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Re: Fuel sending units reading WRONG....time after time
[Re: RapidRobert]
#639002
03/15/10 02:40 PM
03/15/10 02:40 PM
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Joined: Jan 2003
Posts: 6,840
The Swamp
Sixpak
master
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master
Joined: Jan 2003
Posts: 6,840
The Swamp
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Quote:
I didn't realize that they were that problematic. makes me want to get a new stock one & if it reads right then add the 3/8 line myself. Only difficult part would be to swege the flat to get some more contact area to keep the line in place or some sleeve/nuts to anchor it. What are the stock ohms supposed to be? Was it 10 and 70
If you do try to modify a stock one be sure to remove ALL the electrical components off the thing before try to solder a larger fuel pickup tube to the plate...DAMHIK...
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Re: Fuel sending units reading WRONG....time after time
[Re: shadango]
#639004
03/15/10 04:27 PM
03/15/10 04:27 PM
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Joined: Jan 2003
Posts: 5,445
So Cal
Sinitro
master
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master
Joined: Jan 2003
Posts: 5,445
So Cal
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The sending unit is a rheostadt just like a volume control.. The resistance varies which changes the voltage sent to the guage. If you have open readings then the circuit is open during those times pointing to an intermittant rheostadt winding. EZ to check... With the sending unit out of the tank and grounding wire connected. Have a buddy read the guage as you vary the sending unit. Action should be smooth and consistent, if not then the sending unit is likely damaged.. Just my $0.01... 
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Re: Fuel sending units reading WRONG....time after time
[Re: Sinitro]
#639005
03/16/10 05:39 AM
03/16/10 05:39 AM
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Joined: Mar 2009
Posts: 32
pittsburgh, pa
shadango
OP
member
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OP
member
Joined: Mar 2009
Posts: 32
pittsburgh, pa
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In my experience with the last 3 senders, that test works, but its not 1005 accurate. The sensitivity of the rheostat inside is very high. If you have shaky hands at all you will get error. True, if you see a large swing in ohms there is an issue....but smaller swings or smaller dead spots may not be visible until it is installed and being affected by the actual fuel level. In the cheap Spectra one from Rock auto, I found the dead spots by hand easily. On the better units from Roseville, not so easy....seems that the dead spots were much smaller...but still there. We'll see what this one does I guess. I am not expecting much to be honest. At this point I would settle for predictability at least....on the last sender I knew there was a short dead spot at half and 1/4 tank....un-nerving to look down and see "empty' but after a few tanks it was at least predictable. I also keep a log of my mileage so as to know how many miles into a tank I am "just in case". Of course my speedo occasionally goes berserk, above 60 mph.....and affects the odometer....but that is a whole other thread...and one of the projects on my list.... 
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Re: Fuel sending units reading WRONG....time after time
[Re: RapidRobert]
#639006
03/16/10 07:22 AM
03/16/10 07:22 AM
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Joined: Jan 2003
Posts: 6,840
The Swamp
Sixpak
master
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master
Joined: Jan 2003
Posts: 6,840
The Swamp
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Quote:
Quote:
If you do try to modify a stock one be sure to remove ALL the electrical components off the thing before try to solder a larger fuel pickup tube to the plate...DAMHIK...
Sixpack I will follow your advise. Any idea what the ohms are supposed to be?
Sorry, no...I just remember ruining the electrical components on mine when I tried to solder a 1/2" pickup into mine. I got to believe they swedge or solder the tube to the plate first and then add the electrical stuff. Those things aren't really built to be disassembled so take your time.
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Re: Fuel sending units reading WRONG....time after time
[Re: 1_WILD_RT]
#639011
03/16/10 01:22 PM
03/16/10 01:22 PM
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Joined: Mar 2003
Posts: 15,491
the boonies
aarcuda
I Live Here
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I Live Here
Joined: Mar 2003
Posts: 15,491
the boonies
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10ohms = full
72 ohms=empty
It's got a cop motor, a 440 cubic inch plant, it's got cop tires, cop suspensions, cop shocks. It's a model made before catalytic converters so it'll run good on regular gas.
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Re: Fuel sending units reading WRONG....time after time
[Re: RapidRobert]
#639013
03/16/10 08:54 PM
03/16/10 08:54 PM
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Joined: Aug 2006
Posts: 1,609
Southern Cal
Noblewk
top fuel
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top fuel
Joined: Aug 2006
Posts: 1,609
Southern Cal
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Check the 5v Regulator....... The old ones are crap. My Fuel and Temp used to creep up and down with no reasoning. Updated the 5V Regulator and now they are solid. http://www.mopar1.us/instrument.html
66 Dart GT, 402 11.18:109 Best
63 1/2 Galaxie 500XL 406 4Speed 13.20:103 Best
2000 Ram
2005 Durango Hemi.
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Re: Fuel sending units reading WRONG....time after time
[Re: ademon]
#639016
03/17/10 11:02 AM
03/17/10 11:02 AM
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Joined: Jun 2008
Posts: 2,336
Ball Ground, Georgia
Dixie
top fuel
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top fuel
Joined: Jun 2008
Posts: 2,336
Ball Ground, Georgia
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Quote:
We need on of the quality companys that repop parts to think about repoping a hi quality sending unit,
This is not directed at anyone in particular, just an industry observation.
Years ago we had some sending units made by the same vendor Chrysler used then and uses now. When the overseas repro's came out, and were cheaper, everyone started buying those. So, we quit making them. Hey, that's business.
Even today at shows, as I sell off the remaining inventory, people don't care about quality. They want cheap. I can't tell you how many times, I have told people the overseas stuff is junk, it goes in one ear and out the other. Your best bet is to have an original rebuilt like Randy stated above, or buy NOS. Of course, on a 40 year old car, wiring and gauges can all be contributing factors.
I hate to say it my Mopar brothers, but some folks just don't care about quality, and when price becomes the driving factor, it affects the parts we all have to choose from.
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Re: Fuel sending units reading WRONG....time after time
[Re: shadango]
#639018
03/18/10 07:12 AM
03/18/10 07:12 AM
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Joined: Jan 2007
Posts: 1,032
Ohio
dobie
super stock
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super stock
Joined: Jan 2007
Posts: 1,032
Ohio
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I'm working on a '68RR. When I got the car it had the original tank in (I believe.) The sending unit never did work. Then my uncle gave me a new unit bought from Herb's Parts. That one was better, but still reading way off. Last year I developed a leak in the tank so I bought a new aftermarket tank. After putting the new(er) sending unit it, it was off. I took it back out and tried bending the float arm. That didn't work, as it still shows E on a 1/2 tank approx.
Later this year things should start coming apart for the body and paint, so I'll play with it one more time. After that, I'll give up. I've even thought about installing an aftermarket gauge near my triple gauges under the dash. We'll see I guess.
1968 Plymouth Road Runner
383 4 speed
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