Jeff---Backfiring is typically an ignition problem. As the (rear
wheels) drives the engine, fuel and air are still getting sucked into
it. When there is no spark to ignite the mix, it can accumulate in the
exhaust. When spark momentarily returns, we get a backfire. This
momentary loss can happen for a variety of reasons.
If the spark is still present and the engine still won't start, it could
be that the spark is occuring at the wrong time, in relation to the
cylinder that should be seeing it.
Look for wiring that could be drooping, or losing contact when things
get hot.
Check the ignition timing with a strobe light, to be sure it's in spec
at idle, and thru the rpm range to 3,000.
Engines can seem to run well and yet be far enough out of time to where
the spark has a choice of going to the wrong dist. cap terminal.
Sometimes the damper cap on a carburetor can be an indicator as to which
"side" of the engine isn't happy, and it will blow off! (Leaving each
cap really loose will make this apparant, if you don't mind losing one)
Dick
From: jmackd1@yahoo.com(jeff m)
Trusty TR6 dies
My trusty TR6 finally met a tow truck. On the way to work yesterday, got
on the interstate, dropped it into 4th gear to settle into the commute
to the city, all the sudden the car started bucking and missing
horribly, it gave me enough time to get off ther interstate and into a
store parking lot. Before it died it gave a hellacious backfire. What is
interesting is the problem is repeatable. After sitting in the garage
all day, i cranked on it and it fired right up, drove around the
neighborhood, no problem. Then i held the rpm at 3000 and after a minute
or so, it started sputtering and eventuallly died with a huge backfire
again. The engine has good spark and is getting fuel, could this be a
weak coil or weak fuel pump. Car is completely stock except for Crane
XR700 electronic ignition. Oh, it has weber carbs on it too.
Thanks in advance
Jeff
'75 TR6
Austin, TX
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