If the problem comes and goes you can rule out the timing chain. If the
timing chain jumped it would be behaving poorly all the time.
Intermittant symptoms suggest dirt in the fuel system, or electrical
problems. Dirt can cause partial clogging of the fuel flow which may,
after time break loose and you run fine again. Usually not, though, dirt
usually causes the float valve to not close off and you run way rich.
Another source of the problem is the fuel pump. I had a problem where my
TR6 would stop running as though out of gas although the tank was not
empty. If I manually operated the pump the carbs would fill (you can hear
the gas flowing into the float chambers) and then the car would run fine.
I eventually replaced the pump with an electric one and have had no trouble
And you might have a coil on the way out or the cap or rotor is starting to
degrade. Perhaps the wires are breaking down.
Using the screwdriver method is not valid on Strombergs. The mixture
adjustment is much too limited to see any change in this technique. To
propperly adjust the carburettors requires some type of exhaust gas
meterology (eg: gastester by Gunnison).
Additionally, the manual is wrong about the timing. The timing should be
set to 4 deg ATDC with the vacuum line CONNECTED. The vacuum comes from a
special port on the carburettor that provides vacuum only at idle. Once
off of idle the vacuum goes away and the timing reverts to normal 6 or 8
deg BTDC. But this doesn't explain your problem. Fix this and you will
still have the intermittant problem.
Spindle wear only shows up at idle. Once the throttle is open the trivial
amounts of air that leaks past will have no effect.
St. Louis, MO USA
57 TR3 (getting O/D today)
71 TR6 (in storage)
80 TR8 (Still in re-assembly)
Message text written by Ian
My next door neighbor recently bought a 74 TR6 and has been having
considerable trouble with the engine breaking up. At times it runs
and at others the only way he can make it back home is with the choke out.
(That would seem to indicate it's running lean, no? In using the
screwdriver method to obtain the correct mixture, the RPMs dropped whenever
we raised the damper on either carb. We were unable to adjust either carb
to make the RPMs hold steady or increase.) The needles look perfect and
were probably installed 3,000 miles ago by the PO. My neighbor has
some of the vacuum hoses and found a few leaks but that didn't seem to
correct the problem. The timing is set to 4 degrees ATDC with the
distributor vacuum advance hose removed and plugged. However, there
seem to be much vacuum on that small hose and when we re-attach it to the
distributor, the RPMs don't change. He is currently rebuilding the
carburetors and I was wondering what we should be looking for. The floats
appear not to be leaking and moving freely. Is there any way to discern
throttle spindle wear with the carbs apart? My neighbor (yes, this is a
real person--not me) is very meticulous and has set the valves and done all
of the ignition work carefully to spec. We were starting to suspect that
the timing chain may have jumped, but sometimes, the damn thing runs
perfectly while we're tuning it. We shut it off, put the new air cleaners
back on, start it up and it's rough as a cob.
Any thoughts would be appreciated.