i have a 1973 xj-6 recently the fuel pumps stopes working after further investagation, I found they are still working, although I 've lost battery power to the pumps in the trunk, Is there a relay or fuse somewhere , I cant find one ? please help

 

Hey guys can anyone help. This member has asked the same question over the course of a month or so.

My advice, download the electrical diagrams for your car from the link in the FAQ at the top of this section.

 

I had a 1972 XJ6 until about the mid 1980s. The old British cars usually had a WHITE wire from the Ignition switch to the fuel pump (white is Ignition power NO FUSE). The Jag goes through a fuel changeover switch to select the tank pump and level sender so if it had a wire color it would be White with a stripe meaning After a Switch. If there is a fuse in the circuit, then the wire would be Green (Ignition power AFTER a fuse) and it also would have a stripe (AFTER A SWITCH). I have a Factory repair manual for Series I XJ6 somewhere in my pile-o-books but an electrical guide is the best way to find the answer to your questions. Remove the changeover switch and look at the wire colors to see what goes where and see if they match the pump wire colors in the boot. Check for power at the switch and go backwards from there if NO POWER.

Remember that you can have positive power to the pump but NO EARTH and the pump will still not operate!!!!!!!!!!!!!!!!!!!

bob gauff

 

I replied with info but I don't think it helped (no response)
I later looked at the Electrical Guide and found the pumps have NO FUSE and are wired to the ignition switch as I described (WHITE WIRE). All the British cars in the early days were wired this way. If no power then it is NOT A FUSE. Ignition switch, Fuel selector switch or wiring fault????????????????????????????????????????

bob gauff

 

Bob, I've committed your wire colour/stripe description to memory. A really useful tip that's only taken me the best part of half a century to learn.

 

I think it only works on the OLD British cars with less complicated wiring. I used to know from a colour what circuit I was looking at (blue was headlamp, brown was power from the battery, purple was brown AFTER a fuse etc.)
In the days of computer everything, I don't see a correlation between circuits and colours.

bob gauff

 

I am struggling with a 72 XJ6 which I have owned since 1986. It has been ignored in my garage since 1999. Having decided to start it, I found that with no application of throttle, fuel was gushing out of the carbs (which are 175 CD2(SE?) built for the California market) onto the floor.
One newer SU fuel pump seems not to be working, the other was robbed from an XJ-S and certainly gets fuel to the carbs. I bought a pair of rebuild kits, cleaned all the gummy residue out of the obvious locations, thinking the floats/valves must be the problem. Both floats seem to float properly,off the car in a pan of water, no leaks to be seen. The float valves were yucky so I replaced them and cleaned the attached mini-fuel filters. Set the float heights to 17 mm per the instructions but I still have fuel squirting out. Since it is arduous taking the two carbs on and off, I need guidance. I really have no clue why the fuel pump continues to run.

 

The needle seat valves are not shutting off.
If you are using a fuel injection pump then you will never get the valve to seal.

The MAX fuel pressure should be less than 3 PSI.
A fuel injection pump can deliver 150 PSI.


bob gauff

 

Thank you Bob!

 

A new SU fuel pump found on E-Bay, and your caution on fuel pressure, solved my problem. My car started! First time in years!
Thank you all.