Cat 3126b HEUI pump transfer drive question

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by TheNautilus, Oct 3, 2022.

  1. TheNautilus

    TheNautilus Bobtail Member

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    Hey folks…

    Having a transfer pump failure on my 3126. Proved the pump was not working so I changed it. Same condition. No fuel output. I’m now suspecting the drive on the back of the HEUI pump has failed. This seems like an odd failure point. Wondering if anyone has heard of this?

    Thanks!
     
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  3. SmallPackage

    SmallPackage Road Train Member

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    If it is a Freightliner. There may be a little metal inline fuel filter ( about the size of the ones on an old school carbureted car) in the 1/2 plastic line going to the pickup pump right after the tee for the tanks. Usually buried in a hard to see and get at spot behind engine above transmission. They plug up and are not mentioned anywhere in the maintenance service regiment. We removed ours and replaced the line after they plugged the first time.
     
  4. TheNautilus

    TheNautilus Bobtail Member

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    Thanks SP… I have all of that bypassed. I have a single line from a gallon of diesel going right to the transfer pump. I can hand prime just fine but when I crank I get nothing. Not a drop.
     
    SmallPackage Thanks this.
  5. SmallPackage

    SmallPackage Road Train Member

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    I had probably a dozen problems with the heui pump on my ‘99 3126B in the 17 years we ran it everyday. Seemed like every 200-250k miles there would be something going wrong with them. From minor leaks to not pumping fuel. Derating itself down to 1800 rpm and top speed of 45 mph a couple times. They mixed fuel and oil a lot too. More oil in tanks then fuel in crankcase tho luckily.
    But when running good they were awesome pullers for their size.

    We found one way to help them live longer was to never go more then 8k on oil changes. Clean oil was the key. They would start to idle unevenly and get a little vibration in the fuel system when close to 8k so you knew it needed fresh oil.
     
  6. TheNautilus

    TheNautilus Bobtail Member

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    Yeah, the HEUI system seems to be the crux with these engines. I agree with the 8k mileage oil change. They like clean oil for sure.

    That’s good validation for me that you had fuel pumping issues related to the HEUI pump. Not an easy pull on this rig.
     
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  7. SmallPackage

    SmallPackage Road Train Member

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    That is one thing I wouldn’t touch. I would take it to CAT and let them mess with it. It always seemed like a can of worms was opened along with it so I was to spooked to work on it myself. Always seemed like other things that I didn’t have time for has to be replaced/repaired related to the pump failure at same time. Great thing was at the time the company paid for it so it didn’t hurt me, but now I would be stuck with the payment if it goes south again.
     
  8. TheNautilus

    TheNautilus Bobtail Member

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    Jan 17, 2021
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    That’s just it… It’s on my dime. Plus I’m not running because of the fuel issue. This is a HEUI pump problem only because on the rear gear that drives the transfer pump (I’m assuming).
     
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  9. Star Rider

    Star Rider Medium Load Member

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    I saw one once that the drive gear on the front of the heui pump had come loose. Are you building actuation pressure? If the pump isn't turning it won't run the transfer pump.
     
  10. TheNautilus

    TheNautilus Bobtail Member

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    Star Rider… Good point. I have no way of checking for actuation pressure at the moment but I figure I have enough reason to pull the pump and inspect the front and rear gear.
     
  11. Star Rider

    Star Rider Medium Load Member

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    Pull the transfer pump , crank the engine and see if the transfer pump actuator is moving. Much easier.
     
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