Yanmar loses power, slows down & kills

[tallyho8]

Did the original line going from your filter to the pump have any bends in it that would collect the bubbles like your clear tube? I wonder if the problem was the bubbles themselves, or simply the collection of bubbles?

The original line ran UP to the injection pump. Since bubbles will not go down, when they came out the pump they collected in the line by the pump until they stopped the fuel flow.

I used it 4 hours Saturday and 4 hours today with no problems other than when I lifted the front end with the loader while working, it killed once and then quickly restarted.

I do have to remove my clear polyethylene lines soon and put back my regular fuel lines because the plastic melts under extreme heat and could be dangerous.

 

[kenmac]

so, are you saying that the problem is solved ?? If so what fixed it ?

 

[tallyho8]

so, are you saying that the problem is solved ?? If so what fixed it ?

No, the problem is not solved, but I have my tractor running. Please see post 122 for details. I still do not know what is wrong with it and possibly may never know.

 

[rock2610D]

It seems odd to me the a fuel line should run "up" to injection pump. Granted the tank is above the pump, but on my tractor the fuel filter is above the pump too.

Is your filter assembly above the pump?? Is it in original location?

I had a tank cap the did not have a bleed hole in it and collasped my plastic tank because of the suction created by siphon!!

At this point my only advise is the banjo fitting and its immediate copper washers are allowing air in. Touchy here but suction casued by VACUUM can cause air to come in, when there is a leak.

My last ditch effort would be to put a vent free cap on fuel tank. If it does not collaps in noticabley ( mine sucked the tank down about 4 inchs in 1 hour) there is an air leak somewhere. My best guess would be the filter housing or banjo fitting on pump. Banjo fitting 1st because you say you seen air bubbles coming from there.

 

[tallyho8]

It seems odd to me the a fuel line should run "up" to injection pump. Granted the tank is above the pump, but on my tractor the fuel filter is above the pump too.

Is your filter assembly above the pump?? Is it in original location? NO, it's below it in it's original location.

I had a tank cap the did not have a bleed hole in it and collasped my plastic tank because of the suction created by siphon!!

At this point my only advise is the banjo fitting and its immediate copper washers are allowing air in. Touchy here but suction casued by VACUUM can cause air to come in, when there is a leak. I don't have a banjo fitting, I have a bleeder valve and I just bought a new one with washers for $45 which does the same thing.

My last ditch effort would be to put a vent free cap on fuel tank. If it does not collaps in noticabley ( mine sucked the tank down about 4 inchs in 1 hour) there is an air leak somewhere. My best guess would be the filter housing or banjo fitting on pump. Banjo fitting 1st because you say you seen air bubbles coming from there. It does it even when I run it with the fuel tank cap off and no bubbles come up the fuel line from the filter side. The bubbles all come out of the fitting on the injector pump. I have a metal fuel tank and do not want to risk collapsing it and ruining it.

I ran it 5 hours today without problems but have noticed that when I run at a steady speed that no air bubbles enter the line now but when I idle it down air bubbles start entering the line. I appreciate the suggestions everyone has given me and hope I can find out the cause some day.

 

[rock2610D]

"all The bubbles come out of the fitting on the injector pump."

Sorry, mine has a banjo fitting that goes on the bleeder screw on pump. When you type "fitting on the injector pump" what type of fitting is it?

If a non metric banjo fitting was put on a metric bleed screw, it would appear to work and may for a while but will eventually leak expecially if it were drilled to fit.

Maybe checking fitting for cracks???

Here are my thoughts:

1) air bubbles are either replacing diesel fuel that has been used, the only way that can happen is a vacuum is created and air is being sucked in from vacuum created to equalize the volume lost by engine using fuel. If this was not happening AND air entered system then the tank is being pressurized, via pump.

2) I know you stated its air bubbles and I do agree but I believe air is being forced in via vacuum or pump pressure. With a rebuilt pump I am inclined to think its not the pump.

3) since you have bypassed both your tank and filter assby and still had issue. Plus you had pump replaced you have addressed everything between pump and tank. So tank is good, filter assby is good, pump is good. So what is between pump and filter assby that you have not replaced? That should be culpert???

4) my inital guess would be what ever fitting you say fuel line hooks to. Last I would confirm correct size of fuel hose. Using a std hose on metric fitting may cause poor connection and air infiltration issues. I say this because I assume the clear and diesel rated hose may be std and not metric??

 

[tallyho8]

"all The bubbles come out of the fitting on the injector pump."

Sorry, mine has a banjo fitting that goes on the bleeder screw on pump. When you type "fitting on the injector pump" what type of fitting is it?

If a non metric banjo fitting was put on a metric bleed screw, it would appear to work and may for a while but will eventually leak expecially if it were drilled to fit.

Maybe checking fitting for cracks???

Here are my thoughts:

1) air bubbles are either replacing diesel fuel that has been used, the only way that can happen is a vacuum is created and air is being sucked in from vacuum created to equalize the volume lost by engine using fuel. If this was not happening AND air entered system then the tank is being pressurized, via pump.

2) I know you stated its air bubbles and I do agree but I believe air is being forced in via vacuum or pump pressure. With a rebuilt pump I am inclined to think its not the pump.

3) since you have bypassed both your tank and filter assby and still had issue. Plus you had pump replaced you have addressed everything between pump and tank. So tank is good, filter assby is good, pump is good. So what is between pump and filter assby that you have not replaced? That should be culpert???

4) my inital guess would be what ever fitting you say fuel line hooks to. Last I would confirm correct size of fuel hose. Using a std hose on metric fitting may cause poor connection and air infiltration issues. I say this because I assume the clear and diesel rated hose may be std and not metric??

Between my pump and filter assembly are the fuel hose and the fitting on the pump that the hose connects to. First I replaced the hose with a new high quality fuel line and it did the same thing. Then I removed that hose and installed a clear hose so I could see bubbles inside it and it did the same thing. I replaced the fitting on the pump which is like a banjo fitting but it has a push button bleeder on it instead of a bleeder screw. The fitting and washers were $45 and it did the same thing. The old clamps on the hoses were weak clamps that you could squeeze with your fingers and remove. I installed heavy duty hose clamps. To insure that my tank or new filter or hoses were not preventing fuel flow, I filled the tank and removed the hose at the pump and let the fuel flow out the hose into a can and repeated the process 3 times. The fuel runs out the hose very quickly only stopping when the tank is empty. I pressurized my tank and fuel system with my compressor set on 10 psi and there were no fuel leaks anywhere.

I find it strange that when my engine is running at a set speed no air bubbles enter the line, but each time I decrease speed I get a rush of air bubbles coming out the injector pump into the fuel line.

But, this might be normal and maybe all of them do this but since you don't have a clear fuel line, you don't see the bubbles.

 

[California]

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

 

[rock2610D]

Ok it looks like you have covered almost every base you could.

If indeed your issue was band-aided with the vent type hoses you installed, you might see things clear up on their own.

My theroy is that you have air in you system. What did the pump people tell you about bleeding air in your pump? Your band-aided system may purge all air or it may not.

Reguardless of what some may say here there are specific ways to bleed Yanmar motors. Yanmar America has one way and John Deere has another. I used John Deeres method on mine and it worked. I have also used Yanmar America's method and it worked too.

Deere's method as per JD 750 manual (3 Cylinder)
loosen bleed screws on filter until all air is purged.
Retighten bleed screws
On 3 CY motors loosen #1 and #3 delivery valve holders 1/4 turn( these are on top of pump where injection lines attach to pump)
Loosen all injection lines at nozzles


Fuel will gravity feed from tank to fill injection lines

When fuel appears at injection nozzle tighten injection line to nozzle to proper torque and tighten the approperate delivery valve connection on pump. DO NOT TIGHTEN FUEL LINE #2's INJECTION LINE AT NOZZLE YET! (For 3 CY only)

Push throttle full on and start engine. It should run on #1 and #3 cylinders.

When fuel appears at #2 injector stop engine and tighten injection line at nozzle.

System is bled!!




NOW I am going to beat a dead horse again

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.


Next you need to make sure pump is timed correctly. Just like any engine it can act different when cold. If timing is off too much it could start when its cold but not want to run once warm..... But I still am leaning toward govenor

 

[tallyho8]

Regardless of what some may say here there are specific ways to bleed Yanmar motors. Yanmar America has one way and John Deere has another. I used John Deeres method on mine and it worked. I have also used Yanmar America's method and it worked too.

Deere's method as per JD 750 manual (3 Cylinder)
loosen bleed screws on filter until all air is purged.
Retighten bleed screws
On 3 CY motors loosen #1 and #3 delivery valve holders 1/4 turn( these are on top of pump where injection lines attach to pump)
Loosen all injection lines at nozzles

Fuel will gravity feed from tank to fill injection linesYou are saying that fuel will gravity flow from the tank, through the injector pump and through the injector lines all the way to the injectors. I have had some people tell me that nothing can flow through the pump, that it must be pumped out. If you are right and fuel can flow through the pump one way then it could also flow through the pump the other way and this means that if an injector was leaking compression through it, then the compression could flow back through the pump into the fuel line creating bubbles. If this is indeed true, it makes more sense because the bubbles are appearing mostly when I let off on the throttle and the pump is not pumping much fuel, maybe allowing compression to back flow through the system. Even though they checked my injectors to make sure they were popping correctly, I don't know if they could tell if they were leaking back compression. Maybe I should buy one new injector and try it in each of the cylinders to see if this corrects the situation. I do hate to spend $100 for an injector just to test with if this is not a realistic possibility.

When fuel appears at injection nozzle tighten injection line to nozzle to proper torque and tighten the approperate delivery valve connection on pump. DO NOT TIGHTEN FUEL LINE #2's INJECTION LINE AT NOZZLE YET! (For 3 CY only)

Push throttle full on and start engine. It should run on #1 and #3 cylinders.

When fuel appears at #2 injector stop engine and tighten injection line at nozzle.

System is bled!!

NOW I am going to beat a dead horse again

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. I am an amature and having looked at the manual for the governor, do not feel that I am qualified to remove or repair it. I also have difficulty understanding how the governor could make it run bad until I put the air bleed line on it and then allow it to run OK.


Next you need to make sure pump is timed correctly. Just like any engine it can act different when cold. If timing is off too much it could start when its cold but not want to run once warm..... My engine starts immediately when cold or warm and runs perfect except when air blocks the fuel line. But I still am leaning toward govenor

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.