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Good Gracious this thing is driving me up the wall!

994 views 11 replies 5 participants last post by  4320diesel 
#1 ·
my cummins keeps fudging around on the highway now. i was bookin down the highway at 120KM/H engine revs around 2000-2100 and it starts slowing down, and i have the pedal mashed, then it started working again, i figured it was the same old thing its been doing where it wont rev past 2200 with a load on the engine, then it started missing really bad(just like when it gelled up) so i pushed in the clutch and let off the accelerator and it almost died so i reved it back up and let the clutch out. then i tried it again but with the pedal mashed and it wouldnt rev past 2200 with the clutch in. so i kept driving it then the missing stopped, and it worked like it always has and kinda did this on and off a few times and quit doing it. i pulled off the highway onto the grid road home and it didnt do it since. so WTF is this? my OFV dying? LP dying? air in the system? or is my ip pissing with me? i want to drive the truck to work again tomorrow but id rather if it didnt die on the middle of the highway and leave me stranded since its fairly cold outside lol.
 
#4 ·
i didnt know a lift pump would only work intermittanly. i thought it was either work or not work.
 
#6 ·
no i dont have a presure gauge yet. i want one but its about 200 bucks for the gauge and column bezel. ill probably end up rigging up a temporary one for now out of my oil presure gauge i have in the shop and a needle valve and just stick it in front of the windsheild. the lift pump probably has 300,000 miles on it so im sure its due for replacement. anyone have any idea what these run pricewise? and how hard is it to change?
 
#9 ·
300,000 is about the average lifespan of the lift pumps I have replaced. Genos has them for about $100. If you have a Case tractor dealer in your area they are a little less sometimes. Theirs requires you removing one of the fittings from your old pump and using it. I have heard that NAPA carries them also.
 
#10 ·
thanks! ill be replacing it then once i get 100 dollars lol. that and ill check the spring in the OFV with my calipers to make sure its alright. im sure at work my boss can have them in from his bulk supplyer for a bit cheaper but im not sure.
 
#11 ·
I had the same similar problem with my 97 (Still daily driver since New) after several days of what seemed to be endless troubleshooting turned out to be rotten fuel lines ( supply and return ) inside the frame beside the fuel tank. Can't see it or smell it at all. Turned out it was sucking air at higher RPM's. Replaced it, haven't had the problem since. Not sure if this is the same as your problem or not, but hope it helps!!..........brimc.
 
#12 · (Edited)
talked to my boss at work today, he figured an airleak, so i presurized the tank and found no leaks anywhere, then i figured ill clean the sediment bowl, and for the hell of it i unplugged the fuel heater first and heard gurgling and got fuel on my finger. GREAT! i tore that POS outta there and cleaned the bowl and put it back on. removed the OFV and took the spring out and stretched it to .55" and it runs great now i might stretch it a tad more to see if it makes any difference. thank you to everyone and that fantastic write up for the fuel system.
 
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