Jeff wrote:
> > Thanks for all the suggestions, I think I've found the culprit: the
> > pump itself. Basically after checking the list of ideas below, I gave
> > the pump a good tap on the top to see what happened; it stopped,
> > another tap and it started again at full tilt. Bugger, should have hit
> > it to start with! I guess the solenoid is sticking or something.
> >
>
> If the pump is like the old SU type then it is probably the contacts that
> close to power the solenoid. They are just like the points contacts in a
> distributor, and get pitted and burnt. If you are lucky you will be able to
> get the cover off and clean them up with a fine file or emery paper (if they
> are not too badly burnt away).
>
> Regards
> Jeff
It's always worth checking (or replacing) the capacitor (aka condensor)
if the points are pitting more quickly than expected. If the capacitor
fails short circuit, then the coil will stay energised and the pump
will just stop working (in this case, you can disconnect the capacitor
as a "get you home"). If the capacitor fails open circuit, then the
unit doesn't fail immediately, but the points will be subject to
excessive arcing and will eventually fail. The capacitor in the pump
works basically the same as that in the distributor. When the points
open, disconnecting the current flowing through the coil, the magnetic
field from the coil collapses, inducing a voltage spike across the
points. The capacitor is there to mop up this spike and stop it arcing
across the points.
Regards,
Arthur
