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MG MGA - Fule Pump leak

I posted a few weeks ago about a leaky fuel pump. It is now on the bench, and the gasket between the pump body and the central piece (now) needs replacing.

The diaphragm looks OK, so I need to get a new gasket.

There is another gasket between the diaphragm and the central piece. Is the gasket next to the diaphragm really necessary? I expect that the rubber diaphragm should form a good enough seal anyway.

I can't see this gasket in the catalogues though.

thanks

dan
Dan Smithers

Dan, According to the SU workshop manual pump parts are in this order:- Pump body - Joint gasket - Sandwich plate - Diaphragm gasket - Diaphragm assy. - Coil housing. There is no gasket between the diaphragm and coil housing. If you leave out the diaphragm gasket there may be a risk of the metal disc on the back of the diaphragm bottoming on the base of the sandwich plate. Cheers Mike
m.j. moore

Dan - The very early pumps (as used on the TDs and TFs) didn't originally come with the gasket between the diaphragm and the sandwich plate. Since the gasket is now shown in all the illustrations, I always put it in place when restoring fuel pumps, but have often questioned (to myself) the necessity of the gasket. At only about 0.030" thickness, I doubt that this gasket would make a difference in the clearance of metal disk on the back of the diaphragm from the sandwich plate. By the way, if you have removed the inlet/outlet fittings or the filter plug, I would suggest some good thread sealer on the fittings and plug threads to insure no leakage around those threads when you reassemble the pump. Cheers - Dave
David DuBois

Dave. An interesting point that you make about using "some good thread sealer on the fittings and plug threads to insure no leakage". When I installed the fuel pump you rebuilt for me on the 79B I am bringing back to life, it took me a little while to figure out how to do it correctly. Orientation of the pump body and getting all of the leaking fixed. Fuel pumps are not something that I have had to replace on a frequent basis.

That being the case, might I suggest a companion article to the others you have written? Something to the effect of, "How to install your SU fuel pump"? There seem to be some recurring questions asked about this. A tech article on how to best do it, any possible problems, what form(s) of thread sealers to use, etc. would be of significant value to the MG community. I would be very happy to post it along with your other articles, which show, from the site statistics, to be very popular.

Thanks, Les
Les Bengtson

Les - My suggestion to Dan was in regards to the inlet/outlet fittings that are permanently installed in the pump body of the L type pumps as found on the T series MG, MGAs and very early MGBs. These are fittings that are not removed during a change out of the pump. If they are removed from the pump body during repair, it is often hard to get them to make a good seal (particularly against air leaks) due to the deterioriated threads and wahser seats. That is the only place that I recommend a thread sealer be used. On the AUF 300/AZX 1300 pumps used on the later MGBs, the only problems with leakage around the banjo fittings is from a damaged sealing surface of the port face, or the use of a fiber gasket where there should be an 'O' ring on the newer pumps. I will put together something regarding that and the orientation of the pump to put on your web site, but it will take me some time to get it done. I'm trying to catch up on home projects that didn't get done last summer due to illness. Today was repairing a leak in the water line to our house (home ownership is so much fun).
Cheers - Dave
David DuBois

This thread was discussed between 28/06/2006 and 29/06/2006

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