Greetings from a neubee. Been lurking here couple of weeks, trying to learn stuff. Lots of smart and helpful folks here, I'm hoping to learn more and to contribute some when I can.

I am recently the proud owner of '84 F250 regular cab, 460 4bbl, 3/4 ton, 4spd manual trans (granny?). This truck is a beast, or will be once I correct a few sins from previous owner, and get past a few "senior moments" initiated by own-self.. It's gonna be my hunting vehicle, and workhorse. My first Ford.

To the current problem. Previous owner removed the bed, both gas tanks, and replaced with school bus tank - gravity feed + electric inline pump. Major hacking was done on the wiring, and on the fuel delivery and return lines. The fuel tank switch valve (modulator?) mounted in driver's side frame rail was cut out of the circuit..

So, what have I done to make it better? <!---->

I rebuilt the Holley Motorcraft 4bbl. I think I got it "close" to optimal. Probably still some tweaking, but I'll save that story for another thread. Truck runs, idles @1000 RPM, and now drives decent that it's not pumping gas full of rust, black paint chips and years of crud.

I found a rear tank from dual-tank F150, perfectly clean inside, complete with submerged pump, fuel level sending unit, filler neck hoses and metal tube, wiring connector, and mounting hardware. $20 and half an hour to pull it, another half hour to install it. :-)

I reconditioned the submersible pump - changed the rotting rubber hose, added hose clamps. I removed the mess of metal tubing, plugged "filter" and whatnot that I believe you knowledgeable guys call the 'hot fuel option.' I replaced it with an inline fuel filter that has a bypass. My hope here was that the carb floats would control fuel delivery, would provide enough resistance to shunt unused fuel to the return lines, back to the tank. I also found the wires providing power and ground to the in-tank pump. My hack upon the existing hack seems to work. Truck runs - but have yet to try it under heavy load. I have not meausred fuel pressure yet. It mostly works..

I replaces rotting rubber fuel delivery hoses on both pressure and return sides from rear tank all the way to carb.

Sorry if explanation is too verbose.. The net result, It works - well, I should say it supplies fuel to the carb, and returns unused fuel to the tank. Truck runs.

My current challenge is to get the fuel guage to work.

I looked at Haynes manual wiring diagrams. Still Confused.

The fuel level float inside the tank - floats. The float arm seems to be contacting the coil in appropriate manner (changing the resistance, informing the guage of how much fluid remains.. true?)

What I'm not sure about is how to wire it. I pulled the instrument cluster and removed the fuel guage. I want to wire the guage directly to the fuel level sensor, bypassing the all the rest of the hacked-upon wiring.

Not sure, but I do not think I want 12v current. True?

I also think I do not want the hot side of current going into the tank - I want hot side of current going to one leg of the guage, and the "ground" leg is what goes to the tank. True?

Any suggestions are welcome. I'm out back wrenching on the carb a bit more, fixing misc stuff, but will check in now and again. Thanks in advance.

axman

 

Thats is a lot to take in.

All I can say for sure is the lines that run to the sending units and monitors the fuel level "blink" with a test light attached.

 

Hacking your Fuel gauge wires is not a good idea at all.

The Fuel, Oil, and Temp gauges are regulated by a ICVR, instrument cluster voltage regulator that is part of the cluster printed circut. The gauges only use around 1.5 amps to operate.

You cannot hook the fuel gauge up directly. It will burn the gauge up.

 

Thanks, I did notice a wire "blinking" when using test light to identify fuel pump power. I'll try that wire to the gauge.

Thank you, that is exactly what I needed to avoid disaster.

Again, sorry for extra verbosity in initial post. I appreciate the help, and will report progress.

 

The blinking is from and caused by the ICVR, it regulates the voltage and amps using pulses.

 

The sending unit is a grounding type of sensor, so there will be "power" going to the sending unit. Like the others have said, the ICVR supplies a constant current to the guages, the voltage will change depending on current loading.

Watch your other guages and if they are wandering up and down all at the same rate, that means the ICVR is bad.

One way to find out if the fuel guage is working, is by grounding the sending unit wire and see what the guage does. I think with fuel guage wire grounded, the fuel guage will read empty, open wire full(brain farting on this, I know the 87 and up are the oppiset but can't rember)

 

Fuel Gauge wire Grounded, it will read beyond full.

Open it will read below empty.

 

I connected the "blinking" wire (yellow w/blue) to the sending unit.

First try, the gauge went to full, even though tank only had 3 gal. Powered off, checked wiring to the in-tank pump, found those wires reversed. duh..

I corrected that error, the pump still works, but the gauge never moved again. I still have blinking power to the sending unit wire, all the way up to the tank connector.

Other threads today have explained how to check the gauge by grounding the sending unit wire. I'll try that procedure tomorrow.

Thanks again for the help.

 

Grounded the sending unit wire, gauge pegs above Full.
Thanks again for that tip.

I know the float is floating.

Guess the sending unit is broken.. Any fixes there, or just swap it? The unit had been sitting in old gas for a while I guess, the brown yellow funk corroded on it. Smells badly of stale gas.

Does not seem likely to find just that part new <?>, so it means swapping the whole pump and sending unit assembly?

Hunting the boneyard for speedo cable anyway, so we'll see if there's another F-series donor.

 

My 85 F 350 is staying on E, when I know it has a full tank.

solutions please?

Thanks

 

Please start your own thread instead of hijacking this guy's.

 

there is a tee fitting on the fuel line by the carb, this is part of the hot fuel system make sure the PO didn't remove this.the smaller line is a return line with a .0045 orfice in it,with out this return line your intank pump will over heat and burn out.that return line allows cool fuel to cool the pump,because the pump runs constantly.

 

i'll get a pic as soon as it up loads in my photobucket account