Chevrolet Repair: 1996 Chevy G30 Conversion hard to start, oil pressure switch, fuel pump relay

Question
Our van w/ right at 100,000 miles is hard to get to start.  It just turns over, and over.  We've replaced the battery.  When it does start (when it wants to?) it runs well, and then starts the second time usually.  It is when it hasn't been started for a day or two that it is very hard to get started.
Any suggestions?

Answer
Have you listened to see if the fuel pump in the tank is running when you turn the key from off to run?
It should run for two seconds.
There is a backup system for the fuel pump, which is an oil pressure switch, for if the fuel pump relay doesn't work for some reason.
Sounds like yours is operating by that oil pressure switch.
The long crank is while it is building oil pressure, and then the fuel pump turns on.

The relay could be bad, or the crank sensor, or a wire connection. Remotely possible it could be the ECM, but I doubt it.

Van