If the tach was erratic then that indicates a problem in the ignition LT.
If two plugs were firing and two not then I would hazard a guess at a
problem inside the dizzie. Very small gap and a bit of imbalance in the
dizzie cam lobes or shaft wobble? But that doesn't explain why an immediate
restart was OK only for the problem to arise again shortly after. A
heat-related problem i.e. a break or short in a wire would probably need
time to cool down and 'repair' and not allow an immediate restart. Hmmm,
interesting.
Like the one in this months MGOC mag where the engine ran perfectly with the
bonnet up but not at all with it down.
----- Original Message -----
From: "Mike Winney" <mgb@cableone.net>
To: <mgs@autox.team.net>
Sent: Sunday, March 03, 2002 10:42 PM
Subject: Strange Ruff Running Engine Quiz
> Hello all,
> I just corrected a ruff running engine problem that suddenly appeared that
> had interesting symptoms. Thought it might be fun to give the particulars
> and see if anyone out there can come up with the cause. I'll divulge the
> answer by Wednesday PM.
> FACTS---68/9 MGB GT, Engine 18GF(de-smogged) HS4 carbs(62-67), less than
> 700 miles on all ignition components inc. 45D4 dist., Lucas Sport Coil,
Ign.
> switch, points, Condenser, rotor, cap, wires.
> CIRCUMSTANCE---Cold engine starts quickly ,readily revs to 5+k (at 6k
> altitude). After about 30 minutes drive engine began to run very rough.
> Tach needle erratic, could barely keep running at stop. Pulled #1 plug
wire
> with no change in engine speed. Same for #2. Only #3 and #4 were firing.
> Then determined there was no HV in #1 & 2 plug wires. Turned off engine.
> Immediately restarted it and it ran normally again for awhile before
problem
> recurred. I went through my usual check list, but couldn't figure why
only
> #1 & 2 spark loss with 3 & 4 firing normally. And why would the engine
> immediately restart? Problem solved and corrected. If no one gets
answer
> by Tuesday PM then I will give a couple of clues. Good luck!
> Mike Winney
> 68 MGB GT
///
/// mgs@autox.team.net mailing list
/// or try http://www.team.net/cgi-bin/majorcool
///
|