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RE: Fuel Pump Failure (again!)

To: mgs-owner <>, MG Mailing List <>
Subject: RE: Fuel Pump Failure (again!)
Date: Thu, 11 Jan 1996 17:34:00 -0800 (PST)
I know what this is thatnks to the help of fellow list members. I too went 
through SU fuel pumps until someone tipped me off to the adjustment of the 
diaphram post that connects to the sping plate thingy ( good description I 
know )

This is the deal. Someone told me ( sorry for not giving proper credit ) 
that the diaphram adjustment is sometimes not done properly when they are 
assembled or in my case, the rubber shrinks and the diaphram is too taught. 
When the diaphram is pulled up to suck gas into the chamber, the post (which 
looks like a long nail with a threaded end) flips the points to the off 
position. When you look at the points you will notice that they are spring 
loaded and snap closed and open. The problem in my case was that the 
diaphram was too tight and would not allow the post to be pulled up high 
enough to flip the points to the off position. Normally,once in the off 
position the post is released by the coil and the diaphram presurises the 
gas pumping it through the valves. When the diaphram is at it's lowest 
position, it snaps the points back to on and more gas is drawn into the 

In my case, I removed the pump and unscrewed it with the intentions of 
rotating the diaphram one hole to the left to adjust the post so that it 
would come up high enough to flip the points to off. What I found when I 
opened it was that the diaphram was really tight and just didn't have the 
range of motion to both flip the points off and on. It was still stuck to 
the coil side of the pump so I was able to try to actuate it manually. I 
peeled the diaphram off and then (leaving it in the same position) screwed 
it back togather and have not had a problem since. Peeling it off allowed 
the diaphram to realign on the screw holes normally, not being stretched.

Either you have to adjust it by rotating the diaphram or it may be just too 
tight like mine was. I bet I could have said this all in about 4 sentences. 
Sorry about the length for all of you that made it this far.

Christopher Reichle
From: mgs-owner
To: MG Mailing List
Cc: va-britcars
Subject: Fuel Pump Failure (again!)
Date: Thursday,January 11,1996 9:27AM

I have had a second fuel pump go out in as many months on my '73 MGB.
The SU brand pump failed by becoming totally silent.  This one (a
plastic-bodied one from Seven) will click once for voltage applied, and
once when it is removed.  It doesn't "throw over" though.  I got home
yesterday by clicking the ignition on-off to fill the float bowls (5
miles, in traffic.  Yeesh).  The SU responded to tapping for a while
before it completely died.  This one doesn't, and I am afraid to hit it
too hard because of the plastic, anyway.

This is starting to look chronic!  Any ideas?  Thanks!

John M. Trindle | | Tidewater Sports Car Club
'73 MGB DSP     | '69 Spitfire E Stock | '88 RX-7 C Stock
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