Gas gauge test/not working

HEINRICH THOMAS

MEMBER
1983 JEEP CJ7
4.2L
6 CYL
4WD
MANUAL
130,000 MILES

I have a new sending unit, cannot seem to get a ground or hot wire reaction on a test light, will attempt to run a direct ground from battery tonight. I find it impossible to believe I cant clip this test light on anything on the back/underside of this jeep for a ground. I attempted to clip light and touch a positive terminal on a spare battery, I also clipped the test light to the negative terminal on same battery and had no light touching the hot lead to the sending unit. Essentially I cannot find ground or power in the back of this thing. Where do I start?

5 Replies

CJ MEDEVAC

MECHANIC
11,005 POSTS

I take it that the gauge is not working?

Check this out!

http://civilianjeep.info/Strenk/Gauge%20web%20page/basic_troubleshooting_for_cj_gau.htm

Keep asking until we get you right!

The Medic

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Saturday, July 23rd, 2016 AT 4:36 PM

HEINRICH THOMAS

MEMBER
3 POSTS

Yes, I have seen and read that a couple times, I am starting at the back and working forward as not only do I dread taking the dash apart and fear the diagnostics of the gauges I do not own or know how to work a multi-meter. I have done a ton of electrical work on motorcycles all with a simple test light though. I will see if I can get another set of eyes here and try touching the pink/red sender wire to a direct ground from the battery.

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+1

Saturday, July 23rd, 2016 AT 4:46 PM

CJ MEDEVAC

MECHANIC
11,005 POSTS

Verify that the wires to and from the gauges are correct in placement.

One wrong touch of a hot wire will fry the "CVR" (constant voltage regulator) found/ made into the fuel gauge, the 5 volts or so produced by it powers both the fuel and the temperature gauge.

You need a voltmeter!

Harbor Freight has them for about $5.00.

You most likely will only be using the "DC volts" (usually the 20 setting DC) and "Ohms" for testing continuity and things such as coil windings.

The Medic

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Saturday, July 23rd, 2016 AT 6:21 PM

HEINRICH THOMAS

MEMBER
3 POSTS

Little background on the jeep it is a one owner vehicle I got from my father in-law. It has been sitting in his garage for seventeen years, everything is bone stock OEM, un-modified or upgraded, no hacking or rigging.

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Saturday, July 23rd, 2016 AT 6:46 PM

CJ MEDEVAC

MECHANIC
11,005 POSTS

Wonderful!

Things might go smooth!

I do not know if you still have the old sender, it can be checked with an ohm meter.

I always do this with a sender before I install it. Sometimes I can tweak it to be more accurate, or at minimum tweak it to where it shows "empty" (perfectly over the line) and still have a gallon or two below the line. (This might bide me a little time), I still do not worry about running out, I have jerry can on the back of both the 1977 and the 1946 that I always keep full!

Sometimes it is impossible to tweak "Full" and "Empty" to read exact by bending the float arm, however, you can get one or the other close. I do my checks before I install.

Below, I have a sender capable of six inches to twenty four inches, In my case the six inch area was the desire. So I did not need the extension bar (not shown) which enabled a twenty four inch tank depth. I have already done the "geometry" and cut the float arm to the proper length according to the chart that came with the sender.

See my pictures below, these are of the 1946, kind of a short tank under the driver's seat. All that is needed is to alligator on a ground and insure the sender wire is on it. Note the gauge on the dash behind my float settings.

The Medic

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