Jon -
I disagree that the problem is carburation. The fact that several cylinders
are wet indicate that you are getting fuel to those cylinders. I have a few
pretty cantankerous MGs (MGA, TD, and J2) and rarely find that fuel alone
will cause an engine to run that poorly - unless it's not getting any at
all.
Ignition IS enough to cause the problems you mention and while I understand
you have changed out many parts, I offer a few really obvious questions to
ponder:
1) You say that the firing sequence is 1-3-4-2. This has been the sequence
since time immemorial, but that is only the ignition sequence. Are you sure
the distributor is set in proper relation to the camshaft? A quick check can
be made by setting up the distributor to what you believe to be #1
top-dead-center. In this position, the #1 piston should be at
top-dead-center. Check with a coathanger wire in the plug hole or look for
the timing mark on the flywheel.
At #1 TDC, the lobes on the camshaft for #1 cylinder should be pointing
roughly at 10 and 2 o'clock.
2) What is the state of the charging circuit? If the battery is much below
10 - 12 volts, it may be enough to turn the starter, but it may not be
enough to give a really GOOD spark at the plugs. My J2 runs on a tractor
battery and I can crank it all day, but if I don't have a strong charge, it
won't even start. (Not that J2 engines are much like MGB engines, but the
physics are the same, unless Lucas messed with them somehow. <g>)
3) What is the actual spark voltage? If this is too low, the engine may
refuse to fire, or run on only one or two cylinders. Most local garages have
an engine analyzer which should be able to diagnose weak spark or
out-of-time conditions.
I'm convinced this is an ignition or timing problem. In years of touring
with MGs, every single breakdown I or anyone I was travelling with had,
where fuel was suspected, turned out to be ignition. (Except for the odd
dirty or sticking fuel pump.) If the ignition is right and it gets any fuel
at all, it will run! Maybe not perfectly, but it will run.
If you still need help with a quality and inexpensive rebuild of your SUs,
call Jim Taylor in Bartlesville, Oklahoma. I don't have his phone or address
with me, but he should be in the phone book. I believe the street address is
on Harned Avenue. If you can't find it drop me an e-mail at lew@uci.com and
I'll look it up.
Good luck. Let us know what you find.
Regards
Lew Palmer
lew@uci.com
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From: mgs-owner
To: mgs
Subject: Re: '73 MGB, STILL running on #2 only!?? (LONG)
Date: Tuesday, April 04, 1995 9:13AM
Jon writes:
> The only scenario I can imagine is: cylinders
>intake in 1-3-4-2 order, let's imagine that the forward carb is plugged and
>the back one is spitting out mostly gas. This fouls 3&4, then 2 draws
across
>the bypass tube and gets just enough gas to run, but there is none left for
>#1?
Needless to say I don't have any brilliant insights into this perplexing
situation. I am still stuck on one point that dates back to the beginning:
I appreciate your arguements that the car is running on #2 alone (engine
dies when #2 wire is pulled, no change when any other wire is pulled). But
I'm intriged by the dry-ness of the #1 plug. My confusion is: can the
engine (with reasonable compression on all four cylinders) really run
(albeit rough) on only one cylinder? I'm surprised at that (though, not
because of my vast experience on the matter). Any comments from list
members? I'm just wondering if an assumption being made here is false.
Jon: have you checked the carbs... do the pistions rise freely? Is the
throat set reasonably well? Has a needle been bent or dropped out of the
piston? Carburation is about all that's left...
Please keep us updated on your progress. I'm very interested in this
puzzle.
Will Zehring
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