Fuel Tank Sending Unit Rebuild ?

[MadOgre]

What is involved in refurbishing an existing Sending Unit vs buying a refurbished one ?

I am a cheap ass so I would like to do it my self rather than spend $2-300 on replacement ones.

I got a line on 2 tanks with straps, hoses, caps and 3 outlet sending units. They have sat for years though but are in good shape other than a 1/4 tank of some old fuel in them.

I have been looking for the 3 outlets to upgrade the 2 outlet diesels that I am currently using on my gas 350. This way I can vent with the 3rd outlet.

I was planning on getting some Marine Clean and giving them a good cleaning.

Just wondering what is involved in ensuring that the sending units are in good working order ?

 

[marks86]

I just checked rockauto they range from $27-$125

id just buy a 50dollar one from rock auto and be done with it

 

[kleedus]

i just bought a 87 fuel injected sending unit from rock auto its a nice unit was priced good as well

but i found a 87 tank on ebay free shipping cheaper than rock auto with shipping

so i would check ebay for prices

 

[MadOgre]

I am more curious as to what exactly is involved in making a sending unit be in top shape ?

What exactly becomes the problem with old sending units ?

 

[foamypirate]

The bronze in the tank level sender that the arm rotates on can get corroded causing a bad fuel gauge reading. You can usually clean them up with a pencil eraser.

 

[MadOgre]

Pencil Eraser?

 

[kleedus]

kinda like the old school slot cars rub the eraser on the contacts it cleans the crud off of them

dam it now I am going to have to break out my slot car track

 

[chengny]

Basically, the fundamental component of these senders is wire wound variable resistor. The value of the resistance changes (in GM's case, it varies from 0 - 90 ohms) according to the location of a conductor arm that pivots on one end, and slides up and down the wire coil at the other. They look something like these images:

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It's position on the coil is a function of the level in the tank and is controlled by a float that is connected to the arm - at the pivot end - by linkage.

There are three basic things that can affect the accuracy of the sender (when I say that, I mean internally. Lots of things can - and do - go wrong with the associated external wiring):

1. As mentioned above, oxidation/corrosion can build up on the surface of the wire coil (and the tip of the arm where it slides along and maintains electrical contact). This increases the apparent resistance and will cause a low tank indication. The pencil eraser is as good a cleaning method as any. Just don't rub across the grain of the fine wires that make up the coil. The tip of the arm can be polished up with some fine emery (like 1000 grit).

2. The pressure between the tip of the arm and the wires that make up the coil can be lost due to the wear and tear of years of sliding across each other. This - although for a different reason will also cause increased resistance. The required pressure at the interface can be restored by simply bending the arm down toward to coil.

3. The pivot point at the linkage end of the arm can become sloppy (again due to years of constant motion). This one is not so easy to fix (what are you going to do? Bore and bush the housing and arm pivot?) On the other hand it will probably only result in momentarily inaccurate tank level readings. To fix this, stop driving over big bumps. The gas will cease sloshing around in the tank and the gauge will read true again.

 

[MadOgre]

Thanks Jerry. So aside from worn pivot points they can be refurbished ?

 

[chengny]

Thanks Jerry. So aside from worn pivot points they can be refurbished ?

Yeah, I'd say so. Provided you can get them open. They are not complicated pieces of equipment - you'll be all over it.

 

[MadOgre]

Right on cause $80 for 2 tanks, straps, brackets, sending units hoses and caps is a lot better then going new for all the stuff. I guess even if the senders could not be refurbished it would still be worth it.

 

[MadOgre]

A new tank here is $165