Rich..........
All the symptoms suggest excessive richness. Either the choke is not coming
off quickly enough (fault of either the way manual control is attached - or
the manual controller's technique), or a blocked passage in the carb. At the
bottom of the venturi, when you look in from the front, there is a very
small hole. If this gets plugged, the carb will run too rich. See if you can
pass a thin wire all the way down it.
Lawrie
British Sportscar Center
-----Original Message-----
From: Rich Peterson <kerry3@earthlink.net>
To: MGS <mgs@autox.team.net>
Date: Saturday, May 01, 1999 8:20 PM
Subject: '77 MGB with Carb Problems - HELP
>My '77 B appears to have developed carb problems and I can't figure out
>what is wrong. Background: The car has 110,000 miles, good compression
>(130 +/- on all four), luminition electronic ignition, desmogged engine,
>original ZS carb which was rebuilt a few years ago, manual choke
>conversion, new plug wires, new NGK plugs, timing set to 15 BTDC w/o
>vacuum advance and it runs on 92+ octane gas.
>
>The problems I've developed are: Bad misfire while warming up from
>cold; poor fuel economy (20 MPG); excessively rich mixture (black, sooty
>plugs); poor hot restart; idle falls to about 400 rpm when hot (fans
>on).
>
>I've tried to lean out the mixture, but the needle is all the way down
>and it is still running rich. I've lowered the float level, but that
>doesn't seem to make any difference until I hit a certain point - then
>the car won't run. I get about 18-20 inches of vacuum at idle, so I
>don't think I have a vacuum leak. I've readjusted the manual choke
>conversion, so I don't think that it's the problem, although it's the
>most suspect at this point (i've tried swapping the choke body with
>another that I have with no change in the problems).
>
>Once the car reaches operating temperature, it seems to run well,
>although there is an irregular miss at idle. It has good power and
>pulls well throughout the RPM range - I feel a definite surge as the RPM
>moves past 3000-3500 rpm under full throttle acceleration and it feels
>especially strong between 3000 and redline (gotta have some fun to ease
>the pain of my problem . . .he he).
>
>Any guesses? It has me baffled. I'd love to replace the ZS with a pair
>of SUs, but the budget (SO) won't allow it, so I must fix this problem
>with existing hardware.
>
>Regards,
>
>Rich P.
>
|