Well, I've got some resolutions to my queries of late about the green
car, my '71 MGB tourer. To review the exciting adventures in our
previous episodes, I've been suffering from periodic stall-outs at
fairly random times. At first I isolated the cause as the fuel pump,
so I bought some new points and installed them in the existing pump,
as well as cleaning out the hydraulic end of the pump. I did not get
into the middle, mechanical part of the pump -- the spring, plunger,
electromagnet and diaphragm.
Things went well for two or three weeks, then we sputtered to a halt
on the way to school one day. "I know!" Torrey said. "I will get you
a new fuel pump!" I thanked her and said that I'd fixed that one already
so this must be something else. After several tries, the car started
and we continued to school.
Since then I've been assuming that the rebuilt fuel pump was not the
culprit, but just to be on the safe side I installed a clear fuel filter
in the canonical location (replacing the old metal filter that had been
on the car since I bought it). This would let me look into the fuel
lines while under the hood, so that I could see whether I was getting
fuel or not. We also noticed that the ignition coil was getting
very, very hot -- as hot as the valve cover once the engine warmed up --
and have been pursuing that as a possible source of the stalling.
Over the past week I have replaced everything in the ignition system
except the switch on the steering column and the wires from there through
the tach to the coil. I removed the distributor and cleaned it thoroughly,
installed new points, condensor, rotor, cap, wires, and plugs. I timed
the car (and to my extreme delight it started up the first time I hit
the key, and was only a few degrees off -- not bad for eyeballing it)
and was surprised to see the first car I've ever timed that had no
visible points scatter in the timing -- the timing mark on the pulley
did NOT fluctuate, moving only when I turned the distributor to get it
to the right mark (14 degrees BTDC dynamic, for my year). But the car
still died at fairly random intervals.
So I took it in yesterday to Charlie Rockwell, a British car enthusiast
and shop owner who has a sort of Mayo Clinic for sports cars -- a couple
of Sun engine diagnostic computers, a rolling-road chassis dyno, a neat
machine for checking distributors when they're out of the car, and a few
things I probably haven't seen yet, plus the knowledge to use these all
to best advantage.
He gave me some suggestions on what to do in preparation for my smog
test in the upcoming month, and then we hooked the ignition up to the
computer. His oscilloscope verified what my timing light had shown
me, that the ignition timing doesn't vary by as much as a pixel on the
screen, and also that everything in the circuit was wired correctly and
that the voltage and current at every point we checked was just what
it should be. (BTW, I should have pointed out to him that my four-year-old
daughter had rebuilt that distributor. :-)
"So the coil is just getting hot?" I asked. He nodded. "That's weird,"
I said.
"It's not weird," Charlie answered, "it's just British."
And yesterday proved to my complete satisfaction that is IS in fact the
fuel pump that's causing me to stall. The car stalled five times yesterday.
Each time I got out of the car, slapped the fuel pump, heard it glugging
like mad to fill empty fuel lines and float bowls, and I went on my merry
way. I guess it's the mechanical section in the middle of the pump. So
I'll be shopping for a new fuel pump after all. (Danny, maybe you should
call Skip Kelsey for a price quote anyway... :-) I've decided that, out
of respect for the future owner (me, since I don't intend to sell this car
at any date I can imagine), I will replace the fuel pump with a stock SU
unit. This one appears to be the original, and I figure I'll be able to
afford another in 2011. More likely, by then I'll have to replace it
with something that will run methanol or LPG. In any case, if anyone on
the list knows of a source of new SU fuel pumps for less than $89.95, drop
me a line.
(Oh, we also found out why the race car wouldn't run over 4500 RPM at
Laguna Seca in the Labor Day race. Write if you want to know.)
--Scott
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