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MG MGA - No fuel coming through

I am having a fuel supply on my MGA. I have an SU-style aftermarket fuel pump that I used previously on my MGB. It has been bench tested, and it pumps fuel. When all is hooked up on the MGA, however, no fuel comes to the carb. The fuel pump clicks away, but it pumps nothing.
I have reversed the in/out hoses several times to be sure that I had the right ones in the right places, and still no gas. I have used compressed to blow out the fuel lines in both directions from the pump, and air passes freely through both lines. I can hear it bubbling in the fuel tank.
I recently recoated the inside of the fuel tank, using a tank cleaner and recoating stuff. Could I possibly have plugged up some opening? But if I did so, would I still hear air bubbling in the tank when I blow through the line? Can anybody suggest a solution to this problem?

Thanks in advance, Mike.
M.E. Whalen

I should have noted that the MGA was not running before. I am rebuilding it, and I am trying to start it for the first time.
M.E. Whalen

Sounds like reverse polarity...Instead of reversing the hoses, try reversing the (+)(-), and see if it will pump fuel....
Most pumps will run with either polarity, but will only pump fuel with one .If it still won't pump fuel, then you have something plugging the line....
Edward
Edward Wesson 60MGA

Mike, Have a look at the thread 'no fuel' last updated on the 29th September posted by GK George where he had an identical problem and which was traced to the tank (sealant).....................Mike
m.j. moore

Mike - Is your pump the New Zealand made, all plastic pump or the German made pump with a blue end cover? If the pump you have is the New Zealand ECCO pump, I would first check that the pump is connected to the fuel lines correctly as far as inlet and output ports (they are sometimes rather vague is their markings). Next, insure that the pump is oriented correctly - the output port must be at the top when the pump is installed.

If the pump is either the New Zealand ECCO pump or the German clone, reversing the polarity to the pump is not only going to change the direction of the fuel flow through the pump, it will, at best stop, it from operating at all and at worst, damage the internal electronics - just insure that you have the correct polarity to the pump (if it is running, the polarity is correct).

Since you say that you can blow air both directions through the lines from the pump may or may not clear the lines of obstruction. High pressure (anything above 5 - 10 psi) air can blow past an obstruction without dislodging it. You could also have an air leak between the tank and the pump that is causing your problem. The first place that I would check is the fitting at the end of the tank where the fuel line to the pump attaches - that could be loose. You could also have a hole in the internal pickup tube somewhere above the level of fuel in the tank - and of course you could have the ultimate air leak - an empty tank. For further troubleshooting tips, see the Articles, Fuel Delivery Troubleshooting Guide and Air Leak Troubleshooting in the SU Fuel Pump Articles section of my Homepage at: http://homepages.donobi.net/sufuelpumps/
David DuBois

Oops - The first line of the second paragraph above should read ...reversing the polarity to the pump is not only not going to change the direction of...
Cheers - Dave
David DuBois

Maybe sucking air in through a hole in the suction line.
Art Pearse

If the coating has come off the tank, blocking the fuel outlet, then it will still be possible to blow air in. The loose material will just act as a valve. You need to find a way to suck fuel out of the tank to check that is or is not the problem.
Neil McG

Mike
O.K....What year was your MGB? Many were made with Negative ground and an alternator system....(Sorry , I can't remember if the early ones were Pos or Neg.)...
Is your "A" a positive ground car? Or has it been converted to Neg. ground?
Edward
Edward Wesson 60MGA

Why does polarity matter? Its just an electromagnet, on or off, with an iron armature.
Art Pearse

Edward - As I stated in my first post, Polarity is not the problem. If the pump is a dual polarity, unit the pump will pump fuel in the proper direction regardless of polarity. If it is polarity sensitive, it will not pump at all if the polarity is reversed. Either dual polarity or polarity sensitive pumps will only pump in one direction due to check valves inside the pumps.

Art - You are correct on the earlier pumps that used nothing more than a capacitor for arc suppression across the points. Later pumps that use a TVS for arc suppression are in fact polarity sensitive in that the TVS will be burned out with a reverse polarity, but they will continue to pump until the points are completely burned off the toggle. Even later pumps that are all electronic will not work at all with reverse polarity. Even though the basic pumping action is is just an electromagnet, because the trigger circuit is either a Hall effect or an optical interrupter circuit. Cheers - Dave
David DuBois

This thread was discussed between 11/10/2013 and 12/10/2013

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