View Full Version : fuel gauge problems

02-27-2001, 09:48 AM
My 71' ply valiant with only 39,000 orginal miles is having a fuel gauge problem. It didn't start until cold weather arrived and seems to work occassionaly with warmer temps. Had the same problem on my 64' valiant wagon. Doesn't make since to me but thought I'd ask. HELP PLEASE. and if I do need both, where should I look. THANKS RICKROW

02-27-2001, 07:49 PM
What is the problem that you are having?? Does it stay on E. Does it swing back and forth? Does it just stay in one place?

I can give you a better idea as to where to look, if I know all of the indications.

02-27-2001, 11:58 PM
Eholster, what is wrong if it is swinging back and forth. Curious. Have a car that does that.

02-28-2001, 08:25 AM
The gauge shows empty at all times.

02-28-2001, 09:52 AM
Snowman, Thanks for your help, going to try that, let U know how it works. RICROW

02-28-2001, 04:08 PM
If making up a good ground connection does not work for you, you may need a new tank sending unit. Two indications I have seen with my cars. The sending unit is just bad, in which case the gage stays at E with no movement. The other one I had was a cracked brass float on the end of the sending unit arm, which filled with gas and would give me a mostly empty tank indication, or it might come up to about 1/4 when the tank was full. In both cases, I replaced them with new ones from www.laysons.com. One more thing to mention; if the engine temp indication is not working, in addition to the fuel level indication, then the voltage limiter on the back of the instrument panel circuit board is bad. If the temp gage indication is working, then the gas tank sending unit, the gage, or the wiring is the problem. Good Luck!

02-28-2001, 04:16 PM
Rickrow - If you pull the connector at the tank and connect it to a good body ground, does it show full? If not, it is the body wiring, dash voltage regulator, or the guage.

If it soes go to full, then it is either missing the ground strap that connects from the fuel sender to the metal fuel line (or it could have high resistance due to corrosion).

dartnround - For one that is swinging, I would suspect a faulty dash voltage regulator or the sender has come apart or is very loose.

03-06-2001, 08:11 AM
do u have to drop the tank to get to the goundi wire?

03-06-2001, 10:45 AM
The ground strap is on the outside of the tank. Crawl under the car and look at the fuel sender. You will see the metal fuel line (coming from the engine) connected to a short rubber hose. The other end of the rubber hose is connected to the outlet tube of the fuel sender. The ground strap connects from the metal fuel outlet tube to the metal fuel line and rests on the rubber fuel hose. The fuel sender gets its ground from the metal fuel line via this ground strap.

If the strap is missing, a new one can be bought from The Paddock. If it is in place, you can take it off and clean it with a piece of emery cloth (or VF sandpaper) and then clean the outlet tube and the metal fuel line as well.

03-07-2001, 04:42 AM
I've got a problem with my guage too! I fill it up and it sits on 3/4 tank. and then it drops like normal. it's wierd but nuthin big. I don't think it's sticking or something because it drops right when I start driving it.

My old car used to sit on E. we tried everything on it and the funny thing is that one day I bumped the wire that went to the sending unit and it started working! I guess it just shifted the right way. never had a problem with it again! :)

03-07-2001, 08:21 AM
I'm going to run a seperate wire directly to the negative side of the battery just to make sure it's not the ground strap that goes to the tank. My ground strap is coated with undercoating spray which might b causing my bad ground. Also I noticed while I was under the car that the fuel sender is accessible without taking the tank off. I also noticed that the one end of my grounding strap isn't in the proper grounding location where I've been told it should be, I'm changing that too, I'll let U know what happens.

03-07-2001, 12:44 PM
Rickrow - have you tried the simple test yet?? what was the result??

Originally posted by ehostler
Rickrow - If you pull the connector at the tank and connect it to a good body ground, does it show full? If not, it is the body wiring, dash voltage regulator, or the guage.

03-07-2001, 04:24 PM
does the ign. have to be on or not? Off the top of my head, I would say yes but not for sure.

03-07-2001, 07:16 PM
I put a new ground wire from the sending unit to the frame and the gauge did move. It was way below the empty mark to the E. When I put the new ground wire on it, it went to the first mark nearst E. I have to put gas in my tank because I'm not sure how much was in there. I did put the sending wire to ground b4 I did that and nothing happened to the gauge, it stayed on E. Get back to U tomorrow for the results. Thanks for all the help everyone.

03-08-2001, 08:36 AM
I put a new ground on the sending unit and pulled the connector and grounded it, it did not move at all. I guess the next spot would be the dash voltage regulator. Where is that located and what does it look like. All other gauges are working except the fuel gauge. Thanks again for any help.

03-08-2001, 03:20 PM
The only other guage that the dash voltage regulator will affect is the temp gauge. If you have a temp gauge and it is working, I would rule out the dash voltage regulator.

It is a small unit that is plugged into the back of the dash. It has three legs. One is to ground. One is +12V in and the other is kidna regulated +5V out. I say kinda, because it is actually a pulsed +12V.

It could also be a broken wire, between the dash and the sender or the fuel gauge.

03-08-2001, 03:46 PM
My next step is going to run a seperate wire up to the dash from the fuel sending unit to the gauge and see what happens and make sure I've got 12 v on the other side of the gauge, making sure not to touch the sending terminal or I'll fry the gauge.

03-08-2001, 08:15 PM
One side of the gauge will be variable resistance to ground (from the fuel sender). The other side should be about +5V.

An easy test for the gauge is to put 2 D cell batteries together (total of 3 volts). Put the negative side to the sender side of the gauge and the positive side to the regulator side of the gauge. The gauge should come up to a little over the half mark.

If it doesn't, the gauge is bad. If it does, the problem is with the sender wire or the dash voltage regulator or a bad trace on the back of the dash.

An easy test for the wire (key OFF/out) is to ground the sender side of it and then under the dash, measure its resistance to ground. If you don't have an ohm meter, you can connect a test light to the lead, under the dash, and the other side to the hot to the cig lighter.

03-10-2001, 12:16 AM
Rickrow, if your fuel gage is the only one not working, then limit your troubleshooting to the fuel gage sending unit and/or wiring. If the temp gage is working properly, the the voltage limiter for the fuel and temp gages is operating correctly. You can verify this with the use of a multi-meter/voltmeter. With the ignition switch in the ON/RUN position, you should be able to connect the meter between the temp sending unit and ground, with the connector for the temp gage making contact with the sending unit. The meter should show a fluctuating voltage between 0 volts and 5 volts dc (approx). Make the same connection at the tank sending unit, between the electrical connector and ground. If you see the fluctuating voltage, then the problem is the sending unit itself, or a ground problem. If you don't see the voltage indication with the meter, then you will need to trace a wiring problem between the tank and the dash.

03-19-2001, 05:47 PM
Hate to say it boys but I've had plenty of Mopars and only one has had an operable fuel gauge! So far I have found no real remedy! My 68 273 Dart didnt read at all and neither does my 66 belvedere......77 p/u fills to 3/4 and never above but who knows! good luck tho!