How to test unknown fuel gauge.

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Futzy1

Futzy1

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First off, I'm sorry. I'm sure if I did a little more research I could find the answer, but I have to go to work and I'm super impatient.

With that aside, I have been driving my 1973 dart custom for almost 2 years now. My last older vehicle had a bad fuel gauge the never quite made it to full or back down to empty, and unfortunately I didn't find this out until I was sitting on the side of the road on a 110° day. As a result I've just played it safe, and never let my dart dip below a quarter tank.

I've done all the important drive stuff and I'm now working on the smaller things and I'm wondering if there is a way to confirm my fuel gauge operation that doesn't involve waiting for it to sputter out on me.

Thanks as always

Ps when I fill her up the gauge does make it to "f"
 
Only way I know (this IS installed / working in a car right?) is to carry a gallon of "spare" in a safe manner, drain as much as you can (siphon, disconnect pump, drain into can) until you get the gauge "down" and then drive it till it drops. Heck you can just drive it round and round and round and rou........the block as long as the neighbors don't get upset LOL
 
Yeah that's what I've been learning towards. The only other option I can think of would be to disconnect the sender and test the resistance against factory specs. Honestly I'm not sure which would be more of a hassle
 
Factory specs don't tell you much because the float/ arm may be bent some from "factory." They were not necessarily "that accurate" but "you hope" you can run it down to E and keep going awhile LOL

There's a device.......about 50 bucks.........called a "meter match" can calibrate the thing against some variation. Don't know how far they will compensate

TechnoVersions - MeterMatch for Analog Gauge Correction
 
67Dart273 said:
Factory specs don't tell you much because the float/ arm may be bent some from "factory." They were not necessarily "that accurate" but "you hope" you can run it down to E and keep going awhile LOL

There's a device.......about 50 bucks.........called a "meter match" can calibrate the thing against some variation. Don't know how far they will compensate

TechnoVersions - MeterMatch for Analog Gauge Correction
Click to expand...

I've written "a bunch" here (hop most of it is correct LOL) about the problems with these gauges and accuracy. It's not just the senders, sometimes it's also connections in the cluster, wiring, the accuracy of the instrument regulator, etc etc. Here are the factory resistances:

c-3826-jpg-jpg.jpg
 
Yeah I ditched that factory point-type power interrupter general averager, years ago. There was a magazine article that came out in 99 or 2000 or close to that, where a guy built one from a 5v computer part and a resistor IIRC. Well I couldn't get one in my dash fast enough. That solved the drifting inaccurate needle. I think that was an E-burg story; possibly as late as 2003.Probably Mopar Action: I was big into that rag.
Then I dropped the tank and bent the pick-up sock to sit on the bottom.
And finally figured out where the sender had to be to show E on the gauge. Then I poured one gallon of gas in the tank and bent the float arm to indicate E on that amount of gas. Badaboom, now I have exactly 1 gallon in there when it says E. And the new electronic-regulator holds the needle dead-nuts accurate.

OK that sounds too easy. Yeah it took several tries to get the float to the right height,lol.
 
Grounding the sender wire should let you know if the gauge is capable of showing "full" or "empty". This will help in determining if your problem is the gauge or sender.
 
I'm gonna laugh when I check all this stuff, and it turns out I'm just being overly cautious, and it was all completely functioning until I got my grubby hands on it.
 
AJ/FormS said:
Yeah I ditched that factory point-type power interrupter general averager, years ago. There was a magazine article that came out in 99 or 2000 or close to that, where a guy built one from a 5v computer part and a resistor IIRC. Well I couldn't get one in my dash fast enough. That solved the drifting inaccurate needle. I think that was an E-burg story; possibly as late as 2003.Probably Mopar Action: I was big into that rag.
Then I dropped the tank and bent the pick-up sock to sit on the bottom.
And finally figured out where the sender had to be to show E on the gauge. Then I poured one gallon of gas in the tank and bent the float arm to indicate E on that amount of gas. Badaboom, now I have exactly 1 gallon in there when it says E. And the new electronic-regulator holds the needle dead-nuts accurate.

OK that sounds too easy. Yeah it took several tries to get the float to the right height,lol.
Click to expand...

I built one of those for my car when I had the factory gauge and sender and they work just fine.
IIRC it cost me about 85 cents at Radio shack.
I stopped using it when I switched to an Ohm matched set sender and gauge.

guageregulator.jpg
 
Sorry, that was not a critique on you, just my reaction to the RadioShack's failed business model.

I hate that there is no "subtext keyboard" for the internet. Lol
 
67Dart273 said:
I've written "a bunch" here (hop most of it is correct LOL) about the problems with these gauges and accuracy. It's not just the senders, sometimes it's also connections in the cluster, wiring, the accuracy of the instrument regulator, etc etc. Here are the factory resistances:

View attachment 1715165777
Click to expand...

Del, weren't you going to try to make testers for the gauges??/ We cracked the code a couple of years back for the resistors...

@halifaxhops was also going to try to copy one and I have one of his prototype gauge testers that are battery powered...

Those can be used to test the gauge sweep...
 
krazykuda said:
Del, weren't you going to try to make testers for the gauges??/
Click to expand...

Not to butt in where I dont belong, but I'm much more proficient at electronics than automotive, and I'd love to offer a hand anywhere I can.
 
Pretty easy just three resistors and a rotary switch just went a bit further and made mine so It can test the gauges out of the car.
 
krazykuda said:
Del, weren't you going to try to make testers for the gauges??/ We cracked the code a couple of years back for the resistors...

@halifaxhops was also going to try to copy one and I have one of his prototype gauge testers that are battery powered...

Those can be used to test the gauge sweep...
Click to expand...

Going to work part time ate up a lot of time LOL. Yes, really, you can get by with the three resistors, you don't even really need a switch, you can just "alligator clip" them. I've forgotten what wattage they should be as they do draw some current. 1 watt would probably be safe enough for the short time you are testing
 
This would be great to develop a simple tester for the three gauges, gas, oil and water. If the basic parts could be identified, we could build it ourselves. I had a similar tester made by AC many years ago that got destroyed in a shop fire. Have been missing that tester ever since.
 
halifaxhops said:
Pretty easy just three resistors and a rotary switch just went a bit further and made mine so It can test the gauges out of the car.
Click to expand...

Being able to test gauges out of the car is a handy option... :thumbsup:
 
I understand how to test the three senders, gas, oil, temp. Being able to test the accuracy of the gauge out of the car would be great. I'll start- the source voltage would have to be 4 volts. The sender side of the gauge would need three options- 74 ohms, 23 ohms and 10 ohms. To adjust accuracy you bend the needle. How am I doing so far?
 
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