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Fuel pump rod knock

Discussion in 'The Garage' started by mountainexplorer, Apr 24, 2006.

  1. mountainexplorer

    mountainexplorer 1/2 ton status

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    For those who've had a fuel pump rod or pump make noise, how did it sound?

    I have this 350 that makes a knocking/ticking sound that is loudest at the fuel pump. At first I wondered if it was a bearing starting to go, or a lifter. But the noise specifically comes from directly at the fuel pump.

    The other weird part about it is that it only does it when the motor is warmed up. Otherwise the noise is not heard. Once it warms up, the noise appears and stays the same.

    The "knock" is also consistent with the pumps of fuel that can be seen through the fuel filter.

    So who else has had this noise before?
     
  2. plowboy77

    plowboy77 Registered Member

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    Fuel pump

    Yes, I had that happen on my '76. :crazy: The worst part about it was that I had taken the fuel pump off my tired 350 and put it on my fresh 383....then it made the noise! Nearly gave me a heart attack! It was very much more pronounced at the fuel pump as I crawled around the engine with a stethescope. I talked to a local Chevy guy (he'd worked on several more than I had) and he said they sometimes do that. Something about the spring in the pump gets weak?? and allows the pump drive rod to bounce???

    Anyway, I ran it for a couple years that way and now I'm getting rid of the mechanical pump in favor of TPI, So I'll let you know if the noise goes away! :wink1:
     
  3. k20

    k20 3/4 ton status

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    Check the bolts on the crank pulley. I had a knock that coulda been all kinds of stuff, ended up being the crank pulley had come loose a little, and was rattling around.
     
  4. diesel4me

    diesel4me 1 ton status Premium Member

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    Yup...

    my 72 K5 made a tapping noise,mostly at idle when warm..I figured it was the timing chain slapping against the timing cover,since it had over 100,000 on it..I bought a new chain and gears,but just before I tore it down to install them,my older brother showed me how to test for slack in the chain by turning the motor back and forth by hand,and watching the rotor in the dizzy..It was pretty tight!..:doah: ..I was suprised,because I've seen loose timing chains beat a hole right thru the cover before,and cause a leak!..

    Then he had me start it up,and we could feel the "knock" when we put our hand on the fuel pump..it had a bad spring and the pivot pin the rocker arm in the pump rode on was badly worn..put on a new fuel pump,no more noise!!:laugh:

    I figured thick oil when cold helped cushion the pushrod from slapping around,and after it warmed up and thinned out,it would start clicking..I was worried the cam lobe that drives the pushrod might have gotten worn down from the excessive play,but I guess it survived..an electric pump would have fixed that in a hurry,if that were the case...:crazy:
     
  5. mountainexplorer

    mountainexplorer 1/2 ton status

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    Swapped it out today for another one and that was it. the fuel pump on that motor had an arm that was really worn out and loose.
     

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