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MG MGB Technical - SU FUEL PUMP TESTING


Question: If you pick up a used SU fuel pump for the MGB is there a way to test it "on the bench" before attempting the installation?

Thank you,
Ted
'78 and going strong (even though it's only 18 degrees outside)
T.A. Anderson

Certainly. The tricky bit is what to pump. Water is safe, but you dont want to leave any in pump. The original workshop manual has a picture of an elaborate test stand, but a simple test would be to have it pump from one gas can into another. Using a 12V source, pre-wire a positive connection to the flat blade connector on the cap and a ground to one on the pump body. If you are pumping gas(petrol) you MUST be sure your connections are clean and will not spark. Simply run some fuel line from the suction side into one can that is partially full, and another line from the output side into an empty one, secured with hose clamps of course. A simple in-line switch could also be rigged.

You could also do this under the car using the existing fuel lines and electrical connections and use the ignition key as your switch, with the pump lying on the floor (or in the trunk in your case), and the fuel line removed at the carb, pumping into a jar or small bucket.
Have fun, be safe.
Andrew Blackley

T.A.: the fuel pump is quick and easy to install and remove. Nearly as quick as rigging a bench test. Andrew's warning about sparks should be heeded. For safety's sake I would just install it to see if it works.
Terry

It should raise fuel two or three feet at a rate of 1pt in 30 secs min, on the car also. The safe way is to connect it to 12v and block the outlet and the inlet in turn. The pump should chatter rapidly with neither blocked, with the outlet blocked it should stop almost immediately, slow right down or stop with the inlet blocked.
Paul Hunt

I once "rebuilt" an SU pump (replaced the points, actually). To test, I simply hooked it up to the windscreen washer pump connection. When I hit the button on the wiper stalk, I got the familiar "click click click", and knew I had a working set of points.

Strikes me as easiest "bench" to rig up, as there's no crawling around underneath (and this was to be my "spare" as I had replaced the pump already).
John Z

Just been reading Practical Classics (March!). Mentions the need to change fuel pump points after changing polarity because of build up and erosion reversal. Been thinking about changing to neg earth but don't remember this as an issue. Any thoughts?

John
john

Maybe if you left them alone the hole in the one contact would gradually get filled up by erosion of the pip on the other meaning they will last for another 50 years instead of 25 ...

Never heard of having to do anything with them, flatting should be enough.
Paul Hunt

This thread was discussed between 27/01/2003 and 29/01/2003

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