I was given this truck when my grandmaother passed away it has 45,800 original miles on it, it has sat a little, when you let the pump prime up it will start and runs great once the fuel pressure builds up .what may be causing it to loose pressure?

 

That's normal. The fuel pump should run for 2 to 5 second to build pressure in the fuel rails, then it will start and run just fine. The fuel pressure regulator open and closes to let fuel return to the fuel tank so the injectors receive the proper amount of fuel. As the truck sits it loses vacuum and the regulator opens up letting the fuel flow back to the tanks. If the pump is running longer than a few seconds before it's building pressure you may have a bad/weak fuel pump.

 

Thanks for the reply pfogle, Yea this one the key has to be turned on for 5 to 10 minutes (depending on how long it has been shut off). then when you hear the pump shut off it will start right up. but it runs so good you really think it the fuel pump?

 

It could be a bad injector. Or it could be the FPR. You need to check the fuel pressure. Does it sound like the pump is struggling to push the fuel? It may need a fuel filter.

 

The pump should run for 1-2 seconds maximum when you first turn the key to the On position. If it is running any longer then you may have a stuck fuel pump relay or a bad PCM (computer). The latter is a common failure mode of a PCM.