M37 fuel pump question

[Kaiser2boy]

My truck is still running the original dual action fuel pump.It was rebuilt a year or so ago.
Since then it has started seeping oil around the lower end and down over the front axle.
I retightened the screws around the rim of the lower section and there were a few that were not really tight. I hoped that would stop the dripping. It did not. I washed the area very well and drove it a short distance and looked again with an inspection mirror and the oil is not leaking from anyplace but around the lower section along where you can see the edge of the diaphragm.
Anyone have an idea how to fix this and why oil would be comming out there? As I understand the lower end it the vacuum boost end and should not have oil in it. Am I wrong?

[Frank Irons]

Was the diaphragm replaced with a new fuel resistant one? If not it could be leaking.

Frank

[Kaiser2boy]

I can only hope so,
I cant imagine a fuel pump diaphragm that is going to be exposed to gasoline not being made of anything but a gasoline resistant material.

The diaphragm was not hand made it was part of a kit and built by a profesonal rebuilder. I think that if it was some how made of anything that gasoline would attack it would have had a catastophic failure by now. It has been in service for two years or so and has a few thousand miles on it.

[Kaiser2boy]

Frank, I forgot to say in my last post that it is not leaking gasoline , its leaking motor oil.

[Frank Irons]

I understood that you were leaking oil. If the diaphragm is of older material it may not last with the ethanol gas we use today, and may be leaking. The pump on my M37 had oil in the lower chamber also.

Frank

[Kaiser2boy]

Hmm.
The fuel pump end at the top of the dual system is not leaking anything, its the bottom section, its the vacuum boost section that has the oil coming out at the seams. There should not be any gasoline in there to bother it even if it was an older unit.
The mystery to me is that I dont know if crankcase oil is or should be getting into the pump body and if it is, is it under pressure enough to be forced out between the flanges even if they are tight.
I am wondering if there is a crack in the pump housing.
I guess I wil just have to yank it.

[T. Highway]

Do you have any Fording Valves on your engine? If so, I would make sure that they are not in the closed position.

Bert

[Kaiser2boy]

The engine was totaly rebuilt a few years ago and all of the fording valves were removed and replaced with all new pipes. The only fording valve still on the truck is on the master cylinder.
I know what you are thinking that pressure may be building in the crankcase.
I drove around a bit with the oil fill cap off just to test that idea and oil still came out around the bottom of the pump.

Its not a ton of oil but it runs down over the front axle and it looks like the devil. Anyone looking at it would figure its an ill cared for truck.
It creates a spot on the floor about as big as a silver dollar over night. I dont know how much is leaking while driving but it looks like I use about a quart in a thousand miles or so. There is also a drip out of the flywheel plug hole but that is very minor,,,so far.

[Matthew Ziegler]

fuel pump

I'd recommend the civillian fuel pump for a wm300, half as many parts, I had the stock pump on my truck thinking it would improve my vacuum wipers...that was a waste of money.

[Kaiser2boy]

Too funny about the wipers. I reworked my original wipers and they do work.
I should clarify that statment by saying they work as good as they can. vacuum wipers,,,such a stupid idea, when you feed gas to go up a hill or pass they stop due to the drop in vacuum. Its a wonderful design.
Not only that but the vacuum wiper motor is like a clock work inside with all sorts of tiny valves and triggers and springs that have to be just so or they wont work.
People made fun of my old 1953 MGTD for some of its short falls but it came standard with an electric fuel pump and electric wipers.
I actually thought about a vacuum canister like the cars up intio the 60s used to have to hold some reserve vacuum but I dont drive the truck in the rain if I can help it so it would be a waste of time.

[Matthew Ziegler]

vacuum tank

I found a very large vacuum tank in a buddy's parts pile, didn't work. I wound up with some el cheapo electric wipers, not all that great but more reliable than vacuum. I'm thinking that you have a bad diaphram in that pump, I;m pretty sure there's a check valve that the oil would get through if it can get to it.

[Kaiser2boy]

I pulled off the pump, what a fun job.
By the time I got it off it was to late to tear it down. I may get lucky though , after I removed it I could see oil on the gasket face and down the back side of the pump. Some closer inspection showed that the pump to block conection surface was rough . I cleaned off the pump side and it had a fair amount of pitting and was wet with oil.
I dressed up the surface with a flat mill file and got of 99% of the pitting and rough spots. I checked it with a straight edge and it looks flat and square.The gasket was a mess also so I cut a new one and applied gasket sealer on both sides and replaced it. I will wait a day and run it again to see if I was lucky and will not have to tear down the pump.
While it was on the bench I worked the primer lever and kept my finger on the vacuum port and it did build up a bit and held . That gives me hope that its not the actual pump but maybe just a crappy seal joint to the engine. I will know in a day or so. Stay tuned.

[Kaiser2boy]

A Ha, I found the problem. After all of the above I still saw oil dripping, not as much for sure so the pump to engine connection repair stopped 80% of the leak but there was still a few drops hanging on the bolt head that goes up into the bottom of the vacuum end. I wiped it with a clean rag and then wiped all around the area, There was no sign of any oil anyplace but on the 7/16 bolt head. I figured maybe it is not tight so I slid a 7/16 wrench on it and tried to turn it. It turned with little effort at all. I gave it another turn and again very little resistance. I took my fingers and wiggled it and it came off in my hand,,,,it was stripped. Best part is it was not the bolt that was stripped it was the aluminum pump body that was stripped.
I cant post what came out of my mouth when I saw that.

[Matthew Ziegler]

pump

If your interested, I think I have a take off civillian fuel pump from my parts truck, definately needs a rebuild though.

[Charles Talbert]

A Ha, I found the problem. After all of the above I still saw oil dripping, not as much for sure so the pump to engine connection repair stopped 80% of the leak but there was still a few drops hanging on the bolt head that goes up into the bottom of the vacuum end. I wiped it with a clean rag and then wiped all around the area, There was no sign of any oil anyplace but on the 7/16 bolt head. I figured maybe it is not tight so I slid a 7/16 wrench on it and tried to turn it. It turned with little effort at all. I gave it another turn and again very little resistance. I took my fingers and wiggled it and it came off in my hand,,,,it was stripped. Best part is it was not the bolt that was stripped it was the aluminum pump body that was stripped.
I cant post what came out of my mouth when I saw that.

I don't recall without searching the files; but I'm assuming we built that pump at the same time we built your engine. If I'm correct on that, please send it back, and I'll see it gets repaired and returned to you right away, no charge.