'66 Fuel Gauge - Works Sometimes

[Mark]

Here's a puzzle that I'm trying to figure out....my fuel gauge recently started working after the car was stored for a long period of time, but only intermittantly. It reads full, but every time I accelerate hard, the needle drops from full down to 12, then it returns to full when I ease up. By the way, the tank is completely full when this happens, so I can't think that it's the "slosh" factor. Any ideas?

Thanks for the help,
Mark

[Gerard F.]

Re: '66 Fuel Gauge - Works Sometimes

Mark,

You could try cleaning off the terminals at the sender, especially the ground terminal and connector. The usual is that the ground connection is bad and the gage will stick on half full and then stay there, then operate between 1/2 and empty. Also check if there is any moisture or fuel dripping at the sender.

But in your case, where it comes right back up after the hard accelleration, I would suspect a voltage fluctuation, either high or low, when you stomp on it.
If it it operates normally when you are driving normally, it is probably some anomally in your electrical system when you hit it hard.

You might try rigging a voltmeter in the compartment and see what the voltage is doing when you step on it. I use a volticator which plugs into the cigar lighter to check the operation of the voltage regulator. Maybe it is just a simple voltage regulator adjustment.

Too bad Jack Humphrey is in Europe, he'd be the guy to answer your question. In his absence, I'm just filling in and guessing at the electrical questions.

Jerry Fuccillo
#42179

[Mark P.]

Re: '66 Fuel Gauge - Works Sometimes

I'm pretty sure that it is something amiss in the electrical system. There's nothing dripping and the wiring all looks okay. The fuse panel looks a bit corroded (as was the under hood harness that I already replaced), so I 'll start there and make sure all of my connections are good. As stated in another post, this car has a few other electrical issues that need attention, including the voltage gauge, no glove box or interior lights, etc. Recently, from starting to drive the car again, several things have started to work again, so I'm optimistic about it being a minor issue.

Thanks for the info.
Mark

[Gerard F.]

Re: '66 Fuel Gauge - Works Sometimes

Mark,

I was thinking that maybe the problem is in the float arm bending forward and aft, when you hit it hard. This could maybe cause the contact point to give a momentary poor connection against the variable resistor in the sender and give you a false reading. If the gage comes back and operates OK when you are not doing wheelies, then that could be it.

Or it is a loose connection someplace which goes south with inertial force on it.

Is the sender the original type, or one of those cheap repros. I had a repro in that only lasted less then a year. Went back to my repaired original. It sometimes acts funny when the tank is topped off full.

Jerry Fuccillo
#42179

[Mark P.]

Re: '66 Fuel Gauge - Works Sometimes

I haven't replaced it, but it may have been replaced by the previous owner. Is there a sure way to tell? I happen to have one of those "cheap repro units" on my shelf that I hesitate to install on a car. I've had it for a couple of years (don't ask me why) but can't bring myself to put it in.

I drove it last night and it wasn't working again...it only reads half full and never goes below 1/2. I'll crawl under there tonight and check external connections. In my '65, I had the same problem...stuck on 1/2 full until I manually moved the sending unit arm up and down and got it to work. It was just stuck. I don't know that I'll be so lucky this time.

Mark

[Gerard F.]

Re: '66 Fuel Gauge - Works Sometimes

Mark,

Take a look at this thread for the difference in original vs imported replacements:

https://www.ncrs.org/forum/archive23.cgi?review=191075

If the gauge doesn't go below 1/2, it is probably a poor connection or break in the pink (or light green) wire at the sender.

There is also lots of stuff in the archives under "gas sending unit" or "fuel gauge" in the archives, including an on the car test. Just do a search (2002-2005).

Jerry Fuccillo
#42179

[Mark P.]

Re: '66 Fuel Gauge - Works Sometimes

Thanks, Jerry. Good info for someone stumbling in the dark....

[Gerard F.]

Here's another one with the test

https://www.ncrs.org/forum/archive19.cgi?review=151025

Jerry Fuccillo