M35A2, fuel pump not working. How do you prime without.

Hi gents,

Switched out my fuel filters and discovered my fuel pump is not working. Read that you could attach a compressor and push fuel through the three filters. Added an air fitting on the fuel tank. This is where it got weird. At first I had the frame filter off. Pumped air into the tank and fuel came out of the empty front filter. Replaced the filter and pumped away. Had the vent open on the dual filters on the engine. Just bubbles. Then I noticed that the bubbles where coming from the "OUT" fuel line. Never filled the system. What am i doing wrong? Photos show my tank and attachment and my finger points where fuel (bubbles) is coming into the filter.

Did you check the fuse on the in-tank pump ?

Just a thought (probably an obvious one..(You know?)), There is Venting to the system, From various points, Including the Excess fuel RETURN line.
So pumping air into the tank will cause air and fuel to flow through those points.
A better solution is to place any 24Volt inline fuel pump into the supply line.

Another point though, It does take quite a while for air to purge after changing fuel filters.

When you say the fuel pump is not working, exactly what do you mean? 1. Pump does not run. 2. Pump runs, but doesn't pump fuel. I would troubleshoot the in-tank pump first.

I did, fuse was good. Took the whole pump out. Looked ok, have not check for power to the pump.

glcaines said:

When you say the fuel pump is not working, exactly what do you mean? 1. Pump does not run. 2. Pump runs, but doesn't pump fuel. I would troubleshoot the in-tank pump first.

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Just to add to these valid questions.
Sometimes the 'Shims' fall off the bottom of the impeller housing at the bottom of the in tank pump so that although rotating it will not pump fuel.
Take out the pump and service it.
Fuse blown?, Impeller filter blocked with muck. Being a 'Magnetic drive' It will rotate and not pump fuel.
Post up the findings and solution to the problem when corrected.

dmetalmiki said:

Just a thought (probably an obvious one..(You know?)), There is Venting to the system, From various points, Including the Excess fuel RETURN line.
So pumping air into the tank will cause air and fuel to flow through those points.
A better solution is to place any 24Volt inline fuel pump into the supply line.

Another point though, It does take quite a while for air to purge after changing fuel filters.

Click to expand...

That was what I was thinking that my pressure was bypassing. I guess I should trouble shoot the in tank pump.

See post 58 and the others in here...............
https://www.steelsoldiers.com/showt...ried-to-fit-this-pump-in&p=1544676&highlight=

Put a gauge on it and check the fuze, never know what one may find.


Buy a Parker pump and put it in there with a new piece of "under fuel" hose.
Just be done with it for the next 10 years.
The Parker is about 90 bucks now but without it one has a 13,000 pound lawn ornament.

glcaines said:

When you say the fuel pump is not working, exactly what do you mean? 1. Pump does not run. 2. Pump runs, but doesn't pump fuel. I would troubleshoot the in-tank pump first.

Click to expand...

Good question. I pulled the unit and turned on the system. Pump was no go. I need to check to see is it is even getting voltage. The pump was serviced at some point, it was very clean with a new fuel line. This is the first time I have changed fuel filters. Ran fine up until I did the replacement. Checked the fuse, it was fine. I think you are correct, fix the pump, fix my problem. By the way, pumps have gone up in price!

That is the thing with (Some) Deuces, they will start and run fine without the in tank pump, But, get air into the system (As in a filter change), and then they will not start or run until primed again.
Check the pump on the bench, Positive wire to the input, and just ground the case.

dmetalmiki said:

That is the thing with (Some) Deuces, they will start and run fine without the in tank pump, But, get air into the system (As in a filter change), and then they will not start or run until primed again.
Check the pump on the bench, Positive wire to the input, and just ground the case.

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Next step. I have already broke the gasket/seal so will remove again and see. Repainted the bad boy with CARC green sad to blemish all the paint on the screws but it is a military vehicle! Thanks again. My goal is to own a tracked vehicle one day. Very cool you have one. Cheers!

FYI: You can get 24 volt fuel pumps from RockAuto.com around $30 - I've used them and they work fine.

RayK said:

FYI: You can get 24 volt fuel pumps from RockAuto.com around $30 - I've used them and they work fine.

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Agreed. If money is an issue at this time, then just buy a decent 24 volt stand-alone pump. It will have no problem drawing fuel up the 24" or so and then can easily pressurize the lines. Then you have the time to save up the funds for a proper in-tank fuel pump while still using your truck.

If you are just trying to get it going you can manually fill the filters as I did when I changed the filter only to discover the same thing you did. I forget how I did it but it involved a turkey baster and some time. I think I filled the 2 filters through the vent holes. I think the one over by the generator I just filled to the brim and very carefully reinstalled. I did end up replacing my pump but this was just a down and dirty way to get it running again.

Found a Parker pump and it's on the way. Good thing I have cool neighbors, truck is sitting in our cul-de-sac. Now the HOA I belong to, different story!

Troop462 said:

Found a Parker pump and it's on the way. Good thing I have cool neighbors, truck is sitting in our cul-de-sac. Now the HOA I belong to, different story!

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That's why I bought land way outside the city. I couldn't stand to have someone tell me what color to paint my house ! Or that my yard didn't meet the current standards ! Like my Uncle used to say " If I can't take a piss off my front porch without bothering the neighbors then I'm too close to people ! "
I've tried to live by that standard all my life !