Knock in motor- Fuel pump - Team Camaro Tech
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post #1 of 8 (permalink) Old Sep 18th, 05, 10:29 AM Thread Starter
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Knock in motor- Fuel pump

68 327 - Have a distinct knock in the motor. The fuel pressure gauge seems to vary in time with the knock so I pulled the mech. fuel pump to investigate.

What i found was the pushrod seems jammed tight against the inner cover. I know this cant be normal..

Should I remove the cover and pull the pushrod out and inspect( Maybe gravity feed the gas to the carb to see if the knock is gone?)

Also if I take off the bottom cover and remove the pushrod:

1.Do I need to drain the oil first?
2.If yes, then I assume I have to replace th cover without the rod to try running without the pump...Correct?

Last edited by jsouthco68camaro; Sep 18th, 05 at 10:41 AM.
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post #2 of 8 (permalink) Old Sep 18th, 05, 11:42 AM
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Re: Knock in motor- Fuel pump

The pushrod will always fall down when the fuel pump is removed. The fuel pump lever is spring loaded and keeps the pushrod in contact with the cam lobe. If the pump spring is defective it can knock the way you described. Is the pump lever loose feeling? It should have no play up and down. If so buy a new one. When you are ready to reinstall the pump you can use heavy grease to hold up the pushrod. You might need to bump the engine over so the pushrod is on the base of the cam lobe. Some engines have a threaded 3/8" hole in front of the block in line with the pushrod that can be used to hold the pushrod up while you install the pump. Use a bolt with enough threads to allow it to reach the pushrod and snug it in place. Dont forget to remove it! You do not need to drain the oil, But I would use a block-off plate if you run the engine without the pump. Gravity will not get fuel past the needle & seat. You can use a electric pump to test to see if the pump is the problem once it is removed.
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post #3 of 8 (permalink) Old Sep 18th, 05, 11:46 AM
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Re: Knock in motor- Fuel pump

When you remove the fuel pump the pushrod almost always slides all the way down and can be a real pain to get back up. If it concerns you the cover can be removed without draining the oil. If you're going to run it without the pump I suggest putting a block-off plate on while you run it or you're going to have oil everywhere. A piece of gasket material the same size of the cover can be substituted. If the fuel bowls are full the car should run long enough to listen for a knock.
Guess I didn't type fast enough.

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post #4 of 8 (permalink) Old Sep 18th, 05, 11:53 AM Thread Starter
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Re: Knock in motor- Fuel pump

I pulled the pushrod out and started the car- No more knock!

Can anyone recommend a good electric pump?

Last edited by jsouthco68camaro; Sep 18th, 05 at 12:41 PM.
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post #5 of 8 (permalink) Old Sep 18th, 05, 07:04 PM
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Re: Knock in motor- Fuel pump

Quote:
Originally Posted by jsouthco68camaro
I pulled the pushrod out and started the car- No more knock!

Can anyone recommend a good electric pump?
Why bother with all the hassle/plumbing/wiring/mounting issues with an electric fuel pump? Replacement mechanical pumps are about $30.00.

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post #6 of 8 (permalink) Old Sep 19th, 05, 04:56 AM Thread Starter
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Re: Knock in motor- Fuel pump

The pump seems fine. I think the cam lobe must be worn ,causing the knock.
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post #7 of 8 (permalink) Old Sep 20th, 05, 02:12 PM
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Re: Knock in motor- Fuel pump

Clean the oil and carbon from the rod, and roll it on a piece of glass or something flat, see if it is bent. A bent rod will stick causing it not to slide smoothly and would cause a knock.

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post #8 of 8 (permalink) Old Sep 20th, 05, 02:18 PM
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Re: Knock in motor- Fuel pump

Quote:
Originally Posted by 69cama
…Some engines have a threaded 3/8" hole in front of the block in line with the pushrod that can be used to hold the pushrod up while you install the pump. Use a bolt with enough threads to allow it to reach the pushrod and snug it in place. Don’t forget to remove it! ….
And replace it with a smaller one! I learned that the hard way! Hole in engine = oil leak.

Scott from NJ. Stay thirsty, my friends


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