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Car Forum / Ford / Ford Explorer / April 2007Fuel Pump always on when key is on Please Help!
When I turn my key to On but do not start the engine I hear the fule pump running. Is this normal, or should it shut off after a while? Thanks, Bill. > When I turn my key to On but do not start the engine I hear the fule pump > running. > Is this normal, or should it shut off after a while? Yes, it should shut off after a couple of seconds. Does anyone know why the pump will not shut off? Is the pump bad and not creating enough pressure? Or could some other sensor be bad? I do hear a hissing sound near where the fuel enters the engine. Thanks, Bill. > Does anyone know why the pump will not shut off? > Is the pump bad and not creating enough pressure? Or could some other [quoted text clipped - 3 lines] > > Thanks, Bill. The fuel goes to a pressure regulator, then to the injectors, but I don't know exactly how this works. It seems the fuel pump shuts off at some higher pressure than the regulator output, and then cycles to maintain that pressure level. But I don't know how that is done. -Paul That may be true for newer, 'returnless' systems, but not for a '95. It will run continuously, delivering more fuel than the engine can use under the regulated pressure. The excess simply returns to the tank. But that's only true if the engine is running. For safety reasons, the pump runs only briefly to pressurize the system when the key is turned on, and then turns off, until the engine starts. If it indeed runs continuously without the engine running, there is an electrical problem that needs to be taken care of. A sticking relay comes to mind. > The fuel goes to a pressure regulator, then to the injectors, but I don't > know exactly how this works. It seems the fuel pump shuts off at > some higher pressure than the regulator output, and then cycles to > maintain that pressure level. But I don't know how that is done. > -Paul > That may be true for newer, 'returnless' systems, but not for a '95. It will > run continuously, delivering more fuel than the engine can use under the [quoted text clipped - 4 lines] > engine running, there is an electrical problem that needs to be taken care > of. A sticking relay comes to mind. I believe you're right. I know my Dodge will only let the fuel pump run for a few seconds with the engine off, for safety reasons, so what you say makes sense to me. It is controlled by a relay in my Dodge, which is in turn controlled by the engine computer. So a sticking fuel pump relay is a good place to start. -Paul A bad relay would be a simple fix. I may be able to switch the AC relay for a test. I don't think a bad relay answers the question why the car is not starting, unless the pump is shutting off when I crank the engine. Thoughts? > A bad relay would be a simple fix. I may be able to switch the AC relay > for a test. > I don't think a bad relay answers the question why the car is not > starting, unless the pump is shutting off when I crank the engine. > Thoughts? Oh- you didn't day that it wouldn't start. Check the fuel pressure then- there is a Schrader valve like on a tire to do that. It's located on top of the engine, attached to one of the fuel rails. If that is normal (~35 psi) your fuel pressure regulator and pump are OK and the problem is elsewhere. As you say the relay is easy to check by swapping with the AC relay. If that's not the problem, it gets tougher- possibly a shorted wire or bad engine computer. -Paul Paul, thx. I saw where the Schrader valve is. I'll buy a guage that fits this and report back the pressure. I assume it is valid to test the pressure while trying to start the engine? My book on indicates it should be running. I fear it is the PCM. Because I tried to run a test with my Scanner tool, and nothing happened. It just kept the initial tone going. Maybe I should borrow another scan tool to be sure. > When I turn my key to On but do not start the engine I hear the fule pump > running. > Is this normal, or should it shut off after a while? > > Thanks, Bill. What year is it? Maybe the fuel pump relay is stuck. Did you check the fuel pressure? This is a 95 EB 4.0L Explorer. Ulysses, I have not checked the pressure, but I will tonight. This is a 95 EB 4.0L Explorer. Ulysses, I have not checked the pressure, but I will tonight. Paul, I did not take a fuel pressure reading. I am more concerned with the fact that my code scannar cannot perform its test. I will create a new thread for this and after that is resolved, test the fuel if the car still cannot start. I may have a bad PCM. Thanks, Bill. The fuel pressure reads 30 when I am trying to start. Fuel is not getting into the cylinders because I pulled a plug after cranking for a while and it did not smell like gas. What is between the pressure reliev valve and the cynlinders that could be causing this. Could it just be the PCM not working? > The fuel pressure reads 30 when I am trying to start. Fuel is not getting > into the cylinders because I pulled a plug after cranking for a while and > it did not smell like gas. > > What is between the pressure reliev valve and the cynlinders that could be > causing this. Could it just be the PCM not working? I'm no expert but my thought is that if you have spark and good fuel pressure but no fuel to the cylinders then your injectors are not injecting. I suspect that a bad sensor somewhere might also be a cause of this and not necessarily a bad PCM. Have you checked/cleaned your Mass Air Flow sensor and the other one on the throttle body (whatever it's called)? If for some reason the PCM thinks the fuel mixture is too rich it might reduce it too much to start the engine. Also, if the crankcase position sensor is not working the PCM won't know when to fire the injectors and my guess is that it won't fire them at all. Have you verified that all vacuum lines are connected and not leaking? Good luck. > The fuel pressure reads 30 when I am trying to start. Fuel is not getting > into the cylinders because I pulled a plug after cranking for a while and > it did not smell like gas. > > What is between the pressure reliev valve and the cynlinders that could be > causing this. Could it just be the PCM not working? Were you able to get your scanner working? An error code would help to narrow this down. -Paul I have not been able to read any codes. It's like the PCM is dead or a connection to it is. I did a few tests yesterday: 1. IAT (air temp sensor) resistance checks out at 31K olms at 70 degs. 2. Mass Air Flow sensor, voltage check, from the pos to neg terms it was 5.7 volts. I think it should be 10. Not sure what this means. 3. Injector voltage. While cranking the starter it cycled in voltages from 0 t0 0.03 volts. Seems very low, but I don't know what it should be. The PCM cable and pins all look very good. No worn spots or corrosion. I probably have a bad connection somewhere, but with so many wires I don't know where to start. I really want to put in a new PCM if I can find a place that will let me return it (if it does not help.) Any new suggestions? |
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