QuestionQUESTION: MGB----2 door convertible------1.8l OHV 8v------Sept 1976
The SU fuel pump has been replaced with a facet solid state pump and a Brand new fuel tank. The factory points
ignition system has been replaced with a Crane Cams Fireball XR700 optical trigger. The ignition coil, distributor
cap and rotor are new, as are the plugs and leads.The Zenith Stromberg auto (water jacket bimetallic spring) choke
175 CD-2 single barrel carburetor has been re-built at some point in the past although not by me.
When the vehicle runs it runs well, it will run for anywhere from a couple of seconds to several minutes but it
will always die. When it dies it dies gradually by losing power then stalling, after stalling it will not re-start
for several minutes sometimes hours.
I have removed the carburetor and checked the float valve, which is NOT sticking and everything in the carb
itself is clear and free moving, I have tested the fuel pump by leaving it pumping into a gas can for a substantial
period of time (longer than the car has ever actually ran for) without pause in flow. I am at a loss as to what
could be the issue. I do have one concern regarding the the choke which was not secured and completely out of
adjustment but I do not believe this would cause the symptoms I am describing. if you have any input at all it
would be greatly appreciated- Thank you - Paul
ANSWER: Hi Paul. I do have a few ideas:
1) Sounds like fuel starvation to me. Next time the engine dies, go to the back of the car and remove the fuel cap. If it makes a loud sucking noise, then you have the wrong fuel cap. You need a VENTILATED cap.
2) Second possibility is the Facet pump. These deliver too high a pressure for a Stromberg carb to cope with, so they flood. Either fit a genuine SU pump or a Filter King pressure regulator. Also, check the rubber hose on the inlet side of the pump (the tank side), because it could be collapsing under suction.
3) Do you still have all the emissions equipment? If it is legal to remove it, then I strongly recommend that you do so. After 30 years on the car, the original parts can deteriorate causing all sorts of strange problems.
---------- FOLLOW-UP ----------
QUESTION: thank you for the timely response, the hose from the tank to the pump is new the fuel pressure regulator sounds like a good idea, what is the deal with the emissions stuff ? the hose that comes from the carb to the canister? should i disconnect it and blank it off or just disconnect?
AnswerTo be honest, it would be much better to remove everything and fit twin SU carbs instead. This would increase your power from about 70 bhp to 100 bhp, the car would run much sweeter, and you would never have problems with the emissions equipment in the future.
Firstly, check that it is legal to tamper with the emissions equipment in Florida.
If you want to keep the single Stromberg, then I would remove as many components as possible, especially the air pump and EGR valve. Route the fume pipe directly to the suction tube on the carburetter, but fit a plug inside the hose that has a 5/32 inch (4mm) hole drilled into it to restrict the amount of fumes that can be sucked up.
Here is a link to the appropriate section of the Moss website:
http://www.mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=28993
