Takes a while to start then runs well. on 1990 Chevrolet Celebrity

Recently acquired, it runs well but if it sits for awhile between starts, especially overnight, it's very reluctant to fire. After six or so hits, it'll finally catch and all's well. Could this be the fuel regulator allowing fuel pressure to bleed off. The pump makes the normal working noises but the fuel filter could be suspect.

Asked by for the 1990 Chevrolet Celebrity
If the fuel filter has not been replaced in recent memory, it's time now. I'd put a test fuel pressure gauge on the system and leave it overnight. Then, observe the gauge when you shut the engine down and when you start it the next day. If it loses fuel pressure quickly when shut off, I'd suspect the check valve in the fuel pump or the fuel pressure regulator. You can eliminate the regulator by pinching off the return line, then any leakdown is in the fuel pump. During cold start (don't forget to unpinch the return line), you can observe the fuel pressure. It should quickly jump up to and hold stable pressure when you turn the key to RUN. Watch for signs of a faulty fuel pump.
Sorry about the long time in replying - family stuff intervened. Just as I'm getting the starting problem eliminated, a new wrinkle. Intermittently, sometimes at startup or after a lengthy drive, removing your foot from the throttle will allow the engine to die as it slows. Won't idle. At startup it requires throttle pressure to run and removing this to go into gear lets the engine quit. After an extended drive it just takes a little longer to quit. Always starts immediately but with throttle pressure only. the start. Replaced IAC and MAP - out of ideas.