1HDT will not start

[Beech4wd]

Test BOTH batteries with multi-meter while someone turns the key to try to start it.

You should see 12v or more at both batteries.

If one battery has a dead cell, jumping from a 12volt vehicle may not be enough current to lock in the 24 volt solenoid and turn the starter over.

You said you get a buzzing noise when you try to start it?
Weak batteries can cause a very rapid clicking as the solenoid tries to engage, then bounce back, engages again

thanks!! turned out the battery tester they used on it was faulty. Put the dead battery on a charger for a few hours and started right up!