Hello!
Troubleshooting a fuel delivery problem isn't too difficult, but you will need to have a fuel pressure gauge set to do any kind of accurate testing.
The first thing to do is to install a pressure gauge at the engine and check to see if there is normal fuel pressure present when the problem is occurring. You should be seeing 35 to 45 psi present when the engine is not running, and 30 to 40 psi with the engine running.
When you shut the key off, the system should maintain pressure. If you see pressure dropping at all, even over a span of several hours, this indicates leakage somewhere in the system. The system must maintain fuel pressure overnight so that fuel will be available for the first start next day.
If the system is losing pressure, you can determine where it is going by running the fuel pump to bring it up to normal pressure and then shutting it off and pinching shut (vise grips work well for this) a rubber section of line somewhere between the pump and the engine. If the pressure loss stops, then you know it is losing pressure back through a worn fuel pump and the pump needs to be replaced.
If it still loses pressure, the next step is to repeat this test only this time instead of crimping off the fuel supply hose, pinch off the fuel return hose. If this stops the pressure loss, then the loss is occurring past the fuel pressure regulator and the pressure regulator needs to be replaced.
If it loses pressure and neither line stops the pressure loss, try pinching both at once; it is remotely possible there may be both a worn pump AND a leaky regulator on a vehicle this old.
If the pressure loss continues, it is either leaking externally (fuel line leak somewhere) or has a leaking fuel injector. About the only way to find a leaking injector for sure is to remove the fuel rail and injectors from the engine as an assembly, leaving them connected to the fuel lines, and repeating the test while observing the injector tips for leakage.
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