A tale of two fuel pumps

Discuss fixes, upgrades and modifications to your M37

Moderators: Cal_Gary, T. Highway, Monkey Man, robi

Post Reply
NAM VET
1SG
1SG
Posts: 1118
Joined: Mon Aug 22, 2016 6:27 am

A tale of two fuel pumps

Post by NAM VET »

I am sure I am not the first newbie working to restore/modify/repair a newly acquired truck to find some strange and interesting, even perplexing changes from the original military build. When I pulled my motor and started to remove the "bolt-ons" I took a lot of pictures so I can hopefully get it all back together in a reasonable approximation of what it should be. But I did not pay a lot of attention to how some things work. Like my mechanical fuel pump. Just unbolted it, cleaned it, and set it aside. And replaced the aged rubber tubing connecting one port to another. Like here still on the engine.
[URL=http://s663.photobucket.com/user/h ... .jpg[/img][/url]

And the former owner had put in two rear-ward facing bed lights, mounted on a bracket at the top of the aftermarket "hard-top", and told me they were wired to 12 volts. And that he had also added an electrical fuel pump, wired to a lit-if-on toggle right above the ignition switch. The truck seemed to run fine, although I had to learn how not to flood the motor on a hot restart. I got a good look at his rather rudimentary hose connections to the pump the other day when I removed the bed. He had not cut the hard lines, just added some barbs to them, and ran some hose, as you can see in this picture the hoses where routed back and around to get fuel to and from the pump. The wiring is a bit flakey too.
[URL=http://s663.photobucket.com/user/h ... .jpg[/img][/url]

I was always quite worried about my mechanical fuel pump leaking gas into the crankcase, with shall we say deleterious results. Recently I was up to Charles T's place for some questions, and I also dropped off several items for his team to have a "look-see." Left my mechanical fuel pump there.

Well, now that I have finished my brake, vent, and fuel lines with the Fedhill lines, (more about that in another post), I went to hook up my 12 VOLT fuel pump, and after a much tidier hookup, including several hours of running protected wiring, I traced the power wire back up under the dash, expecting to find the power coming from the small switch converter under the dash. Surprise! My 12 volt fuel pump was wired into a fused line straight from the batteries to the flip switch, then to the pump. So my 12 VOLT was running on 24 Volts! I am not sure it that made it pump a lot more fuel, but I have ordered a Facet small 24 volt pump, 5-9 psi, and install it, and may need to add a fuel pressure gage and fuel regulator. I had put one in my former Superformance Cobra. Here is a picture of my much tidier hook-up of my 12 V pump, which will be coming out in a few days. All that work for nothing. My fuel injection hose is only a few inches each side, to my new 5/16 fuel lines.
[URL=http://s663.photobucket.com/user/h ... .jpg[/img][/url]

Then, while I still have my Fedhill flairing device, went back around to the front of the frame, and realized that my fuel lines had not been connected to the mechanical pump at all! So it was only for wiper vacuum. So I am not sure if I will use it just for wiper vacuum, or just remove it all together, and add electrical wipers, or just go without any wipers. How often will I drive in a downpour anyway, and besides, Rain-off works pretty well anyway. I do intend to remove the 24 to 12 volt thingy, which external wiring I can't figure out, remove the bed lights and their wiring.

enough pictures already in this thread.

all the best, NV
NCM
PFC
PFC
Posts: 83
Joined: Sat May 02, 2015 4:34 pm
Location: Charlotte, NC

Re: A tale of two fuel pumps

Post by NCM »

NAMVET, with the 5-9psi pump you'll probably need to add a pressure regulator. I went with the 4-5PSI Facet on mine when the mechanical pump failed and it has worked perfectly.
NAM VET
1SG
1SG
Posts: 1118
Joined: Mon Aug 22, 2016 6:27 am

Re: A tale of two fuel pumps

Post by NAM VET »

NCM, I searched high and low for a small box 24 V low pressure pump, and the 5-9 psi Facet is the only one I could find. I do see the longer cylindrical Facet 24V in a lower pressure, but since I have spent so much time precisely running my in and out 5/16 fuel rear lines, and need to send my Fedhill flaring tool back, because I won't be able to work on my truck for the next week or so, and the longer, side port cylindrical Facet would likely require a complete re-do of my now perfect fuel line at the rear. As it is now, I have spent countless hours on my various lines, making sure that they don't have any pressure or torsion or touch of the lines to the frame or rivets and such. Only at the frame clamps, most of which I have replaced. Even with armor on all my new lines, any undue pressure on a line can ultimately lead to metal fatigue and cracks. I have spent the last few hours researching fuel pressure regulators, and how to run a line to a quality pressure gage. No need to just guess what the new Facet's fuel pressure is. I want to know. Just getting more complicated as I move forward on this.

I think I will run a fuel injection hose from my front fuel hard line to a regulator mounted on the left inner fender liner, then via another soft line up to the carb. Then a line with an isolator to an in-cab pressure gage.

Amazing how I just wake up in the middle of the night, with my sleeping brain trying to work out this or that on my truck.

all the best.... NV
ZGjethro
SFC
SFC
Posts: 643
Joined: Thu Apr 01, 2010 6:57 pm
Location: Aspen, Colorado
Contact:

Re: A tale of two fuel pumps

Post by ZGjethro »

It sounds like you are doing exactly what I have. I'm not sure what the psi is of my 24v facet pump, but I replaced the 12v pump the fire dept had installed. I used the steel lines to the factory fuel filter location and installed a chromed Holley fuel pressure regulator and there. I sprayed it the correct OD paint and ran fuel injections line over the head to the carb. That line was intended to be temporary, but it's been there seven years. I plated off the mech fuel pump and went through electric wipers

I have my pressure gauge on the pressure regulator under the hood. It was simpler and easier, and it is visable to me when working on the motor
NCM
PFC
PFC
Posts: 83
Joined: Sat May 02, 2015 4:34 pm
Location: Charlotte, NC

Re: A tale of two fuel pumps

Post by NCM »

NAMVET, I haven't logged on in about a week, so I just saw your reply. I got my pump from Pegasus Auto Racing; it is actually a marine fuel pump. I'm guessing the is the cylindrical one that you saw as well.

https://www.pegasusautoracing.com/produ ... RecID=9337
isaac_alaska
SFC
SFC
Posts: 557
Joined: Tue Jul 07, 2015 10:44 pm
Location: Fairbanks, Alaska and Nome, AK

Re: A tale of two fuel pumps

Post by isaac_alaska »

that looks like the same exact pump i have installed in my truck, my pump is mounted up in front near the top of the radiator, about as non-ideal location as you can get as far as "the fuel pump should be mounted low, and near the tank", and it still works great. mine has a different brand on it but they appear to be identical
Isaac
Fairbanks, AK
Civilian WM300 on DC3 tires
'52 M37 on 11x16 Michelin
'52 M37 on Apple R-1 tractor tires
Photo Gallery
NAM VET
1SG
1SG
Posts: 1118
Joined: Mon Aug 22, 2016 6:27 am

Re: A tale of two fuel pumps

Post by NAM VET »

In order to not have to re-do my just completed 5/16 hard lines, I put this Facet in, a 4.5 to 9 psi pump. I wanted to be sure it was oriented correctly, and that my already installed hard and fuel injection lines did not rub on any frame or rivet, and have room for my fuel filter. The small square one fit fine. I had already run protected wiring from my dash lite-when-on switch. I made up a small metal sheet to fasten the pump to the welded-on bracket, and it fit fine. I have since added a small wiring clip to hold the power line securely, and put two over-lays of shrink tubing on the Facet wired to further protect it from abrasion. When I get my OEM mechanical fuel pump back from Charles T, I will carefully box it up, and put it on the shelf, and put a block-off plate on the mechanical pump's block site. I made sure to orient the clamps so I can get to them some day from under the truck. Not something I would want to do along side the road, gas dripping on my face and all. And I will order a quality fuel pressure regulator in the engine compartment when I get the motor back in. Was over to the machine shop last week, and will drop by again today, he had my motor mostly apart on a work bench. He has been taking pictures of everything as he comes to that part for me. So far nothing unusual found.

Meanwhile, I got out my HVLP gun, and sprayed the correct early '50's color on lots of small parts I have off the truck, and also did the front fenders. They look nice. Took the cover off my steering box, drained out the incorrect gear oil, and put in 12 oz of the Mobil 600 gear lube. Boy, that stuff is thicker than honey. The horn wiring there was all kinked, so I just pulled it all out, and will replace it later, or may just go with a dash switch for my horn. Besides, I hooked up my 24 volt battery to the horn directly, and all it did was give was a weak bleat. So I will replace it with a 24 volt black Hella horn. Going to rain today and the next few days, so will work in the garage on this and that. Yesterday after church I went thru all my boxes and zip lock bags of this and that, reorganizing the clutter. Even being retired, and usually having pretty much all day every day to work on my truck, I can see why a rebuild can take weeks and months, and perhaps years. I am so often at the several industrial shops for things like plumbing connections and such that now the counter clerks know me well enough to greet me with "Hi Hal, what do you need today for your truck?"

When I was spraying the OD several days ago, my gloves wore thru on the fingers, and the Gillespie paint got under and around my finger nails and finger tips, and I just couldn't get it off, so my fingers looked like they are impacted with dark grease. So before church, I painted my nails with some of my wife's nail polish to make them look less grimy.

Morning sun is coming up before the rains here just south of Charlotte, hot coffee, soon to have breakfast, even the two cats are friendly today.

All the best, guys....

And here is my Facet....
[URL=http://s663.photobucket.com/user/h ... .jpg[/img][/url]

And a shot of Pop, who ate our cat one day when I was out on an operation. When I have time, I will share with you the story of how and when our cat took on a big rat one night in the dark in our "hootch." It didn't go well for the cat, or our commo gear when I went after the rat with a meat cleaver by moonlight.
[URL=http://s663.photobucket.com/user/h ... .jpg[/img][/url]
NCM
PFC
PFC
Posts: 83
Joined: Sat May 02, 2015 4:34 pm
Location: Charlotte, NC

Re: A tale of two fuel pumps

Post by NCM »

Looking forward to hearing that one...
Post Reply