CAV DPA Pump problem

[Unclebilly10]

hey guys, I’m working on my Perkins 4.108. Fresh rebuild. So engine side is good.

I’ve been through and put a seal kit in the pump.

My observation is it seems to be running on mostly 3 cylinders cylinder 3 isn’t contributing and I think I narrowed it to the pump. When I crack cylinder number 3 I can just see a slow drip from the line, The other 3 give a good squirt from the injector nut when cranking. And if it’s idling, cracking injector 3 barely has an effect on its running quality. But the other 3 cylinders nearly stall the engine when opened. I have swapped injectors and the problem stays on 3.

It’s weird because these pumps use the same plungers for all cylinders, and the cam ring doesn’t show wear.

Has anyone ever seen this? I have to make a special socket to remove the rotor and inspect the bore and passages, but I’m wondering if anyone has seen one injector port ever blocked or obstructed?


When cranking With no injectors, it appears all 4 are flowing fuel, but when there’s pressure behind it, I don’t see number 3 discharging as much as the rest

Timing is good. Injectors were rebuilt

 

[Powered By IH]

hey guys, I’m working on my Perkins 4.108. Fresh rebuild. So engine side is good.

I’ve been through and put a seal kit in the pump.

My observation is it seems to be running on mostly 3 cylinders cylinder 3 isn’t contributing and I think I narrowed it to the pump. When I crack cylinder number 3 I can just see a slow drip from the line, The other 3 give a good squirt from the injector nut when cranking. And if it’s idling, cracking injector 3 barely has an effect on its running quality. But the other 3 cylinders nearly stall the engine when opened. I have swapped injectors and the problem stays on 3.

It’s weird because these pumps use the same plungers for all cylinders, and the cam ring doesn’t show wear.

Has anyone ever seen this? I have to make a special socket to remove the rotor and inspect the bore and passages, but I’m wondering if anyone has seen one injector port ever blocked or obstructed?


When cranking With no injectors, it appears all 4 are flowing fuel, but when there’s pressure behind it, I don’t see number 3 discharging as much as the rest

Timing is good. Injectors were rebuilt

What's up with the number 3 injector line? Is the rubber and hose clamp there for a reason?
Are you sure that the injection line seals good and doesn't leak?
Have you tried cracking all the lines at the pump and seeing if that makes a difference?

 

[Unclebilly10]

What's up with the number 3 injector line? Is the rubber and hose clamp there for a reason?
Are you sure that the injection line seals good and doesn't leak?
Have you tried cracking all the lines at the pump and seeing if that makes a difference?

It has had a Brazing repair before I got it seized and never have seen it run since the rebuild.

I have since switched the line because I thought it may be collapsed, Yes I have opened it at the pump end and have the same observation. It seems like it’s a pump head rotor issue certainly but I can’t see how.

Just wondering if anyone has seen anything like this before.