What you are describing may not even be an actual "problem". My 1990 S10 gave me the same thing. I discovered that the system is actually designed to do that! The fuel pump relay is supposed to only energize the fuel pump for a few seconds to pressurize the fuel system so that the engine has enough fuel to start, then shut off. It then transfers control of the fuel pump to another relay. This relay is activated by an oil pressure switch. When the engine actually starts, engine oil pressure signals the second relay to again send 12V to the fuel pump for continued operation. This is a safety feature to protect the engine. If you suddenly lose oil pressure, the fuel pump is shut off, stopping the engine, to prevent burning up the engine. I figured this out after some research and studying the electrical diagrams. If the fuel pump runs fine with 12V hooked directly to it, the pump is most likely OK. A check of the fuel pressure to ensure that it is not weak, would still be a good idea while you are at it!
Thursday, March 11th, 2021 AT 7:07 PM