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Old 06-11-2006, 11:09 AM
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AutoMeter gauges, Fuel Level, Painless Wiring

I have a new fuel cell, painless wiring kit, and auto meter gauges that I am trying to wire up.

I took a buddy for a ride around the neighborhood and the fuel pump started to make some weird noises, so I stopped and asked him to check and see if the fittings were leaking, because the fuel gauge read full.

He opened the tank and it was on empty - oops. No prob the gas station is right around the corner.

Anyways last night I switched the 2 wires on the fuel level sender around, thinking that would fix the problem.

I had my dad watch the gauge while I moved the flat in the tank, and it is doing the same thing - empty reads full, full reads 1/2 tank of gas.

What am I doing wrong?

Thanks,
Sean

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Old 06-11-2006, 03:47 PM
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OK, I am assuming the feul pump was making a funny noise because it was sucking air. I would make sure that you have a good ground first off. The Autometer wiring for the fuel gage is pretty simple, ground, signal, 12v+, and that's it. Did you follow the Autometer adjustment proceedure for adjusting the float on the sending unit?

Vince
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Old 06-11-2006, 04:03 PM
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The weird sucking noise was the empty tank... I thought it would be a fitting leaking because the gauge read full, which I thought was working lol.

But no I didn't follow the adjustment procedure... didn't know there was one Thanks for letting me know about it though, time to do some research

thanks,
sean
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Old 06-11-2006, 04:25 PM
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Doc here,

You need to BE SURE that the Sender is MATCHED to the resistance of the gauge OR it will read in error..If at all..

If the gauge is 0 to 30 Ohms, so must be the Float and sender assembly.If the Gauge Q is 0 to 60 ohms and you support a 0 t 30 sender...it will read 0 ohms at empty, and 30 ohms at full travel, BUT only report 1/2 tank of fuel on a 0 to 60 ohm gauge.

You need to check and match BOTH in order for it to work.

Doc
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Old 06-11-2006, 10:51 PM
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The Autometer guage in my '56 3100 works backward too. I get full motion on it though. When it starts getting close to full I find a station.

I figure it's a mis-matched sender, one that reads zero on the wrong end of the throw.
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Old 06-11-2006, 11:30 PM
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Quote:
Originally Posted by cletis
The Autometer guage in my '56 3100 works backward too. I get full motion on it though. When it starts getting close to full I find a station.

I figure it's a mis-matched sender, one that reads zero on the wrong end of the throw.
Doc here,

CLETIS:

That 56 3100 (I assume is a Chevy pickup) Wouldn't have happened to be a 6 volt positive ground at one time would it? If so the sender is wired backward..

CHECK to see that the TANK is frame grounded, not isolated through a wire and sender wire....and the sender wire goes to the gauge.. or Try another sender from a Negative ground vehicle...

STRATT134:

What wires are you reversing????

The sender should be only A ONE WIRE terminal...

AND if you pull that wire, the gauge should PEG in one direction or the other...

THEN ground it ... IT should PEG in the other direction...If it does that and not peg on one and half..The gauge is operable..replace the sender for a resistance matched unit..

If It Pegs on half one way..It's defective..replace the gauge.

OR to test..get some 1/2 to 1 watt resistors from rat shack, in the following values..(or as close as they stock) 30 Ohm, 60 Ohm, 90 Ohm, 120 Ohm, 150 Ohm, 180 Ohm, 210 Ohm...Cost about $4 bucks..

Starting with the lowest value (30 Ohm) put each resistor on the Sender line to ground..Keep going until you find the resistance value that "Just Pegs" the meter out..That's your system resistance..Say 90 ohms..Then you order a fuel sender for 90 ohms from the distributer..that should set it right..

Of Course , there is option 2..:
{NOT ADVISED}

Carry around a 5 gallon jerry can full of gas..but that is as nerve racking as tossing 15 sticks of dynamite in your trunk, and hoping nobody rear ends you OR it doesn't expand and spill all over the trunk and interior leaving you that "Spring Fresh " Chevron smell...

OR there is Option 3....
{NOT ADVISED}

Throw 10 ping~pong balls into the fuel cell, when you hear Them bouncing around..It's close to manual motivation time...(walk or push..)

Doc
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Old 06-11-2006, 11:36 PM
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Those autometer gauges never work just right even if you get them adjusted right. Vince and doc and cletis are all right, the sender needs to be matched to the gauge. There are about 5 or more ranges that those run in, 90-0 ohms, 0-90, 240-33, 73-10,10-180 all different resistance values for different gauge mfgs. Some read up, some read down. Very confusing if you got set up wrong from the supplier of your gauges. Here is a neat website that might help you figure out what you have and what you need to do or which sender to get.
http://www.egauges.com/AM_Instr.asp
I have had crappy luck with autometer. One time I had to send back 3 out of 5 gauges that I got for a willys truck I built. All 3 were bad from the factory.

good luck, mikey

2 minute edit- hey doc you hit 4000
I like the ping pong balls gauge. I think I'll try that on my harley..

btw- there is a sender that has 3 terminals on it. Batt +, Gnd and sender. I just saw one for the first time a few weeks ago. Those are sold by fuelsafe fuel cell company. I am trying to figure one out because my customer has no instructions. SU012 is the stock # here is a pic.
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Old 06-12-2006, 01:15 PM
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I have this fuel gauge:
American Platinum 5-Gauge Kit
240ohm / 33ohm Fuel Level, 2-1/16'' Diameter

And this tank:
RCI Pro Street Fuel Cells
Fuel Cell, Plastic, Black, 16 Gallons, 0-90 Ohm Sender, Each

(I bet you $20 it doesn't hold 16 gallons!!!)


Well I suck, lol. I don't know about the best way, but the fastest way to learn how to do something right is to screw it up first

Thanks for everyone's help.... about Auto Meter gauges sucking... they look cool though! What other gauges would you recommend?

Doc -- One wire I connected to the little black circle in the middle, and then there is a tab sticking up around the outside circle of bolts, so I put a ground to that?
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Old 06-12-2006, 02:42 PM
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[QUOTE=powerrodsmike]Those autometer gauges never work just right even if you get them adjusted right. QUOTE]

That has not been my experience. Any gauge is going to read funny if you have the wrong sending unit. . I have a set of Autometer Platinum series and they came with the proper fuel tank sending unit and it registers right, as do the rest of the gauges.

Vince
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Old 06-12-2006, 02:53 PM
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Quote:
Originally Posted by 302/Z28
I have a set of Autometer Platinum series and they came with the proper fuel tank sending unit and it registers right, as do the rest of the gauges.
SWEET!!! I just remembered that I have this weird white box in my garage... its' the sending unit that came with the gauges!! I got the gauges like 2 years ago, and the fuel cell about 6 months ago, so I forgot all about it....

So that should be half the problem fixed right there...

Now how do I 'adjust' the gauge/sending unit as mentioned above?

Thanks,
Sean
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Old 06-12-2006, 03:48 PM
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Doc here,

Well, here is your Exact problem..

Quote:
240ohm / 33ohm Fuel Level, 2-1/16'' Diameter
And:

Quote:
Fuel Cell, Plastic, Black, 16 Gallons, 0-90 Ohm Sender,
If you notice, Not ONLY is the sender Resistance WRONG..It's Backward!

The Correct Sender Goes from 290 Ohms (empty) to 30 Ohms..(full)

And your gauge wants to see, 0 ohms at empty..and 90 ohms at full.

Install that New sender you found And you should be gold..

If you want to go for EXACT calibration, all you need do is bend the float, so that the gauge reports "Just at Empty" at the bottom of it's (the float) travel ..and reports "Just Full" at the high end of it's (the Float) ...THEN..work between the two to gain as much linearity as possible..

In a perfect world , it would be as outlined as above ..But where we live , it's just not so..

linearity is thrown into the mix..so The end travel may be more or less than actual..(most folks don't really Care..Close is close enough..)

But if you need it exact (like, fuel for a pit stop..), this is how to "Work" between the two levels to "Average out the amount of travel in regards to reporting on the gauge.

OR go to an Electronic sender..like a piezo sender that is weight dependent and not volume..and reports to a computer device that can be "Nulled" For accuracy.

Doc
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Old 06-12-2006, 04:58 PM
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[QUOTE=302/Z28]
Quote:
Originally Posted by powerrodsmike
Those autometer gauges never work just right even if you get them adjusted right. QUOTE]

That has not been my experience. Any gauge is going to read funny if you have the wrong sending unit. . I have a set of Autometer Platinum series and they came with the proper fuel tank sending unit and it registers right, as do the rest of the gauges.

Vince
I agree with you, no gauge will read right without the right sender.

Here are my experiences with autometer fuel gauges .

I have had no experience with the platinum series, only the pro comp and traditional. In those 2 cases I have used the correct sender that I got from the local parts house as auto meter had recommended.
I know that getting those gauge to read exactly right was not possible, for me anyway..I even followed the instructions.

I could get it close enough to work, usually within 1/8 tank....and I could pick whether it was off on the empty end or the full end but I could never get it just right. ( I guess that is the symptom of what doc referred to as linearity) That is why I wrote "just right". I remember one setup in a 27 roadster I messed around with it for several hours...and still couldn't get it perfect. So I made it read empty while it still had a little gas in the tank.

The rest of the autometer gauges seemed ok once I got hem back from being warrantied.

Maybe someday I'll get it right, but I doubt it. It's my little black raincloud.

Mikey
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Old 06-13-2006, 08:06 PM
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Doc said:
Quote:
That 56 3100 (I assume is a Chevy pickup) Wouldn't have happened to be a 6 volt positive ground at one time would it? If so the sender is wired backward..
No, the '56 Chevys were 12V pos from the factory. The earlier GMCs were 6V negative.

My truck was this way when I bought it and it is accurate enough for me so I just use it as is. However the tank is under the bed and looks homemade. It may not be getting a good ground. I really didn't want to drop the tank and mess with the sender as long as it's working, albeit backwards. But next time I'm under there Ill try to see how it's grounded.
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