I re-did the bushings on my L785 this spring. I used poly shock bushings on dang near every one of them. I do have a lathe, so I put them on a bolt as a mandrel and trimmed them down to fit. Worked great, and a heck of a lot cheaper than what they wanted for new bushings from New Holland!
I bought a L170 with a locked up engine. Someday when I get time (yeah right) I'll yank it and see about rebuilding it... Kits are pretty cheap, like $500-750 on ebay.
My older L785 has the solenoid only on the boom, not the tilt. So with the key off and engine running you can still tilt it. I'd look at that safety solenoid and make sure it is getting energized with the key on and seat safety switch or seatbelt switch or whatever it has activated. Mine is...
On those with the boom and tilt lock is there two separate solenoids locking both the boom and the tilt? Sounds like the solenoid itself might be getting warm after 15 minutes and closing. Check for power at the solenoid when it happens. If it is still powered and grounded properly then you...
Put a battery in it if it doesn't have one and turn the key on. Get someone in the machine holding the boom raise pedal while you lift it with another machine. If yours has the safety interlock system for the boom you'll have to make sure you go through all the steps to unlock the boom...
I just did some looking on Messick's parts catalog for the wiring schematic and think I figured out why mine was so simple to bypass. Mine must be before serial # 733332 and have the following wiring schematic. Only one seat switch and only one interlock valve on the hydraulics that stops...
Ok so I just went and did some google searching looking for a wiring diagram and came across the logic module you are referencing. My L785 does not have that at all. I thought you were talking about the display with the dummy lights that illuminate if you lose charge pressure or oil pressure...
You are simply not getting power to your ignition switch or out from it when in the on position. These skid steers are really simple in the electrical department. Pull the overhead console cover off and probe around with a test light to see if you have power coming up to your ignition switch...