Mechanics

RUNS THEN WILL CRANK NOT START THEN RUN FINE A FEW HOURS LATER

1996 Ford Explorer • 219,000 miles

1996 ford explorer 4.0L V6 pushrod engine. I am pretty sure it is the cam sensor but since this seems to require pulling the intake I want to be sure. The fuel pump will stop running and the vehicle will die then a few hours later it will start right up only to die again shortly to a few days later. I have ran an OBD2 scan with no codes. I have pulled the pump, since this is what I originally thought was wrong the first time it happened put power to it and it ran fine so I reistalled it and the vehicle fired right up then died again a few days later.
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Brat with a BRAT
August 2, 2012.



Check fuel pressure while running and safter stopping engine to see if it holds pressure. Should be 35-45 ke off30-40engine running at idle. Also check connections as they may be bad or have corrosion. You can also check crank sensor as this can cause it as well.

Hmac300
Aug 2, 2012.
No pressure at the rails when it dies it runs fine when it restarts. It has spark but no fuel pressure. On this vehicle the crank sensor controls Ignition timing and the cam sensor controls Fuel injector timing, when there is no signal from the cam sensor the fuel pump will not run. I just want to be as sure as I can that its not something else before I pull the intake to do this since the gaskets for the intake are about $100.

Tiny
Brat with a BRAT
Aug 2, 2012.
Correction it has pressure when it dies just will not rebuild pressure since the pump is not running in a no start condition.

Tiny
Brat with a BRAT
Aug 2, 2012.
Well you can see if power is being relayed to the fuel pump when it does this. Also the cam sensor goes to the pcm and the pcm may have a bad connection not sending to the fp. One other thing to check is the inertia fuel shutoff switch behind kick panel.

Hmac300
Aug 2, 2012.
The inertia switch has never been set off but I suppose checking for power to and from the inertia switch when it does it would be a good idea. So if im correct if the cam sensor is bad when the engine stalls I wont have power to the inertia switch.

Tiny
Brat with a BRAT
Aug 2, 2012.
You also wouldn't have power to the pcm

Hmac300
Aug 2, 2012.
Ok now im stumped, I was trying to get the car to die again, which it wouldn't, so I unplugged the cam sensor and it ran fine without it.

Tiny
Brat with a BRAT
Aug 2, 2012.
In the power distribution box there is afuel pum prelay check that for good connections as well as corrosion. From there it goes to the pcm and #40 sends the signal to the pcm #80 goes from teh pcm to the pump. Anyone of those places could be a bad connection. But you have to find out where the car is not getting power to the fuel pump first. Good luck on this one it sounds like a screwed up wiring harness someplace.
Fuel Pump,  Electric — Explorer

The multiport fuel injection (MFI) system uses a fuel delivery module with integral reservoir. The module is a reservoir which also houses the pump and valving. This design provides satisfactory
operation during extreme vehicle maneuvers and steep vehicle climbing with low tank fill levels.

The fuel pump (9350) is mounted inside the module/reservoir assembly inside the fuel tank (9002). This assembly includes a check valve which is in the outlet of the fuel pump. The function of this valve
is to maintain pressure in the system after the vehicle is shut down. The pressure retention helps prevent hot starting problems. This fuel pump is capable of supplying 95 liters (25 gallons) of fuel per
hour at 310 kPa (45 psi). The fuel pump has an internal pressure relief valve which limits the maximum fuel pump pressure to 850 kPa (125 psi). This only takes effect if there is a system blockage,
causing system pressure to rise too high. The system pressure is controlled by a pressure regulator on the engine (6007).

The fuel pump is protected at its inlet by a nylon pickup element. This nylon element filters dirt and contaminants which could plug or damage the internal pump components while at the same time
allowing passage of small quantities of water which may accumulate within the fuel tank sump.

The electrical system has a fuel pump control relay controlled by the powertrain control module (PCM) (12A650),  which provides power to the fuel pump under various operating conditions. When
the ignition switch (11572) is in the OFF position,  the contacts of the PCM power and fuel pump relays are open.

When the ignition switch is first turned to the ON position,  the PCM power relay is energized,  closing its contacts. Power is provided to both the fuel pump relay and a timing device in the powertrain
control module. The fuel pump runs through the contacts of the fuel pump relay and the inertia fuel shutoff switch (IFS switch) (9341). If the ignition switch is not turned to the START position,  the
timing device in the powertrain control module will open the relay ground circuit (No. 926 LB/O) to the relay after approximately one second.

Opening the ground circuit de energizes the fuel pump relay (opening its contacts),  which turns the fuel pump off. This circuitry provides for pre pressurization of the fuel system.

When the ignition switch is turned to the START position,  the powertrain control module grounds the fuel pump relay to provide fuel for starting the engine while cranking.

After the engine starts,  the ignition switch is returned to the ON position,  and power to the fuel pump is again supplied through the fuel pump relay. The powertrain control module senses engine speed
and shuts off the fuel pump by opening the ground circuit to the fuel pump relay when the engine stops or is below 120 rpm.

Also has the fuel filter ever been changed? I have no further suggestions on this.

Hmac300
Aug 2, 2012.
Every line in your last comment was cut off on the right side but I got the just of it. Thanks for your help im going to drive it around tomorrow and hope it dies in a nice shady spot and put an electrical tester on all of these points and hope I can figure it out soon

Tiny
Brat with a BRAT
Aug 3, 2012.
Ok I replaced the fuel pump with no result. Im starting to wonder if the PCM is bad but im still not sure. I have power to the fuel pump even with the key off but the pump still does not run even with a new working pump

Tiny
Brat with a BRAT
Aug 6, 2012.
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