400SE fuel pump problem

[Hoopy400]

Looking for some help from the accumulated knowledge. Went for a drive yesterday, got about 10 miles from home went it suddenly became very quiet. Luckily happened close to a pull in so I managed to get off the road. Quick check of fuses, all ok. SWAMBO towed me home which was an interesting experience. First test was on fuel pump, no fuel to distributor rail, but pressure in the pipes. Fuel pump off and bench tested, all working ok. Back on car, pump works when ignition is switched on and primes ok but fuel pump does not operate when engine turned over. This suggests that there is no signal to the ECU telling it that the engine is turning over and asking for power to the pump (is this correct ?). Any recommendations as to what sensors to look for and when to go next in terms of diagnosis. Am hoping that there is a sensor that has failed but have not found any guidance as to what that might be. Any suggestions welcome. Many thanks

[lesR]

Could it be the inertia switch that is located on the bulk head? I think it's designed to cut off the fuel in an accident but not sure what or how it fully works.

Les

[RayTVR]

I had exactly this on a V8S (400 engine) . Inertia switch itself was ok but wiring to it fell off when I touched it. Either this or fuel pump relay would be best bet.

[Hoopy400]

Thanks both, will check those out.

[SLB]

On my cars the fuel pump is not on with the ignition, its only on when cranking. The air flow meter sends a signal to the ECU which in turn tells the fuel pump relay to trigger. Maybe the relay is stuck but it sounds odd that yourrs seems to be working completely the wrong way around so has the wiring to the relay been touched?

[Lesliehedley]

If it's a flapper engine then I believe the fuel pump doesn't run until the air flow meter flap moves during cranking. check the pump runs when you move the flap by hand with the ignition on.