When should there be power to the fuel pump. When the key is turned on or only when the engine is running? I have approximately 8 volts to the fuel gauge mechanism when the key is turned on but nothing to the pump itself. I have a replacement fuel pump but am not sure if that is the problem. Fuse is good and there is power to that. (40 amp under hood fuse labeled "pump") Also is the wiring harness on the fuel pump assembly interchangeable? The tag on one harness has a 3 letter code "c_c" , the other ends i "d".
There is power at the fuel pump for aprox 3 seconds as soon as the ignition switch is turned on
then it does not get power again until the engine starts
so if you are checking the power at the pump you need to have someone else in the car to turn on the switch while you are looking at your meter , you have a relay under the hood under a plastic cover at the fire wall that controls the power to the pump .
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Is the SECURITY light lit on the insturment cluster ? Does the engine spin with key in start position ?
Vehicle Theft Deterrent (VTD) System Check
Attempt to start the vehicle.
NO - The engine cranks and starts.
Refer to Engine Cranks but Does Not Run in Engine Controls.
Note the security indicator while attempting to start the vehicle.
The indicator light is ON and OFF after approximately 5 seconds.
• SECURITY Indicator Always On or Flashing, Engine Does Not Crank
• SECURITY Indicator Always On or Flashing, Engine Starts
* Refer to the appropriate symptom diagnostic table for the applicable abnormal result.
the operation of most fuel pumps is controlled by the fuel pressure regulator
when the fuel pump gets to set pressure , the pump is switched of by the ECM at the relay level
maybe nothing wrong with your system just the system working as designed
if you have pressure in the fuel manifold when you turn the ignition on then the pump will not run but will if there is a fuel leak somewhere and the pressure drops off
First check the fuses... with a volt meter.. don't just look at them.. When you turn on the key the ign switch powers up the computer... .. The computer sends a single to a relay.. the relay comes on for 1.5 seconds when you turn the key to on to charge the system.. after you crank it for a few turns the fuel pump come on to keep the engine running. Turn the key to on and listen for that 1.5 sec. pump run.. if you have to go under the car and have somebody else turn the key.. if you hear it running then the fuel pump runs.. if you do not hear it run check that the ign switch is sending power to the acessories/computer. then check the relay to see if it is operating when you turn the key to on.. listen to it and touch it.. yyou should be able to hear it and feel it click. Just because the pump is running does not mean that it is pumping...so the next step is to hook up a pressure guage to the fuel rail and see if there is any pressure. (Harbor freight tools if you do not have one) You can jump the pump with a 12v wire.. jump it at the pump connector on top of the tank. if it runs check the fuel pressure.. if there is none.. or very little the pump is bad.. or the fuel filter is clogged.. or the pick-up filter in the tank attached to the pump is clogged.
The fuel pump will run for about 1 second only and then the system computer shuts it off unless the engine starts or is being cranked over with the starter motor, so repeatedly turn the key off and on to keep it running or at least supplied with power. You will hear a low hum near the filler neck if the pump is working. I have this same truck and have replaced the fuel pump twice. One hint never run the fuel level lower than 1/8 tank or the fuel pump will overheat and that shortens the life of the pump dramatically.
Generally speaking, its supposed to do that. The fuel pump(s) is powered by a relay that turns on for 3 seconds when you turn the key on. If the engine does not start and produce oil pressure, thats all the power the pump gets. If you were in a wreck the pump would shut off when the engine dies even with the key on to prevent a fire. You would need to jumper the relay to make the pump run beyond the 3 second time.
It is normal for the pump to run for two seconds when first switched on to pressurize the fuel system. It will turn on again when cranking and while running. I would still suspect the pump given your symptoms, however other problems could also give you the same symptoms. If it is the original pump from 2002, or more than about 7 or 8 years old, I would definitely replace it, and the fuel filter. Often the pump will go intermittent. I had one that I could restart and get down the road by hitting the bottom of the gas tank a few times!
Check per owner manual to be sure inertia switch is not tripped. Remember, fuel pump only runs for 5 seconds when key is turned ON, then it shuts off if engine is not running. Pump always runs when key is in START position.
Listen for pump to run inside fuel tank for 5 seconds after key is ON.
The PCM power relay turns on the PCM and the PCM turns on the fuel pump relay, which turns on the fuel pump.
If it is similar to Quest, the fuel pump runs for 5 seconds when you turn the key to ON. Then, unless the engine is running, the pump shuts off. It runs when the key is in START position though. Can you hear the pump run for 5 seconds when you turn key to ON? Listen carefully for the hum of the pump in the tank.
Normally, the power relay powers up the PCM and it applies power to the fuel pump relay. Then you get power to the pump.
Also, look at owner manual for all fuses that apply to fuel pump system.
The engine computer turns on the fuel pump for 3 seconds when you turn the key to "ON".
If the engine does not start, the pump will not run.
When you turn the key to "Start", the fuel pump runs all the time the key is held in start.
When you turn the key on, it actiavtes the power relay, which provides power to the PCM or engine computer.
The PCM then activates the fuel pump relay, sending power to the fuel pump.
You should have one wire with 12V for 3 seconds in "run" position. This comes from the fuel pump relay to the inertia switch in the trunk and then to the fuel pump.
You should have one ground wire. black
One wire going to the fuel guage.
You may have another ground iwre ging to a diode before going to ground.