I have a 2000 ford exp. whose fuel pump sometimes does not inject fuel. The vehicle runs fine and idles fine, but starts sporadically. Is it possible that the fuel system is connected to the anti-theft sysytem? I replaced the relays in distribution box and the fuel filter. Any ideas on what the problem could be?

 

Fuel system is NOT connected directly with anti-theft. Need to know more exactly what the problem is: hard starting? Occasional hard-starting?

Most likely cause is the fuel pump itself. They use a DC motor which sometimes will not start-up due to a "dead-spot" on the motor's armature.

If you can hook up a fuel gauge to the fuel rail when the starting problem is present, a low pressure, or no pressure reading will confirm the pump problem.

 

It was basically starting whenever it wanted to, but ran fine once it was started up. The problem became progressively worse. When it's not starting and I turn the key I can't hear the fuel pump start up. Thank you I will check the fuel rail pressure. Is there a possibility that the PCM relay needs to be replaced? Just want to check everything before I replace the pump. Thanks for your help!

 

Unlikely that the PCM relay would be intermittent. If you had wiring diagrams from Ford, you could check that the various components, PCM included, are getting voltage when the key is turned "on". That sort of troubleshooting goes beyond most peoples' everyday abilities.

So, I would look for fuel pressure. If you normally can hear the pump run for 2 seconds, then it shuts off, after turning key to "on", not start, and you do not hear the pump run now, or occasionally, good bet pump needs replacement.

BTW, if you are not aware, PCM turns pump on only for 2 seconds when key is turned "on", to pre-pressurize the lines, and cover the contingency that one wants to sit with key on, eng. off, maybe listening to radio, or whatever. Under that condition, the pump should not be running anyway. Soon as key is turned further to "start", PCM turns pump on for constant running, until key is again turned off. If eng. fails to start, pump turns off again when key is returned to "on" or "off" position.

Hope this helps!

 

Since you hear the pump run when the key is turned to run and the truck won't start, that rules out the PCM relay, the fuel pump inertia switch, and the fuel pump relay.

Checking for fuel pressure at the fuel rail will be a very good indication. In the event you don't have a pressure gauge handy the next time it won't start, try cycling the key 2-3 times to build more pressure and see if it starts right up that way. So turn the key to Run, let the pump run and turn off, turn the key off for about 5 seconds, back to Run, repeat two more times, then try to start the engine. If it fires right up, that would indicate the pump is struggling to provide sufficient fuel pressure for a start up.

-Rod

 

i am also having same problem just replaced the fuel pump and getting 12v at roll over switch but pump seems to not be getting any power or pump went bad from time i got it and tested it and installed it but i don't think that happend due to after installing it wasn't getting anything from it.
but still getting 12v at roll over switch.

please help if you know the color of the 2 wires that come out of the housing of the fuel tank to the fuel pump i can then trace the wires back to find where i am losing power

 

Welcome to the forum. You don't mention the specifics of your Explorer, so I'll assume it's also a 2000 Explorer with the 4.0L.

Did you confirm there is battery voltage from the inertia switch and not just to it? The wire colors at the connector for the fuel pump assembly that control the fuel pump are pink/black (same as wire color from the inertia switch) and black (which is ground). These will be terminal locations 6 and 7 respectively.

Are you pretty confident the pump is not running? Have you checked the pressure at the fuel rail? Have you changed the fuel pump to make sure it's not plugged?

-Rod

 

yes i just got done putting a new fuel pump in ... and at roll over switch loc. at the passanger front kick panel i get power there but pump isn't comming on so guess i need to check resistance at ground and power at the other wire see where i am losing a connection. not sure if roll over switch is last shut off to fuel pump on the 2k ford explorer sport with 4.0lt eng. if it is then there has to be a ground / hot wire break but can't find a wiring diagram online to see if ground might be on a relay or controlled by the pcm


well just checked my ground has no resistance so looks like it's going to be a ground problem but don't want to just ground it to the frame unless i know it's not controlled by the pcm

 

Per the factory service manual, the ground is not controlled by the PCM, it is just a wire to chassis ground (with a couple of connectors in between the pump and chassis). The power lead is what's switched.

-Rod

 

First, 12V should be present to GROUND on BOTH terminals of the inertia switch, but ONLY when the PCM is calling for the pump to be running-- therefore, if the engine cannot start, there will be voltage present at the inertia switch for only about 2 seconds, as the ignition switch is turned "ON", then the PCM shuts off the fuel pump relay, which in turn shuts off the power flow to the inertia switch and pump. In other words, you need to have your voltmeter hooked up, accessible, and readable when the key is turned to "ON"-- you only get 2 seconds of "PUMP ON".

If you want to overcome this 2 second problem, what I do is remove the Fuel Pump Relay, look at it's diagram showing the contacts inside, usually on the side of the relay, the 2 contacts shown as "Normally Open" (no slash mark through them) can be substituted for by a short piece of appropriate-sized wire inserted into the relay socket in the relay box. IF YOU DO THIS, BE SURE YOU JUMPER THE CORRECT TWO HOLES IN THE RELAY SOCKET! While jumpered thusly, when the key is turned "ON", the fuel pump will "think" the PCM did it, and should run, assuming the inertia switch is CLOSED. I would check for voltage between the 2 wires feeding the pump, right at the tank, in the removed harness connector. If 12V is present there, the trouble lies between that point and the pump itself.

Anxious to hear what you find!.. impish

 

Almost. On EEC-IV, and I have no reason to believe EEC-V would be so radically changed, the PCM actually turns things ON and OFF by providing the ground connection to them.

Thus, and I could be wrong, the PCM provides the GROUND CONNECTION for the fuel pump relay, which allows it's coil to become energized. This pulls in the contacts inside, which provide 12V to the pump itself. The relay gets "grounded" to turn on, the pump gets "turned on" in the more usual way.

In the electrical world, it's customary to turn things "on and off" by switching the so-called "hot" connection (12V in vehicles) instead of the grounded connection. The reason for this is in the everyday world, we don't want the unit to be operated, whether pump, wall outlet, electric fan, etc., to remain connected to the "hot" power source when it's shut off, as would happen if we switched the "ground" or "neutral" connection. impish

 

This is true for the complete circuit, but if you go back and read the question I was responding to (post #8 above) the poster was specifically asking about the ground at the fuel pump assembly. At the fuel pump assembly, the power coming TO THE PUMP ASSEMBLY is what is switched by the PCM (via a relay), the ground TO THE PUMP ASSEMBLY is just connected straight to ground, no switches or relays.

-Rod

 

Okay! Semantics, then. I'm not being demeaning, believe me! I firmly believe that the more a guy can undertstand about how electricity works, the easier troubleshooting becomes (and the safer).

I have no doubt that the terms you and I throw around loosely (ground, floated, sunk to ground, ground-switched, "hot", neutral, etc.) are enough to confuse many issues.

Sorry if I offended you. impish

 

No problem, I wasn't offended, but concerned that we could be confusing Paul by reverting to discussing relays and switched ground when he is working on the pump end and wondering about the ground configuration for the pump.

If I had a track record of being correct 100% of the time rather than one where I've overlooked things or not completely understood the implementation from time to time, then I may be offended.

-Rod

 

I know this thread dates back to March, but I am having an intermittent problem as well. Vehicle will start several times in a row, I walk away and come back an hour later and the fuel pump will not cycle. Walk away again, then try it and it works again whenever it feels like it. Sometimes it hesitates when it does fire and stalls out. I have to cycle the pump several times to get enough pressure to start the engine. I replaced the filter and same issue. Explorer has almost 100k on it. Does this sound like the fuel pump is going out? I started taking the tank out, got all the way to the fuel lines, but then decided to see if the pump would work one last time, which of course it did. Cycled the key 5-6 times and the pump worked everytime, so I put the tank back in, and of course it's back to the same thing, starts one time, doesn't start the next time.