M 923 NHC 250 leaking fuel pump/fuel control shaft

[Andyrv6av8r]

Anyone ever had a NHC 250 fuel control shaft leak that they fixed? Mine has a drip that causes me to lose prime after a few days and is causing slower starts. Runs fine after start up but is more annoying than anything. Is it a simple repair like an o-ring or more complex? Is it worth a tear down or just as easy to buy another used serviceable unit? Any insight and recommendations would be appreciated.

 

[73m819]

According my cummins pt book, it is a simple o-ring, the throttle shaft gets pulled, o-ring replaced on shaft then installed, said to use plenty of lubeaplate on the o-ring, be real careful about NOT nicking the shaft or housing.

 

[Andyrv6av8r]

According my cummins pt book, it is a simple o-ring, the throttle shaft gets pulled, o-ring replaced on shaft then installed, said to use plenty of lubeaplate on the o-ring, be real careful about NOT nicking the shaft or housing.

So it seems obvious that I need to unbolt the FC and the shaft comes out from the inboard side? The cover on the outside appears to be riveted on. And thanks for a quick response.

 

[73m819]

comes out the control side, under that cover is a retaining ring, compress it and remove it from the grove, pull the shaft straight out.

 

[aheilmann68]

I am having the same issue with my 250, I removed the aluminum cover plate but could not get the cam to come off of the shaft. I loosened the set screw on the cam but didn't try to apply too much force to the cam for removal. Ill try again when I get some time and soak the cam with penetrating oil. So 73' your saying behind the cam is a snap ring of sorts and the throttle shaft slides right out? Also any idea on the p/n for the o rings? thanks

 

[Andyrv6av8r]

I am having the same issue with my 250, I removed the aluminum cover plate but could not get the cam to come off of the shaft. I loosened the set screw on the cam but didn't try to apply too much force to the cam for removal. Ill try again when I get some time and soak the cam with penetrating oil. So 73' your saying behind the cam is a snap ring of sorts and the throttle shaft slides right out? Also any idea on the p/n for the o rings? thanks

You will have to remove the fuel pump and split it to get to the c-clip. It's on the inboard end of the throttle shaft. Be careful with your gaskets if you plan on reusing them and take special care with that clip; it's tiny! After I replaced the oring, my truck starts easily and runs so much better. If you have any questions, PM me and I'll be happy to send you my number so that we can talk.

 

[aheilmann68]

What o ring did you end up replacing it with, is there a cummins number or a regular diesel safe one ok? Can the shaft be accessed from the motor side of the pump or it really has to be removed? Thanks for your help

 

[Andyrv6av8r]

What o ring did you end up replacing it with, is there a cummins number or a regular diesel safe one ok? Can the shaft be accessed from the motor side of the pump or it really has to be removed? Thanks for your help

I just used a fuel safe oring out of my assortment kit. I wouldn't attempt or even know if it is possible to do on the truck. It's really not a bad job to remove the pump and do it. Give me a call if you like and I'd be happy to talk to you to give you some pointers.
864-978-0243

 

[WillWagner]

The pump needs to come off and the front cover removed. DON'T try to pull that "cam" thing off. put the set screw back in it. DO NOT move the screws on either side of the "cam". Those 3 items are what set the throttle shaft travel. It needs to be an exact 27 degrees so the ports in the shaft align with the ports in the pump. Too much or not enough travel will make performance problems.

 

[aheilmann68]

Great, thanks for the information. I will likely do it later in the month when I have more free time.

 

[TechnoWeenie]

Also any idea on the p/n for the o rings? thanks

I know it's 3 years later, but I have the same problem and this thread keeps popping up..

So, for those looking for the O-ring PN, it's Cummins 100478

 

[Ozzie]

Good morning Andy, I saw this old post of yours and was wondering if you can help me diagnose my fuel pump. I have s 1986 M923A1 855 ci Cummins non turbo and it lost power a few weeks ago. I've replaced fuel filter, cleaned fuel tank and even put an electric fuel pump to supply the fuel pump and it still runs lousy with no power. I am in the process or replacing all the rubber fuel hoses. Thanks, Ozzie

 

[simp5782]

Good morning Andy, I saw this old post of yours and was wondering if you can help me diagnose my fuel pump. I have s 1986 M923A1 855 ci Cummins non turbo and it lost power a few weeks ago. I've replaced fuel filter, cleaned fuel tank and even put an electric fuel pump to supply the fuel pump and it still runs lousy with no power. I am in the process or replacing all the rubber fuel hoses. Thanks, Ozzie

The large flathead screw housing on the top the injection pump. Remove it and pull the small IP filter and see what it looks like. Or leave it out and run it.

 

[WillWagner]

^^ No, don't do that. That screen is not a filter like one would think, it is there for one reason, ONLY to catch pieces parts from a pump failure from getting into the injectors and taking them out too/ It is not something that needs service on regular intervals. If there is debris in it, there is a failure in the pump or a ruptured filter before the pump, but if the latter happens, there will be other parts fail that require the pump to be repaired

 

[kneesnthebreeze]

I have a 85 931a1. the pump is leaking from a triangle-ish shaped plate on the inboard side of the pump. i took the pump nearly almost apart about two months ago and put new seals on everything that i could with my limited knowledge. the "triangle" plate still leaks as the truck gets up to temp, appears as if it is some sort of pressure issue from within the pump. like i said, i replaced most of the seals but i did not yank out what i assume is the fuel shaft. is that o ring what is possibly causing the fuel pressure issue? the truck runs fine but im tired of the constant fuel dripping. also- now there is a constant drip coming from the fuel dampener as well. im pretty much going under the assumption that there is an o ring that i did not replace, causing the pressure issue. any help or suggestions would be greatly appreciated!

 

[kneesnthebreeze]

http://bunkerofdoom.com/travel/ss2009/8109_build/tm/nhc250.pdf

 

[allie]

can you post a picture of your leak or the exact location

 

[Floridianson]

can you post a picture of your leak or the exact location

allie this is a old thread and last post 6-11-18 so don't know if the OP will answer. From your pic I believe your throttle shaft is leaking and pump has to come out.

 

[allie]

Sounds like a big job I assume an Pring is the culprit

 

[TechnoWeenie]

Sounds like a big job I assume an Pring is the culprit

It's an easy job.

couple bolts... couple connectors... big wrench...

Wes walked me through mine, and it was super easy. It sounds complicated but when you do it you'll be kicking yourself for thinking it was so hard. I ordered my parts direct from Cummins... I replaced all the O-rings and seals that were easy to access...