Electric Fuel Pump Conversion

M274 Mechanical Mule Knowledge Base
Chuck W.
G-Lieutenant General
G-Lieutenant General
Posts: 5029
Joined: Wed Dec 18, 2002 1:00 pm

Electric Fuel Pump Conversion

Post by Chuck W. » Thu Jul 09, 2015 2:12 pm

PART 1

For some time now, mule owner Phil Bragg has been asking me to install an electric fuel pump on one of his mules. He is concerned about serviceability, reliability and availability of the Airtex 1202 manual pump. While I was not in favor of this at first, I decided to go ahead and do it for him, but with the following conditions: No rubber hoses. I would use only steel lines and flair connectors. Bullet proof; I would make the installation as close to what I thought the factory would have done if they had used electric pumps.

The pump we selected to use is an Airtex E8251 Marine grade 12 volt pump. This pump costs about $35. (Phil said I could not use a Marine pump on an Army mule.....)
Image

This pump is rated at 2.5 to 4.5 PSI. The mechanical Airtex 1202 is rated at 3.0 to 4.5 PSI, so this is a great choice.

The E8251 uses pipe threads instead of barb fittings, so it will be easy to adapt to the fuel line brass flair fittings I plan to use.
Image

I also machined an aluminum block-off plate for the old mechanical fuel pump.
Image

I started by removing the mechanical fuel pump and all the fuel lines from the bottom of the "T" fitting to the fuel filter at the engine;
Image

I installed the fuel pump block-off plate. The holes in the block are blind, and the blockoff plate is thinner than the mounting flange on the mechanical pump, so it was necessary to cut about 3/16" off each bolt to keep it from bottoming out in the hole.
Image

Next, I fabricated a steel fuel line to go from the bottom of the "T" to the fuel filter.
Image

Image

Brass flair fittings were used for all connections.
Image

Image

Notice how much room there is around the "t" fitting. Very easy access now. This should make removing the carburetor much easier in the future
Image

I used the existing union point on the fuel line, just behind the rear bed support. This way, I only have to create one flair connection.
Image

I'll cut this section of fuel line and reuse the flair nut and flair the line.
Image

Don't forget to install the fitting onto the line before you make the flair!
Image

Completed electric fuel pump, using brass flair fittings. Notice fabricated mounting bracket attached to bed cross member. Like I said, I want this installation to be bullet-proof!
Image

In the next part we'll deal with the electrical requirements for the pump.
Last edited by Chuck W. on Fri Jul 10, 2015 9:26 am, edited 3 times in total.

Gunslinger1$
G-Second Lieutenant
G-Second Lieutenant
Posts: 514
Joined: Sun Oct 13, 2013 6:39 pm

Re: Electric Fuel Pump Conversion

Post by Gunslinger1$ » Thu Jul 09, 2015 4:25 pm

Nice job Chuck!!!

Auto Shop teacher
G-Major
G-Major
Posts: 959
Joined: Mon Feb 03, 2014 12:46 am

Re: Electric Fuel Pump Conversion

Post by Auto Shop teacher » Thu Jul 09, 2015 5:40 pm

Nice clean installation Chuck, shouldn't have any issues with that setup.

old man
Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 490
Joined: Fri Mar 07, 2014 8:32 pm
Location: New Ulm, MN

Re: Electric Fuel Pump Conversion

Post by old man » Thu Jul 09, 2015 6:23 pm

Chuck did this on one of the mules I got from phil, and it is great. I haven't used the choke even in the winter. This documentation is fantastic, great photos showing the process. if the manuals were this detailed I would never have a problem.
Chuck I think you better start machining out more block off plates I think they will be in demand here shortly.
thanks for the great work

gpw6335
G-Captain
G-Captain
Posts: 723
Joined: Fri Mar 03, 2006 9:20 am
Location: Alvin Texas
Contact:

Re: Electric Fuel Pump Conversion

Post by gpw6335 » Fri Jul 10, 2015 6:02 am

Really looks nice.
1943 GPW 103951
1951 M38 27714
1952 M38a1 28888
1969 M274A5
1972 M151A2
1943 MBT
1951 M100
1979 M416
1962 M37B1


Chuck W.
G-Lieutenant General
G-Lieutenant General
Posts: 5029
Joined: Wed Dec 18, 2002 1:00 pm

Re: Electric Fuel Pump Conversion

Post by Chuck W. » Fri Jul 10, 2015 8:13 am

Chuck did this on one of the mules I got from phil
Actually, I didn't do that one, but I think it was Phil's inspiration for this project.

Chuck W.
G-Lieutenant General
G-Lieutenant General
Posts: 5029
Joined: Wed Dec 18, 2002 1:00 pm

Re: Electric Fuel Pump Conversion

Post by Chuck W. » Fri Jul 10, 2015 9:11 am

PART 2

The one problem with an electric fuel pump is......well, it needs electricity to run!

The original pull-start mule's electrical system consisted of an 8 foot piece of wire and a switch. In the "off" position, the switch connected the magneto to ground to kill the engine. In the "run" position, the ground circuit was open.

If you have added an electric starter and a battery to your mule, you have the on-board 12 volt source we need to run the pump, but we need a way to control it. The pump needs to turn on when the engine is starting and running, and turn off when it is not. You could use a simple "On-Off" toggle switch, but if you forget to turn it on, the engine won't start, and if you forget to turn it off, you might overfill the engine crankcase with gas, or at least run down your battery.

My answer is a riding lawnmower switch. Most mowers ground the points to kill the engine, similar to the mule magneto circuit, but the switch also has a 12 volt starting circuit, along with a constant switched 12 volt source for the lights, which can be used for the fuel pump. I use the Power Max 4012 replacement switch that I get from my local Advance Auto Parts store.

Image

Whatever switch you use, make sure it is marked and operates as shown in the schematic below.

Image

I like to mount the switch in a steering column box, like the ones used in the original mule electrical kit. John Emery sells very nice reproductions, complete with the clamp.

Image

Image

Now it's a simple matter of following the wiring schematic shown above. Be sure to include fuses as shown.

For those of you with the original electrical kit, it's even easier, as the Chrysler alternator also requires a switched 12 volt source, so you can simply tap into that wire to power your pump.

With the electric pump, the choke is almost never used. Turn the switch to the "On" position, wait a few seconds, then go to "start". The mule will start almost every time with no choke.

On mules with electric starters but no alternators, I have no idea how this pump will affect battery charge life, as I have been unable to find a spec for the amp draw.

Phil will be watching this mule carefully to see how it does. including starting and operating performance, and will report back.

If anybody is interested, I may put together a kit with the pump, plate, line and fittings.

PBragg
G-Sergeant Major
G-Sergeant Major
Posts: 160
Joined: Wed Dec 13, 2006 5:48 pm
Location: Huntsville, Alabama

Re: Electric Fuel Pump Conversion

Post by PBragg » Fri Jul 10, 2015 2:03 pm

I am grateful to Chuck on taking on this project. It was also fun putting our heads together to develop a solution. We both had ideas but I assured Chuck that he would drive the train on this conversion.

As a former Army maintenance guy I began to have real issues with this design and placement of the mechanical fuel pump. What a PIA! When we restored the mule that Steve currently has (came with an electric fuel pump) I was really impressed on how easily that mule started....no choke required!

Recently had a fuel delivery issue after replacing the mechanical pump just 8 months earlier. Though we discovered the mechanical pump was in fact not the issue the conversion to electric was well worth the effort.

Thinking this through here are what I consider the advantages of this conversion:
When needed the carburetor will be easier to replace.
No longer have to connect the tiny fuel line under the carburetor to the mechanical pump. Had real issues with the limited space to work in.
When the mechanical pump fails it often passes diaphragm material to the carburetor inlet screen. Problem solved.
When the mechanical pump fails it allows gas to enter the crankcase. Problem solved.
Saves on oil changes and filters due to mechanical pump failure.
Can check fuel delivery WITHOUT starting the engine.
Ease of replacement. A failed electric pump could be replaced in minutes compared to hours for the mechanical pump.

Chuck's idea to make this look "factory" was well thought out. From the machining of the block off plate to bending the new fuel line this installation looks like OEM.

Couldn't be happier with the results. Just for grins I turned the key this afternoon and the bad boy fired right up. Lot less cranking on the starter too.
Phil Bragg

2-1968 M274A5s
10-circa 1957 M274 Banthrico promo models
J. Sommer 1/6 scale RC Mule

Gunslinger1$
G-Second Lieutenant
G-Second Lieutenant
Posts: 514
Joined: Sun Oct 13, 2013 6:39 pm

Re: Electric Fuel Pump Conversion

Post by Gunslinger1$ » Fri Jul 10, 2015 4:31 pm

Thanks Chuck! I like the way you did this. I think I will convert one of the mules I use at Knob Creek and see how it does.

Mike_W
G-Sergeant
G-Sergeant
Posts: 47
Joined: Mon Nov 08, 2010 5:20 am

Re: Electric Fuel Pump Conversion

Post by Mike_W » Fri Jul 10, 2015 6:20 pm

Here is another wiring solution that I used earlier this year. It uses a MTD 925-1717 starter switch which retains the separate light functionality while allowing constant voltage to the fuel pump even in the start position.
mule_wiring.jpg
MTD 925-1717 starter switch wiring
mule_wiring.jpg (177.6 KiB) Viewed 2578 times
Mike White
Roswell, GA

Auto Shop teacher
G-Major
G-Major
Posts: 959
Joined: Mon Feb 03, 2014 12:46 am

Re: Electric Fuel Pump Conversion

Post by Auto Shop teacher » Fri Jul 10, 2015 7:31 pm

Great information, thanks for sharing it with us. No need to re-invent the wheel when you have already been there, done that, thanks!

I have a question about not needing to use the choke anymore after the conversion. I understand that the electric fuel pump will fill the fuel bowl before you crank the engine, but the purpose of the choke on a gas powered car engine is to give the engine a richer mixture when the engine is cold and not able to vaporize the fuel very well. Is something different on these little air cooled 2 cyls?

Chuck W.
G-Lieutenant General
G-Lieutenant General
Posts: 5029
Joined: Wed Dec 18, 2002 1:00 pm

Re: Electric Fuel Pump Conversion

Post by Chuck W. » Sat Jul 11, 2015 1:41 pm

removed
Last edited by Chuck W. on Thu Jul 07, 2016 6:53 pm, edited 1 time in total.

Gunslinger1$
G-Second Lieutenant
G-Second Lieutenant
Posts: 514
Joined: Sun Oct 13, 2013 6:39 pm

Re: Electric Fuel Pump Conversion

Post by Gunslinger1$ » Sun Jul 12, 2015 12:59 pm

Chuck
What is the thickness of the aluminum cover you made for the old fuel pump?
Dave

Chuck W.
G-Lieutenant General
G-Lieutenant General
Posts: 5029
Joined: Wed Dec 18, 2002 1:00 pm

Re: Electric Fuel Pump Conversion

Post by Chuck W. » Sun Jul 12, 2015 8:21 pm

1/8" plate.

97 heavyduty
G-Staff Sergeant
G-Staff Sergeant
Posts: 57
Joined: Thu Oct 24, 2013 8:11 am
Location: Saint Paul Nebraska

Re: Electric Fuel Pump Conversion

Post by 97 heavyduty » Sat Jul 25, 2015 8:07 am

This looks like a good winter project. Also this subject needs to be at the top of the forum. Now the problem, what do I do with all my spare mechanical fuel pumps? Thanks Chuck for the post

Post Reply

Return to “MULE M274 Technical”

Who is online

Users browsing this forum: No registered users and 1 guest