INTERNATIONAL 784

If the remote hydraulics are strong then there is nothing wrong with hydraulic pump. There is only 1 hydraulic pump behind the hydraulic filter. The pump puts out about 13GPM which is divided by the MCV valve to direct 2.5GPM to power steering, PTO and brakes and remainder goes to 3pt and remotes. Only use IH Hytran or equivalent hydraulic oil as oil supplies lubrication to transmission and rear end plus hydraulics. There is another hydraulic pump that feeds the T/A only. My brother's experience. He had purchased a log splitter that had been used on an older tractor and the cylinder was full of detergent motor oil and this got mixed with the Hytran oil and caused air bubbles that caused spongy brakes.

Problems:
1)Brakes require bleeding, check the archives on this site under 684 and you should find procedure. Change hydraulic filter and top up hydraulic fluid before attempting to bleed brakes.
2)Re Injection pump, change fuel filter(s) first.
Make sure you have good fuel flow at the inlet pipe to the first fuel filter. Should flow the full of the inlet pipe. These tractors are notorious for getting junk in the fuel tank that sits over the fuel tank outlet and starves the injection pump. Make sure the injection pump throttle and stop/run levers are working properly.
The stop/run lever in the run position should limit against the adjustment screw on the front of the injection pump.

I have had the Bosch injection pump off to replace the lip seal on the front drive shaft but never had reason to open it.

Try some Diesel fuel conditioner.

Hope this helps
JB2

Other times it is caused by lack of hydraulic pressure to the hydraulically activated PTO clutch (220 to 250 psi). This can be caused by clogged hydraulic filter or MCV valve or weak hydraulic pump. There is a pressure adjustment but requires special tools.

Do not operate the PTO with it slipping or you will burn out the PTO clutch.

Simple things first, clean and lube control arm mechanism, check hydraulic fluid level then replace hydraulic filter.

My experience on these tractors if there is a problem with the hydraulics the first symptom is loss of prime to the brakes. Requires constant bleeding of the brakes. Does the parking brake work? or is the remnants of the parking brake band floating around in the hydraulic system?

Good luck
JB2