Fuel Pump Options

[WarrenD]

Here's the short story. When I bought my M-37 last fall, I knew there was an oil leak in the area of the fuel pump. The current pump I was told is a new (or newly rebuilt) unit installed within the last year. The current pump is the dual action type (original) with the fuel pump on the top and vacuum pump on the bottom. As for the oil leak, it seems to be coming from the area around the vacuum pump, oil drips off the nut on the very bottom. I don't see oil on the lip of the block below the pump so I don't think the seal between the pump and the block is the problem. I did tighten the screws around the bottom and the nut, all seemed looser than I think they should be. That stopped the leak cold for a couple of weeks, but it just started up again. I rechecked the screws and they seem tight. Given the location, I can't really see where the oil is coming from, except that it is running down the center rib on the pump casting. Everywhere I put my finger seems to come up reasonably dry.
In talking with an old timer, I was told there is a newer pump (still mechanical) that bolts up and is a single action pump, meaning that it only pumps gas. I'd have to connect the vacuum line directly to the intake to run the wipers, which isn't a major problem in theory but I haven't actually looked at the engine yet to see what's involved.
At this point, I'm looking for options. I know there is a NOS pump (dual action) available with ethanol-resistant diaphrams and I'd rather not do a conversion to an electrical pump.
Is the single action pump a good option, am I better with an original dual action or is there an option I don't know of. My truck isn't a daily driver, will likely see a 1k-2k miles per year but I would like reliability over authenticity.

[M37UK]

To be honest Warren, if you want reliability over originality I would install an electric pump and be done with the mechanical pump issues for good.
Why dont you want to install an electric pump?

I ran my vacuum wipers direct from the inlet manifold for about 2 weeks until I couldnt take the poor perfomance any more so installed 24v electric wipers instead.

Cheers
Stu

[cuz]

The really simple solution is to fix the fuel pump. That big old dual action fuel pump when rebuilt properly will last you another 20 years and has proven for the last Half Century it can handle the work load.

Single action fuel pumps and electric pumps are really just band aids and each has it's own new problems and obstacles to overcome.

If it's the cost of the rebuilt dual pump or it's kit that has you thinking try something different then the single action civvy type pump will also do the job but you'll need to switch to electric wipers or add a vacuum reserve chamber in the wiper plumbing and plan on using just the driver's wiper with an occasional shot on the pax wiper.

[WarrenD]

Stu, Thanks but I really don't want to go that far. I have no desire to install electric wipers, I don't plan on being out in the rain, so the current vacuum ones will be fine if I get caught out. There is a member of the local club who did the electric pump conversion and said it was expensive and a real pain. I'm also concerned with the practicality of having the pump wired to the ignition and don't care to run a seperate switch. I've heard that these trucks are prone to flooding and I could see that happening easier with an electric pump than a mechanical one. I'd still consider it, but it is at the bottom of my list. I do appreciate your opinion and response, thank you!

Wes, thanks! That has been my train of thought but I was talking to M37 guy who's opinion I respect and he brought up the issue of the double action pump causing more wear, etc. I'm leaning toward just replacing the one in there with the original type and hope I get a good one. For a few thousand miles a year I don't want to re-invent the wheel and as you say, these original pumps have worked well for years. It certainly is the least complicated option to date, just disconnect what's there and re-connect the new one. I like less complicated!
I don't have to do anything right away, can't see me being out too much over the winter so I'll wait some and see if anyone else cares to weigh in.

[cuz]

I'm leaning toward just replacing the one in there with the original type and hope I get a good one

No need to rely on hope. I can think of two rebuilders who are sure to return a perfectly good pump to you:

M Series Rebuilds and Then & Now

Since you are honkered down for the winter and spring is only 3 mos. away I'd get the pump off and on it's way this month.

[rc51racer]

If you want reliability then an electric fuel pump is the way to go.

As for the leak I would disconnect the vacuum lines, fuel lines and remove the fuel pump, you can then inspect
the pump. My guess is the gasket between the fuel pump and block is the issue, I made my own from fuel safe
gasket material I got at NAPA and some anaerobic gasket maker.

Personally I like to keep my M37 as original as possible, here is a blog post I did on rebuilding the fuel pump:

http://blog.gieselman.com/post/M37-Fuel ... build.aspx

the hardest part is cleaning off all of the gunk.

[cuz]

[quote]If you want reliability then an electric fuel pump is the way to go.[quote]

Reliability is a trait of all three pumps if properly installed, maintained and of good quality. I have a mechanical fuel pump that has been there well over 20 years and I would describe that as a reliable pump.

[WarrenD]

If you want reliability then an electric fuel pump is the way to go.

Reliability is a trait of all three pumps if properly installed, maintained and of good quality. I have a mechanical fuel pump that has been there well over 20 years and I would describe that as a reliable pump.

That's what I like to hear! Thanks, Wes!

[Chuck]

Warren,that was a newly rebuilt pump from Midwest Military.I had a conversation with John about the leak but we didn't come to a resolution before you took the truck home.The pump had less than 1K miles on it.
Chuck