Yanmar loses power, slows down & kills

[tallyho8]

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!!!

 

[MJPetersen]

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

 

[CAT793]

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).

 

[tallyho8]

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.

 

[dieselgeek]

Could be a bad batch of fuel. It happens some times!

 

[kenmac]

I think you'er on the right track with the fuel. Bad injector pump ? bad or clogged injector/ injectors ?

 

[tallyho8]

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?

 

[LMTC]

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.

 

[greatrandini]

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.....

 

[dieselgeek]

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.

 

[Underwaterdog]

I remembered reading about something similar to this on the board, so I did a search for power loss under yanmar. It is gravity feed isn't it? If so, it is unlikely that the fuel bowl could be sucking air. There have been some issues with the plastic fuel bowls shrinking and leaking, but none that I recall sucking air. As far as the vent is concerned, we learned from one of Kenmac's post that the tank will implode if it is not vented. So the only way I can figure it to suck air would be if the tank is not vented and a leak developed in the lines or the bowl. I remembered reading about something similar to this on the board, so I did a search for "power loss" under yanmar.
Here is one thing that I found under "Loss of power in YM1700":

Originally Posted by jkelley8
I had a similar problem. It turned out to be a bend in the return fuel line sending the unused fuel back to the tank.
Had major loss of power most especially in the higher range gears.

Trying some different search terms will give different results , but my guess is the answer is already somewhere on this board.There were several suggestions, but they didn't post the fix. So please, when you do locate the problem, and I have faith that you will, give us the answer.

 

[tallyho8]

I have not checked the return fuel line and will try to do that later today. I have the original glass fuel filter bowl. I have changed the o-ring and do not believe that it can be the problem. The problem seems to be heat related since it runs fine when cold and acts up after it warms up for 10 minutes. Seems like some part is getting warm and opens a crack that lets air in. I should get my new bleeder valve in a couple more days and hope it makes a difference.

Maybe my thinking is wrong because I have never had a bad injector, but it seems like a bad injector would make it miss like a bad sparkplug and it never misses. It just slows down and loses power and finally kills.

 

[1danny]

I have not checked the return fuel line and will try to do that later today. I have the original glass fuel filter bowl. I have changed the o-ring and do not believe that it can be the problem. The problem seems to be heat related since it runs fine when cold and acts up after it warms up for 10 minutes. Seems like some part is getting warm and opens a crack that lets air in. I should get my new bleeder valve in a couple more days and hope it makes a difference.

Maybe my thinking is wrong because I have never had a bad injector, but it seems like a bad injector would make it miss like a bad sparkplug and it never misses. It just slows down and loses power and finally kills.

Take the muffler off.

Danny

 

[greatrandini]

I did not know that some of the original fuel bowl were made of glass?

 

[1danny]

I did not know that some of the original fuel bowl were made of glass?

Some of them look like glass.

Danny

 

[ProdaddyTX]

The ones I've seen that look like glass are coming over on the vietnamese reconditioned machines, and they're actually a clear and fairly brittle plastic that is prone to developing a hairline crack around the lip. I've never seen that allow air into the lines though... it just leaks fuel. Back when we used to buy and sell those machines we replaced a lot of fuel bowls with the better white-ish ones available from Hoye and Fredricks.
I'll bet the part you've ordered from Hoye solves your problem. Please report back!

 

[BruceR]

The ones I've seen that look like glass are coming over on the vietnamese reconditioned machines, and they're actually a clear and fairly brittle plastic that is prone to developing a hairline crack around the lip. I've never seen that allow air into the lines though... it just leaks fuel. Back when we used to buy and sell those machines we replaced a lot of fuel bowls with the better white-ish ones available from Hoye and Fredricks.
I'll bet the part you've ordered from Hoye solves your problem. Please report back!

You're not doing re-cons anymore ?

Bruce

 

[greatrandini]

The ones I've seen that look like glass are coming over on the vietnamese reconditioned machines, and they're actually a clear and fairly brittle plastic that is prone to developing a hairline crack around the lip. I've never seen that allow air into the lines though... it just leaks fuel. Back when we used to buy and sell those machines we replaced a lot of fuel bowls with the better white-ish ones available from Hoye and Fredricks.
I'll bet the part you've ordered from Hoye solves your problem. Please report back!

Yes, that is like the one I replace with one like you said! If he has one of those it maybe sucking air.

 

[tallyho8]

Still not working!

I installed my new bleeder pump. The pump works fine and does not leak fuel when pumping but it still runs the same.

I took the muffler off as Danny suggested and it still does the same thing, warms up, loses power and slows down. With the muffler off I can hear that it is not running as steady as I thought with the muffler on. When it starts acting up it appears to be running erratically.

I removed the fuel return lines from the injectors while it was acting up and ran it for a while and no fuel, except maybe a drop, is coming out of the injectors to the fuel return lines. Is there supposed to be a constant flow of fuel out of the return lines?

 

[chriswheeler]

As it starts to falter, loosen the lines to each injector. ( at the injector ) If one of the lines loose doesn't make a difference, I'd look hard at that injector.
Chris