Fuel sending unit help

[Jamoaus]

So I have a main tank and aux tank.
My main tank (at the rear) wiring seems like it's cut and the orange wire is going to what looks like an electric pump instead? The fuel gauge is showing full no matter how full and when I switch the tank switch from main to aux, it drops to empty. Anyone have any idea what's going on? Is it the wiring?

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[TAC71]

Are you sure your "electric fuel pump" isnt the switching valve for tanks. I cant see all your pics, so just a guess of what your looking at. The pic of the rear tank shows the wires for the gauge are gone. Looks like the ground wire is there but not connected.
Really need to see pics.

 

[Jamoaus]

Yeah sorry about the pics. I thought it was the electric pump, but I don't think it's the switch valve? I might be wrong

 

[thegreatjustino]

The first photo is a very common Carter electric fuel pump.

Second photo shows the sender unit wires cut. There's nothing going from the sending unit to the gauge. If the orange wire that was going to the sending unit is what's powering the electric pump, that's some PO rigged up crap that needs to be fixed.

 

[Jamoaus]

The first photo is a very common Carter electric fuel pump.

Second photo shows the sender unit wires cut. There's nothing going from the sending unit to the gauge. If the orange wire that was going to the sending unit is what's powering the electric pump, that's some PO rigged up crap that needs to be fixed.

Yeah I'm assuming the previous owner had rigged this up. Assuming the orange wire needs to be connected back to the sender and do I just need accesory power to the Carter pump?

 

[bmc69]

Yeah I'm assuming the previous owner had rigged this up. Assuming the orange wire needs to be connected back to the sender and do I just need accesory power to the Carter pump?

You won't be able to simply "just" connect that orange back to the sender...you will also need to fix the other end of the orange that the PO removed from the gauge circuit and connected to a straight 12V hot source to run that pump. And then you'll have to run a dedicated switched 12V to the pump.

Talk about jack-leg work...sheesh.

 

[Jamoaus]

You won't be able to simply "just" connect that orange back to the sender...you will also need to fix the other end of the orange that the PO removed from the gauge circuit and connected to a straight 12V hot source to run that pump. And then you'll have to run a dedicated switched 12V to the pump.

Talk about jack-leg work...sheesh.

Thank you for all the advice and guidance.
So just to make sure I'm understanding this correctly - the orange wire goes from the gauge to the sender and I'll need a straight 12v hot source to the pump? Is there a diagram or image somewhere I can reference? Sorry about the noob questions here..

 

[awest5321]

Definitely Find the other end of that orange wire BEFORE connecting to the sending unit. You do not want 12 volts connected straight to the tank.

 

[904Bronco]

Couple of things here...
Dual tanks - I am guessing the PO may have repurposed the electric fuel tank level switch in the dash to operate the pump?

Usually there is a an orange sending unit wire from the rear tank and a yellow sending unit wire from the Aux tank. They go to the switch to the left of the steering wheel on the dash and you select which fuel tank level you want to read on the gauge.
You will need to do a little more investigating to see what was done. Is there still a fuel tank select valve on the floor of the bronco. Does the Bronco run off the front tank still?

You want Ignition power to turn the pump on, but you should run a relay with fused 12v from the battery and the Ign power closes the relay. No power would close the relay with the key in Accessory the position.

 

[Jamoaus]

Thank you everyone for the guidance and advice. I did find this in another post that I'm going to implement with an electric tank switcher rather than the manual switch below the drivers seat. I think this is what I have to do.. does it look right? Only thing I don't see on my rig is the Aux pump? Just the Carter pump at the rear..

 

[billh1289]

Thank you everyone for the guidance and advice. I did find this in another post that I'm going to implement with an electric tank switcher rather than the manual switch below the drivers seat. I think this is what I have to do.. does it look right? Only thing I don't see on my rig is the Aux pump? Just the Carter pump at the rear..

Can you post some pics of the sender end of the aux tank, selector valve and how it’s plumbed?

 

[Jamoaus]

Can you post some pics of the sender end of the aux tank, selector valve and how it’s plumbed?

Sure here you go..
It looks like the PO had a black wire going straight to the tank switch?

Aux sender:

Manual switch and plumbing:

Seems like a sh*t show of a mess

 

[billh1289]

Sure here you go..
It looks like the PO had a black wire going straight to the tank switch?

Aux sender:

Manual switch and plumbing:

Seems like a sh*t show of a mess

You could start tracing wires and make your own diagram of existing. That might help you see what you have, how they made it work and what you need to do to make it right. Maybe a dumb question, but in addition to the electric pump is the mechanical pump still installed too?

 

[Jamoaus]

You could start tracing wires and make your own diagram of existing. That might help you see what you have, how they made it work and what you need to do to make it right. Maybe a dumb question, but in addition to the electric pump is the mechanical pump still installed too?

Thanks for the help.

Yes it looks like it's going to a mechanical fuel pump and then to the carb.

 

[Oldtimer]

Can you take a picture of the backside of switch?
What do the other end of the hoses from valve connect to?
Where is the other end of this?

 

[Jamoaus]

Can you take a picture of the backside of switch?
What do the other end of the hoses from valve connect to?
Where is the other end of this?
View attachment 896247

It looks like it's going to the passenger side and ending up nowhere. Not sure what this was originally for?

 

[billh1289]

It looks like it's going to the passenger side and ending up nowhere. Not sure what this was originally for?

Probably the charcoal canister

 

[Jamoaus]

Thank you everyone for the guidance and advice. I did find this in another post that I'm going to implement with an electric tank switcher rather than the manual switch below the drivers seat. I think this is what I have to do.. does it look right? Only thing I don't see on my rig is the Aux pump? Just the Carter pump at the rear..

Ok, so after a big day of rewiring and switching from the manual tank selector to an electric tank selector switch - I believe I cleaned up the shoddy mess that the PO did.

Here's what I did:
- got a new dash fuel selector switch and wired according to diagram on this reply
- reconnected the sender wiring from the main tank and routed it back to the switch in the dash
- installed the electronic tank selector from WH
- re-ran the fuel lines to the new electronic tank selector (got covered in gas. Fun times)
- connected all to the switch as per the diagram.

Now, I only have 1 electric pump mounted to the rear near the main tank. Question I have - when I turn the car to run, I can hear the pump when on main, but don't hear the pump when switch is on Aux tank. Is this correct?

 

[billh1289]

Ok, so after a big day of rewiring and switching from the manual tank selector to an electric tank selector switch - I believe I cleaned up the shoddy mess that the PO did.

Here's what I did:
- got a new dash fuel selector switch and wired according to diagram on this reply
- reconnected the sender wiring from the main tank and routed it back to the switch in the dash
- installed the electronic tank selector from WH
- re-ran the fuel lines to the new electronic tank selector (got covered in gas. Fun times)
- connected all to the switch as per the diagram.

Now, I only have 1 electric pump mounted to the rear near the main tank. Question I have - when I turn the car to run, I can hear the pump when on main, but don't hear the pump when switch is on Aux tank. Is this correct?

I’d say you stated it correctly. It would make sense that you hear the pump kick on if you wired it to the lower row on the switch and to the same side the main tank sender. The thing that I’m not crazy about is running the electric pump through the manual pump. Guess it would be ok if they were rated the same. Someone else will chime in with better insight on it. The new mechanical pumps seem to be hit or miss now especially if you let them sit but they’re capable of pulling from aux and main tanks.

 

[Oldtimer]

How does engine run when switched to aux tank?
If it runs OK then mechanical fuel is working, and there is no need for electric pump at main tank.
Remove electric pump and connect fuel line to main tank.
If it won't run when on aux tank, fix mechanical pump.