My fuel pump relay will not click , the wire from the relay to the pcm , when you first turn key on the voltage will be b+ then it will drop off to 4.5 volts , is that norm , i have pulled the pcm and tested the wires and checked the wire to all other pins , all clean so the wire it good , does any one know if that is normal?, that truck has a bad hesitation ,but if you let up the tps just a little it is a lot better , at low speeds , on the freeway it does not hesitate, so at high rpms it's ok , any idea's ,thanks
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I just looked at a wiring diagram of the fuel controls for this model: there is no fuel shut-off switch in the wiring. It's pretty straight forward, typical fuel pump controls: the fuel pump relay is in the under-hood power distribution center. When this relay is turned on, power is sent to the fuel pump, nothing else is in the path of the hot wire to the pump module so it (the pump) should be working.
So if pump is not on, you can diagnose the wiring right here at the fuel pump relay. First you verify the power feed for the pump is available at the relay. (One terminal at the relay will have battery voltage with key off. If you pull the relay out and use a test light, one terminal position will be hot.) Next you verify the relay is working, sending power to the fuel pump in the gas tank. You do this by having someone cycle the key to on, while you hold a finger on the relay (it's back in place) to feel it click on. You should feel it, maybe even hear it, the relay will energize every time the key is turned to on, and this is what sends power to the fuel pump.` If it all works, and the pump is not on, the pump probably needs replacing. If the pump relay is not clicking on, that's a wiring hassle, including the wire to the engine computer. The pcm is what controls the relay turning on.
Do you know if the fuel pump has ever been replaced in the car? If it is original, it has been a good long run.
you will need to check the plug to the pump on top of the tank. check for voltage. then if no volts trace the wires back. also you should check the relay have some one at the relay listening to see if it clicks when you turn the key. no click no volts no volts may be a warn out relay, if it buzzes change it.
There is a red and white wire feeding the fuel pump relay from a 30 amp fuse. Both the shutdown relay and the fuel pump relay are grounded by the PCM, so if the fuel pump relay is grounded it should be "on" and providing a direct link from the pump to that fuse. You should have battery voltage on that 30 amp wire before the relay and then on the dark green and black wire going to the pump. If you don't have battery voltage coming from the 30 amp fuse, the problem could be before the fuse. That 30 amp fuse is hot all the time, so it is powered by a fuseable link coming off the battery.
I apologize for a delayed response as i was not at my desk.
Check to see if the fuel pump relay clicks when you turn the key on. If
it doesnt click verify one terminal has constant ground if not you will
need to run a new ground wire. If ground is good access pin 46 on
connector 1 of the pcm to check for voltage if no voltage replace pcm if
it has voltage replace green/white wire between pcm and relay. You can
also first try to swap the relay with another one to see if that helps.
If relay clicks then check the 15 amp fuel pump fuse and if blown
replace. If fuse is good verify one terminal on the relay has voltage
at all times and gray wire has voltage leaving relay when key is in
crank position for for a few seconds when turned into on position. If
gray wire leaving relay has voltage but not gray wire at fuel pump
replace the wire.
you can try this:
It is possible with a P0232 for the fuel pump to be running continuously, even with the ignition off. If that's the case and you can hear the fuel pump running, you may be able to disregard some of the following checks. Turn the KOEO (key on engine off) and wait for a few seconds. This allows the PCM to complete it's fuel pump pre-cycle. Now, using your scan tool (if you have one) observe the FP VOLTAGE FEEDBACK reading in the datastream. This reading indicates what kind of voltage the fuel pump is receiving.
If you don't have access to a scan tool, use a voltmeter to read the FP voltage at the fuel tank. If your reading shows any voltage at all present to the fuel pump with KOEO (or if you can hear the pump running), remove the FP relay. If the voltage remains, or the fuel pump continues to run, then there is a short to voltage on the FP voltage supply circuit or on the feedback circuit. Repair as necessary. If the voltage disappears (or the pump quits running) with the FP relay removed then try replacing the relay with a spare one. Upon reinstalling the spare relay, if the voltage disappears, the relay was faulty due to a short. If, though, after replacing the relay voltage is still present, suspect that the PCM FP relay control circuit is shorted to ground.
Check for a short to ground on the PCM FP relay control (ground driver) circuit by removing the FP relay and ohm between a good ground and the PCM FP relay control. There should be no continuity to ground with KOEO (after the FP pre-cycle is completed). If there is continuity to ground the wire is shorted. Find the short to ground and repair as necessary. If you can find no physical short, It may be necessary to snip the FP relay control wire close to the PCM connector where it will be easy to repair and check for continuity to ground with KOEO coming OUT of the PCM. If there is no continuity the wire is shorted in the harness. But if continuity exists, the driver may be internally shorted to ground and the PCM may require replacement.
You can usually go by the wire colors. The fuel pump relay wires are pink, gray, black, and green with a white stripe. When troubleshooting a fuel pump that is not coming on, the relay is the best place to figure out why. You can pull the relay out and put a jumper wire from the battery to the terminal with the gray wire. If the pump runs, you know that isn't the problem. Then turn the key on and use a jumper between the terminals with the pink and gray wires. If this turns the pump on, you know the ignition switch is sending power to the relay, and the fuse is good. Pull that jumper out, but leave the key on. Push the relay back into the socket, but put a jumper from a ground point to the terminal with the black wire. If that turns the pump on, the ground wire is bad. If not, the PCM is not turning the relay on. Reasons for that may be a bad wire from the PCM, a passlock issue, or the PCM fuse/power wire.
INSTALL PRESSURE GUAGE THEN CK, VOLTAGE TO PUMP PCM TURNS ON PUMP RELAY FOR 2 SECONDS WHEN KEY CYCLED ON ,, IF NO POWER CK INERTIA SWITCH ( MAY BE TRIPPED ) IF NO POWER TO INERTIA SWITCH CK FUEL PUMP RELAY IF NO VOLTAGE AT PUMP RELAY THEN CHECK FOR SPARK AT PLUGS IF NO SPARK CK PCM POWER RELAY IT SUPPLIES VOLTAGE TO PCM THAT INTURN POWERS FUEL PUMP RELAY
im not sure of the color wires that should be powered but have you checked the fuel pump relay under the hood? also check that you have a good ground at the pump dont check just the positive voltage check for negative (ground) also