oil fouled plug
 

car wouldnt start after replacing the radiator, so i pulled the first two plugs on the right side (passenger) the first one was badly oil fouled.

what does this mean and what do i need to do to fix this?

(cleaned the plug and the car started...)

If the oil is on the outside of the plug (above the threads) then it's the seals in the spark plug tube. The upper seals are easy, they're generally included as part of the valve cover gasket set.

The lower seals are more difficult, you have to remove the camshaft bearing caps.

The term "oil-fouled" usually refers to oil INSIDE the combustion chamber, on the firing tip of the plug. That's gonna take more work to decide between rings or valve stem seals.

replacing the radiator should not have anything to do with car not starting unless you disconnected some wiring and forgot to plug it back in,, fouled plugs was there from before ,,, Jim advise is a good one ,, there is a write up on the DIY section to replace plug tube seals upper and lower..

One fouled plug won't keep the car from starting . it will misfire on that particular cylinder , there might be other issues