Charles Lee

1981 corvette, stock, I have a feeling it is the mechanical fuel pump. It is brand new, perhaps installed wrong.... It speeds up with the revving of the engine and slows down at idle. happens while driving and while in park idle.

thanks!

210ken

Sounds like the idle is really high, what’s the RPM? As to the clicking, it sounds like a leaf in the blower motor squirrel cage but that wouldn’t change with engine RPM so maybe the cooling fan lightly slapping something.

REELAV8R

You have the camera near the transmission engine connection, is that where the sound seems to be originating from? If so I would guess a flexplate or teeth on the flexplate rubbing the sheet metal shield there.

Charles Lee

No it seems to be coming from the fuel pump area. I cant pinpoint but I think it may be the rod pushing the mechanical fuel pump. But its brand new I changed it out 1500 miles ago

kodpkd

Get one of the stethoscopes with the long rod on it. You will be able to pinpoint the noise.

REELAV8R

The frequency seems way to high, to rapid of a impact noise, for that to be a fuel pump rod.

It sounds like a lawnmower running. So about maybe about 2500 rpm type of noise. You could take off accessory belts to eliminate all those items as a source.

interpon

and fuel pumps lately are a crap shoot..

pspicci

Doesn't really sound like a fuel pump to me either but one thing you can do depending on if you can access the fuel pump easily is before your engine and exhaust heat up grab the pump with your hand. if it is the pump many times you can feel the ticking in the pump. only do this if you have easy access to the pump and be very careful. i have done this on my car but it's a big block with no AC compressor in the way.

67:72

Might it be an exhaust manifold leak at one of the head ports?

Mark60

[QUOTE=Charles Lee;1605054234]1981 corvette, stock, I have a feeling it is the mechanical fuel pump. It is brand new, perhaps installed wrong.... It speeds up with the revving of the engine and slows down at idle. happens while driving and while in park idle.

thanks
sounds like the flywheel is hitting the cover . I would remove it and listen again, 4 screws

REELAV8R

[QUOTE=Mark60;1605058464]Kinda what it sounds like to me too.

Charles Lee

[QUOTE=REELAV8R;1605059153]Ok, Ive eleminated some things.... It is not the flywheel or anything near there. It is not an exhaust leak, I took it to a specialist and they confirmed it was not that. I thought maybe it could be a faulty heat valve, still not sure on that. That leaves a stuck lifter hitting the cam, or possibly a piston bearing which is worse case scenario... But a strange thing happened on my drive back from the mechanic yesterday. the noise stopped. completely. So I let the car sit over night and it pretty chilly here at night in southern california. I started the car and nothing... the noise is just gone. I have no idea, but Im really hoping it stays that way. The carb was just rebuilt and the car is driving amazing. Very pleased. thank you all for your help on this... I still wish I knew what it was.

drwet

Can't explain the noise going away but I have seen this problem with replacement fuel pumps lately. There is a problem with some replacement pumps that seems ot create some clearance with the pump push rod resulting in a noise like you are having. Not sure exactly what it is about the pump - possibly a problem with the shape of the pump arm, but I have seen this problem exactly.

docohm

Get one of these in case it comes back...
https://www.harborfreight.com/mechan...ope-63691.html

pigfarmer

I happened to have a piece of 1/2" EMT sitting there one day when I was chasing a noise and boy, it makes a good stethoscope.I just close my fist around the end so I don't jam the thing in my ear.

No idea but I'd be looking for an exhaust leak - maybe a donut. If it's consistent you can find it. Things like that drive me nuts.