DFitz

Ok, I need some advice. I've been driving it for a bout a week, since a 15 year layoff. Runs great, in fact getting better the more I drive it. Better idle, and much better cold. Transmission is also getting better but still leaks badly. Complete brake and wheel bearing rebuild seems good.

My gas gage seems stuck on full since driving it again. The fuel system was gummed up before I worked on it. Should I give it more time with a full tank, or am I looking at a sending unit? To tell the truth, I can't remember if it ever worked. Need advice.

Tank is clean and was drained with gas changed. No rust inside.

12 MPG on a Saturday 75 mile trip. Original 324 Rocket, 2-barrel.

oldcutlass

If there was gas sitting in there for 15 years and all you did was drain it from the drain on the bottom, then there is a good chance it is full of varnish and crud. You can check the operation of the gauge and wiring if you remove the wire from tank to the gauge and ground it. If it goes to empty then your sender has an issue.

DFitz

Ok, I stored the car with the tank full to prevent precisely that. Little air, no corrosion, no crud, no varnish. When drained, yes the gas had turned, but it was clean, and no crud.

I'll bite, what should I have done or should I do? I was also hoping for some one with experience on failure modes when the gage stays on full for a recommendation before I dig into it....

I will try the lead idea. I do think the gage and wiring is ok. The car is in pretty good shape and has always been garaged.

jaunty75

The gauge is just an ohm meter. High resistance (90 ohms was typical) puts it on full, zero resistance puts it on empty. Pegging at full and staying there is a common failure mode of gas gauges, and, as oldcutlass says, proper troubleshooting begins with checking the wiring as an open in the wire between the gauge and the sending unit or a bad ground can cause the symptom you observe.

Check the wiring coming from the sending unit and make sure the wire that should be grounded really is attached to the frame and that the connection is clean and tight. If this checks out and the gauge still doesn't work, disconnect the wire coming from the front of the car where it attaches to the wire coming from the sending unit and ground the side coming from the gauge. With the key ON, the gauge should immediately go to E. If it does this, the dash gauge is fine, and the problem is likely the sending unit itself. But at least you will have ruled out the easier-to-get-at possible causes first.

oldcutlass

What happens in the tank even though the fuel coming out looks clear, there is sometimes a large gunk buildup around the sender. I run into this all the time bringing cars back from the dead that have been sitting for a long period of time. If you pulled the tank and sender to insure everything was clean then your all good. Perform the troubleshooting technique that Jaunty and I gave you above and see where your trouble lies.

Olds Dad

These are grounded to the body via the steel line from the sender.

If a portion of that line has been replaced with rubber, the ground is gone.

I suspect if there is rust / dirt at the point (clip) where it first attaches to the car, same thing.

I had the same problem with mine (guage pegged full) - I ran a ground wire from one of the sending unit mounting screws and throught the grommet into the trunk and grounded it inside the trunk.

Works perfect.

Just my 2 cents

jaunty75

Thanks. What I described above was what I found when dealing with a gas gauge issue with my '67 Delta 88. I kind of wondered if the wiring was done the same way a decade earlier. Apparently not completely!

Olds Dad

I found this out the hard way...gage worked - took the tank out to replace the tank - reinstalled with old sender but a 6" piece of rubber hose off the sender to replace a kinked piece - and voila..pegged full...

Had to drop the tank again and do the ground wire...

Pain in the backside, but lesson learned.

DFitz

Excellent, this is exactly what I needed to look into it guys. Thanks. Now I have to jack it up again. It's been spending more time in the air than on the ground.

Progress today, new brake system adjusted after pad wear in, finished final brake bleed, fixed the horn insulator and the horn works for the first time in 25 years. Added seat belts, what a pain. Balanced tires. Doesn't shake down the road anymore. Got new speakers today, it'll have to wait till next week. Radio should be back on Sun. Now I just have to find where I put the antenna.

I have to paint new kick panels, went to get paint for that and hat shelf. Need to do that before I put in new speakers.

The kids are astounded. I let them eat in the car, drive it and park in normal spots. I figure it's survived this long, treat it like a regular car. Besides, it will eventually get new paint and interior. Having some fun with it as a daily driver. However, 12 Mpg does suck. It's nice, no one gets in my way....all they see is that massive chrome bumper coming at them, and no problems!

oldcutlass

Mine gets 6-8 mpg, feel better?

DFitz

Wow, mine gets almost twice the mileage!! Yipee!!

oldcutlass

Ahhhhhhhhhhh, my good deed for today!

DFitz

So,....after reading the manual, I presume there is no way to access the fuel sender without dropping the tank?

I hate draining the fuel. It would have been way too easy for an access hatch in the trunk floor.

Olds Dad

Get yer buckets out :/

At least these have drain plugs - unlike modern cars

DFitz

I see lots of fun to be had for the weekend.

DFitz

I was right! Loads of fun. BTW, how do you drop the fuel tank on a '55? Exhaust is in the way on one side, and the filler neck doesn't have clearance on the inner fender well to pull down with the leaf spring in the way. Oh, and I broke both tank mounting bolts. Yeah, just loads of fun. The good news is the tank straps and the tank itself seem to be in pretty good shape. I did run it down as far as I dared without the gage, not knowing really how hungry this monster is--only 6 buckets of gas.

I figured out why the gage always went to full. Tested the wiring and gage, all good. However, the float was stuck on full! It was telling me exactly where the float was. So, I'm afraid that even if I work on the sending unit and clean it up, it will probably get stuck again. So off to donate more money to Fusick.

Olds Dad

I had to secure the car jack stands on the frame forward of the rear wheels to allow the rear axle to "Hang" thus opening up the springs more for more room...I also disconnected the rear tail pipe hanger to allow me to muscle it out of the way.

Forgot about that part of things

DFitz

Yeah, it's the little details. I did exactly that for the rear sway bar rubber and brake line. Stands under the rear end, then use my floor lift to lift the frame cross piece back by the rear bumper. Fusick has the fuel sender, but for some reason they don't have the bolts at the moment. I'll try my local Napa Auto parts to see if they have something close.

oldcutlass

Are the bolts anything special? If not take your old ones to a bolt store or fastener supply house and have them match them up.

DFitz

Thanks, good idea, and I may do that.

It's some type of J bolt. Right now I have no idea how common they are. Might be easy to get, might not. I'll know more this afternoon after I get to Napa. It is possible I could re-use the old bolts too.

I got the nuts about 1 width off, then the bolts broke. It would be tough to get the tank in position on short bolts but It might be possible, or I could just wait for Fusick.

oldcutlass

Did the sending unit have a bunch of crud on it?

DFitz

It did have some corrosion on it--no real crud, not bad though. However the major problem was that the bearing in the float arm seems mostly frozen. The float sticks where ever you put it. Not good. As I said, I could probably clean it up a bit, but not enough to be reliable again, and not have to pull the tank again.

The screen on the fuel pickup was clean as a whistle.

McMaster-Carr has a very close J-bolt to the tank hold down bolts. Close enough to use. Only $9 for a pair.

DFitz

Fuel sender replaced, tank remounted with J-bolts from Napa Auto parts. New sender from Fusick works great. I did add an extra ground wire to the frame for the future just in case. Thanks everyone for the suggestions.

Back on the road before the winter rains. Now working on a bit of the interior. New kick panels, painting those and the rear shelf to match. New speakers after that and reinstall the radio. A bit of work to lube the windows pulleys and cranks, door locks and latches. Plenty to do. Couldn't find what I did with the antenna so I have a new one from Fusick too.

98regency

Hey guys

I have another problem, but similar to this one First, is it normal, that the pointer of the fuel gauge is swinging from left to right when I drive the car? It's not much, just ~1/2" of way.
I thought it could be the sending unit of the tank and so I changed the unit this weekend, but didn't fixed the problem.
And if I put the ignition "OFF" the pinter stucks in the middle of the fuel gauge, but I think the pointer should go to "E".

Tedd Thompson

Mine goes to empty when the key is off, I can't imagine why it would read 1/2 tank with the key off unless for some reason the sender was getting some juice....Tedd

jaunty75

Fuel gauges are just ohmmeters. They only function when they have power going to them, meaning when the key is ON. Where a fuel gauge pointer ends up when the key is OFF is meaningless. It indicates nothing about the condition of the gauge and should be ignored.

98regency

Ok. Where the pointer ends is not the problem. The problem is the swinging pointer while driving. I already changed the sening unit. Could the fuel gauge itself be the problem? Or something with the wire?

jaunty75

This is the key point. What does the pointer do when you're NOT driving? If you're sitting in your driveway with the engine running and the car not moving, does the pointer steady out and give a reasonable indication of the amount of fuel in the tank? If so, then the pointer swinging around when driving is just normal behavior due to the sloshing of the fuel around inside the tank.

My guess is that the swinging is most pronounced when you go around corners or start up or stop at a signal light or stop sign, but that the pointer steadies out when you're going a constant speed on a flat road.

These gauges were never precision instruments. There are supposed be baffles in the tank to dampen the sloshing, but they don't stop it completely. If your gauge gives a reasonably accurate measure of the amount of fuel in your car's tank when the car is sitting still with the ignition on or when it's moving at a steady speed on a flat highway, there is nothing wrong with your fuel gauge/sender system, and you just have to live with the pointer moving around a bit.

What year car are we talking about, anyway?

98regency

When I'm sitting in the car with engine running the pointer doesn't move, but vibrate a little bit. Sometimes the pointer doesn't move when im driving, just how you said in corners, stop and go etc. and the pointer swings too much to give a reasonable indication :S
My workshop manual says, that little movement of the pointer is normal, but I think mine swings too much.
Tomorrow I'm going to make a video, so you can see it.

My car is a 1981 98.

jaunty75

That vibration is a little weird. In the end though, I think you're going to have to live with this. You'll show us the video, and we'll all go tsk, tsk, tsk, but what more can you do? You've already replaced the sender. The wiring wouldn't cause it to wave around, and the fact that it does move more when you go around corners and and start and stop suggests that the normal sloshing of the fuel is the cause. You can't stop the fuel from sloshing.

The only thing I can think of is to replace the sender again. Maybe the one you put in has too loose a mechanism or something like that.

98regency

I just compared with the mustang of my dad. HIs fuel gauge doesn't move anything! And it's very accurate. So i thought it's not normal on my car BUt I show you the video

98regency

So here's the video

jaunty75

It looks to be moving around in sync with the sloshing of gas on the tank, as we already surmised. As I said earlier, though, so what? Having seen the video doesn't give us any new insights as to what might be wrong, if anything is.

I agree that the gauge likely did not bounce around like this when the car was new. You say you changed the sending unit. It's possible the new one is defective. As much a pain in the neck it would be to do, it might be worth getting another new sending unit and putting it in.

What about the gas tank itself? Perhaps one of the baffles has come loose. Is the tank original? New tanks are available for this car.


Frankly, if it were me, so long as the "center of gravity" of the needle's wiggles moved in sync with the amount of fuel in the tank, I'd just live with it. No one stares at a gas gauge all day long. If the wiggling bothers you, then I'd try another sending unit.

jaunty75

One other comment is to ask if you've done the basic checks of the wiring between the sending unit and the gauge. You've had the sending unit out, so you know where the wires are. Disconnect the wire running from the gauge to the sending unit at the sending unit or at the connector if there is a connector in the wire somewhere between the gauge and the sending unit. Then attach the wire coming from the gauge to ground and turn the ignition to ON or just start the car. The pointer should immediately move to E and stay there. Then disconnect the wire from ground. The pointer should immediately move to F (or past it) and stay there. If the gauge passes these tests, then the gauge is OK and the wiring connecting it to the sending unit is OK. Then it's back to the problem being the sending unit.

redoldsman

I will tell you I don't have as lot of confidence in Fusicks sending unit. The one in my 54 is only a little over a year old and is already acting goofy. It wants to stay on full then drop to about 1/2 tank. Of course, there is no other choice. I will not change it again. I will just try and keep the tank full.

jaunty75

I doubt he (98regency) bought his sending unit at Fusick. I don't think they sell parts for 1981 models. rockauto.com shows availability of two versions (with and without fuel return) of Spectra Premium sending units. The same ones are shown on Autozone's website and probably any other parts supplier's website. Spectra Premium is a big supplier of aftermarket fuel tanks, sending units, etc. They're based in Canada.

http://www.spectrapremium.com/home.html

redoldsman

Jaunty

I think it says 55 model.

jaunty75

I wasn't sure who you were referring to as 98regency has sort of glommed on to this thread with the problems with the fuel gauge in his '81 98, and that's what the conversation has been most recently about.

98regency

Yes, the tank is original and on top nearly complete rusted trough. I think I'm changing the tank this winter.

I bought the sending unit on rockauto.com.
I'm going to check the wire as you said, but I think I have no other choice as to live with this dancing pointer
I just wanted to know how much of pointer movement is normal. The workshop manual says it's normal, but I can't imagine how much :S
You have to know, I've never seen this before, so I'm a little bit confused It's new for me and this is why I think it's wrong.

redoldsman

It looks like 98regency hijacked DFitz's thread. I doubt it was intentional but I don't know if DFitz ever got an answer.