I have 71 spit, mark IV. I recently changed the fuel pump because it appeared
to have blown a diaphragm (gas was spraying out of the weep hole). Since the
change the car has not performed correctly. At first the car would crank, but
would not maintain idle. During this failure mode, I noticed that the car?s
idle would degrade (it would move from 1000 rpms to 800, 600, 400 and stop) in a
time frame of about 4 seconds. I changed the oil thinking the gas draining in
the fuel pump had weakened the viscosity of the oil in the crankcase. I started
the car and the same failure mode was present. I also noticed that the
carburetor (Stromberg 150 CDSE) was leaking gas from around the choke area.
This led me to believe that the float was stuck. I removed the carb and removed
the float chamber cover to look for debris and other possible causes. I could
not find any culprits. The float appeared to be working as designed and it did
not have any gas in it. I did notice that the needle valve in the float chamber
was clean but the piston actuated by the float assembly seemed to be a sticking.
I reassembled the carb and attached it to the car. The leak went away but the
car still would not maintain idle. I adjusted the throttle speed screw to
achieve idle. This improved the situation, but the car was not running as well
as it was before the fuel pump failure. Since then I have removed the carb
several times and disassembled the top and bottom looking for potential root
causes to the problem. I have not found anything that could be the cause. The
car acts like it?s running rich and then it will act like it is running lean. I
have reviewed the new fuel pump to ensure that it is performing correctly. I
was wondering if I have missed something obvious or have forgotten a detail in
my haste to ?fix? the carb? I am not convinced that the needle valve is working
correctly. I am planning to test tonight with lung- power (push the piston up
and blow through the fuel hose). How can I determine if the carb has a biased
needle or unbiased needle set up?
I have checked some of the major stuff: the distributor is not loose (timing
should be the same); spark plugs are in and the wire are connected; the car has
plenty of gas; all coil wires are connected, etc.
Any help would greatly be appreciated.
Thank you,
Danny
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