I have a 1985 Jaguar XJ6 Series III.  Car has a brand new battery and
even if the engine turns the car wont start.  These work.  Checked the spark plugs,
battery, etc. Apparently there is no power coming into the fuel pump. 
Need to know where the fuse/relay for the fuel pump is (so this can be
replaced).  Would like a schematic diagram showing from the web
showing this.  Hopefully it only the relay that needs to be fixed (i
truly believe the fuel pump is ok.  Also advise where i can buy/order
the relay for this off the web. thanks a ton.

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Clarification of Question by silvercouch-ga on 17 Jun 2002 20:55 PDT

see my posted comment for clarification

This page does not have a diagram but it has a good description for
working on the fuel pump www.seattlejagclub.org/tech/pump.html. There
are lots of links to other enthusiasts.

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Request for Answer Clarification by silvercouch-ga on 21 Jun 2002 08:20 PDT

The fuel pump is working and Doug Dwyers article was clearly very
helpful. By checking the system - the fuel nozzles are pressurized but
not firing.  I did replace diode relay.  The fuel pump does activate
though with the car on there is no power to the fuel injection
nozzles.  can you please clarify on addressing this issue.

look for a little red box mounted on the firewall of the engine
compartment, this should be the relay switch for the fuel pump,
replace it and see if that does any good. Also, does this problem
happen specifically when it is hot outside?

no promises, but this should be your repair part

http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=15604273&prmenbr=5806&usrcommgrpid=28587747

No the problem with not starting is not temperature related and this
is the first time it has happened.  Is there a fuse for just the fuse
pump(based on your current answer it seems i should replace the relay
switch). can you please clarify.

I always get the Haynes book for any car that I get, in that book they
take whatever car, and totally disassemble it, and then re-assemble
it, showing every step of the way with a photo, and a text
description. I have no doubt that the haynes manual for your car will
show you exactly what you want. It can be found here:
http://www.haynes.com/na101.html#anchor564187

You can order these books online, or you can usually find them at
stores like PepBoys, or most other auto parts stores.

While I do not know specifics for Jaguars, in most cars the main relay
is what supplies power to the fuel pump. I only asked if it was
temperature related because in old Hondas, at least, the fuel pump
often requires great power and the main relay can over heat in the
summer, causing start difficulties during hot weather.

Chances are your main relay has worn out, and sufficient power is not
being supplied to the fuel pump, and thus the programmed fuel
injectors in your model are not functioning properly. A simple
replacement of the main relay should do the trick. If you can, stop by
a local NAPA store (for I know they carry the relay) and plug it in to
see if it fixes the problem, if not, I believe you can return the
part.

Just for fun, check the main relay on your car and see if it is made
by Mitsumi. I know that their old relays had some problems with weak
solder joints and caused this type of problem. There are even stories
of people who have been able to carefully re-solder the joints on the
relay's circuitry and fix the problem, but I do not recommend this.
Good luck, and I hope this info helps :)