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  #1   IP: 108.168.37.23
Old 07-08-2018, 10:06 AM
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Question fuel pump knocking - video

Last weekend I was having some fuel issues, and the good people here helped me out. As a part of my solution, I installed a new fuel pump. Last night I noticed the pump was making a loud knocking noise and the new fuel pressure gauge I installed was jumping. Here is a video: LINK

As the knocking is more evident at the end of the video.

If my issue is the pump, I'm going to be in the US later this month and can get the correct one from MMI.

I should mention the engine runs fine.

Any ideas?
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Old 07-08-2018, 12:15 PM
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Don't recognize the pump (but that doesn't mean much). The way the pressure varies seems odd - perhaps the pump is failing? Might also explain the fluctuation/vibration of the needle. Can't say I heard the knocking..
Before replacing the pump, I'd try running it off the engine (or with the engine off - jumper across the OPSS) and see what happens.
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Old 07-08-2018, 12:22 PM
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I think the jumping on the gauge may be an air leak.
What is your fuel mix currently adjusted at?

I agree with Al that it's hard to hear any "knocking" from the pump.
You should note that the "go to" pump most of us use (Facet) actually makes a knocking sound when running.
What fuel pump is that? Do you know it's PSI rating?
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Last edited by roadnsky; 07-08-2018 at 12:25 PM.
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Old 07-08-2018, 12:30 PM
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Quote:
Originally Posted by roadnsky View Post
I think the jumping on the gauge may be an air leak.
What is your fuel mix currently adjusted at?

I agree with Al that it's hard to hear any "knocking" from the pump.
You should note that the "go to" pump most of us use (Facet)
actually makes a knocking sound when running.
What fuel pump is that? Do you know it's PSI rating?
Here is the pump: LINK

It's 1.5-4 PSI

Fuel mix is 1.5 turns out. I cleaned the carb last weekend

I'll be in the US on the 20th and can get the MMI pump as I know that is recommended.

It would be nice to have a solution in place in the meantime.

Last edited by Graham; 07-08-2018 at 12:41 PM.
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Old 07-08-2018, 12:48 PM
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Any tips on how to find a vacuum leak upstream from the fuel pump?
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Old 07-08-2018, 05:29 PM
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I'm not convinced you have a problem. The fuel pump ticking is normal for pulse type pumps which leads me to your fuel pressure gauge behavior. It's pulsing nature may also be normal because of the type of pump. It's interesting to see the pressure fall in the video showing the carburetor float valve is open, then come back up when it closes.

You might be searching for a problem that doesn't exist.
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  #7   IP: 108.168.37.23
Old 07-08-2018, 12:24 PM
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Quote:
Originally Posted by Al Schober View Post
Don't recognize the pump (but that doesn't mean much). The way the pressure varies seems odd - perhaps the pump is failing? Might also explain the fluctuation/vibration of the needle. Can't say I heard the knocking..
Before replacing the pump, I'd try running it off the engine (or with the engine off - jumper across the OPSS) and see what happens.
Yes, the knocking is hard to hear on the video. I'll try and get a better video today. I'll also try disconnecting the pump for testing.
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