MFI pump casting porous?

[71six]

My 1973 911S has developed a fuel leak originating from the mechanical injection pump area. Upon investigation it seems the cast housing is porous and the fuel is originating from within the pump. Are these pumps magnesium or aluminum and if my assumption is correct about the porosity can this be repaired with a surface treatment of one sort or another, or do I need to start looking for a replacement? All help, advice, pointers, etc much appreciated.
Thanks,
Mark

[Biancaneve]

1973S is aluminum, afaik.

[kentf14]

1973S is aluminum, afaik.

Not all. Early /73 cars still used mag pumps.

[71six]

My car is #1267 so aluminum most likely. Is porosity over time an issue or am I mistaken with my diagnosis? I ask because I can't remember hearing of this issue (porosity) before.

[Olivier]

Penetrant testing is the way to go to answer your question... It will detect cracks, and porosities

Olivier.

[71six]

It appears to be leaking fuel from within the casting. This pump was refreshed by Gus more than a decade ago and never had any issues until now. I have never read of this happening and wanted to know if this actually occurs or if "hopefully" I have diagnosed the origins of the fuel leak incorrectly.
Thanks,
Mark

[gled49]

I've never heard of this before. I would certainly rule out all fittings and connections. Gordon

[Ivan Fuller]

Leaks can be very hard to find due to creep and getting blown around the place. (Can't comment on MFI pump leaks).

I had an interesting leak on third piece of my Speedster engine, freshly rebuilt, matching numbers freshly reconditioned with no expense spared. Several pulley seals, speedi sleeves, sealant everywhere we discovered two areas of porosity in the casting.

Did some research and found a foundry that was set up to do the process (vacuum sealing)

After meticulous degreasing we sent the part off and came back a week later with a bill for the grand sum of $25. (No residue or chemical build-up on any surfaces)

Fitted the part and not a drop leaked since.

Some info here on the principle;

http://www.loctite.ph/php/content_da..._By_Design.pdf

[71six]

To be honest I cannot state definitely which material this pump was made from. (aluminum or magnesium). I purchased it rebuilt 12 years ago from a well known and regarded early 911 owner / builder on this forum to replace the existing one on my engine. Therefore it has no relationship with when my car was built. The mechanic used a bore scope / camera and stated the fuel was originating from behind the riveted Bosch I. D. plate on the side of the body. The pump was fuel tight for 12 years so I'm suspect (hopefully) that this was an incorrect diagnosis of the origins of the fuel. I know that evil ethanol (corrosive solvent) raises havoc with most everything (except the corn lobby in D.C.) and that magnesium is susceptible to corrosion internally as well as externally. Have others had fuel leakage through the body casting?
Thanks for the help and guidance so far...Keep it coming....Please.
Mark

[Chuck Miller]

Mark,

The basic look of the two pump materials (if no one paints the body) is pretty obvious.... Dark for Mag/ Bright for Alum.

Here's a '69 (Mag) and a '73 (Alum)

Hope this helps......