Electrical issue with fuel pumps

[Trevorrudai]

So I lost all power to my fuel pumps. I pop the hood and found a fusible link melted. I repaired the fusible link. I also found another connection that wasn't allowing current to travel through it which was a connection that had the inertia switch wires orange/blue, and orangish/black running through it. The connection served no purpose as it didn't have a fusible link or any type of fuse inside of it so I bypassed the connection completely and just spliced the correlating wires together that way my current wasn't being blocked by the connection. So now I'm getting positive power on the orange/blue wire all the way to my inertial switch. Great. However the other wire that goes to the inertia switch orange/black I'm under the impression should also be getting positive power, is getting ground power instead. It is my understanding that all the inertia switch theoretically does is bridge these two wires a connection allowing the fuel pumps a connection and being able to turn on. What I don't understand is if that's true wouldn't that cause a short in my electrical system? If the inertia switch wad bridging a positive to a ground? I can't figure out why my fuel pumps aren't receiving power and I believe this to be the case. Is one of the two wires going into the inertia switch supposed to be a ground wire? Or should it in fact be a positive wire? I could use any help on this being I am by no means a electrician or a mechanic. I have a Hanes manual with the wiring diagram and all that it shows is an orange/blue wire going to the inertia switch. I'm pretty sure there is another wire that is supposed to go there with it being the orange/black one why is that not on my wiring diagram in the hanes manual?

 

[Curious Hound]

. I also found another connection that wasn't allowing current to travel through it which was a connection that had the inertia switch wires orange/blue, and orangish/black running through it. The connection served no purpose as it didn't have a fusible link or any type of fuse inside of it so I bypassed the connection completely and just spliced the correlating wires together that way my current wasn't being blocked by the connection.

Where was this “connection”? And what did it look like?


There should be two wires at the inertia switch. One should bring power from the fuel pump relay, only when the relay is energized. The other sends that power to the fuel pump.

When you first turn the key on, the fuel pump relay is energized for about 2 seconds. That is to make sure pressure is available to start the engine. Then it turns off until the engine starts. Once the engine is running, the fuel pump relay stays energized all the time.

 

[RonD]

The Fuel Pump electric motors are both grounded
So if you were to test their Positive(12v) wire with an ohm meter it would show as a Ground, because it is(but not 0 ohms)

Same as a grounded light bulb would show as a ground on its 12v contact

The way electricity works is that voltage must flow THRU(not just TO) the device to power it
A "short" is when there is no "device"(no resistance) and all the AMPs on a wire can flow with no restriction, no resistance, wire melts or fuse blows because too many AMPs flowed thru it

The device limits the AMPs that can flow thru it, so one side is 12v and the other a ground(0v) and electricity flows thru it to power it, spin the motor or make the light bulb glow

Put ohm meter on inertia switch wire to fuel pumps and then to a ground in the cab, bolt, as long as you don't see 0 ohms, then there is resistance, so not a short
An electric motor can short out inside, and would then show 0 ohms so a short



There should be a Fuel Pump relay in the engine bay, as said above
The fusible link may have been connected to that relay, and then the wires to the inertia switch would also be connected to that same relay
The computer operates that relay to prevent electric fuel pumps from continuing to run and pumping out gasoline in an accident
The inertia switch is a "backup" cut off, in case computer cut off doesn't work

Power flow
12v(battery)--------fusible link----------Fuel Pump relay-----------inertia switch-----------fuel pumps----Ground