I have a cat 416 backhoe and the boom lever for the rear hoe will not excite the pump. If I pull another lever it will give me pressure to run the boom. All the other controls work

I had a case tractor with a 4 cylinder diesel, dual heads, in-line cylinders. It had a similar symptom. Turned out to be a cracked head. Only one of the two. Water pump had previously failed, this led to overheating and cracking of the head.

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Putting the loader lever in the float position and having it raise the machine off the ground is a classic symptom of low pilot pressure. Setting the pilot pressure involves expensive gauges and a special procedure for setting pump output pressure, differential pressure, and standby pressure. I recommend taking your machine to a dealer to have them set.

Pilot pressure for each valve is 406-464 psi.
Minimum boom float engagement pressure is 334 psi.

check that you can open the rear of the unit, pins on one side and hinges on the other . This reveals the radiator and allows certain access to the motor.

just like any hydraulic system there is A (IN) and a (OUT) on every cylinder and motor on tractor (even steering) loosten (NOT remove) the hose fitting thats on (A or In) to motor and attempt to move joint/device with controls if a steady drip of fluid is present then your problem is device (cylinder,motor) if no drip then follow hose up to power divider or solinoid or hand valve and attempt same procedure , keep moving up the line till you get a steady drip of fluid and last device in liine is the problem device , repair or replace it

ALLWAYS turn off motor and release pressure from hyd system before you attempt to completly remove any device from system for replacement , and note that booms and arms and heavy stuff will relax(fall) with no pressure in system , prepare for this to happen (blocking,chaining)

You would think there would still be some warranty left on it, or at least some free tech help from Cat. Have you checked the rocker switch that moves it into four wheel drive - left side of dashboard. Sometimes these become faulty if used continuously. You can get help at this site below if you want to ask very knowledgeable people, and thank them for any assistance!

sounds like a fluid flow issue. Two separate levers so I doubt it's a Valve issue

Closed for starting, fully open to run.

eather a bad ground wire or the flywheel is bent witch will put to mucth of a load on starter