I need help again

Any topics pertaining to the BMC A-Series engine.

Re: I need help again

Postby Charlie Tolman » Thu Dec 12, 2013 12:54 pm

Thanks for the description on the operation of the fuel pump.
Does the fuel pump arm always maintain contact with the lobe on the cam ?
Is there a blockage in the fuel line between the pump and the carbs ?
Are the carb needle-valves stuck shut ?

Charlie T.
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Re: I need help again

Postby johnmcguire » Thu Dec 12, 2013 11:07 pm

Charlie,
The arm maintains contact with the cam.
I have not installed the carbs and am looking for fuel from the pipe up to them or from the outlet on the pump.
I can easily suck fuel from the tank through the pump and can pump fuel into the pipe to the carbs by using a screwdriver to activate the pump arm further than the cam does.
Ken Hyndman at Moss is sending me different pump with a primer arm in hopes it might work but it is not supposed to fit the 948. I still hope someone has an old one I can try.
Any other ideas as to my error?
John
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Re: I need help again

Postby Charlie Tolman » Fri Dec 13, 2013 1:42 am

Have you tried "priming the pump" by pouring some gas down the line from the carbs to the outlet of the pump ?

I would be tempted to place a section of thick-wall rubber tubing over the fuel pump lever arm, that fits fairly tight on the arm, place some grease on the cam lobe and also on the rubber tubing to reduce friction, and spin the engine via the starter motor, to determine if the fuel pump will work. I believe that the direction of rotation of the cam lobe will not push the rubber tubing off the pump arm. Obviously, this is for testing, only.

You mentioned that your cam has a fuel pump lobe with a diameter near 1.29". How much off-center is this lobe, or what are the maximum and minimum radii with respect to the axis of the camshaft ?

Charlie T.
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Re: I need help again

Postby johnmcguire » Wed Dec 18, 2013 8:34 pm

Problem resolved times two!!
I finally got my courage up and "revised" the cam arm on the pump. It is bronze or brass and I heated it red hot and glowing with a torch and extended it a bit. A couple of heats later I had it just right so it is always engaged and has a little slack at the maximum cam extension. It pumps just fine now.
Then today I received from Moss a pump that fits and works just as it should. Ken Hyndman is their tech person at Moss In Calif. and has been very helpful several times. He too was at a loss to explain why my original pump and the requisite replacement from Moss did not work. He explored their stock and found a pump for a Triumph Spitfire that looked like it should work and had a primer arm. Not only that but it is cheaper! It works like a charm but did require my tapping the input fitting up to a larger size. The sprite pump has 1/2 " fitting in and out, the Spitfire has a smaller inlet fitting.
Charlie and others, I still am at a loss to explain why my original pump needed revision.
Thanks to all, John
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948cc
 
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Re: I need help again

Postby perdido » Wed Dec 18, 2013 10:49 pm

John, glad the problem is solved!
Rut
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Re: I need help again

Postby Charlie Tolman » Thu Dec 19, 2013 1:36 am

Nice to hear that the Spitfire fuel pump works well.
I assume that the Spitfire pump arm is similar in shape to your re-formed Sprite arm.
However, I still wonder about the design of the two Sprite pump arms ?

Charlie T.
Charlie Tolman
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Re: I need help again

Postby johnmcguire » Thu Dec 19, 2013 8:20 pm

Charlie!
So do I. I have no explain action as to why they did not work. The original worked fine once I moved the arm and the replacement did not work either.
Who knows?
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948cc
 
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