Fuel tank sending unit

[WPVT]

This general topic has been covered in other threads, but before I remove my fuel tank to repair the sending unit, I thought I would describe the situation to see if anyone had experienced a similar problem.

My truck is a 1954 1/2 ton. The fuel gauge doesn't work at all until the tank is almost empty, at which point the needle swings wildly from left to right. This happens very dependably...it's not erratic. A nice feature to get one's attention, but I'd prefer that it worked conventionally. My cab floor access panel does not line up with the opening on the tank, so servicing the sending unit means dropping the tank. 

Has anyone had that specific malfunction ? It seems to me that the wiring and ground must be OK, and that the problem must be the unit itself. 

[TodFitch]

Sounds to me like the sending unit. The original style had resistive wire wound around a form and the wiper, connected to the float, moved across the wires to produce a resistance proportional to the float position. That wire is worn by the wiper and often breaks. If/when that wire breaks you get readings like what you describe.

 

The fortunate thing, at least on the car side, is that a pretty standard set of resistance values was used starting in the 1950s so getting a replacement shouldn’t be too hard. For the early 1930s single wire senders the resistance range is not one that is standard nowadays to the options are a bit more limited.

[bkahler]

DCM Classics has replacement sending units.  I think they have two styles, original and a modern conversion.  I opted for the modern conversion for my truck.  It was a drop in replacement.  

 

Brad

[wallytoo]

i used a unit for an 80s jeep wagoneer.  modified the arm by cutting it in the middle, using a paint can bail, straightened, and soldered between the two ends of the arm.  it has worked excellent for over 10 years now.

[bkahler]

That was a good solution to the sending unit problem.

[wallytoo]

1 hour ago, bkahler said:

That was a good solution to the sending unit problem.

 

yeah, i looked for a unit that had roughly the same resistance range as the original, in the correct order, ie, low resistance full/high resistance empty.  don't remember which it was , but the range of the wagoneer unit was 78 to 10 ohms, which is very close to the original dodge unit.  and, i purchased it for less than $40 brand new, vs the dodge remakes/nos that wanted $150 or more at the time.

 

i just added enough "bail" in the center of the new unit to match the length of the original unit from the tank, and positioned the float accordingly.  and rather than trying to join the ends, i used about 2 to 3 inches of overlap at each end to solder things together.

Edited November 3, 2020 by wallytoo

[MBF]

W2. Do you have a p/n for this unit.?  What year Wagoneer?   Thanks.  Mike

[wallytoo]

2 hours ago, MBFowler said:

W2. Do you have a p/n for this unit.?  What year Wagoneer?   Thanks.  Mike

 

i dug out my files.  i do.  from crown automotive.  jeep 5361468.  paid $30.88.

 

70 to 79 wagoneer.

Edited November 3, 2020 by wallytoo

[1949 Wraith]

Is your truck still 6 volt? If it has been converted to 12 volts have you checked your reducer?

[WPVT]

Still 6 volt. Pretty much all original, low miles.

I'll remove the tank this week and pull the ailing sending unit.

[Classic Moose]

I've found replacements at Tanks inc. for less money than some of the vendors. think they may buy then there themselves 

[MBF]

Thanks W2 for the info