I recently picked up this truck and am in the process of changing the electrical fuel pump pulled the tank and pulled the pump and noticed there is only one green wire even going to the pump I followed that wire through the cab and in the engine bay where it literally was not plugged into anything. does anyone know what this green wire is supposed to be wired up too? I’m assuming the battery? The pump and hanger look to be OEM. Sorry if I am asking a dumb broad question but it seems like the previous owner tried to rig this thing up and botched everything up

 

That's not a fuel pump. That's your fuel level sender unit. A 79 has a mechanical pump on the motor. Did the fuel guage work? I'm guessing not if the green wire isn't hooked up.

 

I thought that was the pump at the bottom of the sender where the wires run down? Previous owner has a full head in the back of the truck with a mech fuel pump attached to the head and now has a block off plate on the head he put on. I pulled that block off plate and mocked up the old mechanical pump he had in the back but it doesn’t want to sit flush and the T stat housing gets in the way. But also under the dash there’s a fuel pump relay.. wouldn’t that mean it came factory with a electric pump?

 

That is the fuel pump. Looks original to me. I think that wire should go to the fuel pump relay? Some good info here:http://toyotamotorhome.org/forums/in...iring-diagram/ It is for previous generation but should be similar. Fixing my fuel pump wiring has been on my to-do list for a while (I replaced my in tank pump but some previous owner bypassed the relay so my pump runs all the time when the key is on) so I'm interested in what you find out.

 

That’s what I’m confused on looks super original even has the OE Denso number on some off it. But the green wire that ran to it literally is just hanging out in the engine bay no where near the battery. Anyone switched over to a mech pump? Can’t seem to find a write up or anything on it

 

Scott I’ll check it out thanks brotha almost want to just go to mechanical if I don’t have to mess with any wiring.

 

That was my first thought too, but if I remember correctly the mechanical pump system had one more fuel line running between the engine bay and the gas tank. I believe there is a return line to return excess fuel from the mechanical pump back to the tank that my truck did not have. So I decided it would be easier to replace the electric pump.

From '80 fsm
Compare pic above from '80 fsm to your gas tank.

 

That was my first thought too, but if I remember correctly the mechanical pump system had one more fuel line running between the engine bay and the gas tank. I believe there is a return line to return excess fuel from the mechanical pump back to the tank that my truck did not have. So I decided it would be easier to replace the electric pump.

From '80 fsm
Compare pic above from '80 fsm to your gas tank.

 

The single wire coming from the in-tank fuel pump should go to the fuel pump relay, or as Toyota like to call it, the "Circuit Opening Relay" or COR. On carburated 20R's & 22R's, the relay is wired into your Oil Pressure Sender. The Relay basically acts as a safety device. In the event of a crash & a ruptured fuel line, when the engine stops running oil pressure is lost, the Oil Pressure Sender switch closes, energizes the coil in the relay, and switches fuel pump power back to the "Start" side of the circuit. This prevents fuel from a broken line from being shot onto a hot engine & causing a fire, which would be very bad if you were knocked unconscious from a wreck.

To maybe make this a little easier to understand, here's a wiring diagram of the circuit from my '78. All carb'ed models up to 1994 should be very similar:


Also note the presence of a Fuel Pump Resistor. This part is usually located in the engine bay passenger side. MIne is mounted on top of the fender well. scottd mentioned something about wiring the pump to run all the time when the key is on. Some people do this to bypass the relay, but you lose the safety feature. I'm also unsure if such a bypass would also include the resistor or not. I do NOT recommend bypassing the resistor, because your fuel pump will not last as long. They are designed to run on something like 9.8 volts when being powered in the "Run" position. The circuit design only sends full battery power to the pump in the "Start" position. After the engine starts & oil pressure comes up, the relay switches it back to "Run". So the majority of the time the pump runs on less than full battery power. This is not a problem, because the pump is designed to provide more than adequate flow & pressure at that voltage.

This COR Relay is also present on EFI models, but the main difference in the circuit is that it uses the MAF as a signal source instead of the Oil Pressure Sender.

 

This is only true with carbureted trucks with electric fuel pumps. Once the 22R was released, it came with a mechanical fuel pump that is driven off of the cam.

 

The 22R has got the mechanical fuel pump on the side of the engine, like old87yota said, and driven off the cam.
But the 22RE heads still have the port for the mechanical pump, it's just blocked off with a plate. It's still there, though.
Do, one could, conceivably, convert to a 22R from a 22RE. Lots of changes around the engine, but the engine would be pretty much unchanged.

Kind of a nifty set up, IMHO. I think Toyota planned well.
Pat☺

 

Beg pardon for not being exactly precise. I thought it would be evident since the discussion was about an electric fuel pump?

 

My point was the fact that 22Rs came with mechanical fuel pumps, so the electrical wiring diagram showing a COR connected to an oil pressure switch does not apply to 22Rs and also doesn't apply to some 20Rs as well.

This means that the diagram isn't applicable after 1980 or so, when Toyota decided to use only mechanical fuel pumps for our carbureted Trucks.