I was standing by my friends TA today and it as running and I heard a noise that sounded like a fuel pump, but it was under the hood. It quit and then a few seconds later it did it again. What could it be?

 

A.I.R pump maybe? Was the car cold? What year is it?

 

It is a 98. Not cold either.

 

AIR pump. It's normal.

 

ya, But That only comes on when car is cold. I think?

 

It definately was not cold. What is the A.I.R. pump?

 

Doesn't that stand for air injecting regulater?
I think only 01-02 have this.

 

Pretty sure all years have them.
But maybe it was the A/C compressor, if the engine was not cold.
That's the only other cycling type of sound I can think of besides fans.
If his A/C sounds that loud, he should probably have it checked out.

 

It didn't sound like AC really. More like a fuel pump.

 

It sounds like it't the air pump. My 99 does the same thing right after start up wether warm or cold. runs longer when it's cold.