86 Econoline,250,302 140K. Never had a problem befor. I just got in and tried to start it and NADA. I heard it buzzing for30 seconds, then it stoped. There’s no power to the fule pump, either withj just the key on, or when cranking. When is the pump supposed to get power? What should I check?
Some cars the pump got it’s power from the Oil Sending Unit. If the sending unit didn’t detect oil preasure then it would kill the engine by shutting off the fuel.
How did you check for power?
If you checked voltage, done by connecting to the hot lead and to ground, then you may have anything from a bad relay to a bad oil pressure unit (as Mike suggested), perhaps even a bad inertial sensing switch.
If you checked current, done in series in the circuit, then the pump itself may be fried and open. There’s not any current through an open circuit.
Start the checking by seeing if the fuse is ok. Then move on to the relay if that is good. The pump should have power at least for a few seconds after the key is turned to the RUN position, even though the engine isn’t running.
I checked the fuses in the fuse block over by the driver side, above and left of the break pedal area. All were ok, except for one small fuse not marked. I’ts located in the lower row and the last one on the right side of the block. I removed the block mounting screws and found twe thin blue wires for that fuse. There was no power to either wire. Dont know what it’s for. I checked the wires at the pump with a volt meter, as well as with a test lamp, as I said no power. Howerer, I did not test from terminal to ground. I will check that today. Can you please tell me where the relay can be found and if that’s good what would be the next step after that?
The relay is probably in a relay box under the hood, but the best way to find it is with a manual. Haynes should do the trick. You’re probably going to need the schematics anyway.
I got power to the pump on the frame as well as the on in the tank, by bypassing the relay with the key off. The pumps dont pump ,iether with just the key on or cranking. I can hear them both wherling though when I bypass the relay. I replaced the relay but that did’t help. I disconnected the fule line just befor the regulator and no fule comes out while cranking. Again , no power to the pumps. There must be something else not allowing the pumps to power up. I checked the harness at te relay and there is 12 Volts between two terminals. Could there be seperate fuses for the relay and pumps?
Time for a wiring diagram. Ford used inertia switches in many vehicles of around this vintage (to shut off the fuel pump following a collision). These switches have a reset button.
The fuel pump relay gets its control + signal from the inertia switch which is behind the passenger side kick panel which, in turn, gets its power from the ECA relay. The ECA grounds the control when it recognizes the starter circuit and/or RPMs. The ECA relay is on the same bracket as the fuel pump relay. The 2 relays are identical except that the ECA has a diode to protect the computer circuits. The computer controls the relay ground on the tan/light green wire. If everything is back in order and that wire is probed with a grounded test light with the ignition on the fuel pump may turn on. If so attempt to start the engine. If it starts post your success here. I might save you some time and money.
When the engine is not running there is no oil pressure, right? So, then the engine would never start untill the cranking engine built up oil pressure, right? Did I misunderstand you? Do you mean that if the oil pressure fails, while the engine is running, the oil pressure switch will open the circuit? Anyway could you plesae tell me how to check, or bypass the oil pressure switch?
nickr1932,
Here’s your earlier post. You can find any post if you write down the exact title (like “No power to fuel pump”), Click “Search” on the red banner above, and enter that title in keywords; then, click SEARCH.
You can download these pages to a file in your computer; even, print them out.
The fuel pump(s) operation is a two-step process. The engine computer energises the fuel pump relay. The energised relay, then, sends power to the fuel pump. What you are missing is the signal from the engine computer. It decides to send a energize signal to the fuel pump relay when it gets a signal that the engine is turning over (cranking, or running). The cranking/running signal could be from the distributor, or a crankshaft, or camshaft sensor.
You need the repair manual to tell you where to check for which signal.