Fuel Pump Relay Failure
Symptoms
Engine cranks but won't start. No fuel pressure at the rail. Fuel pump does not prime when ignition is turned on (no whirring sound from the boot area).
Cause
The fuel pump relay fails from age and heat cycling. The XJ-S fuel pump is mounted in the boot (near or in the fuel tank depending on model year), and the relay is a common failure point. The inertia switch (safety cut-off that trips in a collision) can also trip from a hard bump or vibration, cutting fuel pump power without any visible damage.
Fix
Check the inertia switch first, it's in the boot and has a reset button on top.
If the switch hasn't tripped, test the fuel pump relay (swap with an identical relay from another circuit to confirm).
Replacement relays are $20-40.
If the fuel pump itself has failed, replacement is $200-400.
Always carry a spare relay, it's a $20 part that can strand you.
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