Reply to: COLOR TUNE NOT FIRING?
Shortly after I got my TR2 I used the colortune to tune it. The colortune
showed me that cylinder 3 was not firing at idle. When I revved up the motor,
cylinder 3 would come on line, and in fact, the car ran pretty well. I diddled
with the rear carb, and got cylinder three running at idle. Moving the
colortune over to do the front carb, I now found that cylinder 2 was dead!
Again, only at idle. Frobbing the carbs would move the problem from cylinder
to cylinder, but always one cylinder was dead at idle. I never actually traced
the problem in a scientific manner, but I found out that I had weak valve
springs. They had sagged to where the free height was the same as the
installed height. In fact, I could open any valve by pushing it down with the
palm of my hand. New valve springs fixed the problem, with the exception that
when installing them I discovered a blown head gasket! I had been using
compressed air to keep the valves up, and heard this burble-burble-burble out
of the radiator :-(. I wound up doing a "cheapie rebuild": I pulled the
pistons and sleeves out, replaced the crank bearings, replaced the rings,
cleared out all the passages, straightened the head with a big file and a
machinist's straightedge, and lapped the valves. Then I bolted it back
together. Now the Colortune showed idle on all four cylinders. And the car
was about as fast as it had been BEFORE all of this :-(.
My guess about the non-firing-at-idle cylinders, was that the weakly-closed
valves were letting exhaust gases into the intake tract in precise phase to
prevent the "bad cylinder" from getting any intake gas. It wouldn't take much
exhaust gas to pretty well destroy the manifold vacuum. What do you think?
- Jerry
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