Aloha,
OK I need help. I have a 93 XJ6 with 80,000 miles. Three months ago it refused to start. After listening in the trunk I could not hear the fuel pump. I changed the relay and the pump. Started and ran great. Than last month it stalled on the freeway and refused to start. I got it towed home and listened for the fuel pump. It did not turn on. Pulled the pump for a new one (Bosch). Car sputtered so I opened the rail to check pressure, Lots of fuel comes out. Try to crank and it starts. After 10 minutes it dies again. Fuel pump does not turn on. Try on position and the pump does not turn on. But I could hear the pump go off and on during the crank. Open the rail and blow out a lot of gas. Could the fuel be getting too much pressure and turning off the pump? Looking for any help. Fuel pressure regulator? Crank Sensor?

Car has spark. turns over strong, rail full of gas but fuel pump turns off.

 

avensdad:
(Welcome to the forum, by the way!)
I once had an intermittent fuel pump issue due to a failing relay. I know you already replaced it, but it doesn't hurt to swap it out again with one that is known good from another system just to eliminate the possibility.

If I recall, a quick and dirty test of the pressure regulator is to remove the vacuum line and if fuel comes out you know there is an internal problem. I also believe that if the CPS is working, you should be reading a couple hundred RPMs during cranking. If not, that's generally a sign that it has failed.

I'm not the expert on these things, but this is what occurs to me off the top of my head. Others may chime in.

Best of luck!
Scott

 

Hi avensdad,

The fuel pump relay and the fuel pump wiring circuit are prime suspects. Also, on our '93, there is an electrical connector in the wiring between the fuel pump relay and the fuel pump. The connector is behind the battery, and on our '93 the connector either worked itself loose or I accidentally loosened it while changing the battery. See the photos at this link:

Welcome to Jag-lovers - Members Photo Viewing Page


If that connector looks alright, I would recommend that you follow this diagnostic procedure, courtesy of Bryan N at the Jag-Lovers forum:

1) With ignition OFF
2) Remove fuel pump relay (black base, right rear corner
trunk above BFM)
3) Do you get 12 volts at pin 30 (Brown/yellow) of the fuel
pump relay base from fuse C6 in right fuse box?
4) If yes, jump pin 30 (Brown/yellow) and pin 87 (Blue/red)
in fuel pump relay base - does the pump run continuously?
5) If pump does not run, fault is in the wiring / connector
between fuel pump relay and pump
6) If pump runs, suspect fuel pump relay is defective.
7) Replace / re-fit fuel pump relay
8) Remove oxy sensor heater relay (yellow base on firewall)
9) Do you get 12 volts at pin 30 (Brown/pink) of the oxy
sensor heater relay base from fuse C4 in right fuse box?
10) If yes, jump pin 30 (Brown/pink) and pin 87
(Blue/purple) in oxy sensor heater relay base - does the
pump run continuously?
11) If pump runs, suspect oxy sensor heater relay is defective
12) Replace / refit oxy sensor heater relay
13) Remove EMS main relay (black base on firewall)
14) Do you get 12 volts at pin 30 (Brown/yellow) of the EMS
main relay base from fuse C1 in the left fuse box?
15) If yes, jump pin 30 (Brown/yellow) and pin 87
(White/brown) in EMS main relay base
16) Try this both with the ignition ON and the ignition OFF
17) Do you hear the fuel pump give its half-second priming
burst? [You can repeat this many times and you (or an
assistant listening at the open filler neck) should hear the
half-second 'whirr' of the pump every time you jump pins
30 and 87 of the EMS Main relay base]
18) If yes, suspect the EMS main relay OR the EMS ECU is
defective (the latter, very unlikely but possible)
19) Turn ignition OFF
20) Replace / re-fit EMS main relay
21) Remove Ignition 'ON' relay (on a '94 it should be in a
white base on the firewall but on a '93 it may be buried
under the dash behind the radio)
22) Do you have battery voltage at pin 30 (Brown) of the
Ignition 'ON' relay base?
23) If yes, temporarily jump pin 30 (Brown) and pin 87
(White/pink) in the Ignition 'ON' relay base
24) Do you hear the half-second priming burst from the pump
each time you jump those pins in the Ignition 'ON' relay base?
25) If yes, suspect the Ignition 'ON' relay is defective or
fuse A5 (fuse A3 on ‘94 models) in the left side fuse box -
but if either is defective, you will get NO dash lights when
you turn on the ignition.
26) If when you jump pins 30 and 87 of the Ignition ‘ON’
relay base you do get dash lights but you do not hear the
half-second priming burst from the fuel pump suspect the EMS
Main relay.

Please keep us informed!

Cheers,

Don