Fuel Leak / Injector Pump / Bosch Governor / Cover Plate

[GlennLever]

Ok, I have had a small drip for awhile now.

I thought it was from a hose and have had Cummins look at it several times now.

Today I decided to look at it myself.

This is the mark it leaves after sitting for two days.



I crawled under the unit and the hoses did look dry, and with a flash light shining straight up I found a drip. It is not clear in this photo, but it gives you the location. Starter is to the right (front of the motor home (DP))



So we zoom in a little bit and you can see the drip. When I was under the unit I did not know what the part was, but it turns out it is the bottom of the governor housing.



I went topside and opened the engine compartment and it appears the fuel is leaking from this cover plate.

At first I was concerned with the fact that the bolts holding the plate in place might indicate a heavy spring being held in place by the cover. I now believe it was a warranty safe guard to keep people from playing with the governor settings.



It is quite wet below the plate and not so wet above it. I believe that wind has been blowing the fuel up.

I wiped the part plate clean and find.





I have found it extremely hard to find reference material on the net about Cummins, but I did fine a video on the disassembly of the pump.

Bosch Inline Pump Disassembly Part 1 of 2

I watched the video, there is VERY little conversation or expiation of what is going on but I did capture a screen shot of the cover removed.



My hope is the o-ring has been compressed over time and is leaking. A friend of mine has suggested that the O-rings in the injector pump have been destroyed by the low suffer fuel and I have fuel bypassing the pump into the governor under pressure and that is why I have a leak.

I do use fuel pump lubricant in my fuel.

Has anyone had any experience with this?

[GlennLever]

MEXICOWANDERER wrote:
I can state FOR A FACT that sulfur is a major contaminant and destroyer of natural and synthetic rubber and nitrile.

Carefully remove the o-ring seal.

You are going to need a splotch of tire and tube patch cleaning liquid. Bad for the skin and anything else it touches. Use nitrile medical or mechanic gloves.

Use a rag. Wet the rag with fluid. Gently wipe around the o-ring several times with the tube tire patch cleaning compound. The rag contact area will turn pitch black. Don't slop this stuff on! But allow enough to wet the rubber. Use a wath or clock. One minute of wiping. You will have to re-wet the cloth to make it a full minute.

Wipe dry with a clean dry cloth.

Smear silicone dielectric grease around the o-ring. Allow it to "soak-in" for five minutes then gently wipe off excess but don't try to scrub off all the grease.

Reassemble. Check for leaks.

I did this on several Cummins 855 PT injector pumps. The process is valid.

Nothing seems to substitute for tire tube patch cleaner. It definitely swells the rubber slightly. No leaks in 7-years following repairs to my own bus PT pump.

While search the net on this pump came across a lot of reference to the PT pump. I assume this is not what I have.

Does the PT pump have an access plate like this?

I will follow your procedure if I cannot locate a new o-ring.

[MEXICOWANDERER]

I can state FOR A FACT that sulfur is a major contaminant and destroyer of natural and synthetic rubber and nitrile.

Carefully remove the o-ring seal.

You are going to need a splotch of tire and tube patch cleaning liquid. Bad for the skin and anything else it touches. Use nitrile medical or mechanic gloves.

Use a rag. Wet the rag with fluid. Gently wipe around the o-ring several times with the tube tire patch cleaning compound. The rag contact area will turn pitch black. Don't slop this stuff on! But allow enough to wet the rubber. Use a wath or clock. One minute of wiping. You will have to re-wet the cloth to make it a full minute.

Wipe dry with a clean dry cloth.

Smear silicone dielectric grease around the o-ring. Allow it to "soak-in" for five minutes then gently wipe off excess but don't try to scrub off all the grease.

Reassemble. Check for leaks.

I did this on several Cummins 855 PT injector pumps. The process is valid.

Nothing seems to substitute for tire tube patch cleaner. It definitely swells the rubber slightly. No leaks in 7-years following repairs to my own bus PT pump.