NHC-250 IP rebuild? - Steel Soldiers::Military Vehicles Supersite

halftrack · 02-19-2008, 16:37

Is rebuilding a 5 ton NHC 250 injector pump something that a mechanically inclined individuall like myself capable of doing or is it not worth it and just get a replacement. I am thinking that a diaphram is bad in the pump.

papercu · 02-19-2008, 20:42

Maybe this will help? Wayne

http://www.utterpower.com/injectionpumps.htm

Cdub · 02-19-2008, 20:44

I would say yes......!!!

Read and do as much research as you can.......Get some advice along the way.

Take your time.......don't be in a rush to finish.

If you don't have the necessary tools and they're not that costly then get them. You can't go wrong with buying too many tools.

If you mess it up the first time then do it over and get it right.....

How do you know if you can do it if you don't at least try........????

seya,

Craig

mitchellracing · 02-19-2008, 20:54

i rebuilt the pump on mine . i got a rebuild kit from truck pro because cummins said they no longer rebuild their own pumps . the kit comes with all the seals orings the governor patrs. the kit was $38.50 and the guy at truck pro said to make sure all the surfaces were clean and dont use silicone. just dont move the fuel screw inside of the thorttle shaft and you should be fine.i have a couple pics of the pump took apart if ya need them.

WillWagner · 02-19-2008, 21:09

Those pumps don't have a diaphram. What makes you think you have a "bad" one? I have built them moonlighting, but, if you want it to run right, have it done at a reputable fuel shop. You could have low fuel pressure, you build it, and it will most likely have the same issue. If you had a leak, and it ran good, i'd say do it yourself, but for a performance issue, have it done. FYI, it should cost around $150 max to fix it unless it needs a throttle shaft and housing.

halftrack · 02-20-2008, 07:58

It looses prime everytime and and I know it is not from sucking air from the pump to the tank. When I did get it running, it ran perfectly with lots of power. I believe it is letting air in from some where in the pump letting the fuel drop back into the filter housing. The fiter housing is pack full of fuel everytime so I know it is not a leaky fitler housing. Its frustrating but Through trial and error I concluded it must be in the IP some where but it is hard to believe that knowing that when it is running it runs perfect.

73m819 · 02-20-2008, 08:05

jason, you would be SUPRISED how small a air leak will cause this, does it surge at idle

halftrack · 02-20-2008, 08:34

No it does not surge at idle. However, the M818 surges at idle but I know it has a air leak in the fuel switch valve. Is that what causes that surge?

WillWagner · 02-20-2008, 08:39

Before you take it apart, do some troubleshooting. Get a clear line, Ace hardware has the line, just clear PVC hose, and a couple of push on # 10 swivels...If you can't find them, I can send you some. Install the line, run it at high idle-no load and watch the line. No big bubbles, you're good. Big bubbles, your issue is downstream. If that's all good, let it sit overnite and check the hose to see if fuel is there or has bled back. If it's there, you have other issues, pump or injectors. If it's not there, there is a leak. The pump body is pressurized and a leak there usually results in an external leak, but that doesn't mean the th. shaft isn't leaking. There is a quad ring between the gear pump and the pulsation damper. I'd do the damper and the mounting ring 1st. Good luck, take pics.

One other thing I forgot. Sometimes the coils on the fuel shut off, swell. That can cause hard starts and low power. There is also a disc inside there that, if it has a deep groove in the rubber, or has lost a portion of the rubber, or the wave washer has broken, will let the fuel bleed back. It will start hard every time, but run good after it dies finally lite.
HTH

halftrack · 02-20-2008, 08:45

Excellent ideas will and 73m819. This is exactly why I belong to this forum. The wealth of knowledge.

I thought about a clear hose but thought it would collapse due to suction pressure. Nevertheless, I am going to try it now. And yes, I will take lots of pictures.