rotorwrench
Well-known member
1988 with OBD 1 is getting back there in an era where they were trying to develop the technology with very little standardization yet. The pressure regulator can only be checked with a fuel manifold pressure gauge. If it has a check valve then it has to hold pressure and should maintain it for a while after the engine is shut down. The scanner for those systems should read MAP and throttle position in the normal range. It likely won't have any fuel pressure monitoring capability and that's why it won't throw a code.