Fuel gauge problems now with youtube video

[moonrunner1972]

Folks I decided to put the technology of the 21st century to work for me in hopes that it will help me find the answer to my problem regarding the inop/erratic fuel gauge in my 73' Polara. Please take a moment and watch the videos below. As always, thank you for the help and advice.:clapsarcastic:

http://www.youtube.com/watch?v=1-Gx...ADvjVQa1PpcFNaOW4jgicRoYcnmt2e9XNg_wb90tMjw14=

http://www.youtube.com/watch?v=G4gX...ADvjVQa1PpcFNaOW4jgicRoXWfxx1wl1lXUouQ46LCUFA=

http://www.youtube.com/watch?v=rljp...ADvjVQa1PpcFNaOW4jgicRofUk_Q3UY6Uy1b_NwjTgyAg=

 

[BillGrissom]

I can't view the videos at work. If you have a temperature gage (instead of just a warning light) and it also jumps around, the problem is probably the voltage regulator for the cluster, which is a small shiny rectangular can plugged into the back of the cluster circuit board. Except those w/ earlier cars (~1966 & earlier) or cars w/ a "rally cluster" (tachometer, into 70's), which have the Vreg inside the fuel gage. If both gages jump, it could also be a bad ground for the cluster. It is unlikely that the fuel gage itself is bad. You could temporarily wire in an aftermarket gage to test (get one for Chrysler). You can get at the sender wire in the "body connector" that is usually behind the driver's kick panel. You could also just use a multi-meter set to 1K ohms scale.

Most commonly, the problem is in the sender in the tank. Simplest (and common) is a bad ground strap across the rubber hose off the sender. Clean the clip or run a new ground wire to the sender body (or tube). A leaky float is common, but that usually sinks the sender permanently so it always reads "E". The sender pickup is just a variable resistor ("rheostat" for geezers). It can get erratic. Most senders are fairly cheap on ebay. Next time I remove my Newport's tank, I'll try installing an A-body one since my after-market gage also reads erratic, plus I need a fuel return tube. I might have to bend the tubes and rod slightly, but might work.

 

[blackmamba]

Hello! Did you finally fix this problem?

 

[1970FuryConv]

For the ground at the fuel sending unit, often the strap from the outlet pipe at the fuel sending unit (FSU) to the fuel line does not give good ground. Either the strap does not clamp tight enough at the base of the outlet pipe or corrosion and dirt around the fuel line does not allow it to give good ground. With every C-Body I've owned, I've taken a 14 gage black wire, stripped the end, and used a small fuel line hose clamp to clamp the stripped wire end tight to the base of FSU output pipe. I use the FSU wire grommet (for the 18 gage blue wire) to run the ground wire into the trunk. Crimp on a ring connector to the trunk side of the ground wire. Drill hole in front upright wall of trunk to LS of spare tire mount. Clean mounting area and a screw with wire wheel on a drill. Screw ring connector into inclined front wall of trunk. Test the ground with a test light connected to a wire from battery positive or with ohmmeter connected to battery negative. With that good ground, usually my fuel sending unit works.

Since you have been through 3 fuel sending units and have proven that your sending wire and gage are OK, IMHO ground is the only thing left.

 

[blackmamba]

i did the same thing on my 1968 Monaco and my soon to be restored 1967 Polara Coupe.

 

[BillGrissom]

I also did the "stranded wire under hose clamp" ground on my 65 Newport's fuel sender years ago. The factory ground clip is often missing or too corroded to work. It would be nice if after-market gages had a lug for a ground connection, but still the same "connect to fuel tube" approach. The factory method worked for a few years to get them past the warranty period.

 

[1970FuryConv]

Imagine if a fuel sending unit producer would put a simple spade terminal for ground on the sending unit. A threaded stud for a ring connector would work too. We could rid the Mopar world of this problem once and for all.

 

[moonrunner1972]

Folks, I appreciate all of the feedback. It sounds like a simple fix for a problem that has plagued me for years. Would it matter where you mounted the ground wire? Correct me if I misread the reply, but as long as the 14 gauge wire runs from the FSU and you perform the test(s) as referenced above, the gauge should work? I ask simply because I wouldn't want to drill a hole in the trunk for no reason.

 

[BillGrissom]

Don't you already have a grommet feed-thru for the single fuel gage wire? Just push the ground wire thru the same hole.

 

[1970FuryConv]

Folks, I appreciate all of the feedback. It sounds like a simple fix for a problem that has plagued me for years. Would it matter where you mounted the ground wire? Correct me if I misread the reply, but as long as the 14 gauge wire runs from the FSU and you perform the test(s) as referenced above, the gauge should work? I ask simply because I wouldn't want to drill a hole in the trunk for no reason.

I ran the 14 gage wire thru the grommet hole and mounted it on the vertical portion of the trunk floor to the left of the tire mount. That way, if you are getting occasional water on the trunk floor, the wire mount shouldn't be affected. Just so we're on the same page, the entire body of the car should be grounded. In other words, if you ran a test light off battery positive and touched clean metal on the trunk floor, the test light should light. You should have a ground strap from the firewall to the back of the engine that gives you body ground. If you don't like test lights, you could measure body ground between the trunk floor and the negative battery cable using an ohmmeter. The resistance should only be a few ohms.

 

[moonrunner1972]

Don't you already have a grommet feed-thru for the single fuel gage wire? Just push the ground wire thru the same hole.

I do have a hole in the grommet where the blue wire that feeds power to the FSU is routed through. The reluctance I have is in regards to drilling a hole into metal. My plan is to try the fuel clamp method referenced above, but connecting it to a ground under the car to ensure the gauge works before I commit to drilling a hole.

 

[moonrunner1972]

I ran the 14 gage wire thru the grommet hole and mounted it on the vertical portion of the trunk floor to the left of the tire mount. That way, if you are getting occasional water on the trunk floor, the wire mount shouldn't be affected. Just so we're on the same page, the entire body of the car should be grounded. In other words, if you ran a test light off battery positive and touched clean metal on the trunk floor, the test light should light. You should have a ground strap from the firewall to the back of the engine that gives you body ground. If you don't like test lights, you could measure body ground between the trunk floor and the negative battery cable using an ohmmeter. The resistance should only be a few ohms.

Thank you! By chance, do you have a photo of the modification?

 

[1970FuryConv]

If the mod was in this picture, All you would see is a ring terminal at the end of a wire that is screwed into the trunk floor with a sheet metal screw. I drilled a hole into that shiny black vertical portion of the floor to the left of the tire mount. You can see the grommet to run the wire thru to the right of the spare tire mount. The idea is to get good ground with no future rust or corrosion. If you wanted, you could run a long ground wire from the fuel sending unit all the way to the negative battery terminal, although that would waste a lot of wire versus drilling one hole for a screw that would be covered up by your spare.