No 1 plug may not be firing. Clip your timing light onto each plug in turn
and check that it flashes. Alternatively remove the lead from each plug in
turn and connect it to a spare plug which you lay on the block - check that
all spark. Could still be a bad plug, though, 'cept you have replaced
yours. Another way is to remove each plug lead in turn (if you do this with
the engine running watch out for shocks) and listen to how the engine
responds. If the rough running gets even worse on three of the cylinders
but remains the same on the fourth, than that cylinder is not firing for
whatever reason. Then you have to determine why.
PaulH.
----- Original Message -----
From: <wtsnyder@juno.com>
To: <mgs@autox.team.net>
Sent: Wednesday, February 28, 2001 1:52 PM
Subject: Engine Running Rough
> Hello list. I'm back to a problem I've been ignoring to work on other
> things for the past month. I purchased a '72 BGT with a later 1979 18GV
> engine. It was running very well at the time of purchase except for a
> very loud aftermarket fuel pump (the little box type). After a short
> jaunt to town and back, I was climbing the last hill in my driveway when
> the engine began acutely running very rough. Plug #1 one seemed to be gas
> fouled. This engine is fitted with aftermarket sidedraft Mikuni carbs and
> has the 1975-1980 45DM distributor with electronic ignition (amplifier
> box mounted on passenger fender well under coil).
>
> Since the initial episode, I have:
> 1) Replaced the dizzy cap (it appeared to have a hairline crack near
> where the #1 plug wire attached).
> 2) Replaced the plug wires.
> 3) Gapped and fitted new plugs.
> 4) Replaced a leaking fuel tank.
> 5) Replaced the fuel pump. (Special thanks to Barney Gaylord for his
> advice and tech article on aftermarket low cost fuel pumps and their
> fitting!)
> 6) Rebuilt rear brake cylinders.
>
> Yesterday, I put petrol in the tank and cranked the engine. It still runs
> just like it did before the work.
> Any advice on where to go from here? I have a timing strobe, but I am a
> neophyte in its use. Could the timing chain have slipped a link and
> thrown the timing way off?
> Everyone's input and advice is appreciated as always.
> Bill Snyder
> '66 MGB
> '72 BGT
> PS I was able to purchase the '72 BGT parts car with LH type OD tranny
> for $200. I plan to eventually fit that tranny on this problem GT if I
> can get her running well.
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