Kubota 21 hp engine stalling.

[dangerdoc]

I have the Kubota ZD21 ZTR mower. It has less than 300 hrs.

Mower will run OK for about half an hour then starts losing power to the point where it can no longer mow. I replaced the fuel filters withous improvement. Temp guage stays in the normal range.

Any ideas?

 

[Grandad4]

Just a general speculation that it's probably a fuel flow issue. These little diesels are otherwise darn near impossible to kill. Since you've already replaced the filters, you'd need to work your way through the rest of the system... tank, lines, fuel pump, etc. to sort out the specific issue. While it could be something internal to the fuel injection system itself, I'd reason it's unlikely since the engine does run OK initially. I think one guy figured his fuel cap was not venting properly and it caused similar symptoms after running for a while.

 

[dangerdoc]

Just a general speculation that it's probably a fuel flow issue. These little diesels are otherwise darn near impossible to kill. Since you've already replaced the filters, you'd need to work your way through the rest of the system... tank, lines, fuel pump, etc. to sort out the specific issue. While it could be something internal to the fuel injection system itself, I'd reason it's unlikely since the engine does run OK initially. I think one guy figured his fuel cap was not venting properly and it caused similar symptoms after running for a while.

I've tried opening the fuel tank when it starts stumbling, there is no appreciable vacuum and the engine does not improve.

The hoses look OK, no crimps noted.

I hate to think how much Kubota charges for a fuel pump.

I'm going to take a look at it again this weekend, I may end up taking it to the dealer but this time of the year, they are tied up with farmers needing to get their equipment in the field, I could end up with my machine in the shop for weeks. With the way the grass is growing, I may not be able to find my house by then.

 

[Volfandt]

I've been hearing/seeing this type of problem posted more frequently it seems.
Mainly with older higher hr engines.
It would appear to be a fuel delievery problem thats heat related.
Looks like the easy fixes have been tried (filters & plugged fuel cap).

Things to check.
Make sure theres no fuel line laying on the head/block as this may cause vapor lock.

It's possible that the valves are out of adjusment. Heat expands metal and the valves may not be seating all the way when warmed up.

Make sure all the lines are good and tight, especially around the injectors.

A test to try. With the engine cold, get some one to crank it while you crack a fuel line at the #1 injector and make note of the pressure. Needless to say tighten back while its still cranking/running.

When it starts acting up, do the same test and compare the pressure. If the pressre seems the same I'd suspect the injector, valves or something else within the engine.
IF the pressure is lower I'd suspect the fuel injector pump, any and all fuel system components from the injector pump back towards the fuel tank.
Good luck
Dave

 

[dangerdoc]

I've been hearing/seeing this type of problem posted more frequently it seems.
Mainly with older higher hr engines.
It would appear to be a fuel delievery problem thats heat related.
Looks like the easy fixes have been tried (filters & plugged fuel cap).

Things to check.
Make sure theres no fuel line laying on the head/block as this may cause vapor lock.

It's possible that the valves are out of adjusment. Heat expands metal and the valves may not be seating all the way when warmed up.

Make sure all the lines are good and tight, especially around the injectors.

A test to try. With the engine cold, get some one to crank it while you crack a fuel line at the #1 injector and make note of the pressure. Needless to say tighten back while its still cranking/running.

When it starts acting up, do the same test and compare the pressure. If the pressre seems the same I'd suspect the injector, valves or something else within the engine.
IF the pressure is lower I'd suspect the fuel injector pump, any and all fuel system components from the injector pump back towards the fuel tank.
Good luck
Dave

Thanks.

I originally thought I may have a back safety cut off because when it first started, it would generally start lugging when I hit a bump. I'm still trying to figure out if that is useful information.

 

[ibnxe]

Even if you have changed out the filters, you want to be certain that there isn't a fuel delivery issue. Remove the fuel line between the tank and the first filter. There have been cases where a plug develops at the outlet to the tank, causing fuel starvation. This is an easy check and should be ruled out before looking at the fuel pump.
After this check, remove the fuel line between the fuel pump and the engine. With the key on, you should see good fuel flow. These two checks should rule out any fuel issues.
Good luck...

 

[ae_ted]

I just bought a 2001 700hr used ZD21. after using it 2 times it developed same problem. Dealer picked it up and is fixing it now. I should know something by weekend. I will let you know what they found. They were going to start by replacing the filters and going from there.

 

[dangerdoc]

Even if you have changed out the filters, you want to be certain that there isn't a fuel delivery issue. Remove the fuel line between the tank and the first filter. There have been cases where a plug develops at the outlet to the tank, causing fuel starvation. This is an easy check and should be ruled out before looking at the fuel pump.
After this check, remove the fuel line between the fuel pump and the engine. With the key on, you should see good fuel flow. These two checks should rule out any fuel issues.
Good luck...

Looking back, I did not get soaked with diesel when I changed out the filters. I think I need to look closely at the line between the tank and the pump.

Thanks for the help.

 

[kubota bob]

I have a ZD21 and had a similar stalling problem last year in May at 314 hours. Whenever I would start to push the steering levers forward to move, the engine would almost die, then pick back up. The dealer told me to replace the fuel filters - I did and solved the problem.

Two weeks ago at 381 hours similar symptoms, except the engine would slow down as I was mowing, not upon initial movement as before. I figured that it was something else wrong with the fuel system. Talked to dealer and we both thought that it was too soon to have plugged filters and though that it must be the fuel pump. I bought a pump and two filters. I just replaced the filters and problemn solved. The deler did say that he has seen fuel problems over the last year or so being dirty and causing premature filter plugging. I will return the $120 fuel pump that I didn't need.

Kubota Bob

 

[dangerdoc]

I have a ZD21 and had a similar stalling problem last year in May at 314 hours. Whenever I would start to push the steering levers forward to move, the engine would almost die, then pick back up. The dealer told me to replace the fuel filters - I did and solved the problem.

Two weeks ago at 381 hours similar symptoms, except the engine would slow down as I was mowing, not upon initial movement as before. I figured that it was something else wrong with the fuel system. Talked to dealer and we both thought that it was too soon to have plugged filters and though that it must be the fuel pump. I bought a pump and two filters. I just replaced the filters and problemn solved. The deler did say that he has seen fuel problems over the last year or so being dirty and causing premature filter plugging. I will return the $120 fuel pump that I didn't need.

Kubota Bob

I want to thank everybody that helped.

I took off the cover and pulled the fuel line, blew the whole thing out. That combined with the new filters resolved the problem.

I mowed long enough to get a good sunburn today and no stalling at all. A Kubota diesel engine sure makes a sweet sound when it isn't starving for fuel.