letting the fuel level get low will overheat the pump since the fuel is used for cooling the pump.

 

Have heard the same, some say 1/4 tank, some say 1/2 before one risks overheating the pumps.

Bottom line, IMHO it is a design SNAFU if the pumps can't handle fuel levels falling to levels that the car is designed/capable of operating. Either the pumps should have been designed differently or there should be a 'reserve' of fuel that is enough to keep them cooled under all circumstances but can't be burned. The latter seems ridiculous though if significant fuel 'reserves' are required... after all who wants to cart around a significant amount of fuel that can't be used?

To be fair, this isn't a problem unique to Jaguars.

.

 

change the fuel filter, In case debris got inside inside it, also our fuel pumps are sort of universal. So a aftermarket unit or 2 can be had cheap on line. and also you can upgrade the flow a little with the entire system being overhauled.

 

I never took a failed pump apart, but that one looks absolutely gruesome. I wonder how low the fuel actually needs to get, for those results? I ran mine out of gas, because the previous owner played with the tank sending unit. I got it fixed(by playing with the tank sending unit), but that pump must have gotten glowing hot. They are designed to take a certain amount of heat......Glad you found your problem, before it became a PROBLEM.....Be cool....Mike

 

Hi Mrplow58,

I was rather taken back by the condition of one of the pumps, myself and I have yet to dissect the 2nd pump, but what I found strange is that the fuel pump fuses (2nr 20amp) had not tripped out, neither had the relays and there was no indication on the "message display" of any errors.

I have always kept the tank half full or full, so one of the pumps may have failed some considerable time ago. However, with the new pumps, the car feels alive and FAF again.

The plastic must have been exceedingly hot to melt on the armature and between the magnets.

I clearly need to drive the car in a more enthusiastic manner!!

To ensure that both pumps are constantly working of course and also I need to keep an eye out for nearest Petrol Stations...

 

It's my understanding that the fuel flowing through the pump supplies the cooling, rather than mostly the fuel level around the pump.

 

Why wouldn't that be the same as for an external pump's cooling? It also receives all its cooling (and lubrication) from the flow-through gasoline. I always thought that the "Gotta keep the tank 1/4 full" was just urban legend, along with, "If you let your tank get low you will suck up debris" (ummm, ... just where do you it's sucking from ALL the time, ma'am?).

Is it possible that an IPO let Freddy's tank run to empty a few too many times and the pump just happened to eventually fail on Freddy's watch?

Does the low tank / burned pump scenario also apply to the 4.2 guys with one pump? I usually only stop for fuel when on cross-countries and that's often quite sometime after the low fuel light illuminates.

 

1/4 tank seems to be the most regular level recommended.. My wife used to run them low.. The pump failed.. I yelled at her and now never below 1/4 tank and no more failed pumps. It had burned up on my car but Never melted like that!

 

I also gave my wife some "strong vocal encouragement" on multiple occasions to fill up before the gauge drops to 1/4 tank remaining. It took some time to get her on board but after frightening her with a few "low on gas burns up the fuel pump meaning you'll be stuck on the side of the road and dealing with whatever ax murderer stops to check you out" stories, she finally came around. I haven't seen her gauge below 1/4 tank in quite some time now and I hope it stays that way....