The Stovebolt Site Forums The Shop Area The Electrical Bay Gas tank sending unit

I read the other threads I found in the search but was unable to answer my question.

My gas gauge was working intermittently, I mean very seldom did it read anything other than empty. So, I purchased a new unit from Classicparts.com. I switched the new one in for the old one and Nothing! ok, so I attached a ground from the floor to the top of the sending unit and it read a little over full, maybe 3/4 of a tank. When I was replacing the sender I saw there was about a 3/4 of a tank of gas. I figure GREAT! I fixed it. NOPE.

So I drive to the gas station to after I thought I did a good job, to fill the tank. Fill'er up and the gas gauge reads the same as before.

The gauge I put in was a 30 ohm unit, not sure what the one I took out was, but I figure it didn't much matter cause it didn't work.

These things are so simple- could I have the wires switched? wrong ohms on the sender?

Thanks for the help in advance.

There are 5 machine screws holding the sending unit down, and unlike modern units, the angles between the 5 units are all exactly the same. So it is possible to get the sender turned so that the float makes contact with the side of the tank and gets stuck there. I would check that first.

Also, with my stock sending unit, the float would make contact with the floor of the tank. This means I would always run out of gas with an eighth of a tank still showing on the fuel gauge. The float should NEVER touch the bottom of the tank, so make sure you check that too.

I'm going to have to disagree with Hot Rod Dad. The 30 ohm sending unit hole spacing is not the same for all of the fasteners. The sending unit will only go in one way. By appearance they look the same but they aren't. There's enough difference to keep you from getting it in wrong. A 6" scale and two minutes measuring will prove it.

I guess the first thing I would check is the ohm range the sending unit shows from the empty position to the full position. It should read close to 0 @ empty and close to 30 ohms @ the full position. If that reads correct and you have a 30 ohm gauge that you know works check your wiring again. Good luck.

There is a ton of information on this problem if you will do a search. Why don't you see what your gauge wants by putting a variable resistor in place of your sender? This will tell you, one...your gauge is working, and two...what your sender needs to be sending to the gauge.

I'll try to get back out to the garage tonight and see whats going on... Then let you know what I find.

Thanks guys.

Here's a guy in KS who is an electrical wizard, it might not answer your question, but he gives tons of info on diagnosing your problems

http://www.fifthaveinternetgarage.com/tech_tips/tech_tips_gas_gauge.html

Thank you. That info makes good sense and I will use it to help diagnose my problem. Sounds like the first thing to check is my grounds...