I can't completely shut off the shower faucet. When I push the valve in, it gradually pushes back and water comes out the shower head. I replaced the O rings on the cartridge and put a bit of vaseline on the rubber O rings. The faucet is Moen and was installed about 1977.
Any tips?

I replaced the O rings on the cartridge

Does that mean you used a rebuild kit from Moen?

Does that mean you used a rebuild kit from Moen? No. I found 2 O rings at the home center that fit

Well, apparently they didn't "fit"

Moen guarantees their faucets for life. Call 1 800 BUY MOEN (1-800-289-6636) for a free replacement cartridge. You probably have the 1200 cartridge.

Agree with Hkstroud

You aren't forgetting to re-install the copper horseshoe shaped clip (see image) are you, Gandeweg?

Further note here is that petroleum-based products such as vaseline are said to degrade orings and cause cracking over time. For long term results use a silicone grease or plumbers heat-pruf grease for all oring applications in the future... ;)