I have a 1988 xjs , I am getting no voltage to the right bank (B) injectors this somehow is related to the fuel pump relay.If I wire the fuel pump to the battery it starts and runs fine on the left bank , I have two other xjs's so have have been swapping parts over , it's not the ECU nor the power resistor .Can anybody please help? Phil.

 

Have you checked the rotor arm? On the Marelli system it is a split unit but I'm not sure what the symptoms of failure are.

 

Hi , Yes , I'm getting fire to all 12 plugs.

 

all 12 injectors have a permanent feed via the ' main relay ' next to the fuel pump relay in the boot,

the injectors will always have 12v with the ignition on, the wires then go to the power resistor behind the right hand headlight ,

the wires then go to the injector ecu in the boot ( trunk ) which using several signals fire to ground to complete the circuit for the injectors

i would suggest that the ' main relay is either faulty . or not the right one

the main relay ( in the trunk over the battery ) is denoted by having a red strip on the relay top , the main criteria for the main relay is that both output pins No87 must have power going out to the injectors, if only one pin 87 is powered then one bank won't work

usual suspect is a ' normal ' relay has been installed with only one pin out for terminal 87

hope this helps

BB

 

on further study of the wiring diagram for the injectors it appears that the fuel pump relay also gets its power from one of the output pins of the main relay ,

when you power the fuel pump directly the power is back feeding directly to all 12 injectors as described above ,allowing the car to run ' normally '

i would deduce the ' main relay ' is the wrong relay and you need one with two pin 87 outputs ,

BB

 

Hi BB, Thank you so much for your help you were absolutely right , the fuel pump relay had packed up and I had replaced it with the wrong one along with the main relay, now running great again, thanks again.
Phil

 

cool

happy motoring

BB

 

Good sleuthing, BB

Cheers
DD