941 B Loosing prime

[asleiman]

Gentlmen
Help, II have a 941B Track loader , that I use occasionally all , in the winter time I changed the Injectors thinking that would help. It started to loose prime. Changed filter , water separator and hand priming pump. No luck it seems to be sucking air . I found no leaks. My last resort is to rebuild the pump. I would like too find a logical reason.


Thank you

 

[DMiller]

Nozzles won't cause air intrusion, the remaining components could but should show signs as filter/separator fuel level when removed low to empty and as this has the fuel tank above the system any air intrusion would be a leak when not running.. The injection pump/transfer pump a potential but they will usually show out as fuel in the oil after use of a period of time.

How old is the fuel? Is it greyish or blackening? If is algae contaminated will shut off flow thru the fliters and will require drain, cleaning the tank, flushing lines and replacement of the fuel. Just adding algaecide will clog filters ever faster.

 

[asleiman]

Thank you DMiller,
Fuel is not old , , when I bleed it , it is red color.
I use the hand pump to prime it , sometime I dont get fuel out when II loosen the the injector.
Iam curious if the pump rack or check valve stuck open

 

[asleiman]

DMiller , You have provided a lot of information ,
just to understand, if there are no fuel in the oil , then pump is ruled out to be OK
then all line from inlet to fuel tank need to be checked ,
I changed fuel filter and water separator. . separator had some bad stuff looked black

 

[DMiller]

If already found black fuel start there. Algae in the fuel will make a slime goo that can block up fittings, lines, sediment screens. Drain the tank first, go from there.

 

[asleiman]

Hello again,
drain the tank , fuel looks good , watched drain , 10 Gall.
took off and cleaned all fitting , hoses and lines from the pump and back , all looks good and clean
Found no cluprit the far

 

[DMiller]

If have tank empty look into the bottom, make certain nothing floating inside that could block fuel.

 

[asleiman]

Noticed the fuel cap center bolt that hold the screen had fallen out ,
cleaned it and reattached with some locktite

 

[thepumpguysc]

If its kickin your behind to the point of giving up.. Detroit sells a 1 way check valve for the fuel line in different size barb ends, to slide between rubber fuel lines..
You can install 1 between the inj. pump & fuel tank.. just a thought..
I'm sure there are different manuf. of them by now, but the ones I'm familiar w/ came from Detroit.. just google it..

 

[kshansen]

Just wondering which fuel system this engine has, scroll or sleeve metering. Pre-chamber or direct injection?
S/N off engine and or machine if they are different might give some more clues of where to look.

One idea if it is in fact a sleeve metering pump is in this file:

 

[asleiman]

S/N : 80 H 5236
it is sleeve

 

[asleiman]

Here is the 941 B Running , it lost prime , from the sound of it she sound good

 

[kshansen]

Not sure if this will work but will try to attach the info on the "Systems Operation" for the fuel system. Note that this is somewhat of a generic set of description as it is for various versions of the 3304/6 engine.

In the diagrams it shows some with a "Siphon Break" and others with out "Siphon Break" if you read down the pages far enough you will see the statement that,"Siphon Break" is used on a machine with fuel tank located below the fuel pump housing.

Hopefully this goes through and after studying how the system works it will give you an idea of how you are loosing your prime.

Okay, got a error message saying the file is too large so if you can "Start a Conversation" as the new format of this forum calls it and send me an email address to send it to I'll give that a try.

 

[asleiman]

Kshansen , I posted new post with email

 

[asleiman]

If its kickin your behind to the point of giving up.. Detroit sells a 1 way check valve for the fuel line in different size barb ends, to slide between rubber fuel lines..
You can install 1 between the inj. pump & fuel tank.. just a thought..
I'm sure there are different manuf. of them by now, but the ones I'm familiar w/ came from Detroit.. just google it..

Hey Pumpguysc,
This pump has a check Valve , in everything I read about it( in the manual) , I have not been in one of those pumps.
in fact it has 2 check valves a and depend on which model you have they suggested to eliminate one of them.
Please provide me with a part number if yoou have it

 

[kshansen]

Kshansen , I posted new post with email

Sent the file direct to your email, hope it is not too big a file.

 

[asleiman]

Just an date ,
DMiller suggested that I look inside the tank after I empty it. this morning I took my extended light it reach to the bottom , I looked could not see anything that may float , in fact the tank looks real good.
took the screen out at the cap , it had some debris junk. good thing still a separtor and filter prior to going thru the pump

 

[Mobiltech]

That style fuel injection pump has the gerotor style transfer pump mounted in the front of it . A common problem with them is the drive shaft seal wearing out and allowing air into the transfer pump and fuel draining back. You will have to remove the fuel pump to fix it.
The seals are shown on the inset to the right on the picture. The transfer pump is at #6

 

[kshansen]

That style fuel injection pump has the gerotor style transfer pump mounted in the front of it . A common problem with them is the drive shaft seal wearing out and allowing air into the transfer pump and fuel draining back. You will have to remove the fuel pump to fix it.

Yes, that's why I was trying to eliminated the "Siphon Break" and any of the check valves in the side cover of the pump first.

Actually I believe this pump has two "regular gears" in the front.

But still the pump assembly would need to come off to gain access to those seals.

 

[Mobiltech]

Your right. Sometimes I get ahead of myself. I've done a lot of these and usually I end up doing the seals and replacing the gear and key in the transfer pump. It's not a big deal after you've done a few. I wouldn't recommend it for the average backyard mechanic though.