"90% of all carburettor problems are electrical." Except that in
this case it was the other way around!
This being a beautiful day in New England, I wanted to move the GT6
out of the driveway so I could pull the Spitfire out the garage. I
had last driven it maybe three weeks ago, but it had been running
like a champ at the time. When I fired it up it didn't want to run
smoothly. It seemed as if some of the cylinder were firing, but
poorly. Cracking the loud pedal open just made it shake more.
Pulling more choke usually makes it run stonger up to a point, and
the engine was cold. Well, okay, summer-temp warm. In this case
pulling the choke more did nothing at all, no black smoke, no change
in the how it ran, no nothing.
A check of the cables and linkages showed all to be connected and
functional. My first thought was that one float had stuck closed, so
that side was getting no gas. This car has twin SU's, so carb work
is quite easy. I pulled the float covers off and both looked just
fine, about the same level of gas and both needles free. Ah well,
that must mean it's electrical after all.
Checked the point gap, normal. Checked the timing, exactly where I
left it. Checked a few plugs, just fine, gapped just right. The
rotor and cap looked okay, though the rotor spring contact had gotten
a bit rusty. All the plug wires were in place. A bad condensor
should have made all the cylinders run poorly or not at all.
Hmmmm... Okay, so it wasn't electrical after all.
Next I thought maybe it had developed an air leak. Perhaps the lift-
the-dashpot-pin trick would show a problem. I pushed on the front
carb's lifting pin, and it worked just fine. I pushed on the
rear carb's lifting pin and it wouldn't budge. What the...?
So I pulled the dashpot cover off and lo! the plunger was stuck solid
in the cover. The spring-loaded needle was free and the dashpot came
out of the carb body just fine, but it was stuck in the cover. Minor
pressure with the fingers didn't free it. Finally I drained the oil
from the filler, placed it upsidedown on a piece of wood on the
workbench and tapped the plunder with the wooden handle of a hammer.
It moved! A few more taps freed it completely.
I couldn't find any obvious piece of dirt or shellac from dried gas,
but that must have been what happened. Golly, it had been sitting
for only three weeks. Don't know if the problem was with the damper
shaft or the dashpot's fit into the cover, but I cleaned everything
and put it back together. It ran like a champ.
Sometimes electrical problems really are the carburettor.
--
Jim Muller
jimmuller@rcn.com
'80 Spitfire, '70 GT6+
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