Rescued XJ40 fuel pump query.
#1
Rescued XJ40 fuel pump query.
Hello all. I recently saved an xj40 from the crusher. Late 94. Rust free 3.2 high spec. Lovely colour. But deeply neglected. Already unloved these models are dwindling in number so I had to save her. So a repaint and service later and she's safe.
My query is, there was a fuelling issue. No power going to rear blue pump relay. I bypassed this relay to start pump and get car driving. Does fuel pump run constantly in normal course of events? And if so could I run a new live source to relay from switch on dashboard to double as an anti theft measure? Or will I burn out pump shortly? Thanks J. I will post pics soon. She's lovely!
My query is, there was a fuelling issue. No power going to rear blue pump relay. I bypassed this relay to start pump and get car driving. Does fuel pump run constantly in normal course of events? And if so could I run a new live source to relay from switch on dashboard to double as an anti theft measure? Or will I burn out pump shortly? Thanks J. I will post pics soon. She's lovely!
#2
The pump needs to run continuously if the engine is running. The relay is disabled if the key is shut OFF or the inertia switch is tripped.
Inertia switch is there to prevent the pump running in case of 'accident' or IMPACT.
You don't want fuel to be fed to a fire in the event of a crash.
This might be the reason the relay has no power??
bob
Inertia switch is there to prevent the pump running in case of 'accident' or IMPACT.
You don't want fuel to be fed to a fire in the event of a crash.
This might be the reason the relay has no power??
bob
#3
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Hi jjd,
I'm happy to hear you've saved another XJ40 from the crushers and I'm looking forward to seeing photos!
The fuel pump relay receives its control signal via the Oxygen Sensor Heater Relay, which is mounted on the right bulkhead in the engine compartment. The battery power for the fuel pump relay comes from Fuse C2 (25A) in the fuse box at the base of the right A-pillar. The O2S heater relay receives its battery power from Fuse C4 (10A) in the same fuse box. You might check those fuses, then try swapping in another relay for the O2S Heater Relay to see if the problem is resolved. If the relay is the original blue Hella, they are known to be problematic.
You can download the Electrical Guide here:
Jaguar XJ40 Electrical Guide 1993-1994
Please keep us informed.
Cheers,
Don
I'm happy to hear you've saved another XJ40 from the crushers and I'm looking forward to seeing photos!
The fuel pump relay receives its control signal via the Oxygen Sensor Heater Relay, which is mounted on the right bulkhead in the engine compartment. The battery power for the fuel pump relay comes from Fuse C2 (25A) in the fuse box at the base of the right A-pillar. The O2S heater relay receives its battery power from Fuse C4 (10A) in the same fuse box. You might check those fuses, then try swapping in another relay for the O2S Heater Relay to see if the problem is resolved. If the relay is the original blue Hella, they are known to be problematic.
You can download the Electrical Guide here:
Jaguar XJ40 Electrical Guide 1993-1994
Please keep us informed.
Cheers,
Don
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