I dug an old SU fuel pump out of my junk box and experimented with the
arcing points problem that is the weak part of this pump. The early pumps
had no arcing protection (capacitor or diode) and hence points would pit
badly and eventually stick together (weld actually). A sharp blow with a
hammer would unstick them, temporarily.
In later years a capacitor was placed in parallel with the points (just like
in the distributor) and even later a diode was used in parallel to the coil.
My old fuel pump had neither. I tried various capacitors first. Small
capacitors were ineffective. I tried an old one out of a distributor and
that reduced the arcing by about half. I finally tried a very large
capacitor (it wasn't marked so I don't know how many mfd) about the size of
a shotgun shell and it eliminated almost all of the arcing. The electrical
values of these capacitors and diodes was discussed on the list yesterday.
Then I tried a diode and it reduced all of the arcing. I don't know the size
(current/voltage) but it was small enought to fit under the plastic cap that
covers the throw-over assemply and points. Hence, I would add a diode to any
SU pump that didn't have one.
Finally, a suggestion for polishing old, pitted points. If they are not
pitted too badly, any set of points can be renewed fairly nicely by
disassembling them (if possible) and polishing them using a high speed
grinder such as a Dremmel tool. Use a grinding disk and polish the points on
the side of the disk, not the edge.
here
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Olin Kane
okane@usa.net
Albuquerque
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