I have a b18b in a 1990 civic dx
I've already replaced the O2 sensor so I'm sure that it isn't it.
The code only shows up after the car has been running for a little while. Not just when it warms up. I can run it forever, reset the ecu, start it up and maybe 5-10 min later it start flashing again.

I'm only getting 38psi fuel pressure on the outlet side of the filter and the car did sit for almost a year before I got it so I'm thinking maybe dirty filter and bad gas. But if that were the case shouldn't I be getting the code sooner?

 

The fuel supply system CEL is one of those CEL's that a little harder to pinpoint and troubleshoot. It usually take a little time of driving for it to trip just as you mentioned, similar to the O2 sensor heater circuit CEL. Since the car had been sitting and the filter is a cheap and easy replacement, I would replace that regardless. Check to make sure that you don't have any small leaks in the fuel line to the rail or at the injector seals also.

 

Thanks for the input. I had already checked for leaks and didn't find any but I did replace the filter and since teh car was almost empty I filled it up with 93 today. It ran great and guess what...no code I drove it up and down the street for a little while just to make sure and it never came on.

I appreciate the help