How do you know when the Injection pump P7100 is bad or going bad??

Here it is: 1995 Cummins dodge 2500, 12V, NV4500 Manual transmission, 122K miles on truck.

When unit is cold it starts, holds 23PSI fuel pressure at idle, (gauge installed at inlet of injection pump). When I run it for 5-10 min. (hot weather is worse) out of nowhere I can hear a clicking noise coming from the engine and it will shut off (the fuel shutdown solenoid is not dropping out). It usually starts right back up and will run a few minutes and then same thing again. On start up it sounds normal, but when the clicking noise starts it is a dead giveaway that it is going to shut down. When the clicking starts the fuel pressure gets very erratic. It will fluctuate between 18psi and 25PSI at 1750RPM. When I let off the throttle it shuts off.

What has been done:
1. New fuel lines (factory OEM) from the fuel tank to the cab.
2. New rubber lines. (it changes from metal to rubber at the cab).
3. New lift pump
4. New fuel filter
5. New screen, gaskets, and fuel heater in the prefilter bowl
6. New elbow fuel hose off of fuel prefilter bowl
7. I almost forgot,, new pickup, sending unit, and screen in fuel tank
8. New Overflow valve in IP pump

I do not know of any fuel line part that has not been replaced between the tank and the IP. So,,, I guess it makes me feel like the Injection pump is bad.

Can anyone tell me what the symptons are when it goes bad? Is there a way to actually test the pump because I can't find it in the factory manual?

This thing has me beat. The fuel pressure can be at 22 PSI at idle and when it starts to click, and miss, it will immediately shut down. The weird thing is, I can drive it a few miles and it will run fine, shut it down, walk away for 10 minutes, get back in and start it back up and out of nowhere is starts acting up. It has done this several times and seems to be getting worse. I have a ton of new parts on this truck and I cannot throw good money after bad any longer. Most of the mechanics in the area are guessing at my problem, so I am trying to get some info before I allow someone to replace the IP pump.

This is my last shot at keeping the truck. I have installed NEW Jasper NV 4500 transmission, Jasper transfer case, along with many other new parts and I still cannot drive it. Over the past 6 years I have put 19K in the truck and my wife is killing me over it. If it is diagnosed with a IP problem I am going to have to just sell it as is and take the lose. Any help would be greatly appreciated. Thanks

 

It sounds like you might have gotten a bad lift pump off the shelf. They make a tick when they go bad. When the p7100 went bad on my '95, it wouldn't idle,ran only on 3 or 4 cylinders,had no power, and the throttle would get really stiff when all this was going on.

 

Interesting, I figured the fuel pressure would be very low when the lift pump failed. So, I did not consider it being bad. Thanks for the input

 

The early p-pumps had problems with something inside sticking and causing the symptoms I had and mine would do it when it was 100+ outside. If it does turn out to be the p7100, try to find a used one off a 96-98 they had the problem fixed by those years.

 

That seems to coincide with my problem. I have never had a problem with it during winter months, but when it gets hot outside I cant drive it without being broke down. Thanks for the input.

 

Another thing to check would be the weep hole on the lift pump. We had one at work that seeped and gave us all kinds of problems. It turned out the rod in the pump got cocked during installation,and cummins exchanged it for free.

 

I was going to say get a new overflow valve. Maybe your new one is bad? The overflow valve essentially regulates fuel pressure.

Clicking can be from the lift pump. I noticed mine started to click after I stretched the overflow valve spring to try to get a few more psi out of it.