[Healeys] fuel pump
Bob Spidell
bspidell at comcast.net
Sat Apr 22 20:35:19 MDT 2023
Hoo boy ... SU pumps have been a personal bugaboo for decades. I have tried:
- points with capacitors (SU and home-rolled)
- points with diodes (SU and home-rolled)
- points with TVS diodes
- points switching power transistors
- SS with SU conversion kits
- SS from SU
Earlier pumps had no arc-suppression, then SU added capacitors (similar
function to condensors with ignition points), then diodes in a
'flywheel' circuit, to shunt the large voltage/current 'backflow' from
the pump body/solenoid. The SU SS pumps use a Hall Effect sensor to
switch a transistor (similar to what Pertronix uses). The late Dave
DuBois--who all but dedicated his retirement to designing a bulletproof
pump--used an optical sensor for switching (I believe he also designed
the points/transistor system which was unsuitable because it DIDN'T
allow sufficient current across the points to clean them).
It's a crapshoot; some owners report years of reliable function from
points-based systems; some SS units don't last long at all. Dave DuBois
was a meticulous rebuilder--he would run pumps on a test rig for 24
hours before shipping--but I never got infinite reliability with them.
Like Richard said, you can keep a points pump going with a whack from a
hammer, or pull the pump off, file the points and readjust the preload
on the solenoid to get you home (I once rebuilt one in a hotel room).
I've got 2 or 3 pumps for my BN2--I forget which one's in there--but
always carry a spare. Towards the end of my extended trips--up to 5K
miles--I carried two spares in my BJ8 and have enough parts and partials
to assemble a couple.
It's been a few years, but the last time I sourced points sets they were
crap; they appeared to be made with a shiny metal like silver, and they
should be made out of tungsten, which is a dull grey color. The 'silver'
ones would start eroding within just a few miles. Anyone know if decent
points are available (last I heard there's a similar issue with ignition
points)? One issue with points is their arcing, if not sufficiently
suppressed, generates ozone which can quickly corrode internals, so make
sure the one-way vent valve on the control end is functioning properly.
FWIW, I haven't seen a failure that I can definitively attribute to
contemporary fuel blends.
It's some consolation, I suppose, that even modern fuel pumps are known
to fail; but with some of them you have to pull the tank out to get to
them. And don't get me started on engine-driven pumps with 6V ignition
systems (it's a toss-up if the engine starts before the battery dies).
Attached photo is either one of Dave's rebuilt units or an OEM SU; I
still don't have a clue why that happened (I think Dave eventually went
to a Hall Effect setup, too; my memory is blurry).
On 4/22/2023 5:47 PM, Jean Caron wrote:
> Why not rebuild the fuel pump?
>
> Jean
>
>
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