92 F 150 fuel pump

I'm working on a 92 F 150 and the fuel pumps will not work. I have traced it to an electrical problem and as far as I can get is to the relay under the hood. I'm getting the proper voltage but if I jump a wire here I can get the pumps to work. I have replaced the ignition switch, relay and checked the automatic fuel shut off switch. If anyone has any info please share!

Thanks

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Ripcord
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Is this PUMPS as in plural for dual tanks? Or is it single tank?

So basically what you are saying is that if you pull the relay out of the picture and jump from power (pin 30) to load (pin 87), the pumps work? If that is the case you have either a bad ground or bad power to the control side of the relay. The relay pins are as such:

85 & 86 are control circuit, it doesnt matter which is power, and which is ground. (2-3A is all that is required on this circuit for it to work. It creates a magnetic field in a winding.) 30 is power into the relay for the load (usually 30A powersource)

87 & 87A are output to the load (you will only see 87 on a 4pin relay, but on 5pins they have 87A which is for an alternate load to be switched on when the main load is turned off, sort of like turning fog lights off when you turn on high beams. 87A would be the foglights, and 87 would be the high beams. When you turn on high beams the load shifts to pin 87, but when low beams are on, the load shifts back to 87A for fog lights.)

Do me a favor, put an 1156 bulb across where pins 85 and 86 would insert, and see if it lights up pretty bright. If it does that circuit is good. Then do the same thing across the other two terminals. While you have the bulb lit, put your voltmeter on the circuit, put the positive on one pin and the negative on the other pin (you want the DVOM in parellel with the bulb, NOT series.) You are doing a voltage drop test here. You should see 12V on the meter. If you see less, then you have resistance in the circuit somewhere, and its acting like an alternate load in a series circuit splitting the voltage between the loads. You can also do a voltage drop anywhere on the circuit to find high resistance. Just do like you did with the bulb in the circuit, but this time you are seeing if the voltage is trying to take another route to ground. Put one lead on a connection and put the other lead at the other end of the wire. If you see anymore than 0.2V on your meter, then you have resistance in your wire. That resistance can be anything from a bad splice, to a bad ground, to just corrosion on a terminal somewhere. The reason you dont want to just see if there is voltage available there, is because a single strand in a wire can show the potential to do work, but once you load the circuit, the voltage is dropped across the resistance.

Hope this helps.

Ford Tech

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Ford Tech

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