Knocking fuel pump?

Discussion in 'High Performance Modifications' started by DirtyScotty, Oct 9, 2005.

  1. DirtyScotty

    DirtyScotty Veteran Member

    I have a knock from my engine that sounded like it would knock with every revolution of the cam. With the stethoscope i listened to alot of different places on the engine. Noisiest on the fuel pump. I pulled the pump and installed a block off plate. Started the motor and the knock was gone. The fuel pump is a new Holley 110gph mechanical. 327-11 part number.Have any of you guys heard of a knocking fuel pump before? Are these pumps known to have problems? Is there a chance that the cam lobe that runs the pump is the problem? The cam is a XE274 which I have read some bad things about.
     
  2. 73454

    73454 Guest

    The pump driveshaft is what was making the knocking. It could have done damage to the fuel pump eccentric, but since you converted over to electric it is a non-issue.
     
  3. retorq

    retorq Veteran Member

    4,921
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    May 13, 2003
    Kingman, AZ
    I bought a used 350 engine for my Camaro some years ago, we had it up on the chain moving it and it took a tumble. It fell about 3 feet, damaged the fuel pump. The knocking was almost like a rod, I got scared, when we swapped the pump it went away.
     
  4. Mountaineer

    Mountaineer Veteran Member

    I had the very same problem with this pump this summer. I went through 2 of them, at idle the noise was the loudest. I talked to Holley, they said send it them and it could take up to a month to figure out. I sent it back to Summit, they replaced it, I had the same noise with the replacement pump, sent that one back to Summit for a refund.

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  5. Gary S

    Gary S Administrator Lifetime Gold Member

    21,443
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    Apr 14, 1999
    Bismarck, North Dakota
    I've never had a Holley pump, but the factory fuel pumps often do that when they wear out. They wear out at the pivot point of the pump arm, and start knocking. I've always found that to be an enjoyable failure because when I first hear it, I think the engine has a problem, only later to replace the fuel pump and fix it for $15. Feels good.
     
  6. DirtyScotty

    DirtyScotty Veteran Member

    73454. I did not change to an electric pump. I just ran the car with what fuel was left in the bowls. I am going to put on another stock pump to make sure that the pump is the deal. Thanks for the replies guys.
     
  7. Damon

    Damon Veteran Member

    12,939
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    Nov 16, 2000
    Philly area
    Yeah, just about any mechanical pump can cause a knock like that if it's worn out. Sounds kinda halfway between a valve tap and a rod knock- and yes, it can drive you nuts figuring out what's making the noise.
     
  8. DirtyScotty

    DirtyScotty Veteran Member

    I just put on a stock pump that was lying around. Noise almost totally gone. Way quieter than with the Holley pump. The stocker pump still makes some knock though but nothing like the Holley. I put the Holley back on again to hear the diff again and it is huge. I should have just went with the electric pump in the first place.
     
  9. Twisted_Metal

    Twisted_Metal Administrator Staff Member Lifetime Gold Member

    26,129
    553
    Feb 26, 2004
    Bloomington, MN
    I've had that happen twice. The first time, I played with the valve lash thinking it was a lifter/rocker issue. I couldn't get the knock to go away. The pump crapped out when the arm folded a few days later and replacing it fixed the knock. [​IMG]

    It's the first thing I check now when I hear something like that.
     

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