Hello.
On my 1994 XJS, 6.0 the pump N1 turns on when the ignition is turned on, but only continues running for 3.5 seconds.
Is it normal that it does not continue running, even if I loosen the injection rail connection fitting? the flow that comes out during that time is great...
I expected it to continue pumping until the circuit reached a certain pressure or the regulating valve began to return fuel to the return...
The car doesnt start. Crankshaft sensor impedance is 0.75k Ohmios. Inertia switch ok.
Thank you for your help

 

Jaguaralfonso,

The pump running for just a few seconds on initial Ignition On is correct.

Is the pump then running again when the starter is cranking the engine? Also, so you have sparks at the plugs when the engine is cranking?

Paul

 

Thank You!The pump does not pump when I turn the starter motor. I'm checking the crankshaft sensor, which gives an impedance of 700 ohms. Can a failed crankshaft sensor prevent the N1 fuel pump from doing its job?
The last day the car ran last week, it showed low voltage on the dashboard, only 11 volts running. I have to check the alternator, but I thought that with a new battery that I connected with cables, the car should start even if the alternator didn't work

 

The pump does not carry gasoline during the moment the starter motor rotates. It only has gasoline when I turn the ignition, without activating the starter motor. The crankshaft sensor does not seem to work, because while the engine is turning, the rev counter does not go up.
If the crankshaft sensor does not tick, is the pump not working?

 

Thank you so much to everybody! It seems that I have already detected the error. As soon as I changed the crankshaft sensor, the car started easily. It made me suspect that the tachometer did not read anything during the attempt to start with the starter motor.
Now I'm going to check the alternator, since the voltage shown on the dashboard is very low.

 

Jaguaralfonso,

Well done on fixing the starting issue!

Don't pay any attention to the voltmeter on the instrument panel, other than to confirm it's probably under-reading because of poor contacts on the cluster!

Measure voltage at fast idle and idle direct at the battery terminals. Then confirm by measuring at the bulkhead +ve and -ve terminals. That's a far better indication of what your alternator is actually doing.

Cheers

Paul

 

interesting information! Thank you. I don´t understand why just pump for a few seconds even if doesnt reach the right pressure....

 

It is a safety measure. If in a crash the engine stops, the fuel pump will stop and not feed a fire with high pressure petrol!

 

Correct pressure will be present in a properly operating system with ignition signal, as you discovered.
No need for fuel pressure if you have no spark, your marelli ECM was not instructing the EFI to operate.
Slightly different circumstances but continueing fuel delivery in the absence of spark is the cause of the marelli meltdown endued by some.