# Belarus 250AS Quits after a few minutes



## blueheron (Mar 5, 2017)

I've got a 1980ish Belarus 250AS, and I have a problem I can't seem to figure out.

I can hand prime the fuel pump, start the tractor and run it for about 10-15 minutes. After that, it starts to lose power and then eventually dies out. Throttling up seems to do nothing. If I try and immediately start right after this happens, I cannot unless I hand prime and then it will start then die. If I let it sit for an hour or two and come back, I can repeat the same process, start, run for 10-15 minutes then dies.

I have replaced and fuel filters (Stage 1 and Stage 2), drained the tank, cleaned the tank and put fresh fuel in. I was thinking the tank may have had some debris that was clogging the system. I've also made sure all of the bolts/fittings in the fuel system are tight. I've drained the fuel pump oil and replaced to the drain plug as well. If the tractor is off, and I hand prime, I can hear the fuel moving through the system after about 10-15 pumps and eventually hear it circulating back to the tank so I am unsure that the lines are clogged. I've read that air may be getting into the system but unsure how to figure out where that might be happening.

I am leaning towards replacing the fuel pump (~$250) unless I can come up with something else to try. Any ideas?


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## FredM (Nov 18, 2015)

are you bleeding from the injection pump to the injectors ??

if not crack the injector pipe nuts at the injector about 2/3 turns loose, prime the injection pump with the fuel pump then have someone turn the engine over with the start key and you can watch the injectors, when you get a good splurge coming out and no air, tighten a nut and the engine should catch, tighten each nut until the engine is running, then crack each nut in turn again to make sure the air is bled out of the system.


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## blueheron (Mar 5, 2017)

I have not tried that. Are you talking about the nuts where the fuel line goes into the block on top of the engine? The are two I believe. One for each cylinder.


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## rhino (Jan 9, 2017)

Next time it does it, crack fuel cap loose slowly and listen for air being sucked in. If you hear air leave cap loose and try to start engine. The vacuum should suck the fuel in threw the line to fill the void.:usa:


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## FredM (Nov 18, 2015)

blueheron said:


> I have not tried that. Are you talking about the nuts where the fuel line goes into the block on top of the engine? The are two I believe. One for each cylinder.


you will see the pipe union nut that holds the injector pipe to the injector, crack that, if you haven't bled the injectors, then there will be air in the injection pump and the injector lines, you will have to roll the engine over a bit while bleeding the air from the system and once you get a solid pulse and no bubbles tighten the nuts and the engine should fire up, when you get it running, crack the injector nut a little to make sure the air has gone, do both injectors in turn.


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## thepumpguysc (Jan 25, 2015)

You can take the lift pump apart & check the piston & spring under the BIG nut in the front.
& you can take the smaller nuts loose to check the valves & springs.
When it shuts off, is there fuel in the filters? IF NOT, you have a blockage in the tank.
I know you said you cleaned it but.. IF the filters are empty, all your doing is sucking the fuel out of the filters and they're not filling back up.. could be pulling a vaccum from a plugged fuel cap vent.. Did you check to see if theres a filter screen in the shut-off valve AT THE TANK?
I think you'll find the filters are empty and that's why you cant start it back up.. Then the fuel dribbles back down the line, fills the filters back up and off you go again..
I hope this helps.. TPG


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## blueheron (Mar 5, 2017)

I bled the lines at the injectors today with someone else starting the tractor, I was able to get a good flow going and tightened once a good stream was leaking out. It ran for 5 minutes or so then when I tried to lift a bale of hay, it died out. Wouldn't restart w/o hand pumping but then would die almost immediately.

I also let is sit and tried again, and when it started to die, slowly loosened the gas cap but it didn't help. I couldn't hear any air going in or coming out.

After a second attempt at bleeding the fuel lines at the injectors and taking the fuel line that pulls from the tank off and blowing out, I was able to run it for about 20 minutes, move two large round bales of hay then it fizzled out.

I haven't tried what "thepumpguysc" has suggested yet. Does this provide any more helpful info?


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## Fedup (Feb 25, 2014)

I see a number of posts suggesting "try this" and "try that", all seemingly aimed at a suspected fuel supply side problem. You have probably covered all those bases by now. No mention yet of the fuel escape/return side of this equation. While I'm not familiar with the pump on a 250 series, I ASSUME it has a return line/fitting somewhere for excess fuel to escape back to tank. This is often connected to the injector return line somehow then leading back to the fuel tank. In this case I would look for a banjo type fitting, possibly smaller than the supply side fittings, but maybe not. At this point I wonder what would happen if this line or fitting were cracked slightly when the engine is slowing RPM and trying to die. If by chance opening this up and allowing some fuel(and internal pressure) to escape makes a sudden difference, then perhaps the fuel supply may not be a problem at all.


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## thepumpguysc (Jan 25, 2015)

It looks as tho the inj. pump has an inlet AND an outlet banjo bolt on the back side of the pump. I'll bet money the outlet banjo is an overflow valve and set to pop-off at a certain pressure to build "gallery pressure" to supply a certain amount of fuel in the fuel gallery to allow the pump to pump. IF that spring in the overflow valve is broken, it would allow fuel to enter the pump but not hold enough fuel in the fuel gallery for adequate pumping, hence the shutting off.. and restart only when you build pressure w/the hand primer.. I'm not saying that's the problem, but rather, that's how it works..
I would still check the filters after it shuts down.. AND check for a screen in the sh-off tap or fitting AT THE tank.. seeing you blew back thru the line & it ran longer.. DO all these running checks w/ the fuel tank cap OFF, just to eliminate a vaccum situation.
Let us know how its working out.


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## blueheron (Mar 5, 2017)

There is a return line back to the tank. I have replaced that rubber hose, it's a 1/4 internal diameter versus the 3/8 of the supply. It does connect to some copper lines as well, I haven't examined those but the manual hand primer will push fuel back to the tank after several pumps, though I will say that the manual pumps leaks when I pump it. It leaks fuel as I pump, but not when tightened back down after pumping.

I had someone else outside of the forum suggest that maybe there is still debris floating around in the system, so I may need to remove and clean the filters again. Ill check the return line, plan to clean the filters again and try and diagnose if all of the filters have fuel in them when the engine quits.


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## HarveyW (Sep 15, 2014)

Just a thought, if the manual pump leaks while pumping, it may be a source of an air leak into the system??? Is there a packing nut you can tighten??


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## HarveyW (Sep 15, 2014)

Just a thought, if the manual pump leaks while pumping, it may be a source of an air leak into the fuel system??? Is there a packing nut you can tighten on the pump to stop the leak??

Are the fuel filters new, or just cleaned and returned to service??


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## blueheron (Mar 5, 2017)

Thanks for all of the feedback and suggestions. It's going to be a few days before I can work on the tractor again but I'll let you know what happens next. I ordered new fuel filters and gaskets and called to check about a seal or o-ring for the manual pump that is leaking. I ended up ordering a new booster pump that includes the manual pump assembly. After speaking with the parts department for the tractor manufacturer, they suggested that may be the problem; they have seen others of this model act the very same way with the booster pump failing. Basically, the booster pump doesn't build up enough pressure and ends up not sending enough fuel to the stage 2 fuel filters. It wasn't very expensive so I thought I'd give it a try.


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## thepumpguysc (Jan 25, 2015)

To bad you already ordered a lift pump..
You could have bought a kit that included all new valves, springs and an updated handprimer for about 25.00


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## blueheron (Mar 5, 2017)

Well, I put the new booster pump on, cranked it up and it ran good for about 30 minutes, enough to pick up some round bales and move them. I was done using it so I parked it. That was a couple of weeks ago. I thought the problem was solved....

Now, when I go out, it cranks up and fizzles our after 30-45 seconds. If I use the booster pump and manually prime, it cranks up again, then fizzles out.

Any idea where I should look next?

Thanks.


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## thepumpguysc (Jan 25, 2015)

Did you ever check to SEE if the filters were DRY after it shuts off??
That will tell you in about 1 minute what the problem is.. supply from the tank.. not keeping the filters full..


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## blueheron (Mar 5, 2017)

OK, so I cranked up the tractor and waited for it to die; took about 30 seconds. I opened the drain plug of each of the filters (Stage 1 and both Stage 2) and they all released fuel. I decided to go ahead and try and bleed the lines again, starting at the stage 2 fuel filters and working toward then engine. I was able to get it running and keep it running after a few stops/starts while bleeding different banjo bolts and lines.

It was starting to run rough so I took the fuel cap off and it came back to life. Put the cap on and off for a bit and tried to clean the vent out the best I could. After all of that it stayed running for about 15 minutes steady until I shut it off. I started it and stopped it several more times and let it run for a bit.

Crossing my fingers that is stays that way. Does this help figure out the problem? Was it just air in the lines (I didn't bleed after I installed the new booster pump) or is there something else going on?


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## thepumpguysc (Jan 25, 2015)

SOUNDS LIKE the vent in the cap is/was plugged.. just loosen it and run the tractor.. if it stays running replace the cap..
The clogged vent was choking off the air & creating a vaccum that the pump couldn't overcome.. just like holding your finger over the end of a straw and sucking on the other..


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## willys55 (Oct 13, 2016)

Bazzinga!!!!


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## blueheron (Mar 5, 2017)

Well, back to the drawing board. I ordered a new gas cap and installed. Today, I went to start the tractor, started then died after 30 seconds. Loosened the new gas cap and same results. Seems like every time I have a lead on the problem it turns out to be something else.

After 3 attempts today to keep it running, it seems like the first filter in the Stage 2 fuel filters is not getting fuel. When I opened the drain plug, barely any diesel leaked out, as opposed to the second filter in the Stage 2 filters it pours out. I am wondering if maybe the mechanical fuel pump is actually bad!? If I loosen the drain plug on the 1 filter in Stage 2 and manually pump, it will draw diesel but after I tighten and start, it may not be.

Any more ideas?


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## jhngardner367 (Apr 5, 2011)

Check the fuel pickup tube,to see if it's cracked.


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## blueheron (Mar 5, 2017)

Turns out to have been the stage two fuel filters after all. After removing the filters temporarily for a test, everything fired up and I had good pressure coming through the fuel lines. Visually the old ones looked OK and were recently replaced, but I guess I had a lot of micro particles in the system the was restricting flow.

I put two new filters in and bled the system and everything is running good now. Fingers crossed that I am back up and running but so far so good.


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## Tractorhelp431 (Jan 9, 2019)

blueheron said:


> Turns out to have been the stage two fuel filters after all. After removing the filters temporarily for a test, everything fired up and I had good pressure coming through the fuel lines. Visually the old ones looked OK and were recently replaced, but I guess I had a lot of micro particles in the system the was restricting flow.
> 
> I put two new filters in and bled the system and everything is running good now. Fingers crossed that I am back up and running but so far so good.


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## Tractorhelp431 (Jan 9, 2019)

Hi. I’m interested to see if this permanently fixed your problem. I have a Belarus 250. (Actually T25) and I am having the same problem. Recent new injection pump and won’t stay running


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## pogobill (Jan 31, 2012)

I'm Thinking that the filter change fixed his problem, whether it was that or properly bleeding the system afterwards remains a question. blueheron hasn't been back here for almost two years, since the filter change.
I'm hoping thepumpguysc will pop in here soon to help you out.


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## thepumpguysc (Jan 25, 2015)

TH431>> Have u removed YOUR filters & ran the engine to see for yourself, if yours runs properly.??
What have YOU done to diagnose the problem.??


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## Tractorhelp431 (Jan 9, 2019)

thepumpguysc said:


> TH431>> Have u removed YOUR filters & ran the engine to see for yourself, if yours runs properly.??
> What have YOU done to diagnose the problem.??


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## Tractorhelp431 (Jan 9, 2019)

I


pogobill said:


> I'm Thinking that the filter change fixed his problem, whether it was that or properly bleeding the system afterwards remains a question. blueheron hasn't been back here for almost two years, since the filter change.
> I'm hoping thepumpguysc will pop in here soon to help you out.


Hi. Tks replying. Ya I was having the exact Same issues as he was. I changed the filters as per routine maintenance. Worked great for a couple days and would stall out. Then run for a few minutes and stall out again. Never dreamt that the new filters would plug up that fast


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## Tractorhelp431 (Jan 9, 2019)

Hi. I was to weirie to run without the filters. I changed the filters a couple weeks ago Just never thought they would plug up so fast. They looked fine So I drained the tank. There was some crud in there. Took the first stage filter apart. Cleaned it. Checked the second stage filter head to make sure all channels were open. And they was. Reassembled. Blead the system. Would run for 30 sec and stall. Today I picked up new filters. Installed and it’s been running for 30+ min. Seems fine. I guess where I just put new filters in recently I figured that would be to obvious.


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