96 fuel problem

I have a 1996 ford 2 dr explorer sport. I got the vehicle for free from my father in law because it stopped running and its a little rusty and he didnt want to deal with it.

So i replaced the fuel pump, becuase i noticed to wasnt running when i tried to start it.

After replacing the pump the vehicle started right up but the fuel pressure was never as high as it should be and sometimes it would idle and run rough I tried replacing the fuel pressure regulator but that didint help. So i just left it like it was. The other thing i noticed is that if u started it and drove it and then shut it off you had to wait about an hour before it would start back up. If you didnt wait an hour it wouldnt even fire or want to start.When i used it in winter i would just let it run all day and it would run fine and never die but as soon as you d shut it off you had to let it sit for an hour.

Well its been like this for about 4 months now and i would like to fix the problem for good. I tried reading the engine codes but i cant figure out the darn blinkin lights, everytime I do it i get different numbers.

So I am wondering what other things it could be? I just checked the fuel pressure and i only get about 18psi at an idle.

Any ideas would be greatly appreciated.

Thanks

Have you replaced the fuel filter?

-Rod

its a 4.0 ohv? im pretty sure the fuel pressure should be 40psi with the vaccum disconnected, 30 at idle, to wait that long to be able to start the engine doesnt make any sense,. obviusly something is wrong, you can start from checking the fuel pressure, if that is ok then jump to the electrical stuff. what else you have done to find the problem.

Yes i replaced the fuel filter when i changed the fuel pump sorry i forgot to mention that.

I just recently bought a fuel pressure tester and I tested it and its an about 18 at an idle

I replaced:
fuel pump
fuel filter
fuel pressure regulator
to try and fix the problem.

I dont know what else to replace

Would something be wrong witht he fuel pressure sending unit to cause this?

I have no idea what it could be or what to do.

You might want to make sure you have full voltage under load to the fuel pump. Unfortunately you'll have to drop the tank to do this. If you have a corroded connection, you might have a supply wire that cannot handle the current draw of the pump.

I'm not sure if 1996 uses the Pulse Width Modulated fuel pump supply. If so, you won't have a fuel pressure regulator or a return line, instead you'll have a fuel pressure sensor. If something is wrong with the sensor circuit, that could explain the low pressure. I don't have a factory service manual for the 1996 though to look up which system the 1996 Explorer uses.

-Rod

So what should the voltage be to the fuel pump? Also would i test it at the plug by the top of the tank?

Where would the fuel pressure sensor be located?

Thanks again

I'm not sure if 1996 uses the Pulse Width Modulated fuel pump supply. If so, you won't have a fuel pressure regulator or a return line, instead you'll have a fuel pressure sensor. If something is wrong with the sensor circuit, that could explain the low pressure. I don't have a factory service manual for the 1996 though to look up which system the 1996 Explorer uses.

-Rod


It has 2 lines coming out of the top of the tank if that helps you......

The fuel pressure sensor would be on the fuel rail at the intake. The voltage at the pump would be battery voltage (12-14.4Vdc) which, if a PWM returnless system, may read less than this depending on the fuel pressure sensor reading and the measuring device. If using an oscilloscope, the voltage amplitude will still be battery voltage, but it will be switched on and off rapidly, creating a square wave of varied duty cycle.

-Rod