2003fish

I've got something that's leaving me quite stumped. There's a humming/buzzing noise that's coming from under the car, which can be heard in the car as a loud buzzing or whirring noise. In tracking it down, it appears to be the fuel line to the engine. If you go under the car while running, you can literally feel the line vibrating (which I'm sure is the noise that's coming into the car). If you put your hand on the driver's rear seat floor board you can feel it in there, too. The sound of the noise moves with the engine speed, so if the engine revs up and down, so does the noise. And this noise is happening all the time, it's not an intermittent problem. I don't think it's the fuel pump, because of the noise moving with the engine. Fuel pumps operate at a constant flow irrelevant to the engine rpm. But, just to make sure, I checked it by running the car and unplugging the fuel pump while running to see if the noise stopped when the pump stopped, and it didn't. So that tells me that it's not the pump.

I followed the line up to the engine, which goes to go to the fuel pressure regulator. While the engine is running, you can still feel some of the vibration in the line even up there by the engine. So, could it be the fuel pressure regulator? I'm not sure if even that would be related to engine rpm either, but there's really only two things on that line - the pump and regulator. I guess I can't rule out the fuel pump 100%, but it just doesn't seem to make sense. There's also a little coupler-like thing in the line about 1.5' from the regulator. Not sure what that is or does, or even if that's relevant. But the feeling in the line is like quick short bursts of pressure, similar to what you'd feel on one of those 12v air compressors you can use from the car. Those lines have like a pulsing feeling on them, and this feels the same way.

I also thought that maybe the EVAP system was doing something, maybe a bad valve somewhere that was back feeding pressure into the tank or something and it was coming back in the fuel line. But while it was running I went through and disconnected all the different evap hoses that would affect that and nothing made it stop, so I kind of ruled that out.

This started happening quite some time ago, and does not affect the way the car runs at all it seems. But it is definitely loud inside the car and is super annoying. I really would like to get this problem figured out but it's really got me stumped! And the fact the car still runs fine has me rule out the fuel pump even more, or even the pressure regulator for that matter.

Any help or insight on this would truly be appreciated! Thanks!

LeX2K

It could be the pulsation damper (Lexus naming) not horribly expensive. I had to post this, look a the pictures! Did they really photograph a rusted out broken part?
https://www.toyotapartsdeal.com/oem/...270-62010.html

There are also 3 vacuum switching valves on top of the intake check those out as well. Also what is 17330 the pod looking thing on top is that a vacuum diaphragm?
https://www.japan-parts.eu/lexus/us/...&pa=1733020010

2003fish

Haha! Yeah, that part is totally rusty looking! How funny! Well, a pulsation damper definitely sounds like what might not be happening. And I thought that was the pressure regulator, but apparently I was wrong! $65, though. And it's rusty! lol

I did look at those three vacuum switches on the intake. I unplugged the electrical connector from each one at a time which didn't do anything either. I'm assuming that vacuum diaphragm on the intake regulated air flow to the air box for cold weather or something, like in the old days?

LeX2K

Reminds me of that (props for knowing about it) but it's not that I'm guessing for EVAP?

Don't buy a generic version since an unintended fuel leak.....well you know. Salvage yard part would be ideal a cheap way to test. Part was used on many Toyota/Lexus with a V6 in a 20 year span.

2003fish

Well, I think you were spot on with that. I went out and messed around with that screw that was on it, and by turning it in and out all the way (until it popped out and leaked fuel all over! lol) I was able to make that sound quieter a little, so I think that's definitely the culprit here. I'm going to try to find a replacement part for that and keep my fingers crossed. I was hoping that I could just make it quiet enough by adjusting that screw, but no dice. I'm guessing that thing is just bad.

I appreciate the help and pointing me in the right direction!

Thanks!

LeX2K

I'd say you found the problem.