MFI pump porous?

71six · 10-07-2015, 01:14 PM

Do the 69-73 MFI pump castings become porous over time? Late 1973 to be specific? Never heard of this so asking.
Thanks,
Mark

Porboynz · Porboynz's Garage

They can leak from many places but so far I have not seen a leak caused by a porous casting. There is no oil pressure to speak of inside the pump so why would it leak that way?

71six · 10-08-2015, 04:32 AM

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

356RS · 356RS's Garage

What part of the pump casting area are you seeing the fuel leak?

MDamen · 10-08-2015, 11:06 AM

Metals do not become porous. They may develop cracks, or mating surfaces may leak, but not outright porousness of the casting.

I expect some metallurgist may correct me on a technicality. but I believe this to be true for the aluminum castings and oil/fuel fluids.

MDamen · 11:23 AM

I have my pump apart right now. If you can identify where you are seeing the leak, I can take a close look at my pump and see if there is a leakage path.

71six · 10-08-2015, 11:40 AM

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 early 911 owner / builder 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.
Thanks for the help and guidance so far...Keep it coming....Please.
Mark

MDamen · 10-08-2015, 01:31 PM

I'll take a look tonight and post some pictures. My pump is from a 72T.

71six · 10-08-2015, 01:38 PM

It's apparently a magnesium casting. Has any one seen or heard of these failing and seeping fuel through metallurgic deterioration over time perhaps due to our less that stellar E 10 fuel? Thanks and all help and input appreciated.
Mark

MDamen · 10-08-2015, 06:03 PM

Here is the plate on the side where the fuel is.
There could be a leak from the fuel line or fuel fitting that is right next to the plate. Or there could be a fuel leak from one of the six fuel exit fittings.

Dodge Man · Dodge Man's Garage

Casting metals are usually surface porous but a leak usually means a crack, leak, etc... (as above) I did bearing way slides on cast iron machinery years ago.

tharbert · tharbert's Garage

Hmm, that's awfully close to the pressure side of the pump. I'm in the crack/leaky line camp.

BURN-BROS · 10-09-2015, 01:39 PM

Fuel getting into the oil of the injection pump is a sign if an internal crack. IIRC, around the delivery valve. There is a procedure to check for such cracks. I would send the pump to mark Jung to verify it is a crack or simply a sealing issue.

MDamen · 10-09-2015, 01:45 PM

Fuel goes into the pump at about 14 psi through that banjo fitting on the right. It then gets pumped up to 150 psi or so by the pistons in the pump body and sent out to each cylinder through the valves/fittings at the top.

71six · 10-09-2015, 03:19 PM

Indeed once the pump is removed it is going to MFI Werks (Mark Jung) for an assessment.