Mechanics

NOISE AFTER FUEL FILTER REPLACEMENT

1993 Honda Civic • 4 cylinder FWD Manual • 211,000 miles

Just the other day, I decided to replace the fuel filter as it was due according to the maintenance schedule for my 1993 Honda Civic DX.

I followed the service manual procedure to disconnect the negative battery terminal and release the fuel pressure by opening the fuel filler cap. The bolts were stuck fairly tight and there wasn't a good place to get leverage. I had to use a bit of PB Blaster to soak the threads, hoping to loosen the bolts. Eventually I was able to loosen everything and put it back together with a new replacement filter.

Btw, I poured the fuel that was in the old filter into the new one before installing it (so I didn't waste the fuel or just let it evaporate into the air). I made sure to pour it through the opening that attached to the fuel rail, not the other opening (from the fuel tank).

After I installed everything and closed the fuel cap, I started the car. Car started fine and sounded normal. It was only after the car started to warm up enough to stop the "fast idle" when I noticed a strange sound that I have never heard from my car (I've had this car for almost 6 years).

It's hard to describe but it's almost like a muffled, mini diesel engine sound. It's only really audible inside the cabin. It seems to be coming from somewhere near the firewall, close to where the fuel filter is. I tried listening to the engine with the hood open but I could only hear the usual noises of the crank/pistons/etc.

I felt for any vibration that would lead me to the source of the sound and found that the hose (see attached picture) leading to the fuel rail pulsated in sync (at least in frequency) with the noise I heard from inside the cabin.

Is something clogged or is anything constricted?
Thanks for any help you can provide.


FYI,

I have a recording of the noise at http://jbum.tripod.com/noise.mp3
Avatar
Jbum
August 14, 2011.




Recheck the filter seats, if the filter is not seated securely, fuel pulsation would result in the filter vibrating and emitting the noise.

KHLow2008
Aug 14, 2011.
The filter is on there super tight with no possibility for movement. I also had someone else listen from inside while I held onto the filter tight with my hands to absorb any possible vibration. The noise didn't change.

The more I listen to the noise, it just sounds like the vibration of the crank is being transmitted into the cabin, perhaps more than before. The car is running fine otherwise. I'm out of ideas.

The sound file conveys more of the engine noise than I hear in person so it might not be that representative of the noise I'm hearing either.

Tiny
Jbum
Aug 15, 2011.
Ok, since the noise is not from the filter, check for any hoses or pipes around the filter area that could have been shifted/affected while working on the filter.

Note if anything connecting from the engine is vibrating causing the noise.

KHLow2008
Aug 15, 2011.
Ok, I will do that when I get the chance.

One question. Do fuel filters have components inside that may jiggle when you shake them? My new filter had something slightly loose when I shook it but not enough to cause any concerns for me.
But now I'm wondering if that isn't normal, it may explain the slightly knocking-like noise as the fuel line pulsates.

Tiny
Jbum
Aug 15, 2011.
More observations.

I listened very carefully on my drive back home. One thing I noticed was that this noise occurs when fuel is consumed but it not present when no fuel is used. When I engine brake at RPMs relatively higher than idle, the noise seems to disappear. When I press the gas pedal, even slightly, the noise returns.

Of course, at higher highway speeds, other noises drown it out so I probably do not hear it then.

Could this be related to my previous question about something loose in the filter itself?

I may try replacing it with a new filter that doesn't have looseness. I would use the old filter but it's been discarded already.

Tiny
Jbum
Aug 16, 2011.
No, the filter should not have anything loose inside it. You most probably have a faulty filter that is causing the resonating noise.

If you check your old filter, I believe you have the answer there.

KHLow2008
Aug 16, 2011.
Jbum,

I'm having the exact same problem with mine. I adjusted my valves, thinking it was that, and found they were barely out of tolerance. I asked the previous owner (a friend of a friend) about the noise, who said it had always made that noise. It does sound like a diesel inside the cab. It does quit upon deceleration and resumes upon any amount of fuel input. I downloaded your sound and it's exactly the same as what I'm hearing in my car.

I noticed the last post was about seven months ago. Have you replaced the filter or found the source of the sound?

Thanks, Lasher638
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Tiny
Lasher638
Mar 28, 2013.
Lasher638,

I actually have not replaced my fuel filter since the incident. I got busy and figured it was not causing any issues so it wasn't a high priority for me.

I'm pretty sure it's the fuel filter as that is the only variable. I will get to it eventually, perhaps later this year. If you happen to replace the fuel filter first, please let me know and confirm if that fixes it.

If the bolts and tighteners weren't such a pain in the neck, I would do this sooner.

Tiny
Jbum
Mar 28, 2013.

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