Control Valve


Here is the control valve getting ready to have the retaining clip pressed into the bore.

After trying to tap it into place using the handle of a screw driver, it became clear that if the clip flew across the room I would never see it again. So this is what I used. My largest pair of channel locks with duct tape on the jaws.

Here is how it came out. Dead flush with the bottom of the valve. Just like the pump shop guy told me to do. I shook the valve back and forth and it rattled. I could also see a gap between the piston and the clip. Since the chamfer at the bottom of the bore takes up about 25% of the clips length, I though it would be a better idea to drive it in a little further.

I used the tip of a philips screwdriver to move the clip in more. I just tapped the handle of the philips screwdriver with a wrench. It took very little force. If you look closely I overshot and went past the chamfer a bit. The piston and spring no longer rattle. I tried to pull the clip out a bit more but could not do it. We’ll see how it runs.

The local Cummins parts house, FJM Trucks, called a pump rebuilder and got me the answer. I described to the rebuilder on the phone what the parts looked like. He told me the tiny hole in the piston faces down into the bore where the control valve (pressure regulator) sits. The rebuilder says that guys that play with pump pressures have this happen more often. But it happens in stock pumps as well. The clip goes in only until it’s flush with the bottom of the control valve. The top of the control valve can be pounded down with a drift and hammer to increase the pressure he said. Also he mentioned that if I did that the pump would have to be calibrated again. Now worries here, this old girl is staying stock. The pic shows the correct way this valve goes back together.

I installed new orings as soon as I got the control valve apart. That way I didn’t mix up any orings with other assemblies.

This control valve head takes only a 10mm wrench. It was very tight. So I had to use some leverage to get it free.

Here are all 4 o-rings on the control valve. This also shows the orientation of the parts. The governor shaft seal is installed but is still waiting for it’s washer and jam nut.

Control valve with o-rings removed without adding any scratches.

The control valve had 3 parts loose when I took it out of the pump body. In this pic I installed the spring and piston into the control valve. The only thing remaining was this clip. It seems like it would be a press fit.

I hope this is how the control valve parts go back together. I used a magnet to pull them out of the bore the control valve screws into.

No place for the spring and piston to be held in the cavity that they came out of. It must mean that the parts are held in the control valve with the circular clip.