David
You could check that the petrol tank breather system is not blocked by
running with the petrol cap off or loose.
It should be fairly easy to take off the petrol return hose at the tank (I
think its on top?) and test the return flow without the engine running but
with ignition power power to the pump.
The rich running problem could be a broken (or leaking) diaphragm link bolt.
When manifold pressure rises it pulls the roller up the datum track and, I
presume, weakens the mixture. I had one break on my car and it was as if the
choke was half on.
The diaphragm link bolt is only made of threaded plastic and IMHO is a weak
point. It may be difficult to tell if its broke by just looking, as springs and
pressure tend to keep the link in place instead of falling over. You can test it
by taking the plastic side cover off and reving the motor to get full vacuum
then you can see if the roller and side pieces are sucked up the datum track.
Fixing it is only a matter of taking off the Depression chamber, fishing out the
link roller etc. and replacing it.
I would rather replace these rollers FIRST rather than altering the datum track
setting as the replacement job is straightfoward.
Dont give up - the end result is well worth the effort of troubleshooting.
Peter H
73 TR6
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