Yesterday my XK8 just died. No fuel pressure in rail. I checked the fuse and it was blown, replaced it and no humming noise from the pump. I replaced the pump still not working. I have 12v from the fuse whem turning over the engine. I put fuel in the intake and it starts for 10-20 sec. help


2001 XK8

 

Check the electrical continutiy of the link lead wires in the tank that connect to the fuel pump. That roughly 1"x1" molded 'block' on the wires is an electrical filter. Sometimes when the pump fails it also burns out that filter and the entire link lead and filter needs to be replaced.

 

White XKR I know what your talking about. I did some more test the white wire connention I unpluged and test voltage when turning over the motor I didn't have 12v to any pins. I did have 4.6v on one (ny wire). This wire plug is before the pump.

 

You said you have power to the fuse when cranking. Is this fuse #7 in the trunk? If this fuse has power on both sides, then the fuel pump relay and fuse are good.

OUTSIDE of the tank, the fuel pump power wires are Brown with a with a White tracer (+12v) and Black (ground). If you do not have power between these two wires when cranking and you do have power on both sides of he fuse then there is a wiring problem.

INSIDE the tank the fuel pump link lead wires are white (+12v) and black (ground).

I am confused by what wire plug you are referencing with a white wire 'before the pump'. There should not be a white wire OUTSIDE the tank providing pump power.

 

WhiteXKR My mistake I didn't have the engine turning over when test the wire (a long day) The white connection is mid way from the fuse box and thetop ofthe tank. by the way what is that black 1"x1" unit called in the tank and where can I get it
Thanks

 

It is actually called the fuel pump 'link lead': LJE3075BA. You can get it from a local or online dealer.

Jaguar Parts - Direct JPLV Porsche Parts.com

 

Or, just replace with suitable fuel rated wire such as tefzel/teflon jacketed #12 or #14.

 

This is fine if it is just the wire that is burnt, but if it is the electrical noise filter that has gone open, you should replace the link lead with the Jaguar part that contains the noise filter.

Though it will 'work' without the electrical noise filter, it may cause audible effects in your radio and possibly interfere with other car electronics if it is just replaced with fuel rated wire.

 

Having done exactly that, it doesn't cause any interference in my experience. Others have done the same without reported noise problems. The suppression function can be done with a passive ferrite suppressor on the wires leading to the external connector if someone is really concerned. In any case, any EMF from within the tank is completely shielded by the grounded tank itself.

Denso patented a "in pump" noise suppression module, so Walbro followed up with a patent for a external noise suppression module as a competitive response. And Jaguar fell for it.

The link lead has only ever been observed to burn on the ground side. This makes me believe that the suppressor plays a role in this as otherwise a power circuit is agnostic as to the effect of power flow on the +ve and -ve sides.

So, I chose to eliminate the suppressor for two reasons:

1. cost
2. eliminate a potential future problem

 

First off, it is good that your empirical results show that this filter is not necessary. It is certainly a way to save a buck on a way overpriced part.

The issue would appear to be conducted noise, not radiated, so the fuel tank grounding may not be relevant.

If this was a case of Jaguar engineers 'falling for' the need for noise suppression when there was no actual legitimate need, then that is a dissapointing narrative of their gullibility and abilities. I would like to believe otherwise.

My conservative engineering side would advise caution, perhaps there where some rarely occurung interference effects, or possible long term degradation susceptability in some electronic modules to the conducted noise spikes.

Make your choice and take your chances I guess....

 

The only thing I can point out with respect to electrical noise tranferred to the power leads external to the tank itself is that the ferrite toroids are easily obtained and quite easy to fit on the external leads after the fact since the wires are accessible from outside of the tank.

If you examine the Walbro patent, you can see that it is a bit opaque ... as are most patents, but it definitely contains inductors. Inductance does funny things to power circuits.

I believe that the simpler the circuit, the less chance of future problems. And of course, it is much cheaper. Even after paying to have tefzel/teflon wiring delivered by Fedex.