fuel gauge sender leak

[Mark H.]

The fuel gauge on my ’64 stopped working the other day (stuck on ¾ full of all things – not a symptom I saw described in the shop manual) so I went to check the electrical connections at the sender tonight. I found that the connections were ever so slightly damp and smelled of fuel. It does not appear to be leaking from the lock ring – the wetness appears to be seeping from one of the connectors – the one with the nut under it. The sender was new a couple of years ago (high price American unit). Has anyone ever encountered this? Do I dare try to tighten the nut under the connector? Of course, I just filled the tank. I’ve never noticed a drip under the car, so it is an extremely slow leak. But, since it’s fuel, I am a little scared to just ignore it (or even drive it). Drain the tank and pull the sending unit?

[Joe L.]

Re: fuel gauge sender leak

Mark------

Tighten the nut and I think the leak will be done with. DON'T hog it down, though! Just gently tighten it with a small open end wrench. I think that you will find that it's slightly loose.

[Gerard F.]

Re: fuel gauge sender leak

Mark,

I had the same thing on my 67 with a new gas gage stuck on 3/4 tank, but no leak. You can try tightening the sender to fix the leak but I doubt that that will work as there is a stop in mounting nut mechanism whereby you can only tighten it so far. The washer between the tank and the sensor is a big O-ring.

Fixing the leak is probably not going to fix the sender. I found that one of the leads to the variable resistor on the sending unit within the tank was actually broken off.

There is a thread in the archives on testing the sender in May of 2002. You can test the sending unit on the car by disconnecting all 3 leads (tan, pink or lt green, and black(ground). Put an ohm-meter between the two non-grounded terminals. Then move the float within the tank. The meter should read around 90 ohms when the tank is full and 0 ohms when the tank is empty. If the meter stays steady or moves in the opposite direction (like mine), you have a bad sending unit.

Changing the sending unit is really not hard at all. Get a replacement unit complete with the washer, new nut, and the special nut wrench. Also get a new flexible fuel line and clips from the sender to the steel fuel line, as you never know what the condition of that line will be once you take it off.

Take a long drive and get the tank down to less then 5 gallons. Then siphon the rest out into a 5 gallon gas can until the tank looks empty. You have to remove the top part of the tire carrier for working room around the sender. Disconnect the flexible fuel line at the sender and drain the remaining fuel in the tank and fuel lines into a pan.

Then with the special nut wrench turn the nut on the sender counterclockwise.
It's less then a quarter turn and I was surprised how easy it was to loosen. Then manipulate the sender out of the tank, no force.

Once you remove the sender, I think you can figure out how to put the new one in, it only goes in only one way. The electrical connectors should be all different sizes and types, so you can't make a mistake in reconnecting.

I was really afraid to screw around with the gas tank, and now I laugh at how easy it was, while my fuel gage works perfectly now.

Jerry Fuccillo
#42179

[Gerard F.]

Re: fuel gauge, also

Also Mark,

If you get a new sender unit, you can test your fuel gage before you put the sender unit in the tank. Just connect up the leads outside the car and turn the ignition on. With the float up, the gage should read full, with it down, empty.

If this doesn't work the problem is with the gage or the wiring.

Changing the sender unit is really easy. My wife will testify that she didn't hear one expletive m/f coming out from under the car. Changing the gage is a different story, as you have to pull the whole dash instrument panel to get to the gage. This created a trip to the chiropractor and many expletive m/f's for me.

Jerry Fuccillo
#42179

[Joe R.]

Re: fuel gauge, also

Mark,

I'll agree with Joe that you might get lucky and by tightening the nut just ever so snug you may fix your leak. Cleaning the plugs of the gas, dirt and oily substance just may fix your gauge problem.

Jerry had some good advice but just didn't read your post very carefully. Good luck with the sending unit. If it's the expensive Delco unit you should have no problem but if it's the cheap China imported one, just chunk it and get a real Delco unit. Most of the Delco units have lasted better than 30 years so one Delco at a higher price is a good investment.

Regards,

JR

[Gerard F.]

Oh, yea!

I guess I didn't read Mark's post carefully about the terminal nut, so I checked the sender that I took out. Under each of the two terminal nuts, is a washer, and then an insulating spacer. Under the spacer is a little rubber gasket or grommet for leakproofing. If the nut was loose, the terminal would tend to leak, tightening the nut could correct the problem. Dirt or gas on the terminal could effect the reading on the gas gage or lock it into a stationary position. (It should be noted that after I blew enough fuses with mine, I completely disconnected the sender and the gage stayed on 3/4 full)

So Mark, you might save some money and time by following Joe's and JR's advice.

Jerry Fuccillo
#42179

[Mark H.]

Re: Oh, yea!

I snugged the nuts under the terminals up a little, cleaned the contacts up a bit, applied dilectric grease and put back together. I need to watch for a while to see if there is any more seepage (so far, so good) and drive a bit tomorrow to see if the gauge reads properly (with a very full tank it is now pegged full). Thanks for the suggestions.

Mark