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Joined: Mar 2017
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Backyard Mechanic
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OP
Backyard Mechanic
Joined: Mar 2017
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I have a '50 Fleetline which I converted to 12 volts, the problem I am having is when the car warms up the fuel gauge fluctuates radically. it starts to spike towards full and drops back only to repeat the process again. the car currently has a 1/4 tank of gas. Any tips ?
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Joined: Jan 2009
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ChatMaster - 750
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ChatMaster - 750
Joined: Jan 2009
Posts: 935 Likes: 12 |
If you installed a new tank it might not have baffles to keep the gas from sloshing around resulting in what you are seeing. Otherwise I have no idea.
Dick
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Joined: Nov 2001
Posts: 29,863
Tech Advisor ChatMaster - 25,000
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Tech Advisor ChatMaster - 25,000
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The Mangy Old Mutt
"If It's Not Junk.....It's Not Treasure!"
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Joined: Jan 2008
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ChatMaster - 750
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ChatMaster - 750
Joined: Jan 2008
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If the gauge goes to full and then back might indicate a poor ground, you might try running a ground wire from the sending unit to the frame. Many years ago I switched a 51 sedan delivery to 12 volts and did not add a resistor for the gas gauge, it work but was about 1/4 tank off, don trembler which way now.
Dens Chevys 1927 Speedster 1928 coupe 1941street rod 1947Fleetline 4 door 1949 1/2 ton Pickup (sold) 1954 210 4 door 1972 Monte Carlo 2003 Corvette convt..
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Joined: Mar 2017
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Backyard Mechanic
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OP
Backyard Mechanic
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The car does have a Runtz brand resistor on the gas gauge and the fluctuation is while the car is idling.New tank and line. The car isn't on the road yet.
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Joined: Nov 2001
Posts: 29,863
Tech Advisor ChatMaster - 25,000
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Tech Advisor ChatMaster - 25,000
Joined: Nov 2001
Posts: 29,863 |
The Mangy Old Mutt
"If It's Not Junk.....It's Not Treasure!"
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Joined: Mar 2017
Posts: 201 Likes: 2
Backyard Mechanic
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OP
Backyard Mechanic
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theoretically, it shouldn't be defective as it is a new unit. Unfortunately I am not inclined to crawl under the car in the cold on a gravel driveway to test the unit in question.
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Joined: Dec 2007
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ChatMaster - 4,000
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ChatMaster - 4,000
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I like your word "theoretically". My experiences the last few years confirm that "new" does not necessarily mean "working like the original".
One practice I have adopted is to do whatever I can to test the operation of a part before I install it. It has saved me some grief and extra effort.
One other thought. Do you know if your new sending unit is a 0 to 30 ohm or 0 to 60 ohm unit?
Rusty
VCCA #44680
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ChatMaster - 2,000
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ChatMaster - 2,000
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I had a leaking seam on my restored 83’ Chevy diesel blazer fuel tank so I bought a new tank and a new sending unit figuring it’s better to change out the 35yr old unit. Put the tank and new sender in and it worked great for 2-3 months then went to empty on a bump and stayed there. When I unplugged the tank lead (my blazer has a factory plug on the sender line on the chassis rail) the gauge immediately went to full so it’s the sender. Or should I say my “new” sender. Should have left the original 35yr old one in!????
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ChatMaster - 1,000
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ChatMaster - 1,000
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Change is not always a good thing ! 
p.k.
1956 BEL AIR 2 DOOR HARDTOP
I've spent most of my money on Booze,Women and mechanical things. The rest I just Wasted........
Remember , I'm not Always Right. But I'm Never Wrong !
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Joined: Sep 2002
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ChatMaster - 2,000
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ChatMaster - 2,000
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I would suspect the Runtz unit. It is not a resistor but a solid state regulator. It is probably reacting to the charging circuit.Try clipping a capacitor on to the supply of the Runtz unit. You might even try the type of capacitor that is used in the distributor.
My 1951 1 Ton is now on the road! My 38 Master 4 Door is also now on the road .
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Joined: Mar 2017
Posts: 201 Likes: 2
Backyard Mechanic
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OP
Backyard Mechanic
Joined: Mar 2017
Posts: 201 Likes: 2 |
Update on the fluctuating gauge. While the vehicle was warming up the other day, I tapped on the face of the instrument cluster and the needle dropped, only to start to rise again. I repeated this several times while the car warmed up. I suspect I may need to retighten the nuts for the wiring and "Runtz" connecting to the gauge, or the gauge itself may be faulty.
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