OEM Mechanical fuel/Vac pump, vs just Electrical pump?

[NAM VET]

As recently posted, I just realized that my mechanical pump was not even connected to my fuel lines. It is up being rebuilt now at Charles T's place. I removed the aftermarket fuel pump mounted by the tank, and also found out it is a 12 Volt pump, wired to my 24 volt system! I am not sure what PSI it was rated at, so perhaps it contributed to my occasional hot start flooding problem. I am installing the small box 24 volt Facet, I don't have room now for the longer lower PSI cylindrical Facet, having already done my lines, and my intent is to add a quality fuel pressure regulator.

But having read other's posts on mechanical vs electrical pumps, I am thinking about not re-stalling the rebuilt mechanical pump, as before I removed it, it only functioned to provide wiper vacuum. Besides, I am not sure running a "dry" mechanical pump is helpful for its reliability, and if I ever want to use it as designed, it might need another rebuild anyway. And hooking it up downstream from an electrical pump may prematurely damage its valves, dealing with pressurized inlet gas.

So I am leaning to is just using the Facet, a block-off plate for the mechanical one, & putting the later on the shelf. Which leads me to consider wiper vacuum. Here in SC, we do get monsoon-like rains, but Rain-X works well, and besides, how often will I be out in the rain anyway. So I can later put in 24 V wipers, or just leave them non-functional, and just for looks. Then too, one part to fail is better than two parts to fail. On the other hand, the military must have thought the mechanical system was adequate, but perhaps electrical pumps were unreliable then, and hard to waterproof. So maybe staying all original is a reasonable decision, too.

Any forum thoughts from others making such decisions?

and now for a picture....

After my first 6 mos in the field in the Plain of Reeds, I requested further field duty, and went way south to the very tip of RVN, as a District Senior Advisor, normally a Major's slot My only way around was in my Boston Whaler, with twin Johnson 40's, two motors because it was hard keep both running. It was a several hour trip up to Province HQ up in Camau, An Xuyen Province. We had to be back home before dark as the local Chuck owned the river then. I rarely made the trip. Besides, the local Vietnamese liked to load up or Whaler with so many body guards the Whaler would not get up on plane, it just plowed thru the water.

The other young Captains up at HQ had an easy life, AC comfort, good chow, movies at nite in the club, and wore comfortable civie clothes. I, in the year I was In-Country, never even had a non-issue T shirt. By then my jungle fatigues were worn and faded and torn. I much preferred my "country Gentleman lifestyle", with no command influence or interference to hassle me. He is a picture of young officers, can you guess which chap is the field guy, and which are the REMF's?

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Here is a shot of my overloaded Whaler, with SFC Tom Coon, looking over one of our Ex VC bodyguards, with his XM 203 rifle. Note the other Vietnamese on the radio. They never stopped talking, I had a hard time keeping them supplied with radio batteries. Terrible operational security.
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[Elwood]

For maximum reliability and functionality, I'd go electric fuel pump and electric wipers.

[ZGjethro]

I second going electric all the way. I put in a low pressure Facet pump on the rear crossmember and found some "American Bosch" 24v military wipers which are as unabtrusive as the original vacuum wipers. They work well but I have to park them manually

[NAM VET]

thanks for the advice. And I was just thinking, why did I think I needed to run my fuel line along the driver's side frame, then over to the other side for the carburation?? When it would have been a shorter route on the passenger side of the truck. Then the fuel line would not have to go under the radiator frame. Like it does now.

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[Elwood]

Probably because that's the way the fuel line was originally routed? Most likely because the first trucks had a fuel filter mounted on the generator regulator bracket, on the left side of the engine compartment, and the fuel line was routed up from the frame, through the filter, and back down to the frame, then up and across the engine crossmember to the fuel pump.

If authenticity is not an issue, and you don't have the first style of fuel filter, then you could route it whichever way works best for you.

If you haven't discussed the electric wiper question with Charles at M Series Rebuild, I believe he has a heavy duty setup that might work for you. A search through the forum archives will dig up some good info on this type of conversion.

[ZGjethro]

Years ago when I first got my truck, I floated the idea on this forum of running the fuel line on the passenger side. Some people thought it wasn't smart with the exhaust there. I can't remember if the issue was vapor lock or catching on fire. Innever got around to that and just put a Holley fuel pressure regulator, filter and pressure gauge, where the original fuel filter was. I have a "temporary"'fuel injection line going over the head to the carb

[just me]

The line is on the left cause the exhaust is on the right. Standard automotive practice. I run mechanical and went from electric to vacuum wipers. It rarely rains here and the correct vacuum wipers work far better than the M151 wipers it had at first. The electrics were too much in my sightline for me to keep.
I have no issues with mechanical pumps (and points and condensers) so don't want the added complications of correctly installed and wired electric pumps. And the quality of the new aftermarket pumps leaves a lot to be desired compared to the older SW and AC pumps.

[NAM VET]

Sometimes I have to remind myself that the military, above all else, wanted these trucks to be tough and dependable in a combat environment. Being able to get that ammo to the front, even with battle damage, hauling desperately needed reinforcements to where they were needed, even with mine damage, towing the 105 to fend off a determined enemy, means that it was vital that the truck take what no civilian vehicle could. So putting the fuel and brake lines inside the frame, and as far from a hot exhaust as possible does make sense, whereas in a non-military vehicle it might not be so vital. Being able to pull out a broken axle, and take the twisting and torsion of rugged terrain, all these capabilities and more were lessons learned from WWII. LIkewise, keeping things as simple as possible for field repairs, to keep them running, often with maintenance with simple tools, by soldiers who could be inventive, if not highly trained as mechanics.

I have read that these M 37's were the first military vehicle that were designed specifically for their military mission, and not some adaption of an existing civilian platform. And the experience of the just completed war had to have a great impact on how they were to be built. So the military absolutely wanted a vehicle that would be less likely to fail at the critical point of a desperate battle.

In the Battle of the Bulge, a recently deceased uncle was driving a Sherman in Belgium, and ran over a German Teller anti-tank mine. It killed the entire crew, less him, and every single one of the infantry squad riding on top. He survived, and spent the next year in the hospital, and when I was a kid, he would let me feel the steel still imbedded in his arms. Combat is tough on vehicles, and even more so on the soldiers who fight it. Our M 37 trucks were designed and built to take as much battle damage and still complete their mission as a wheeled vehicle can. So when I wonder why this or that component of my own M 42 is the way it is, and then realizing that it makes the truck less vulnerable to small arms fire, or shrapnel, or the rigors of inhospitable terrain, makes me admire the engineers who made it so.

Lets see if I can find a picture that illustrates what military vehicles have to be capable of. I think I have posted this picture before. But any military vehicle can only take so much....

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[Elwood]

Tough, dependable, and simple, yes, but these are, after all, soft-skinned vehicles not intended for combat. They're support vehicles. There's not that much about their design that is uniquely military, other than a few things like the lighting system, the 24 volt waterproof electrical, and the deep water fording capability.

I don't believe that routing the fuel lines inside the frame rail is all that different. My '63 Studebaker is done that way, and if I remember correctly, so was my '56 Chevy 1/2-ton (although that one did look like it had been through combat ). Yes, the lines have an "armor" wrap on them, but that's more for off road rock protection, than for any sort of combat, such as a mine.

The axles are a typical full-floating design, similar to anything in a contemporary heavy commercial truck. Granted, 4x4 light trucks were not then a commonplace item like today, but they were available, and the four wheel drive technology in our M37s was not ground breaking or military specific, even when they were new; remember, the civilian Power Wagon, itself derived from the WWII Dodge WC trucks, had been in dealerships for five years before the M37 started production.

And the suspension is certainly a very conventional design for the era. Most of the components, from the 1933-designed flathead six to the four speed gearbox to the transfer case to the brakes, steering, etc. is not unique or especially different technology from standard commercial vehicles of the time.

Not sure where you read that the G-741 series was the first designed specifically for a military mission, but I'd dispute that argument. The earlier Dodge WC series did not have a civilian equivalent at the time, nor did the Bantam/Willys/Ford Jeeps. And all of these vehicles were derived from automotive practices of the day.

[NAM VET]

I agree with much of your post. It would have made sense for the "clean sheet" design of the M37 variants, to use the best of tried and proven components. And then put them in a total package optimized for the intended "support" mission of these vehicles. Perhaps the best example is the 6 cylinder motor. These were not meant to be light-skinned reconn vehicles. But even support vehicles operate in hazardous circumstances.

A little story. When I graduated from ROTC at Nebraska in the summer of '69, after infantry, airborne, and ranger school at Benning, I was posted to Schweinfurt, Germany, as a Lt mechanized platoon leader, 1/30, Third Infantry Division. Challenging times, with all of the army's focus on the rising tempo of the Vietnam war. People and equipment were in short supply. My highly respected younger company commander had been shot 23 times in Vietnam, before he was able to point out the sniper who kept shooting him from a tree top.

Anyway, by then the M37 vehicles were largely phased out of the active army; I certainly had no experience that I can recall with them. They had been replaced by the temporary expedient Jeep pick-up. But since they were only an interim while the next wheeled vehicle was to be available, there were no major or even minor repair parts in the enormously deficient supply system. Our company had 113's and a single M114 for the CO, so I had very little experience with any wheeled vehicle, although his 114 was always "down", so on any field exercise, he had a flat hood jeep. The lack of even minor spares for the Jeep pickups meant that they were sent to salvage for minor "issues."

I will say that observing the weapon's company with their 114's with 30mm Vulcan chain guns were a formidable sight at a range.

My engine machinist told me to call him this afternoon and he will have the specs on what I need to order to get going on the rebuild . He already has the new valves and valve seats and their components.

As always, I put out my American Flag on the porch. I like this picture, the old and the new, 300 miles out in the desert....
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[52PLOWERWAGON]

I went with electric fuel pump and my wipers are on there way

and above you mentioned that all military vehicles can only take so much


something else I realized the other day that made me like them even more

they were made to be worked on in the field while being shot at
now that's saying something about serviceability

[NAM VET]

I don't have any hope of finishing my own M 42 to a correct standard, per '52. I do want it to resemble what It might have looked a half century ago, without compromising its drivability and durability. Hence, I am going to stay with the NDT tires, they are all good, the spare is old, but still holds 40 psi. I have decided to paint my motor and things attached to it black. I bought some hundreds of grade 8 bolts and fasteners from Fastinal, and a big bag of square washers from Snake River. Where possible, and visible, I will try to use the original military bolts and my new square washers. But where necessary, or where I run short of the OEM bolts, then I will use my new ones. My engine compartment will look nice, but with the Purisil hoses and different colors, and perhaps a few stainless hoses, it won't stand tall at any replica display. Plus my dash will have my aftermarket switches, and on and on. So it is not strictly necessary for me to use OEM things like a fuel pump just for appearances, or trophy attempts. I just want it to go, work, and give me the enjoyment I am looking forward to. When I retrieve my fuel pump, and my starter and generator and carb back from Charles T, I will ask for his experience in the most likely to be reliable on the road, and perhaps off road, and then go with that.

For a lighter picture, here is the wait staff at the little 'cafe" in my compound. It was also their home, note the dirty floor, rotting coconuts under the benches. But the happy, smiling kids. I often had a Ramen noodle soup there for my lunch, with bits of whatever flycovered meat they had hanging. But with boiling water poured over it, it was fine. They also had river ice, for my beer 33, all sorts of sediment in my glass. It came down every few days by barge from Camau. Several of these kids were war orphans. No matter ow muddy it was somehow they were always sic and span. The taller girl on the left in the second picture was My, an orphan. I had my parents send me some trinket jewelry, and when I gave to the children, it was as if I had taken them to Tiffany's.

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[Marmalute]

Something to think about:
In the past when driving M37s I owned on a regular basis outfitted basically as a "stock" vehicle, I would often add a vacuum reservoir in series with the vacuum system for the wipers. These reservoirs were usually from Saab or Mercedes cars and often be stationed someplace under the dash where they would not be seen. The functional benefit to the wipers was that there was alway enough good vacuum to operate them regardless of how many long hills needed to be climbed.

[m-37Bruce]

Something to think about:
In the past when driving M37s I owned on a regular basis outfitted basically as a "stock" vehicle, I would often add a vacuum reservoir in series with the vacuum system for the wipers. These reservoirs were usually from Saab or Mercedes cars and often be stationed someplace under the dash where they would not be seen. The functional benefit to the wipers was that there was alway enough good vacuum to operate them regardless of how many long hills needed to be climbed.

This is a good idea, I have often thought about doing the same.
Thanks Marmalute,

[NAM VET]

Removed the 12 volt electric pump, and installed a small, "box" 24 volt Facet this afternoon. I had already replaced my 5/16 hard lines, protected with new armor. And had run a 14 gage, fused line from the dash switch all the way back, with it also protected with over-tubing. Put sealant on the Facet's nipple threads, and the instructions for the Facet suggest it works best with the inlet aimed slightly downward. I was constrained by my already installed hard lines, with short runs of 5/16 fuel injections lines. And very importantly, to ensure my hoses did not touch any part of the frame, avoiding friction damage. The holes on the welded frame tab did not line up to mount the Facet, so my conditions per above, I made a square plate out of aluminum. I had a thin sheet of aluminum, so used my brake to fold it and double it, then mounted it to the frame bracket. Not easy, hard to get my fingers behind it to hold a wrench on the nuts (with Lock-tite on the threads). Then using one of the two flange holes and another drilled in my new aluminum plate, fastened the Facet so my soft hoses aim perfectly, avoiding any contact with the adjacent frame. Put heat shrink on the wires, and connected it all up with more heat shrink.

Kinda hard to describe, but here it is now. I aimed all the clams so I can get to them from below when the need to replace the pump arises. I will put a fuel pressure regulator in the engine compartment when I complete those lines when I install the motor. I have to add a small line clamp to the frame to absolutely ensure it never abrades.
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and for a picture.....

This was my home for my second six months in IV Corps. Heli-pad just outside the compound, lots and lots of wire, my home was in the left half of of the metal building, lower left in the picture. The ride paddies had not been cultivated for many years. Home sweet home. My Whaler is tied up in the small canal which lead out to the river visible in the distance.
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