Why wont my john deere d140 move when I ngage the double foot pedal

Try the following test. For safety purposes remove spark plugs. Now with engine off and key in run position turn PTO on. You should hear the clutch engage (clunk). Grab both sides of the clutch pulley and try to rotate the pulley. If the clutch is properly engaged you will not be able to rotate the clutch pulley without turning the engine.

Here's the link and I'm sure you will get the solution of your problem.
JOHN DEERE D140 SERVICE REPAIR MANUAL

Make sure there isn't anything binding the deck belt or blades. Check the spindles for free movenent. If all that is good then it might be the linkage that is supposed to adjust the throttle when the engine is under load or it might be a carb issue...especially if you run ethanol gas in it.

does it have electric PTO ? if it does then you should be able to hear it click with ignition on and engaging pto switch if it does not then you have to look for a bad safety switch located under seat and brake pedal try unplugging pto clutch and putting 12 volts dc to one wire and grounding the other wire if it clicks its ok if it does not then safety switches are the probable cause witch is causing an open circuit.

Turn off the blades

check your idler pulleys. ipl indicates there 3 each and one different depending your serial.

there is a small handle on the back of most riders allowing you to free wheel the machine. If you can push your machine freely now then push the handle in and it should drive

check and see how much fluid in trans mission and change hydrostatic transmission filter

These John Deere Garden Tractors have a RIO (Reverse Implement Option) on the PTO. If your PTO is engaged and you back up, the PTO will automatically stop. To reset it, depress your PTO engagement switch to the OFF position. Take your foot off the reverse pedal. Pull up on the PTO engagement switch. The PTO should restart. To use the RIO feature, pull up on the PTO switch for a second or two just before you step on the reverse hydrostatic pedal. The yellow RIO indicator light should come on your dashboard and you can now back up with the PTO still running. Works great for snow blowing when I don't want to keep resetting my electric PTO clutch to keep restarting my snow blower.

If your PTO will not restart, you may have a PTO switch starting to fail, or a likely logic problem in your electric PTO control module, or one of your forward/reverse indicator switches, which is linked to your PTO control module along with the overtemp circuit, is stuck/faulty.