ZD25 Runs Bad

[Eric Larson]

The last time I ran my ZD25 (diesel, zero turn mower), it started and idled fine but as soon as I ran the throttle up and put it under load, the engine started running bad, low on power and putting out lots of smoke. I idled it back down and it ran OK again. After lots of experimenting, I ended up finding that it would run OK at part throttle and intermittently would run OK at full throttle.

I have a few thoughts but wanted to hear from anybody who's had this happen.

 

[85Hokie]

First - check your air cleaner, see if there is ANY restriction there.

Second - when was fuel filters changed last? How old is fuel too?

 

[GreensvilleJay]

agree..
WHEN was last time you ran it ? If more than a month ago, you'll probably need to drain tank,replace all fuel filters,and fill tank with fresh ,new fuel.
Hopefully you won't have to CLEAN the tank due to black algae...

 

[Eric Larson]

It ran bad late last fall and has been sitting over the winter.
My service records are at home (and I'm not). The fuel and air filters aren't very old but I had in mind changing the filters and dumping the old fuel.
How do you tell if there's a black algae problem in a black fuel tank?

 

[Dave_eng]

It ran bad late last fall and has been sitting over the winter.
My service records are at home (and I'm not). The fuel and air filters aren't very old but I had in mind changing the filters and dumping the old fuel.
How do you tell if there's a black algae problem in a black fuel tank?

Get an IR temp gun and use it to check exhaust temp on each cylinder.
Temps should be close but if they are not you have narrowed down where your problem lies.
Dave

 

[GreensvilleJay]

so..not run in over 3 months, maybe 4 ?
DUMP the fuel, CLEAN the tank, CHANGE fuel filters...
Pull fuel guage assy out, and use a high powered LED flashlight to see inside the tank.

 

[Eric Larson]

so..not run in over 3 months, maybe 4 ?
DUMP the fuel, CLEAN the tank, CHANGE fuel filters...
Pull fuel guage assy out, and use a high powered LED flashlight to see inside the tank.

Sounds like a great plan.......I'm on it. Thanks!

 

[Eric Larson]

Sounds like a great plan.......I'm on it. Thanks!

I did all that and the mower runs great again. Here's what I found:

No sign of black algae or anything weird in the fuel tank.
I cut both fuel filters open. The first one (between tank and boost pump) was pretty dirty. The second filter (after the boost pump) looked like new, and they're both the same age.
Air filter was pretty dirty and definitely needed replacement.

Thanks for the thoughts,
Eric