zd21 will not start

boilerdawg · Jun 20, 2013

Hi all,

I have a zd21 that i bought new in 2002. It will crank but it wont start. last time i used the mower it wouldnt stop when i turned the key off. it idled rough but wouldnt quit. i throttled it down, stood up, engaged the arms with the brake on and it wouldnt quit. finally it did quit after several minutes. well today i got to crank it. it starts but its idling rough like it did when it wouldnt stop. i notice that the fuel guage is going off and on...i mean from about a third of a tank to no power. the guage cycled like this several times. as the guage read properly the mower ran fine, but when the gauge had no power the mower idled rough and the engine would eventually die. i thouht its the ignition switch, so i jumped it. the same problem occured with the guage and idling. i hooked the switch back up and now the fuel guage will not power on at all. the engine cranks and tries to run but it will not. i also notice the the "CLICK" you normally hear when you turn on the key from the fuel solenoid is not present. the glow plug/preheater works fine. i think its something electrical. ive checked the wiring for shorts, anything noticably wrong. i cant see anything out of the ordinary. is there a way of jumping all the safety interlocks? what should i try next? any ideas on what it is?

appreciate any help or ideas....thanks in advance.

Dozernut · Jun 20, 2013

Had the same problem with my ZD21, it would not start. The problem was a bad fuel stop solenoid. The solenoid sits on top of the engine and is very easy to take out and install a new one. The electrical component is simply unplug and plug in the new one, about 5 minutes or less for removal and installation.

Could be something else but you can check the solenoid. Raise the hood and find the solenoid, round with rubber coating linked into the throttle type linkage that controls fuel flow. Turn the key on, the solenoid should extend to allow the fuel to flow, key off it will contract, if this is not happening then you will most likely have found your problem.

boilerdawg · Jun 21, 2013

Dozernut said:
Had the same problem with my ZD21, it would not start. The problem was a bad fuel stop solenoid. The solenoid sits on top of the engine and is very easy to take out and install a new one. The electrical component is simply unplug and plug in the new one, about 5 minutes or less for removal and installation.

Could be something else but you can check the solenoid. Raise the hood and find the solenoid, round with rubber coating linked into the throttle type linkage that controls fuel flow. Turn the key on, the solenoid should extend to allow the fuel to flow, key off it will contract, if this is not happening then you will most likely have found your problem.

Thanks for the response. Would this solenoid make the fuel gauge act stupid?

Dozernut · Jun 21, 2013

No, the fuel gauge on mine has not worked right in years, I make sure to fuel up every time I mow. They seem to be a lesser quality item on a higher quality machine. For me it is not worth the expense or time to repair it.

boilerdawg · Jun 21, 2013

Dozernut said:
No, the fuel gauge on mine has not worked right in years, I make sure to fuel up every time I mow. They seem to be a lesser quality item on a higher quality machine. For me it is not worth the expense or time to repair it.

ok i took a 12v jumper from the battery to the solenoid......it works. so its definately not the solenoid. is there some sort of control box where all the safety locks run through??

Dozernut · Jun 21, 2013

You probably have a short or corrosion in the wiring somewhere. Try the ignition switch again, it could be getting worn. I have had to replace mine. They are easy to replace but removing the shields to get to it is the hardest part. The only control module I am aware of is the glow plug controller. If the glow plugs are not working that will hamper starting, but you said you checked that. Sounds like a faulty ignition switch.

Dozernut · Jun 22, 2013

Are you sure the solenoid is activating when you turn the key on and off? You said you jumped it and it worked but did not say if it was working when you turn the key off or on. If not then you have a bad key switch, a short or corrosion. I think I have a shop manual for that engine but my shop is disarray right now, if I can find it I will post a copy of the page you might need.

David_Kb7uns · Jun 22, 2013

Usually there is a relay timer control for the key stop solenoid so the solenoid energizes when the key is turned off or the interlocks trip.

David Kb7uns

kuboman · Jun 22, 2013

The stop solenoids usual position is on. when you start the engine then shut it down the stopping function energizes the stop solenoid fowr about 10-15 seconds, long enough to make sure the engine stops rotating. The timer circuit is then interrupted and the solenoid goes back to start position. It could cause your fuel gauge to mess around but one way to check that is to unplug the stop solenoid turn the key on and see if the gauge settles down. Or you have a grounding problem and good luck with that. Start at the battery.:confused3: