[TR] Fuel pump problems

[Randall]

> The mechanical fuel pump has a rubber diaphragm that stiffens 
> in time - especially when exposed to alcohol.  I replaced my 
> TR6 pump with an electric which has no such issues 

Actually, many electric pumps do suffer from the same problem.  The original
SU electric on my Stag, for example; and the original AC on my motorhome gen
set for another.

The one on the gen set didn't stiffen, though; instead it turned to a very
sticky jelly; which spread through the fuel lines and into the carburetor
before the pump quit working entirely.

In addition, some of the older pumps (like both of those above) have points,
which cause no end of problems.  Ask any MG owner about having to tap on the
pump to get it going!

By way of contrast, the original mechanical pump in my former daily driver
TR3A got rebuilt back in the 80s (when CA was using MTBE instead of ethanol)
and was still working fine when the car got wrecked in 2005.  Probably
200,000 miles of mostly city driving.

Then I rebuilt the original pump on my current 56 TR3 in 2008, and it still
works fine today.  I retired a couple years ago, so I don't drive as many
miles; maybe only 60,000 on it so far.  

Electric pumps wear out too.  My 95 Buick is on it's 3rd pump (that I know
of) and hasn't quite turned 300,000 yet.  Rather frustrating, as the factory
pump became intermittent.  When I had it towed to the shop after it wouldn't
start (and I had verified lack of fuel pressure and power to the pump); it
started right up for them!  Then when I went to pick it up, it wouldn't
start again.  Post mortem showed a burned segment on the commutator along
with a ragged edge in the actual pump chamber that was probably catching and
stalling the rotor.

My bout with lack of fuel delivery on the TR3 turned out to be accumulated
crud in the fuel line (twice I told the body shop specifically to cover the
fuel inlet while sanding, both times they failed to do it).  It would shift
around and almost completely block the flow, usually only after I had driven
10 or 15 miles.  Blowing shop air backwards into the tank turned the
remaining fuel absolutely black!  But solved the problem.  (I added a paper
element fuel filter to catch the floating crud.)

-- Randall