Nolan Penny and Dawn Mask wrote that SU fuel pumps are being sold
without a capacitor now. That's true, but not the whole story.
The capacitor was used to reduce the amperage across the points and
allow them to last longer. The problem with capacitors is that they break
down over time (just like ignition condensers), the pump points begin
to arc and burn, and the pump quits. Tapping with a hammer causes the
points to bounce and you get a few more miles out of the pump.
SU made a design change a few years back (early 80s?) and replaced
the capacitor with a diode. The diode also prevents the points from
burning, but doesn't break down over time like a capacitor does. The
only problem with diodes is that they are polarity sensitive. If you
convert from positive to negative ground and hook up the pump
backwards, the diode will fry instantly and the pump will quit.
That's why SU now sells both positive ground pumps and negative
ground ones.
One way of telling if you have a diode style pump is that the plastic
cover over the points area has an extra "bulge" on the end that looks
like someone pushed an ignition condenser into the plastic from the
inside when it was soft. Earlier pumps with the capacitor do not
have this bulge.
Someone may have already pointed out these things, but being a Digest
subscriber I am always a day behind.
Cheers, PK
Paul D. Kile
kile_paul@aphub.aerojetpd.com
(916) 355-5162
GenCorp Aerojet
POB 13222
Dept 5784 Building 20019
Sacramento, California 95813-6000
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