Mechanical fuel pumps

[shibbs]

Evening all,
I am trying to trouble shoot and get to the bottom of a problem that is really starting to P*!s me off!!!
Does anyone know what the symptoms will be for a mechanical fuel pump that is not working properly or is there a way to test one?
Also, in what way do they fail, do they degrade, giving certain symptoms or do they just give up (i.e - i'm barking up the wrong tree?) ?

Cheers all..

[ColinR]

The usual reason for a mechanical pump failing is the rubber membrane getting brittle and splitting. I suppose the cam or foot that drives it may wear away but that is unlikely. The other possibility is the foot (sorry don't know the correct name for it) sticking open so it is not being driven correctly by the cam which would give a limited fuel flow.

There's not much to them so they are easy to strip and clean up.

On Fords if the membrane split is used to pump petrol into the sump so watch out for the oil level rising. If it does STOP and do not run the engine until you have sorted out the problem!