Yanmar loses power, slows down & kills

[Underwaterdog]

One more question as to the air issue: After it dies after running a few minutes, do you have to bleed it or does it start back on its on after it cools off? And if it does start back without bleeding, does it run as long as it does after bleeding it?

 

[tallyho8]

What MJP said about the injector leaking back makes the most sense to me. I wonder if they check for that when they test it. But it may not show up when cold. The injector could have a chip or a crack in it that expands as the engine heats up, thus allowing air to back flow into the lines, and would explain this, except I can't understand how the air would get all the way back to the fuel bowl:

What confuses me is that if the injector allowed compression to leak back into the line and make that cylinder miss out, then when I swapped injectors and put that injector in another cylinder, the other cylinder should miss instead of the same one. But the same cylinder keeps missing when warm.

Even though a very professional shop tested my injection pump (when cold) and said it was good, I am still not convinced that it is good. I don't know much about injection pumps but as an example: when you have a sprayer bottle of windex or anything else, and the sprayer quits pumping, if you check it, it will frequently be reverse pumping the liquid down into the bottle when you squeeze the trigger. I am wondering if one cylinder of the pump is doing this after it heats up, thus pumping air into the line.

 

[tallyho8]

One more question as to the air issue: After it dies after running a few minutes, do you have to bleed it or does it start back on its on after it cools off? And if it does start back without bleeding, does it run as long as it does after bleeding it?

This is a good point. When it is cold it always starts instantly, even without bleeding the line first. It will always run about 10 minutes before missing out. This is when the temperature gauge gets about 1/4 way up.

I tried to order an injector today from one of our very reliable Yanmar dealers and he talked me out of it and suggested the name of a diesel mechanic that I should phone tomorrow before proceeding any further.

To be continued..............

 

[MJPetersen]

I have been thinking about this some more!! Tally mentioned to me that when he pressurized the fuel tank (slightly) that the engine smoothed out. My question is this: When they test pumps, do they just gravity flow fuel to the pump or do they have a pump that forces fuel to the pump? I was theorizing that if they use a pump, then is it not possible that the inlet to the pump is partially blocked and after running for 10 minutes it uses the fuel up that it has faster than the gravity delivery can push past the obstruction and this causes the inj pump to pull air past a seal somewhere?

I do not know Yanmar pumps, but is there an inlet screen or filter for the fuel? Is there a place where a small bit of debris could slow or block fuel flow to the actual individual injector pump plungers? Is there a seal that could possibly leak air into the system if there were a negative pressure? I cannot answer these questions without taking my pump out--and I am NOT going to do that

But maybe someone who knows these simple pumps could expand on my theorizing, or tell me I am ignorant--that would be ok too. Just my thoughts on a frustrating problem.

The problem with my theory about an injector leaking air back into the system is that he eliminates the air at the bleed screw on the inj pump. My idea of the injectors would cause you to have to bleed the injector, but getting back to the inj pump seems to me to be unlikely.

Well Tally, maybe today you will be able to talk to someone that can sove your problem for you.

Mike

 

[tallyho8]

BIG DISCOVERY TODAY!!!!!!!!!!

I phoned the recommended diesel shop but they don't work on tractors, only injectors and pumps so I decided to do more research.

It is DEFINITELY air getting in the line. To test my theory of air getting in the line from the injection pump, I went out and bought a piece of clear polyethelyne tubing to temporarily use as a fuel line so I could see inside the line at what was going on. I installed the fuel line and bled all the air out and started my tractor and let it warm up. After a while, bubbles started floating up in the fuel line from the injection pump. They did not come from the other side of the line leading to the filter. The low quality video I have attached shows the bubbles coming up from the injector pump. The photo shows how much air is in the fuel line when I stopped it. When I let it continue to run, it runs till the line is full of air then stops.

This is proof to me that it is probably a bad injector pump but could it possibly be a bad injector letting compression feed back through the injector pump?

A rebuilt injector pump is $400 and a new one is $660 so I want to be absolutely sure before I spend my cash.

Is there anyone who can find fault with my findings or diagnose the situation differently?

http://members.cox.net/tallyho/AirInLine.mpg

 

[jimmer2880]

I have nothing of any value to add other than I'm glad you finally know what is going on. That was a great idea putting that clear line on, with the bend facing up to collect the air.

 

[Underwaterdog]

I found a link that may or may not help. It is mainly about Bosch and VE, but, It has a reference to the Yanmar Pump and a picture of a cross section of one. It has a vane pump that acts as the feeder. Then there are plungers that feed the injectors. If this is true, then they are not completely gravity fed. I think I have read before that you are in the A/C business too, correct me if I am wrong. I have seen hydronic pumps with a bad mechanical seal suck air and cavitate air into the system. However, when you shut the pump down it leaks water out the seal and they are centrifugal pumps made to pump volume at low pressure. The vane pump has got to have a drive, and that drive undoubtable has a seal on it. If the seal were bad, it may be able to suck air. The problem here is you can't see the drive shaft while it is running. When you had the pump off did you see a drive shaft? If it were pushing air into the cylinder from the injector, could the air get past the piston, the vane pump, and back to the inlet line? I wonder if you could take the pump off, hook up your fuel can and line to it, and see if it leaks? I am assuming the crankcase pressure is near atmospheric pressure since it is vented.
Pressure (PSI) = feet head x 0.433 x specific gravity
Specific Gravity of Fuel Oil = 0.85 approximately
Without giving an example of the math, if the tank is 2.7 feet above the injector inlet, it will have 1 PSI (Net Positive Suction Head, NPSH). If you elevated the fuel can to 13.56 feet, that will give you 5 PSI at the fuel inlet of the pump. That should be enough to see if the shaft seal is leaking. Here is the link I mentioned before. Robert Bosch type VE Diesel injection pump
I hope this isn't totally off the wall. If the DW comes out and sees you with a hose running from a fuel can sitting on the roof of the house she may call the men in the white coats to you.

 

[tallyho8]

Underwaterdog
My injector pump is nothing like that one. It is much simpler. It has no driveshaft because it works off the cam and had 3 plungers, one for each cylinder. Each of these plungers must have seals that can go bad and let air in. You can see one similar on Hoyes site that is for a 2 cylinder here. INJECTION_PUMP: Yanmar Tractor Parts

I am almost dead certain that this is the problem and I am going back to the diesel shop that said my pump is good tomorrow to discuss this with them. I feel that they tested to make sure my pump was pumping but did not test to see if it was leaking air out the seals.

Now my biggest decision is whether to buy a new pump or rebuilt or get this one rebuilt.

 

[Underwaterdog]

I saw some pretty scary prices on pumps on this post before, but if the pump you linked for the 1500 is close in price to yours for a new one I would go for the new one and be done with it. That one may be an aftermarket brand, but I'm sure Hoye wouldn't sell it if it weren't good quality. I haven't had a lot of luck with rebuilt parts in the past. Rebuilt kind of means re-paired. Remanufactured is better, if it is truly remanufactured. I have had better performance from new parts.

 

[tallyho8]

Hoye doesn't have new pumps for my model and the dealers who do want over $660 for them so I have decided to get it rebuilt locally for $275. The place doing it was highly recommended so I am hoping that I have a well rebuilt pump in 3 days.

I will not consider the problem solved until I have it running again for at least a few hours but I'm hoping for the best. Today was a beautiful 67 degree sunny day and I could have done a lot of clearing on my property if my tractor had been running.