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Discussion Starter #1
Hello

Need to replace the sending unit on my 70. Multiple manufacturers produce them but I read reviews where some are not worth the problem of installing-failing quickly or ohms not correct so gauge doesn't work, etc. Many of the reviews were old however. Which sending unit have you used recently with success? Only want to drop the tank once and install a reliable sending unit.

Thank you in advance.
 

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I have used the ones from Classic Ind on a couple of cars with no problem, just measure your fuel line so you know what size it is , so you get the right one, it's either 5/16" or 3/8". I just use an openend wrench and see which one fits over the line. Very easy to change
 

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Discussion Starter #4
Thanks firebird and sudden for reply.

I only saw 3/8" listed for a 70. I will check my line before buying.

90 ohms is what is needed for guage to register correctly?
 

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Thanks firebird and sudden for reply.

I only saw 3/8" listed for a 70. I will check my line before buying.

90 ohms is what is needed for guage to register correctly?
Using your stock gauge? If yes, then yes, 90 ohms (full tank). If using aftermarket, check with gauge manuufacturer to be 100% sure.
As sudden suggested, ensure you sweep before you install to be sure of proper operation.

In the event you're not sure of a method to do so, simply hook-up a Volt/Ohmeter's red lead up to the fuel sender's "pin" (where the car's fuel sender wire connects to the sender) and the black meter lead to the fuel sender's ground (black) lead. Set meter on the 200 Ohms Range (or anything above 100 ohms and less than 200 ohms) and manipulate the float up and down s-l-o-w-l-y and don't over do it. Give the meter a chance if digital readout type. With float in highest position, expect a 90 Ohm result. Lowering it slowly should reflect a decreasing resistance value until it bottoms out (0 Ohms).

Another way would be to connect both Fuel sender leads to the appropriate wiring on the car, get wifey off the couch to watch the Fuel Gauge while you turn key to ON position and manipulate float up and down. Your fuel gauge will reflect the change - Again, do it slowly to allow the gauge to react appropriately. Instruction of how and what a fuel gauge is will depend on your particular "wifey".
 

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Thanks firebird and sudden for reply.

I only saw 3/8" listed for a 70. I will check my line before buying.

90 ohms is what is needed for guage to register correctly?

Here is the 5/16" one from classic, I just put this in my son's 68, worked good.



.
 

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Discussion Starter #7
thanks firebird. I just checked my line its 5/16. Strange i saw on right stuff website that 5/16 fuel line is for a six cylinder. Mine nova born a 307.
 

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Hello

Need to replace the sending unit on my 70.

Only want to drop the tank once and install a reliable sending unit.

Thank you in advance.
Have you done any tests to verify that the issue is just with the sending unit ?. Sometimes the two tests of ungrounding the gauges sender wire and then grounding it can give one a false positive and ideally the gauge needs to be tested with some specific value resistors to mimic the sender positions.

Jim
 

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Discussion Starter #12
Thanks for the replies guys

Jim - i tested the gauge at the tan power lead in the trunk. Can get it to swing from e-f by grounding it out.

Went under car and cleaned the ground wire body connection to bare metal and still got just a past full reading.

Next I went with a jumper wire from the ground block on the sending unit to the negative on my battery and still get a past full reading on the gauge. Whether the sending unit ground wire was connected or not no difference.

That was the extent of my testing did I miss anything?
 

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Watch this. It's about testing using my 68:


Like I said with the two tests you have done you "could" get a false positive. I had this problem from not testing enough with a guy that came over to my house years ago and we then figured out he had a sender issue AND a gauge issue.He just did the basic testing with grounding and ungrounding the sender wire. I too years ago thought the two tests were enough but have since found out differently.

Also do a search on the site as I have talked a LOT about testing things. I just don't want someone to think "just" a sending unit is the problem only to have other issues right after that and then start forgetting how the system works. The fuel gauge system is very basic but is has a few parts that all have to work in unison.

Jim
 

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Hello

Need to replace the sending unit on my 70. Multiple manufacturers produce them but I read reviews where some are not worth the problem of installing-failing quickly or ohms not correct so gauge doesn't work, etc. Many of the reviews were old however. Which sending unit have you used recently with success? Only want to drop the tank once and install a reliable sending unit.

Thank you in advance.
I used the sending unit from ground up ss396 on my 71 last year and it works great.
 

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Discussion Starter #16
I am glad to hear that Rush. From testing I believe its time to replace the unit and that is the one I purchased. Waiting for it to arrive.
 

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Discussion Starter #17
update

The fuel sending unit was bad, replaced it yesterday with new from ground up and gauge works like as it was intended.
quick note for anyone purchasing this sending unit, the fuel line needed a little re bending in my case to fit correctly. but I think most us are expecting this from repro parts
 
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