fuel pump knocking - video

[Graham]

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?

[Al Schober]

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.

[roadnsky]

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?

[Graham]

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.

[Graham]

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.

[Graham]

Any tips on how to find a vacuum leak upstream from the fuel pump?

[ndutton]

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.

[Graham]

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.

Thanks, good point. I tightened everything up, and the knock is not as pronounced. The gauge is also not jumping as much. I'm going to order the correct pump from MMI and have it on hand. This cheap pump was only intended to get me to the end of the month where I can get the correct one.

[ndutton]

Quick question

Did this pump replace a mechanical pump on the engine or did it replace another electric pump?

[Graham]

Did this pump replace a mechanical pump on the engine or did it replace another electric pump?

It replaced another similar electric pump.

[Graham]

Here is what the fuel gauge looked like after I tightened everything up: LINK

This is just on the dock. Need to take her out for a proper test run tomorrow.

[Sam]

Your "Holly" pump is either a knockoff or a rebranding of the Facet posiflow pump 42S. My friends boat has the Facet version [About $50US] mounted on the engine in place of the original mechanical pump and it has worked well for many years. I have used the older "cubed" version for 20 yrs and just replaced it and is mounted next to the engine below the tank on the wall. Pump rated the same 1.5 - 4psi and my new Marshall [Liquid filled] gauge shows a fairly steady 2.75 psi. I'm told the air filled gauge needles might jump around. The Moyer Facet pump I am sure is a more substantial designed pump.. I just used what I had good experience with in our short Midwest sailing season and could easily upgrade if needed and might one day. Some where on the Facet web page they had a list of rebranded pumps- you might want to check. If you paid 15 - 25$ then it is probably a Chinese knockoff.

[Graham]

Your "Holly" pump is either a knockoff or a rebranding of the Facet posiflow pump 42S. My friends boat has the Facet version [About $50US] mounted on the engine in place of the original mechanical pump and it has worked well for many years. I have used the older "cubed" version for 20 yrs and just replaced it and is mounted next to the engine below the tank on the wall. Pump rated the same 1.5 - 4psi and my new Marshall [Liquid filled] gauge shows a fairly steady 2.75 psi. I'm told the air filled gauge needles might jump around. The Moyer Facet pump I am sure is a more substantial designed pump.. I just used what I had good experience with in our short Midwest sailing season and could easily upgrade if needed and might one day. Some where on the Facet web page they had a list of rebranded pumps- you might want to check. If you paid 15 - 25$ then it is probably a Chinese knockoff.

Thanks for the note. I paid $133 CAD for the pump and the gauge. I needed it quickly so no time to bargain hunt or wait for a shipment from the US. In time I'll replace it with the MMI pump.

[Graham]

To close this up.

My pump was knocking because of a vacuum leak at the fittings coming off my gas tank. Somone sealed the fittings with plumbers tape and over time they started to leak. I used PERMATEX Aviation Form-A-Gasket No. 3 sealant to reseal everything. = no more knocking.

Problem solved

Thanks for the help!