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In-Tank Fuel Pump Dilema

SasquatchSanta

New member
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Location
Northern Minnesota
Over the past few months, after having trouble with my original in-tank fuel pump I've been going back and forth between running stock in-tank pumps and OD Iron's in-line pump. I'm sharing this so you may gain some insight from my experiences.

First ... I suspect that I was also having fuel jelling problems when my original in-tank pump failed. I'm not saying the jelling problems caused the pump failure, only that it seemed to happen at the wame time. When the first pump failure happened the truck was idling, warming up in my drive way on a below zero morning in January. What got my attention that something was wrong was when the engine shuttered and died. I guess that's a pretty sure sign that there is a problem. :shock:

Figuring if it died once, it would probably die again and the next time it wouldn't be in my driveway I decided to address the problem when the snow was gone. I've since learned that once the engine is running the IP booster pump will pull fuel from the tank and keep the engine running. I should note that I read in a TM that the in-tank pump is needed during operation to supply positive pressure to the boster pump. (my words, not the TMs). Sooo ... what this all means is that I probably had a fuel jell problem AND a pump failure at the same time.

I purchased one of OD Iron's in-line "thumper" pumps. Everything went fine until I decided to get cute and remove the in-tank pump and install a 1/2" pickup tube in it's place. I removed the stock in-tank pump because at the time I didn't know if it was causing restrictions that could possibly overwork the OD Iron pump. As it happened, removing the original pump and the therefore it's screen was a big mistake. The tube that replaced the pump did not have a screen and there lies the problem. I should note that I later learned that the original in-tank pump does NOT cause a restriction on the OD Iron in-line piump.

A few weeks later I was tooling down I-494 in Minneapolis during rush hour traffic with an 18 foot trailer in tow and the engine suddenly died. This is everyone's nightmare. Over the roar of traffic could hear the thumper pump doing it's thing so I cracked open the petcock on the spin-on primary fuel filter. Very little fuel came out. I sprayed myself down with mosquito repellent and proceeded to changed the filter. With the new filter still very little fuel came out of the petcock. Stored under the drivers seat, beside the spare fuel was also a spare in-line pump. I installed the new pump and within 30 minuted was underway.

Needless to say, the trip back to the boarder was a white knuckle affair. All I could think was, if that thumper pump quit once the new one could also quit and I'm out of spares. Once again, just like when the original pump quit working last winter, it didn't make sense that the ending died but, once again, it did.

When I arrived home emailed Mike at OD Iron. He responded immediately and offered to replace the pump on a no-charge basis. I declined because I wasn't sure my problem was the fault of the pump. I TAKE MY HAT OFF TO MIKE for offering to replace the pump BUT I've been around long enough to know that it isn't always the vendor's fault.

My old friend Honest John Bizal of Midwest Military said he had a stock pump that he thought was good and sent it to me for a try. He didn't invoice me so I was going to see if it was a good pump. I finally got around to installing it but before I did I installed a fuel pressure gauge between the primary filter and the IP booster pump. It was no doubt overkill but after having the Minneapolis freeway experience I wanted some backup so we installed the in-tank pump in parallel with the OD Iron pump. If one went out all I had to do is to turn a valve and swap fuses and I had the OD Iron pump to fall back on.

Both the in-tank pump and the thumper pump generate around 6 PSI of pressure --- that was until yesterday when I noticed that the in-tank pump's pressure was dropping. In a 40 mile round trip it dropped from 6 PSI to 1 PSI. When I got home I noticed the in-tank pump sounded like it was running rough. Not knowing if the low pressure was a fuel filter problem I quickly switched over to the thumper pump (see attached picture). The fuel pressure shot up to 6 PSI --- obviously not a fuel filter problem. Looks like ANOTHER in-tank pump bites the dust.

ANOTHER DEVELOPMENT --- I cut into the original OD Iron pump that failed on the Minneapolis freeway and found 6 small pieces of dried gasket material that looked like mouse turds lodged in the outlet orifice that were plugging the pump. These came from material materiel in the bolt holes being pushed into the tank when the round cover plate was installed

As previously stated, I had removed the original pump and it's screen and had not installed a replacement screen. This was a BIG MISTAKE. Considering what was lodged in the outlet orifice I'm surpriced the engine ran as long as it did.

Now that I know what caused the OD Iron pump failure --- that it was "operator error" and not the fault of the pump I'm going to quit monkeying around with intank pumps.

I'm also installing a second fuel pressure gauge --- the second one between the pump and the primary filter. With a gauge before and after the primary filter I'll know when if I have a fuel filter problem OR a pump problem.
 

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SasquatchSanta

New member
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Location
Northern Minnesota
This evening I decided to inspect the in-tank pump that has been producing low fuel delivery pressures.

I removed the pump fron the tank thinking that the shims in the bottom might have come loose. It was still all in one piece. I checked all the wires to make sure there wasn't a lose connection and turned the pump on to see what it sounded like out of the tank. It sounded a little rough and ran at inconsistent RPMs. At one time it slowed almost to a stop. I could gently shake it and the speed would change. One would think if the motor was hanging up it would pull enough amps to blow the 4 amp fuse (it may be a 5 amp fuse?).

I'm not much when it comes to electric motors. Anybody got any ideas as to what could cause this?
 

cleb

New member
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Location
Huntsville, AL
Mine is doing the same thing I think. From what I can tell, there is a motor and a magnet inside that sealed unit. On the lower unit there is another magnet that is spun by the one in the sealed motor unit. Take off the lower unit (They are one way screws so you will need a pair of pliers, etc), and make sure that spins freely. My motor is messed up, possibly like yours. It grinds and doesn't pump, etc. I think the magnet is falling off the shaft in the sealted unit. I think I'll hack it apart when I get around to replacing it.
 

saddamsnightmare

Well-known member
3,618
80
48
Location
Abilene, Texas
August 30th, 2008.

Dear Sasquatch Santa:

Man, I don't know what you're doing to that deuce, but you must be getting :Coal" in your tank instead of your bag!!
You northerners are sure hard to please when it comes to deuces and fuels...... I had to replace the in tank pump on my M35A2 (it was probably never working since I got it last October) due to a loss of prime condition proved the pump was inoperative... The old Red River Arsenal mechanic that worked on it said that was only the second deuce he'd seen in 37 years to have an in tank pump fail..... I replaced it and she started right up!!! If you'd quit trying to pump and burn liquified reindeer dung hydrocarbons.... your pumps might last better!!!! If Uncle meant the deuce to burn reindeer droppings, we'd all be farming reindeers!!! :p :p :p
Time to trade up to a U100L Unimog, Santa, your rounds will go much, much faster!!!!! rofl
Cheers,
Sincerely,

Kyle F. McGrogan

1971 Kaiser Jeep M35A2 Wo/W "Saddam's Nightmare" Desert Storm and Vietnam Veteran Deuce
1968 Johnson Corp M105A2 Cargo Trailer
1967 Hercules MEP023A Gas Gen-Set APU
1963 Swiss Army Cargo Unimog, S.404.114 MB "AKA the Swiss Money Pit!!!" :beer:
 

SasquatchSanta

New member
1,177
18
0
Location
Northern Minnesota
Hummm ... Raindeer Dung.

That might be a good reason to keep Rudolph around for a little while longer.

If I have to bail him out of jail one more time he's history. He didn't get that red nose from eating sugar cookies

Never fear ... Old Santa will have the red rocket up and running by christmas. :D
 
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