Hey, I have a early 80's JD 550 runs clean and starts first crank cold and same when hot most of the time, every 4-8th hot start it needs 2-4 5 second crank sessions to get it running, throttle position seems to not matter. fuel solenoid is getting voltage, I figure the fuel solenoid is tired and needs to be replaced, any other thoughts? Thanks.
Oakland Oregon? Me too! My dad has a JD350C and the fuel tank is pretty nasty inside. The fuel filter plugs every now and again and when that happens it starts hard. The other thing to check would be the valves. If they are out of adjustment that can cause hard starting.
So you can hop off after it fails to start, check the voltage at the injection pump, hop back on and it still fails to start? Next time disconnect the line from the injection pump and touch it back to the terminal for a second, see if you hear a click, and if you can shield the light enough see if there is a tiny spark. Or, disconnect it when it fails to start and check the solenoid with an ohm meter, most likely it will be a low reading(good) or open(bad).