You could reset the pump without checking the chain. The most important reason to check the chain is that beyond a certain limit it starts to damage the pulleys. They are really expensive. Plus of course your cam would be running out quite badly as well. It is still about the simplest thing to do at this point. It can really make a difference. As long as the chain is within allowable wear limits of course retime the pump. If you are prety sure you have good primary fuel flow and the linkage is normal. Checking the pump timing is a regular maintenance thing that is seldom done on some cars.