1986 series 3 xj6 fuel pump 4.2
 

when your car is idling do you hear your fuel pump buzzing? eratically?
Does your pump get power when the ignition is on[engine not running] or only when cranking?
Just had to tow the xj6 home as would only run on aerosol starting fluid, there is fuel at the rail but im doubting the pressure, as i was driving the revs were dropping as if being starved for fuel until it would only run at idle then not at all.
Richard

To my ear, my correctly working fuel pump has a very consistent hum. Not quite a buzz or rattle but it definitely makes noise and if its very quiet you can hear it from inside the cabin with key in II position and car transmission in 'D'. The noises should not be erratic when idling whatsoever and I would imagine erratic-ism could have two causes: improper electric signal controlling delivery OR internal failure of the fuel pump itself.

Pump should get power with the key in the II position and the car transmission in 'D'.

I'm not sure but I don't believe that the pump gets power with key in III position with transmission in 'P' prior to crank but I would imagine so.

If you can, fit a fuel pressure gauge to the rail so you can get clear readings to identify the source of the fuel delivery failure. This certainly sounds like a bad/failing fuel pump to my ears from your description but I'm sure others with more experience will chime in and ask the right questions. Perhaps consider fuel pressure regulator at the front-side of the rail as well.

I agree


I'm a bit confused by position II and III designations.

On a 6 cylinder Series III the fuel pump will not power-up until the key is turned fully to the 'start' position (is that what you mean by "III"?).

Simply turning the key 'on' will not power-up the pump


Agreed again !

Cheers
DD

Update, the problem was the fuel change over solinoid deciding not to work so a full tank of fuel was not getting through while the pump was sucking from a dry tank, for now i have fitted a brass t piece with a ball valve on each side so i will have to open the boot to change over

:icon_eek:
Don't forget to select the same side tank on the dash switch or you'll pump all the fuel into the wrong tank thru the return!