Fuel Sending unit

[JJSZABO]

Here is a problem I ran into - letting you know so you don't do the same thing.


I installed a new gas tank on the drivers side when I restored the frame.  I went ahead and installed a new GM 90ohm fuel sending unit for the drivers side.  When I was restoring the bed, I bought a new bed that had a fuel fill hole on the passenger side.  So......knowing the tanks are interchangable, I removed the tank from the drivers side and installed it on the passenger side.  I turned the fuel sending unit around so the three pipe are facing in toward the interior of the truck.   

Now the problem:  When I installed the Dokota digital gauges, and had everthing working, I put fuel into the tank and my son is now driving the truck around.  The fuel gauge is reading only 31% when the tank is full.  Once the gas drops below 31% the gauge works fine.  I think the float for the sending unit is hitting the side of the tank.  I think I have to buy a sending unit specifically for the passenger side.  I have good ground to the sending unit so, I do not know what else it might be.

Any other suggestions or do I have to drop the tank?

[Captkaos]

I would have to agree, sending units are specific left vs right.

[VileZambonie]

I don't recall anything being in the way of the float arm in either direction. I'm pretty sure I reversed mine on my 74 but I can't remember for sure if I did.

[JJSZABO]

Thinking about this some more .......

Here is a picture of the drivers side fuel sending unit:


When I reversed the sending unit - the float should be facing the rear of the tank.  Therefore, the float should not be hitting anything.  I need to start diagnosing with my multimeter to figure this out.  I am going to check the ohm output of the sending unit at the unit itself.  Then check again to see if I have good ground. 

I want to make sure the Dakota Digital guage is reading properly.  Hopefully, I wont have to drop the tank.

[ccz145a]

Just something to add. With the float facing the opposite direction the "slosh" effect is going to be worse. Since the float was designed to sit in the middle of the tank and now it's offset. But, this is the least of your worries, need to get it working first.

[JJSZABO]

Good point ccz.

I was thinking of reversing it around again so the outlets are pointing outward and using longer fuel hoses.  That way the sending unit is facing the correct way.  But before that, I need to find the reason for the incorrect reading.

Thanks for the replys guys

[gmtech2]

you may not have the correct ohm sending unit. some aftermarket gauges use their own sending units, you can unhook the wire at the sending unit and connect it to a potentiometer and then to ground and change the resistance, this would check to make sure your gauge works correctly. if you put an ohm meter in line with the potentiometer you will know what your full level on your gauge needs for ohms and what empty is then check to see if it matches your sending unit

[JJSZABO]

Gmtech2 Thanks for the reply.

When I received the new sender I checked it with an ohm meter.  When I moved the float manually I read 90ohms at full and 0 ohms at empty.  I programmed the Dikota Digital gauge set to read GM 90 as there are many choices (for GM there is 30, 90 and 120).

Is that correct to have a 90 ohm sender?

Where would I get a potentionmeter?

[gmtech2]

that should be correct. i guess you will have to check to make sure your float isnt hitting anything. Double check your ground to! hope this helps

[Captkaos]

it is 0-90ohm.  Did the gauge ever read correctly?

[JJSZABO]

I don't know - the DD gauges are new and only hooked to this new fuel sending unit.  The old fuel sending until didn't read at all when I took it out and the mechanical stock fuel gauge was broke.