Please help me identify this new noise!

[cfleury14]

Hello all,

My 1985 Carrera 3.2 (daily driver) started making a strange noise today. It is running totally fine as far as I can tell, but there is a high-pitched hum/whine that seems to be coming from deep in the passenger footwell (or perhaps on the other side of the firewall, toward the front of the car). It only happens when the engine is on and running. It does NOT happen when the key is in ACC position. I have not noticed any change in performance. I can not seem to hear anything when I am outside the car.

I took a video of the sound - please watch it here:

https://www.youtube.com/shorts/OZrxiVZwH9Y

I am putting the phone down in the passenger footwell closer to the front of the car in the video because that is where it is loudest.

No ventilation, A/C, heat, or blower motors are on.

My first thought is that it is the fuel pump and is a sign of impending failure (hoping this isnt it but that's what came to mind).

Thank you all in advance!

Chris

[997at]

I hear two distinct sounds. One is a humming...not sure what that is. The high pitched whine sounds like the fuel pump. Normal sound from the fuel pump I think. Mine has had that sound from the fuel pump forever...although I can only hear it from outside the car.

[porsche930dude]

Sounds like the fuel pump. Maybe the cussioned mount has broke and its laying on metal and transmitting it through the car.

[echecsqueen]

That area is where the ac recirc is….

[chrisbruck]

Sounds like a fuel pump to me to... plus on that side the ducting passes through the firewall and may make it sound like it's coming from that area. How does it sound outside and under the front of the car.

As an FYI... I had my FP replaced about 6 months ago and it's quite noisier than the old one that died. It's a new Bosch unit and the mechanic said some of the new ones are "loud" but it could also be slightly rubbing on the underside of the car. The mount for it isn't the most robust and it can shift around. I haven't had time to look at mine to see if that's the case.

[Discseven]

Chris... how long have you owned the car? If a short time, then you may not be aware of some mod made by former owner. Fuel pump... is simple matter to jack car up, support it, and get under to sense if pump is indeed the culprit. Somewhere along the line I've heard that pumps can change their sound depending on how much fuel is in the tank. I don't know if that is fact or fiction. I've dealt with a number of pumps over 40+ years of Porsche'ing. There is not a consistent behavior to note (in my experience) except for eventually giving up the ghost. Some made noises sometimes, then it went away. Others were silent to the end. Quirky comes to mind.

.

[cfleury14]

Thank you all for the responses. To answer a few questions - I have had the car for 8 years, and this was definitely a new sound (I drive it nearly every day and feel like i know it very well). Strangely, after sitting for 2 days, now the sound is gone when i start the car.

It certainly sounded like a fuel pump to me. This current pump has been in for as long as I have owned the car.

Interestingly, on thinking back, on the start immediately prior to me noticing the noise i had to crank it much longer than usual for the car to start. I know that there is a fuel pressure check valve on the downstream end of the pump. The fact that it took more cranking than usual makes me wonder if there is a problem with the check valve, and if maybe the pump was noisier than usual because the valve was either gummed up or stuck. Either way, now that the noise is gone I think I am safe to go back to driving it every day (anybody think otherwise?). In the meantime, I am going to order one of the new Bosch pumps and a new check valve, as I am sure that this current pump's days are numbered one way or the other. Maybe I will just swap out the pump and valve when the new ones arrive...

Thank you all - as always, very grateful for the input

Chris

[Otter74]

Sounds just like my fuel pump did year before last.

[cfleury14]

Out of curiosity - what happened when your fuel pump sounded like that?