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MGB 1972 MGB, Head Gasket replaced...runs very poorly.
- Thread starter borjis
- Start date
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oy vey!
Replacement gasket had no effect...so the moss fancy one is probably fine.
I'm thinking at this point is HAS to be ignition related....and that not having
proper working ignition is affecting vacuum...so I'm going to try another distributor
cap and possibly plug wires and new plugs and bypass the coil to distributor wire
with a new one. That wire is VERY brittle and seems untrustworthy.
The problem and the way it runs and that I seem to be smelling unburned fuel
is leading me this direction.
Replacement gasket had no effect...so the moss fancy one is probably fine.
I'm thinking at this point is HAS to be ignition related....and that not having
proper working ignition is affecting vacuum...so I'm going to try another distributor
cap and possibly plug wires and new plugs and bypass the coil to distributor wire
with a new one. That wire is VERY brittle and seems untrustworthy.
The problem and the way it runs and that I seem to be smelling unburned fuel
is leading me this direction.
ok getting closer...this seems to be an ignition problem.
Twice yesterday while barely running, with pedal pressed half way it ran perfectly for a few
seconds, then ran poorly then perfectly again for a few seconds.
I put brand new plugs in...same issue BUT when I pulled the 4th plug, (engine was warm by this point)
I saw a mist / fog smelling like gas arise out of the spark plug hole.
I've been smelling unburned fuel this whole time having the problem and my brother said he
saw black smoke coming out when I tried driving it a few weeks back.
Also, I pulled #4 plug wire and it runs THE SAME poorly way! - no difference!
I have a brand new distributor cap and plug wires arriving today or tomorrow, I think it could
be one of them.
Twice yesterday while barely running, with pedal pressed half way it ran perfectly for a few
seconds, then ran poorly then perfectly again for a few seconds.
I put brand new plugs in...same issue BUT when I pulled the 4th plug, (engine was warm by this point)
I saw a mist / fog smelling like gas arise out of the spark plug hole.
I've been smelling unburned fuel this whole time having the problem and my brother said he
saw black smoke coming out when I tried driving it a few weeks back.
Also, I pulled #4 plug wire and it runs THE SAME poorly way! - no difference!
I have a brand new distributor cap and plug wires arriving today or tomorrow, I think it could
be one of them.
So my brother who repairs british cars on the side, finally had some time to take a look at my situation.
Compression test: 150 psi on all 4 cylinders - GOOD
Spark test: good
distributor test: good
He said: It's the carburetor, remove it and bring it over for a rebuild.
I take the carb off and low and behold....there's a POOL of gas in the manifold!!
We take the weber DGV apart and find that the power valve diaphragm is not only badly wilted,
but has 2 small tears in it!
Someone earlier in this thread had mentioned ethanol damage....well you were spot on.
It would seem the carb is actually the problem all along and that my mgb is flooding badly as a result.
So I have a weber rebuild kit on the way and will report back next week when it's been done
and if that solves the issue.
Compression test: 150 psi on all 4 cylinders - GOOD
Spark test: good
distributor test: good
He said: It's the carburetor, remove it and bring it over for a rebuild.
I take the carb off and low and behold....there's a POOL of gas in the manifold!!
We take the weber DGV apart and find that the power valve diaphragm is not only badly wilted,
but has 2 small tears in it!
Someone earlier in this thread had mentioned ethanol damage....well you were spot on.
It would seem the carb is actually the problem all along and that my mgb is flooding badly as a result.
So I have a weber rebuild kit on the way and will report back next week when it's been done
and if that solves the issue.
okay so finally, as my friend put it: "The Demon of Morris Garage has been VANQUISHED!!!"
I need to remind myself when something is having weird issues that don't make sense, it's highly likely to be multiple problems
and thats exactly what was going on here. It was the coincidence of other failures happening just after the head gasket
blew that threw me way off.
so these were the issues:
1. Ethanol damage to the Power Valve diaphragm in my Weber DGV - causing flooding
2. flaky points - causing erratic ignition timing. verified by a timing light once carb was rebuilt..tdc marker was all over the place and not stable.
The points were brand new and installed just a month before when I had my distributor rebuilt locally. They did a fine job, but those points looked a little
different to the points normally seen. They definitely were mgb points and worked fine initially, but something in them was wrong after the head gasket
blew and I never touched the distributor.
They were closing at an angle and not head on (flat against each other) as the points are supposed to.
If it helps anyone else, the actual (problem) points themselves were shorter and wider than
the one I just installed which are taller/narrower looking. And both the metal springy piece and the plastic part that bumps the
distributor shaft corners was shorter. Last, the threaded stud section of the points where the condenser and coil wire connect,
it was plastic on the problem one and metal on the newer points (with a plastic washer to isolate.)
Car is running great again, though I have an oil leak in the back of the new rubber valve cover gasket....easily fixed.
So that's it guys.
Thanks for all the comments and assistance in slaying this son of a bitch that robbed me of a month's worth of summer driving.
I need to remind myself when something is having weird issues that don't make sense, it's highly likely to be multiple problems
and thats exactly what was going on here. It was the coincidence of other failures happening just after the head gasket
blew that threw me way off.
so these were the issues:
1. Ethanol damage to the Power Valve diaphragm in my Weber DGV - causing flooding
2. flaky points - causing erratic ignition timing. verified by a timing light once carb was rebuilt..tdc marker was all over the place and not stable.
The points were brand new and installed just a month before when I had my distributor rebuilt locally. They did a fine job, but those points looked a little
different to the points normally seen. They definitely were mgb points and worked fine initially, but something in them was wrong after the head gasket
blew and I never touched the distributor.
They were closing at an angle and not head on (flat against each other) as the points are supposed to.
If it helps anyone else, the actual (problem) points themselves were shorter and wider than
the one I just installed which are taller/narrower looking. And both the metal springy piece and the plastic part that bumps the
distributor shaft corners was shorter. Last, the threaded stud section of the points where the condenser and coil wire connect,
it was plastic on the problem one and metal on the newer points (with a plastic washer to isolate.)
Car is running great again, though I have an oil leak in the back of the new rubber valve cover gasket....easily fixed.
So that's it guys.
Thanks for all the comments and assistance in slaying this son of a bitch that robbed me of a month's worth of summer driving.
