Today, I was messing with the pressure in my transmission while my friend was checking my valves. I am a diesel mechanic in the marine corps and well, he's a supply man. I guess it's alright to have access to cool gear but, wow he needs to learn about mechanic work. He did the valves alright but while i was working down there he told me he was gonna put in my new overflow valve. I agreed, thinking it wouldn't be that difficult, i got done underneath and went to start the truck. I cranked for 30 seconds nothing, it cranked very strong but did not turn over. No big deal, maybe air in the line. I primed the pump 15 times and tried again. It started ran very rough and died. I started it again and did the same thing but i put my foot into it revving to 1500 rpm for 10 seconds then let offer, idled at 500 for a few seconds then jumped back up to 800 where it should be. I thought all was well. Packed everything up and drove off. I went to turn on the main road, gunned it, since the temp was already at 140 degrees and it shuttered and shook like a dog shaking itself dry, then died going 35 mph. I came to a stop started it up and drove back to my shop. I opened the hood to see what was wrong and was met with a big surprise, my buddy put the overflow valve on the wrong side of the pump. He replaced the entrance valve to the pump. I started laughing, than got a little ****** off thinking he just cost me a new p7100 pump, marines aren't known for keeping their cool. I fixed his screwup and after a case of beer later we were blood brothers again. I am worried i caused damage to my pump or the overflow valve. The only cummins we deal with are on our five tons which are outdated. I usually deal with detroits and if i could fit a detroit in a dodge i would, however these cummins are great engines. Any help would be appreciated, thanks guys.

 

Wow, im suprised that thing even started! Very amazing. I would think that the OFV would have sealed completely off flowing the wrong way. Im realy stumped

 

yeah, im not sure how it started either. It runs better than it did before after i fixed it. i'm guess it was just a fluke, but i'm pretty sure my pump is ok along with the overflow valve. Working on diesels in the military is pretty fun, except fixing them in 140 degrees in Iraq, but you get used to it, wouldn't want any other trade. What my friend did is nothing compared to some of the so called experts that i work with. I've seen a detroit diesel run away on a dyno and our ssgt thought he new how to stop it, he grabbed the closest thing he could get his hands on, which was a phone book, and blocked the turbo, BAD IDEA!!!. 2 seconds and that monster of a turbo sucked that phonebook in and sent it right into the engine, good by 900+ cubic inch detroit, i couldn't stop laughing. I bet you a cummins could've ate that phonebook and spit it right out, lol. I love the cummins motor and would rather have the 5.9 in the humvees than those 6.5litre gm pieces of junk with that crappy 700r4 tranny sittin behind it. I don't understand the logic of having over 12,000 pounds of vehicle and armor with so little muscle under the hood. just my $.02.

 

Your buddy isn't the first one to do this, there have been quite a few folks come here with a problem similar to yours over the years. Hard to diagnose because you figure no one would replace one part with another that looks way different.

Another hard to diagnose one is brakes that won't bleed when the person installs the brake calipers on wrong side and they are upside down.