Bosch Fuel Pump noise (whine)

[High Life]

I replace my fuel pump last year at this time - due to a high pitched whine (buzz) that you could hear while the engine running. The whine (buzz) was so loud that people in the next lane was asking about it.

So I replaced the Bosch unit with a new Bosch 69466 unit and now - 1 year later (and about 6K miles) -the replacement Bosch unit has suddenly developed this whine (buzz).

I have driven other vehicles (most recently a BMW E30) that developed a buzz for a month or so - then immediately left me stranded on the side of the interstate. I tested the theory that the whine (buzz) was normal and it definitely was not.

I am debating on reaching out to Bosch to find out the warranty etc. I bought the unit from Amazon - it has a Bosch box, the stamping look to be authentic. It was $140..

Anyone else have an issue with their Bosch fuel pump? or a fuel pump cry of death?

['78 SC]

Did you clean the in-tank screen? My fuel pump made a terrible noise (cavitation?) that went away after cleaning the (filthy) screen and tank. That was 25+ years ago and I'm still on the original fuel pump.

[High Life]

Originally Posted by '78 SC

Did you clean the in-tank screen? My fuel pump made a terrible noise (cavitation?) that went away after cleaning the (filthy) screen and tank. That was 25+ years ago and I'm still on the original fuel pump.

Ooh! Good suggestion - will go look at that this afternoon.. I can just pull the sending unit yes?

[spuggy]

I think Steve may have something.

I replaced my original 250K 911S fuel pump with a Bosch 044, because it was making a noise, (and because AFR was trending lean under boost over 5.5K RPM or so).

The 044 was just as loud as the original pump (and still is 12 years later) - and it made no difference to my CIS tuning issue (flow/pressure were both in spec with either pump)...

I know it's difficult to describe the "normal" sound of a serious electric pump (I'd say "whine" or "buzz" is a fair description, and they're pretty loud) - but the fact that the noise of your old pump developed a different quality - and now the replacement has too - would seem to indicate that something's not right.

['78 SC]

Filter removed from below. Obviously you need to drain tank and take appropriate precautions.

Removing level sender will let you see into tank.

I removed my tank to flush, rinse and dry it.

Be careful.

[UROParts]

While you're at it, don't do this. https://youtu.be/euP6zdmfx_8

[SCadaddle]

Removing the level sender unit from the top of an SC fuel tank won't let you see the filter screen in the bottom of the tank, because it resides inside and under the lid of the plastic swirl pot.

The "trick" tool to removing the fuel tank drain plug and screen is a spark plug socket that has flats around the top of it----you put a socket extension into the socket from the open end of the socket and fit the flats of the socket into the drain plug.

[High Life]

Opened up the top to take a look - I could see the filter..



Nothing obvious.. but of course its not as good as a view with it sitting in your hand..

The tank had been coated at one point..





Not sure how difficult it would be to dislodge the filter - that nut seems awfully big... I do have several old spark plug sockets with the nut on top..

I wonder how tough it is to remove... Is there a gasket I need when re - torquing?

[Mark Salvetti]

That's interesting, your swirl pot is missing its lid. Probably not a huge deal, I'm sure it's meant to keep fuel from sloshing out of the swirl pot when driving aggressively on low fuel.

You always read warnings here about not coating a swirl-pot fuel tank, because the coating doesn't stick to the plastic and then it comes off and clogs the filter. But yours actually looks OK, so hopefully that's not your problem.

My Craftsman spark plug sockets don't allow you to insert the socket extension from the open end. If you have the same problem, the hex in the filter is 7/8". Go to Home Depot and get a large bolt with a 7/8" head. Double-nut it, and you can use that to loosen the filter.

There is a gasket. I would want a new one - no fun if you reuse it and then you find it leaks when you have a full tank.

Mark

[High Life]

Originally Posted by Mark Salvetti

That's interesting, your swirl pot is missing its lid. Probably not a huge deal, I'm sure it's meant to keep fuel from sloshing out of the swirl pot when driving aggressively on low fuel.

The stuff you learn on this forum is amazing... I really dont know the story other than I have records of the coating...

I appreciate the measurement on the 7/8 bolt - I'll grab one at Lowes..

['78 SC]

Some useful links:

Excellent photos of 1975 CIS tank internals and in-tank filter. Also warning against fuel tank coatings.
Fuel Tank Restoration !! Many Pictures

In-tank filter replacement (tool, part numbers, torque)
Fuel Pump and Fuel Tank Filter Replacement


While the filter is out, thoroughly clean the groove and pipe located just above the threads the filter screws into (photos in post #4 of first link above). I found a bunch of debris compacted into the groove and pipe. I suspect this was blocking fuel supply to the pump and was my main problem.

Good luck.

[nomore]

Just replaced this filter on my 74. My tank looked way worse than yours. I took the filter out and it was varnished half way up the screen and clogged. Someone had also coated the tank at some point and it had failed leaving a sludgy mess I had to get out. My pump is also noisy, we shall see how it goes when I hook it all back up.

[High Life]

UPDATE..

I pumped out the gas tank from the gauge sender from atop the tank.. I had about 10 gallons..

Used the socket trick and pulled the filter:



As you can see - it had some debris.. Also PO (or his mechanic) used some RTV sealant on the threads... It was only on the threads - nothing in the tank..

Cleaned the filter then install new gasket..



I ran a pipe cleaner around the ridge - but did not find the pipe.. Looking at this pic - it doesn't look like the one on the thread that was posted earlier.. no pipe from leading away from the ridge..?



Overall satisfied - not a lot of debris - coating not flaking off from what I can see



cleaned the threads and the surface - installed clean filter and torqued to 18 ft pounds... I hope to heaven it wont leak..

[High Life]

A couple more from the bottom


Coating looks good.

[93nav]

Thanks for the followup.

[High Life]

Problem becomes that the filter is not the source of "cavitation" or strain on my 1 year old Bosch pump...

So back to the beginning..

Do I have a second bad pump? (First pump did the same thing a year ago) OR is there something else causing the pumps to go bad or act this way and what could it be...

[Dave Kost]

Originally Posted by High Life

Problem becomes that the filter is not the source of "cavitation" or strain on my 1 year old Bosch pump...

So back to the beginning..

Do I have a second bad pump? (First pump did the same thing a year ago) OR is there something else causing the pumps to go bad or act this way and what could it be...

Make sure the tank is vented properly. The pump will struggle to make pressure if is not vented but it will keep trying to until failure or.......

PS I've heard of tanks collapsing because they were not vented.

[E Sully]

The fuel pump inlet pipe leading from the ridge is below the swirl pot, you should push a flexible cleaning rod in from the outside of the tank to make sure the line is not partially clogged. It may be that not having the cap on the swirl pot may be causing aeration of the fuel.

As mentioned, you should make sure the fuel evaporative system is working to make sure the tank is properly vented.