Hydraulic Pump Question

You may have some debris or junk in there that's stuck in the exhaust port and jamming the valve when you try and remove it. The valve has a taper on it, and that may be where you're hanging up.

If you can't persuade it out by twiddling and tweaking, the only recourse may be to remove one of the plugs in one of the cylinder heads that gives you access to the pump outlet gallery, which is also the exhaust port channel, and apply air pressure. The plugs are on the rear face of the cylinder head assembly, and you want one of the upper ones. This would blow debris backwards through the port - hold the exhaust valve as far in as it will go while doing this.

I can't recall whether there's a relief hole in the back of the exhaust valve bushing but I think there must be or you'd always have a suction trying to hold it in = open. If the relief hole is plugged up, that might also be the cause of your problem.

HTH

llater,

llamas

If that's so, and you want to try the compressed-air trick, there's no need to remove a plug from a cylinder head. Just apply pressure to the cylinder line port in the pump base - where it connects to the standpipe in the hydraulic case to go up to the cylinder. Hold the exhaust valve as far in as you can while doing this, and if there's kaka in the port, it may blow out.

Seeing Ed's linked data also reminded me that you can get to the inside (front) end of the exhaust valve by snaking a long, thin pin past the yokes and into the back end of the exhaust valve bushing. There's holes cast into the front of the pump base that give you this access to both valve bsuhings. If you can get contact, you may be able to apply a light tap to the exhaust valve and see if it will slide free. I would be very wary of doing this, though - if there's something hanging it up, and you wallop on the valve, there's a good chance you'll score the valve bushing or the spool.

HTH

llater,

llamas