Yanmar loses power, slows down & kills

[rock2610D]

If injection pump was rebuilt correctly than I do not believe compression can leak from cylinders to fuel system.

NOTE: in order for gravity filling of injection lines the delivery valve MUST be lose. IE THE 1/4 TURN IN PROCEEDURE!

If delivery valve is tight than no gravity feeding is going to happen.

 

[jimmer2880]

cavitation?

Is it possible that the pump is cavitating at the lower speeds, but at the higher speeds it is not? Is it even possible for these pumps to cavitate? I wouldn't know how.

I was just thinking of how when I pump diesel into a 5 gallon can, I'll get a bunch of foam unless it's going in nice and slow (again, opposite of what's happening. But - sometimes opposites are related).

I know this sounds opposite of how cavitation usually happens, but it is the only explanation I can think of for the lack of air bubbles at heigher speeds (other than, the air bubbles are moving faster than the speed of light )

Dang - I really wish I had a clue about this stuff.

 

[jimmer2880]

Another off the wall idea (just throwing more junk out there to contemplate).

Vapor Lock.

I really don't understand exactly how that would happen in the carburated car days (Gas, of course, never heard of it on a Diesel). But, I understood it that if the fuel-line would get too warm, bubbles would form and create a bubble in the fuel-line.

 

[tallyho8]

I wonder if moving the filter higher would keep the pump intake flooded, while bubbles would rise clear back to the fuel tank.

This is essentially what I did when I rigged my bleeder line.

 

[RobJ]

Another off the wall idea (just throwing more junk out there to contemplate).

Vapor Lock.

I really don't understand exactly how that would happen in the carburated car days (Gas, of course, never heard of it on a Diesel). But, I understood it that if the fuel-line would get too warm, bubbles would form and create a bubble in the fuel-line.

Diesel has a much higher boiling point than gas. That's why the products that make up gas come off the top of a distillation tower at a refinery. LGP, naptha at the top, then the keros, diesel, VGO, and ATB's at the bottom.

 

[RobJ]

I need more input from other skilled deisel mechanics as to whether or not compression could leak back through a defective injector and through the injector pump.

Not likely..

 

[RobJ]

Govenor!! Get a manual on these gadgets. My JD manual in very informative.

Did you know the govenor over fuels motor during startup? It can do this because counter weights are not spinning. By overfueling during startup the engine appears to run correctly until overfueling stops and govenor starts working with respect to a started engine. This is where I think you have issues. Please take a second and thrid look at govenor.

The governor kicks the fuel back at just a few hundred rpm. You can hear and see this at startup. If the governor is working properly with the new fuel line set up(load on, load off, etc), I'd rule it out. Probably the easiest thing to break in the govenor is a spring. And if this breaks you'll probably have a runaway or no speed selection. Generally the speed control lever, spring, govenor, and fuel rack are all connected.

This is a weird one but glad it's running at least. I use to have to remind myself...it was working before...what changed.

Rob

 

[tallyho8]

Just a note to let everyone know that I have used my Yanmar about 45 hours in the last 2 weeks with no problems at all with it rigged up as previously mentioned. I still keep wondering what the problem is that made me have to rig it like this.

 

[California]

Just a note to let everyone know that I have used my Yanmar about 45 hours in the last 2 weeks with no problems at all

Congratulations!!

 

[MJPetersen]

That is great Tally that you can and that your tractor is usable, but boy is that nagging that it is NOT right like it should be. Where is that air coming from and why does it enter the system? I have spent a fair amount of time thinking about those question, and have not come up with anything.

Mike

 

[tallyho8]

That is great Tally that you can and that your tractor is usable, but boy is that nagging that it is NOT right like it should be. Where is that air coming from and why does it enter the system? I have spent a fair amount of time thinking about those question, and have not come up with anything.

Mike

As previously mentioned, I installed a clear fuel line and can see bubbles coming into the line from the injector pump when I lower the throttle.

I do not know why, wish I did, that is the big question.

 

[MJPetersen]

Yes I remember that you identified the source as the pump, but where in the pump is the air getting in. That is what I meant. Yes it is a bit frustrating.

Mike

 

[greatrandini]

Did you ever replace that old hard plastic fuel bowl?

 

[tallyho8]

Did you ever replace that old hard plastic fuel bowl?

No, I didn't. It sure doesn't seem like it has any leaks.

 

[dqdave1]

compression test

 

[tallyho8]

compression test

I've never done a compression test on it, but it is starting instantly even in cold weather, and running perfectly with it rigged the way I have it. I would be willing to bet that the compression is perfect.

 

[scottr5150]

Read through this whole post. Oddly enough have what sounds to be a very similar problem with a Ford/New Holland tractor. It's a 28 HP 3 cyl with what sounds like a similar fuel system consisting of a sediment bowl, filter, etc... My issues typically happened while mowing and under a lot of a load. Now their more frequent to the point the tractor is not usable other than for loader work. The odd thing is when I put a new fuel filter in last summer, thinking that was the problem, it seemed to get worse. Think I'll start my quest there. I live in Northern Iowa and have not had an issue in the winter or when cold. Apprieciate this post and everything you have endured as it should help me. Do you still have the problem?

Thanks!!

 

[tallyho8]

Read through this whole post. Oddly enough have what sounds to be a very similar problem with a Ford/New Holland tractor. It's a 28 HP 3 cyl with what sounds like a similar fuel system consisting of a sediment bowl, filter, etc... My issues typically happened while mowing and under a lot of a load. Now their more frequent to the point the tractor is not usable other than for loader work. The odd thing is when I put a new fuel filter in last summer, thinking that was the problem, it seemed to get worse. Think I'll start my quest there. I live in Northern Iowa and have not had an issue in the winter or when cold. Apprieciate this post and everything you have endured as it should help me. Do you still have the problem? Thanks!!

No, I have had no problem since I made my air line.

 

[guyd]

Hi - newbie here. YM1510 in the UK here...

Sorry to drag this back up - but I have had an almost identical problem. It would start easily and run fine, until it was warm. Then, only when using significant throttle, ie more than 1/3rd, it would bog down, slow, seemingly running on 1 or 2 cylinders, and I tried to keep it running by flooring the throttle, and most of the time it would catch back on and keep running. If it died, it would start again instantly on the key. If I left it on tickover or only very small throttle openings, it would drive around all day.

I replaced the fuel lines, but being lazy, didnt bother with the 'jubilee clips' or worm drive clamps. The problem was the same. The installation of hose clamps has fixed the problem - it was air getting in.

 

[guyd]

actually - update to this situation. Continued use at high throttle openings has resulted in the same problem.

I wondered if heat was an issue, so poured cool water on the injector area of the engine. this appeared to fix the problem for a bit. reapeat three times, same result whilst flail mowing some 3 feet high grass for the guy next door. ran much much better shortly after the cold water treatment.