Fuel Flow

Discuss fixes, upgrades and modifications to your M37

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tinmedic
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Fuel Flow

Post by tinmedic »

I have a 52 M37 that has developed fuel flow issues in the past few months up to the point where it no-longer starts. I have replaced the fuel pump, fuel pickup and corresponding gaskets. Back story, she left me on the side of the road a few times due to fuel issues. I pulled the cover plate in the bed and found that there were only 3 screws holding the pickup in place and they were only hand tight. The gasket was made of something. That would explain why I smelled fuel every time I filled up as it was sloshing out the top of the tank. The inside of the fuel tank was very clean so I put in a new fuel pickup system and new gasket and sealed her up the right way. She seemed to be running fine and then I noticed that I had fuel pouring from the fuel pump when running. Fixing the pickup issue created a new one, go figure. I parked the truck where it sat for at least 3 months and ordered a new fuel pump from MWM. After installing the new pump I still can't get her to start but I dont know how long it should take to get fuel back to the carb. Everything under the hood is original except spark plugs and fuel pump and it only has 5100 miles on it. Any ideas would be greatly appreciated.
NAM VET
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Re: Fuel Flow

Post by NAM VET »

Electric pumps push a lot better than pull fuel. And some have more or less of an ability to "lift" fuel from a tank. Did you replace and check your fuel filter? Maybe you have an airleak interfering with the ability of your pump to pull fuel from the tank. I recently as part of my truck's overhaul, I made all new fuel lines, and added an electric 24 Volt Facet, way back on the rear inside frame rail, with a plastic see-thru Wix filter just before the pump. At first, I had power to it, but it did not make any clicking, so called Pegasus Racing, and he told me to be sure I had an actual 24 volts to the pump. I didn't, so put 24 V to the pump, and it pumps marrily away. I have a bypass plate where my mechanical fuel pump was.

I would start at the tank, and move foreward at each connection.

NV
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Re: Fuel Flow

Post by tinmedic »

NV, I actually have a 24V Carter here to install, I just haven't done it yet. I don't think I am getting fuel to the pump, much less the carb. The fuel filter is next on the list as I haven't looked at it since I bought the truck almost 2 years ago.
just me
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Re: Fuel Flow

Post by just me »

If you have the original fuel lines on the truck, they are almost certain to be rusted and restricted. If you let it set for months with ethanol fuel in the carb, white rust will likely also be a huge source of trouble.

You can loosen the fuel line at the carb and use the primer lever to see if fuel is reaching the carb.
Did you forget to open the isolation valve after changing fuel pumps?
"It may be ugly, but at least it is slow!"
tinmedic
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Re: Fuel Flow

Post by tinmedic »

Just me, If that is the little brass valve on the bottom right hose then it is open. When I removed the old pump I expected to get some fuel spilling out but it was dry.
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Re: Fuel Flow

Post by NAM VET »

this past spring, while my motor was out and to the machine shop, I put in new vent, brake, and fuel lines, from their source to their end. I used the Fedhill nickel/copper lines, renting their high quality double flare too. It wasn't hard, but it wasn't cheap either. But I took off the bed of my truck, making it vastly easier than working from below. And it would be impossible to run the fuel lines directly from the tank, as they would be under the bed, and unreachable if the bed is on. Removing the bed on my truck was simple and quick, as the wiring is attached to the frame, and not the bed, other than two minor rear running lights. At least, if your six bolts and nuts are not too rusty. You do need to remove the two rear shackles to get a wrench on the nuts there. I used my engine hoist, and lifted it right off.

But if you want an easier solution, you probably could make a short run of fuel injection hose from your tank outlet to the place where you will mount your fuel pump. On the driver's rear frame just in front of the axle is a good place to put your Carter. There is a small plate there on the inside of the frame, to which you can add another plate with a few bolts, putting your Carter there. By the way, I bought a 24V Marine Facet pump from Pegasus Racing, the small cube one, it was listed as I think 5-9 pounds or so, with a Wix plastic filter right in front of it, with fuel injection rubber lines for a few inches, so I can easily replace the fuel filter from below if necessary. It costs about 50 bucks, but is a lot smaller than a Carter pump. I ran new wires from a dash switch, but at first had only 12 V until I put it on the proper battery terminal, fused of course. I put some pictures on a thread awhile back, if you do a search, it might still be up, unless Photobucket has killed it. The Facet is only about two inches square, easy to fit it inside the frame.

If you want to continue with the higher "quality" fuel injection hose, you can buy a small reel of it, and use fuel injection clamps, I got mine from Summit or Jegs. Since you will be pushing the fuel forward from the pump, you won't to worry about an engine mounted pump collapsing it with suction. It would be very easy to run it from tank to pump and then to engine, without the hassle of precise bending of the 5/16 hard fuel lines. By the way, I added an expensive fuel pressure regulator in the engine compartment, thinking the Facet's higher pressure pressure would necessitate it to avoid overpowering the carb's float, but even with the regulator set to max flow, it only has about 3-4 pounds on the pressure gage mounted on the regulator so I don't think you would need to add that complexity. Fuel injection hose won't rot like cheaper hose will.

When I called Pegasus Racing when I had "juice" to my Facet, but it would not run, and he told me to be sure I had 24 V, which I easily corrected. He added they never get one of these not counterfit Facets back, as they are extremely reliable. Carters are good too, but are larger.

In summary, it would be easy to run fuel injection hose from tank to filter to pump, and then to carb. Whatever adaptors you need, Jegs has a vast assortment.

Good luck.

NV
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Re: Fuel Flow

Post by NAM VET »

just me
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Re: Fuel Flow

Post by just me »

An electric pump is unnecessary complication. The mechanical pump works fine if the entire system is in order. I replaced all my fuel, brake and vent lines from under the truck with the bed on. Wasn't horribly difficult and I only spent two days on it.
Try removing the feed line from the top of the tank and at the pump and blowing a few pounds of air through it from front to back. If it won't free flow at 5lbs of air, the lines are shot and need to be replaced.
I had to boil out the tank and replace the lines before I eliminated my fuel issues. Now, it is as good as new with no extra switches, wires, pumps, rubber hoses, leak prone hose clamps and Jerry rigging.
Repairing the base cause is always better than adding systems to mask the original problem.
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Re: Fuel Flow

Post by NAM VET »

Just Me has another way to approach your problem. Charles T rebuild my OEM pump, but with the risk of a rupture of a diaphragm I thought the possible quick damage to my bearings with diluted oil was just too much to worry about. One advantage of the mechanical pump is that it shuts off as soon as the motor quits running, like in an accident. I wired my pump to a dash "aircraft" toggle switch, so as long as I am not too impaired in an emergency, I can "slap" it down and shut my pump off.

I think if one is careful and meticulous and uses quality components, an electrical pump is a reasonable alternative. For instance, I protected all my wire with a polyethyene or Loom over wrap, soldered my connections, used shrink tubing over heat sealed connections, fused, and used Fuel Injection hose and clamps, and added insulted/coated hose and wire clamps to the frame along the way. Added a racing fuel pressure regulator with a gage, although I don't really think it turned out to be necessary. I made sure no new FedHill fuel (or other of my new lines) had any possibility of abrasion or wear against a frame part.

I am sure millions of older cars had reliable simple mechanical pumps, and our M37's soldiered on with theirs too.

Let us know how your choices and solution works out for you,

NV
tinmedic
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Re: Fuel Flow

Post by tinmedic »

If I decide to use the electric fuel pump it won't be until after the fuel system runs fine without it.
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Re: Fuel Flow

Post by ashyers »

tinmedic,
I had a similar issue a while back. Ensure that you have all of the fuel line fittings secure. We had one that was left a bit loose on the inlet side that allowed the pump to suck air and loose prime.

Andy
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Re: Fuel Flow

Post by tinmedic »

Thanks Andy. This weekend I am going to go over the lines from tank to pump to see if I can find anything.
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