M35a3 m109a4 fuel system upgrade

[bigflew]

My m35A3 quit 1 year ago what I found was a feul tank check valve plugged. Easy enough to clean. But also replaced fuel and return lines . It ran good all last summer. It started and ran good when I got it out this spring.... once. Then would not start.
Here is the repair in short.
I found contamination in lift pump check valves (probably algee) I cleaned them first.
But seeing that the 3116 in these dose not have a pre filter but does have the housing here is my solution.
First order a fule filter for a Cat 3116.
You will have to bend the steel line a little to make it go on also get a 90 degree 1/4 pipe fitting to move the oil sending unit.
Remove the existing fittings from housing .
You will first need to get 2 9/16 straight thread o ring to 8 AN adapters also 2 8AN to 10 An adapters (I could not find 9/16 to 10 An )
What I did was cut main fuel line and used crismp on style 10 AN fittings to attach to new fittings on housing ( I used 1 90 degree and 1 45 degree)
Next I put a pick-up screen on tank pick-up pipe to prevent tank check valve problem.
I removed return line at tank and pressurized tank to get fuel to pump ( line off at pump until fuel came out.
It still took a lot of cranking to get running.
I think having a pre filter is a good plan.

 

[HDN]

I'm a little confused - where did you put the pre-filter? I can't tell from the pics unless it's actually an in-line screen at the check valve that you're talking about?

It does take awhile to prime the truck with the fuel pump to get the motor started. When I changed the fuel filter last it took 10 minutes of cranking in 10-second cranking intervals to get it started.

 

[glcaines]

I found that if you open the petcock on the bottom and make sure it is cleaned out with a piece of wire and then crank the starter with the petcock open until clean fuel runs out the petcock, it takes very little cranking to start the engine after a filter change. I actually leave the petcock open until the engine starts, perhaps 10 revolutions before starting once the filter is full of fuel. Also, cleaning the check valve at the tank isn't sufficient. I drained my tank and pressure washed the inside of the tank, all surfaces. There was gummy residue in spots on the side of the tank and something else that looked like coffee grounds or cigarette tobacco. I then filled a garden sprayer with isopropyl alcohol and washed the tank out to remove the water. I then put a hair dryer in the filler opening and dried it out. I haven't had a plugged check valve since. I also keep Optilube XPD in the fuel.

 

[bigflew]

I'm a little confused - where did you put the pre-filter? I can't tell from the pics unless it's actually an in-line screen at the check valve that you're talking about?

It does take awhile to prime the truck with the fuel pump to get the motor started. When I changed the fuel filter last it took 10 minutes of cranking in 10-second cranking intervals to get it started.

The pre filter is the yellow filter in the pic.
The military had it bypassed but the housing was still.there so I basically just re plumbed it back into the system

 

[HDN]

The pre filter is the yellow filter in the pic.
The military had it bypassed but the housing was still.there so I basically just re plumbed it back into the system

I was hoping that wasn't what you were talking about - that's really strange! That's the primary fuel filter for the motor with the built-in water separator. Why anyone would bypass that is beyond me, it's kinda important! I'm glad you got it fixed

This is why the Army shouldn't have Private Partz in motorpool fixing your stuff unsupervised

 

[bigflew]

I was hoping that wasn't what you were talking about - that's really strange! That's the primary fuel filter for the motor with the built-in water separator. Why anyone would bypass that is beyond me, it's kinda important! I'm glad you got it fixed

This is why the Army shouldn't have Private Partz in motorpool fixing your stuff unsupervised

That is the way the army received the 3116 motors . There is a filter in between the pump and the injectors.

 

[HDN]

That is the way the army received the 3116 motors . There is a filter in between the pump and the injectors.

I took another look at your pictures and I see what you're saying now, especially since the primary fuel filter is mounted upside-down on the side of the motor. That housing you have in your pictures is mounted rightside-up. I never noticed a second filter housing on my motor, so I'm going to have to take a closer look the next time I have the hood open!

That said I haven't had any fuel problems since I bought the truck that a filter change couldn't fix, so I'm thankful for that!