Yanmar loses power, slows down & kills

   / Yanmar loses power, slows down & kills #1  

tallyho8

Elite Member
Joined
Aug 1, 2004
Messages
4,998
Location
Who Dat Nation west of Westwego east of Ama south
Tractor
Kubota L4400, Kubota ZD326
My great running Yanmar 1802 started acting up today. It was running fine and started losing power and slowing down. After a few minutes it killed. It started back up but only runs slowly and speeds up and slows down and kills. I thought it was a stopped up fuel filter and I changed the fuel and air filter. No difference. I have a primer pump by the filter and one by the pump. When I pump the one by the filter it shoots out a good stream of diesel. When I pump the one by the injector pump it shoots out only a little dribble of fuel but this finger pump may not be working well. I removed the hose by the injector pump and diesel flows out of the hose very well. Now, I can start it and it will run ok for a couple of minutes then start slowing down. I'm about sure it is some type of fuel problem. Could my injector pump be going bad?

I have never had any problems in the years that I have had it. It usually starts instantly when I touch the key. I have never had to use the thermostart even in 30 degree weather. The oil pressure is good and it runs very cool. There are no leaks. HELP!!!
 
   / Yanmar loses power, slows down & kills #2  
My initial response is to ask if your tank is vented. On some Yanmars the vent is incorporated in the fuel strainer in the tank fill opening. Try it with the tank lid loose and see if it makes a difference. Secondly, I thought that maybe there is something floating around int he tank or garbage in the on/off valve.

Mike
 
   / Yanmar loses power, slows down & kills #3  
Sounds like your fuel system is sucking air , could be from around the filter housing ( o-ring on the bowl ) or one of your priming pumps,maybe hose clamps or foreign material in the tank. Low power and the engine dies not always fuel starvation(blocked filter).
 
   / Yanmar loses power, slows down & kills
  • Thread Starter
#4  
CAT793 said:
Sounds like your fuel system is sucking air , could be from around the filter housing ( o-ring on the bowl ) or one of your priming pumps,maybe hose clamps or foreign material in the tank. Low power and the engine dies not always fuel starvation(blocked filter).

This is what I was wondering. The fuel is gravity fed into the injector pump and there are no fuel leaks. Could there be a leak in the line that would suck air and be too small to leak diesel?

My tank is full of fresh diesel. My next step is to again remove the fuel line at the injector pump and let all 4 gallons of the diesel drain into a can and check the insides of my tank for any impurities. The fuel runs out of this line very fast so I know the gas cap vent is ok.
 
   / Yanmar loses power, slows down & kills #5  
Could be a bad batch of fuel. It happens some times!
 
   / Yanmar loses power, slows down & kills #6  
I think you'er on the right track with the fuel. Bad injector pump ? bad or clogged injector/ injectors ?
 
   / Yanmar loses power, slows down & kills
  • Thread Starter
#7  
This morning it started right up and ran fine for 10 minutes then started slowing down and losing power. I changed the fuel lines from the tank to the filter and from the filter to the injector pump. I drained the tank and put in new diesel. No change, it starts up then starts slowing down and losing power. I ran it with the fuel tank cap off and the radiator cap off so I could check the circulation and look for bubbles.

I put a piece of cardboard in front of the radiator to warm it up to 1/4 way on the gauge. I could still stick my finger in the radiator without burning it. The water is flowing very well and is very clean and green. The oil is clean with no signs of water. The oil pressure is good. The exhaust has a little bit of blue smoke coming out when run at 2500 rpm but I can't see any at lower speeds.

I ordered a new bleeder pump from Hoyes today because mine is not pumping well and has a small fuel leak when pumped. Maybe it is drawing air in through there and causing the problem. If nothing changes after I replace the bleeder pump, I know of nothing else it could be but the injector pump. Has anyone seen an injector pump that ran fine when cold but started acting up after it warmed up?
 
   / Yanmar loses power, slows down & kills #8  
tallyho8 said:
Has anyone seen an injector pump that ran fine when cold but started acting up after it warmed up?
Bad injectors do that with some regularity. Ok, more accurately stated, it is not totally uncommon for a bad injector to run fine cold, then turn to **** after ten minutes or so.
 
   / Yanmar loses power, slows down & kills #9  
It's Tally ho not Tally Wacker! Before you do anything drastic order yourself a new fuel bowl and o ring from hoye. Then re-bleed the system and see what happens. I was told on this forum that the orig fuels bowls shink after a long time.....
 
   / Yanmar loses power, slows down & kills #10  
can he put a mightyvac on it and check for suction leaks? That's trick we do on the Cummins diesels. It sure sounds like the o-ring leaking, it would seem to match his symptoms.
 
 
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