help needed: want to fix the gas gauge once and for all

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steveh

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Probably like most, I've been runnin with an inop fuel gauge for a long long time on my 69 dart. Well the wife is driving it near daily now since we moved to Hawaii and I also have to get it through the state safety inspection so its a must fix now.

Following a troubleshooting guide from this link
http://www.moparfins.com/repairs/fuel_gauge_repair/fuel_gauge_repair.htm

All the components seem to work

Voltage limiter: Ground the wire (on gas and temp sending units seperately) got pulsating test light and the needles started to climb slowly

wires: multimeter gave me a good solid tone when I checked the wire for continuity from the wire connector at the tank to the female end of the pin connector that plugs into the circuit bord.

sending unit: putting out 75-76 ohms (don't have a 0-100 setting but use 200ohm setting)

1) what am I missing?
2) what else should I check
3) if I'm using the 200ohm setting, do I have to divide the reading in half cause 35ohms would be about right for half a tank which is what I think is in there

additional info: bout a yr ago I bypassed the amp gauge. Apart from that I've done nothing with the wiring. I'm the 2nd owner and have had it for 25yrs so its unmolested.

Greatly appreciate any assistance. Got less than a week before my temp registration runs out for HI so I gotta get this fixed this week
Steve.
 
You need a functioning fuel gauge to pass inspection? How in the hell do they go about testing it?
 
dude, the functioning fuel gauge is really needed to pass the wife's inspection!:smile:
 
Pull the wire off the sending unit it and ground it. Get in the car and turn the key on and the gauge should spike if operable. DO NOT leave the key on very long, just long enough to see if the gauge works.

If the gauge does come up check your ground clip from the sending unit to the fuel line. It looks like this:

Let us know what you find.
 

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Is your grounding strap where the fuel line at the tank turns to rubber then back to steal getting a ground ? check for continuity from the gas tank to the fuel line about a foot away. no ground no fuel gage.
Then check the fuel line under the hood for a ground to the fire wall.
Just a thought.. mine quit because of this in my 66 a body.
 
bad sport and memike...

pulled the grounding strap...scratched it up the best I could with a rat tail file, sanded the fuel line fitting on the sender to knock the rust off, but couldn't clean the connection above the tank...barely managed to get that end of the ground strap re connected.

wasnt comfortable with the grounds either so I also ran a jumper to a body ground and with the sender connected and the key on, got no movement out of the gauge.

let me back up a second. As I described in the OP, when I grounded the sending unit wire to the body, the gauge moved, but it was slow and didn't peg out...is that normal?
 
steveh said:
As I described in the OP, when I grounded the sending unit wire to the body, the gauge moved, but it was slow and didn't peg out...is that normal?
Click to expand...

I believe it should spike to full, maybe 67 will chime in here, he is the electrical guru on the board.
 
Memike,

educate me here pls...What do you mean when you say "check the fuel line under the hood for a ground to the fire wall" I'm a bit of a noob with a multimeter.
thx
Steve
 
bad sport...

It certainly didn't spike...more like floated up gradually...13 yr old son was my calibrated eyeball watching the gauge
 
I believe you'll find the guage "pulses" it's way up to full, when grounded..

run an auxilliary ground to the tank sender,, that should do it..
 
steveh said:
bad sport...

It certainly didn't spike...more like floated up gradually...13 yr old son was my calibrated eyeball watching the gauge
Click to expand...

Probably a bad gauge. You say your temperature gauge IS working?
 
yeah, its never that simple is it.

Temperature gauge is inop too, but when I ground the wire at the temp sender, the temp light pulses too and the gauge rises.

the temp gauge pin on the back of the circuit board is loose...gonna solder it later today. But that connection cant be all bad cause the needle rises when I ground it at the sender.

I'm stumped, but that aint hard to do
 
You need to think of the gauges all the way from end to end, as a system, and just about every component and connection can have a pitfall

POWER. Power to the cluster comes from the "IGN 1" or "ignition run" wire to the harness connector and the pins on the board. THESE PINS can be loose, dirty, broken, or the harness connector the same. Of course you actually have to HAVE good solid battery voltage.

GROUND The gauge VR and lighting circuit needs a ground. As old as these cars are, it's good to hook up a separate ground pigtail to the board ground screw, and run it to a nut/ bolt/ star washer on the dash lip or column support

PC BOARD. ON my 67, some of the connector pins were broke and loose. In my case, they were so bad, I bought two Molex style connectors from Rad Shack and wired pigtails to the board traces. In any case, inspect, clean, repair the harness connector

The VR socket on mine is brass spring fingers which were NOT making contact with the board traces. I had to solder jumpers from the contact fingers to the board

VOLTAGE LIMITER. It can be bad or NOT ACCURATE. Do yourself a favor and buy a good modern solid state replacement

On mine at least a couple of the gauge studs were not making contact with the board. Loosen/ tighten the nuts a few times, or replace them with "real" nuts.

GAUGES Can be inaccurate. HOW old are they, again?

I gambled that both of mine would not be the "same amount off." You can compare them using 1.5V alkaline batteries

See this thread:

http://www.forabodiesonly.com/mopar/showthread.php?t=205270&highlight=gauges

CONNECTORS AND WIRING

The temp gauge goes through the bulkhead connector, a source of trouble

The fuel gauge goes through the kick panel connector to the rear harness, not very common, but can become corroded

BOTH gauges can have troubles with the original molded connectors, breaking internally, loose, corroded.

The fuel sender MUST have a good ground. If in doubt, and you can't do anything else, use a small hose clamp, scrape the fuel outlet clean, and wrap a wire around it several times, then put the hose clamp over that. Ground to the body.

SENDER ACCURACY

I made my own sender/ gauge tester, but you don't have to:

http://www.forabodiesonly.com/mopar/showthread.php?t=179517

If you do nothing else, go to Rad Shack and buy 4 -- 100 ohm, 1/2 watt resistors and put them all in parallel. You can substitute this combination for either sender, and after allowing the gauge to fully stablilize, either the fuel or temp should give you a 1/2 scale indication.

You can buy other resistances to use, they are:

L = 73.7 Ohms (empty)
M = 23.0 Ohms (1/2)
H = 10.2 Ohms (full)

If you have an accurate ohm--meter, you can check your fuel sender directly. Run the tank to near empty (carry a spare can?), then park it level, and drain out the pickup with a hose until fuel starts to spit or quits. In the chart above, the sender should show about 73 ohms. One source I found lists a little higher, 78 ohms, but there is some leeway.

'S 'bout all I can think of fer now, except it seems to be a agreement that all repop senders are crap.
 
67dart273,

Very good advice...I've read about your circuit board saga in several of your other responses to similar posts...thanks for sharing.

I will relook everything you mentioned...

looks like the limiter is working...getting a pulsing test light, but it may not be working at 100% will definately go with a solid state set up

were livin in Hawaii now so takes a while to get stuff. I'll keep at it and post updates here looking for an additional assist.

more to follow
 
i just got my fuel g working.... new vl and sending unit worked perfect for 3 months now there is a problem with the sending unit and the gauge stoped working i hope it sumtin easy like a float broke off
 
Just because a mechanical limiter sends some pulse voltage doesn't mean its correct amount/rate. Throwing a new limiter or solid state regulator in there may or may not cure it.
Just because the gauge pointer will move doesn't mean the gauge is anywhere near accurate. All of these parts are 40+ yrs old.
To assume that most owners have inop gauges is wrong. They can be repaired to work like new. Many have sent their gauges off for repair. A few of them have wasted a lot of time and money on "do it yourself' efforts first.
When you and/or the wife get tired of playing with them I'll be glad to fix them for you.
Good luck
 
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