other 1969 Fuel Sender - Repair?

[vtglenn]

Is the fuel sender on these units repairable or shall I pop one out of a parts car?  I can barely see through the screen but that might be normal guess I.

Yard car runs nice with fuel line in tank, but have to prime carb through interesting hole in float chamber!

 

 

Thanks!

[Beaner7102]

Yes they are repairable, depending on the level of damage inside.

Remove the sender from the tank, pop the screen off the bottom (leave that to soak in carb cleaner or POR-15 Marine Clean for about 24hrs).

There is a tiny nut on the bottom of the sender, undo that to slide the tube off, exposing the inner workings. 

 

Check that the very thin resistor wire (thin as hair) is still conected from bottom to top on both sides and the float is still making contact with the wire.

If the thin wire is broken at one end it can be re soldered back. But if its broken in the middle I think its toast - unless you can replace the whole wire with a new one of the correct resistance.

 

Re assemble and test before putting back in to the tank (fit wires, hold upside down - gauge should read full, hold right side up - should read empty). 

The sender can also be checked without removal with an ohm meter across its terminals. A full tank should read below 10 ohms and an empty tank should read about 70 ohms. An open circuit or high resistance would indicate a sensor defect

 

Also, If you need to prime the carb to get it to run, you have a small leak in the mechanical fuel pump

 

I fixed a sender that I was sure was dead, the wire inside was like a birds nest and it took an hour to untangle it. But its been great for 7 years now. Have a good look before going to other options. 

 

HTH Beaner7102

Edited October 3, 2013 by Beaner7102

[vtglenn]

OK. Yes, I have to prime the carb to get things running, but it will not run with the sender unit in place. But it runs fine with a hose lying in the tank through the sender hole. So just to clarify;

• the fuel sensor works and all the gauges work (no bad grounds!)
• is there a check valve in the sending unit? My shop manual is glued together from the weather at the fuel section (and others also) Is there a diagram of this unit online anywhere?
• I will check the fuel pump, but it seems to put out a pretty good stream
• Is there a bench test for the fuel flow?

Thanks!

[Mike Self]

Sounds like the screen at the bottom of the sender/fuel pickup is thoroughly plugged up, and has possibly plugged up the fuel pickup pipe too.  As has been pointed out, remove the screen from the bottom and clean it thoroughly, Look up inside the aluminum tube (or remove it--just be VERY careful around that resistance wire; it really is hair thin) to make sure there's no residual gunk up in there.  And blow through the pipe to make sure it's clear. 

 

Also--make sure the hose that connects the pickup pipe to the plastic fuel line in the trunk isn't all cracked and crappy.  A mechanical pump won't suck fuel if it can suck air through a cracked or porous hose, and those old fabric-covered hoses are prone to cracking. 

 

The fact that the fuel pump draws with a hose stuck in the gas tank but not through the sender/pickup indicates the problem is in the sender/pickup or the connector hose. 

 

cheers

mike