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Lift pump going bad?

Discussion in '5.9L 12 valve Cummins' started by idiTravelAll, Mar 26, 2021.

  1. idiTravelAll

    idiTravelAll Full Access Member

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    Went to CA to pick up a vehicle last weekend (horror story) on the way home we were headed up a pretty steep hill on i10 and noticed my fuel pressure gauge getting wonky I mean this thing was all over between 0 & 30 psi was running but definitely felt it bog down when the needle went to 0. Fortunately we were close to a rest stop so I pulled in, about a half hour later my wife finally gets through to Geico roadside (@ the same time I found a guy with 5 gallons of diesel) My fuel gauge doesn't work and we had a real rough ride back on this tank with LA traffic I normally just be sure to fill up around 4-500 miles (40gal) Turns out Geico roadside (maybe just not in CA) wouldn't deliver diesel :shoot: Old timer that had the 5gal of diesel juice refused my 20bux, I told him its gonna cost him atleast 20 to refill it, still refused my 20. Nevertheless fires right up Fuel pressure is normal... pulled into the nearest station for a fillup... it only took a half tank just as my mileage calculation was telling me. We get to Goodyear, AZ and same thing starts happening.. pull in... half tank.. yesterday was cruising and yep you guessed it same thing.. fill up.. half tank.

    Long story short my truck has erratic fuel pressure once I'm down to a half a tank, I know it's not the straw on the sending unit because I used Larry B's Trident fuel hose.. my common sense tells me this is a lift pump going bad, anyone disagree?
     
  2. Mt_Man

    Mt_Man Full Access Member

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    Curious. Digital gauge with sender or wetline mechanical? Did you loose power when you saw the fluctuations? Does it stay acting weird till you shut off the truck and the back on? Seems like it could be some partially blocking the pickup tube. Not sure what vehicle you have the 12valve in or how you are set up. What kind of lift pump factory or aftermarket? How many miles on that lift pump?

    I had a lift pump go bad on my 97 dodge 12vavle. I had great low end power but above 2000rpm was a slug I. I was empty no weight. Happened on the way to work. Luckily I carry a spare with me and swapped it out. Looks like the factory lift pump made it about 160-170k miles. I have read they can fail in different ways too.
    Cheers
     
  3. Mt_Man

    Mt_Man Full Access Member

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    Oh yah you did loose power. Kinda sounds like a lift pump. Weird that it happens around half tank.
     
  4. idiTravelAll

    idiTravelAll Full Access Member

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    Its a '97 p-pumped 12 valve, auto trans, and its in my '73 IH Travelall with 40gal tank, I've put nearly 4k miles on it without issue.. one thing I forgot to add was I installed a TorkTek OFV but even that has atleast 2k on it by now. The fuel psi gauge is an electric glowshift (couldnt beat the price 100 w. Snubber) and I've been satisfied with it. The truck I picked up with 232k on it and runs great, appeared to have been meticulously maintained minus the fact the KDP wasn't blocked off until I did it at 239k(during the IH repower)

    When I installed the OFV I decided to drop fuel pressure a tad, for now I've decided to bump it back up and see how it behaves. I will definitely be grabbing a lift pump and spare fuel filter, current fuel filter is Napa premium/gold? and been in for around 9k miles. I will be swapping that out and cleaning out the pre-screen filter which I was unaware of the last time I changed the fuel filter.
     
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  5. Mt_Man

    Mt_Man Full Access Member

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    Yah it kinda sounds like a lift pump. I am not sure. But it's pretty cheap to start. The likely hood to having something plugging the pickup tube is slight with pump fuel. Prefilter is good to check. Good to check. Cummins dealer can look up your engine serial number and list off all the parts. Which is pretty handy. My dodge came with a carter lift pump. I just went with a Cummins lift pump. But I think carter's are supposedly good ones too. Interested in seeing what brand you go with.
    Yah I wouldn't think the ofv would fail that quick, I am not sure though.

    Tip when your changing it. Is to have someone hit starter while you are watching the cam lobe and see when it's out of the way and it will slide right in. As I recal it's not super fast. Or if you have the engine barring tool that would easier. The other way I have seen is to replace with studs and use the nuts to pull it down. Either way is good.
     
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  6. idiTravelAll

    idiTravelAll Full Access Member

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    I've gotta be sitting around half tank now so if its going to happen after bumping fuel press. up its gotta be soon. I read that Carter is OEM liftpump so I will stick with that, good to know on the liftpump install, I didn't know you had to bump the cam into position, I did read its easier to ditch the bolts and pop some studs in place to line it up the toss some nuts on there.
     
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  7. Mt_Man

    Mt_Man Full Access Member

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    Yah me neither but buddy was helping and we fussed with it for a while then he was like hey jump and tap the starter. Boom easy after that. I also cut the metal inner finder to allow good access. The plastic hides it when it's all back installed.
     
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