Engine whine

I have a 1990 Colt with a 1.5L engine and manual transmission that makes a loud mechanical whining nose after you start it up. I kind of sounds like the power steering pump on a Ford truck when you have the wheels cranked all the way to one direction, but much louder. I removed the belts to rule out the alternator and the water pump. I was told it might be the oil pump on the front of the engine. Does anyone have any ideas what it might be?

Thanks.

could be the timing belt adjuster pulley

I purchased the car about 6 months ago, and a few months after that noticed a slight whining noise coming from the engine.