too much vacuum?

[terry717]

If I put a different oil cap on and it starts going through fuel pump relays, is it possible that something is plugged somewhere else creating such a vacuum that the pump is overworking the fuel pump relay causing it to stop functioning after a 5 minute trip? Scenario is: Car was doing fine until I changed the oil cap (OEM cap was busted), then all of a sudden it will go on a short trip, I shut it off, and then the relay stops working. If I change the relay its fine again for another trip till I shut the car off. I have jump wired the fuel pump relay now as relays are getting expensive. Any suggestions...I'm stumped. I plan on soon replacing a lot of items on the car..ie, pump, filter, plugs wires cap rotor, and every relay, as the car sat for a year before I got it. I just am going to be sick if even after replacing everything the problem still exists. Is it possible too much vacuum could cause this. I don't see an actual PCV valve listed in any manual I have. Where would I start? Thanks in advance! Pulling the oil filler cap when it is running lowers the rpms, is this normal? Is the cap supposed to be vented?