wiring fuel sending unit - The 1947 - Present Chevrolet & GMC Truck Message Board Network

impalaboy9 · 01-17-2011, 05:23 PM

Hey guys got a Boyd's AL gas tank. Awesome product strongly recommend it. It came with its own sending unit and I'm trying to wire it up to the new dash I built. I have all new gauges. I wired the fuel gauge up by grounding it and hooking the other side to 12v like the directions said the third wire I assume measures resistance. I ran that wire back to my sending unit but the tank reads full and it only has 5 gallons in it. Is the other prong on the sending unit used to ground out the unit itself? Also, the two prongs on the sending unit aren't marked does it matter which is ground and which goes back to the gauge? Thanks for the help.

**TR65** · 01-18-2011, 12:17 AM

impala,

Check that your gage and sending unit are compatible.

Our trucks used 30 ohm senders.

Later trucks used 90 ohm senders.

Current senders are 240 ohm and they work backwards from the old ones (high ohms when empty).

Your gage has to match the sender. You can check the sender ohms with a ohmeter. It should go from zero ohms at empty to the nominal ohms when full. Your gage should say what sender ohms should be used.

A 90 ohm sender with a 30 ohm gage will read full with just a little gas in it.

TR

**Captainfab** · 01-18-2011, 12:18 AM

Are you sure that the gauge and sender both operate within the same ohms range. There are at least 2 different ohm ranges for GM fuel gauges and sending units, 0-30 ohms and 0-90 ohms. Then there are the other auto makers with their own 16-158 ohms, 240-33 ohms and 73-10 ohms. Ordinarily the fuel sending unit is the ground for the gauge. If the sending unit has 2 connections, one should go to the gauge and the other to the frame/crossmember as a ground. You might want to verify that with Boyd.

impalaboy9 · 01-18-2011, 08:43 AM

Thanks I'll break out the meter and the ....... instructions lol

*lakeroadster* · 01-18-2011, 08:45 AM

Quote:

Originally Posted by impalaboy9

Also, the two prongs on the sending unit aren't marked does it matter which is ground and which goes back to the gauge? Thanks for the help.

On my tank the ground is the smaller prong nearer the edge of the unit. The sender prong is the bigger one near the center.

01-17-2011, 05:23 PM	#1
impalaboy9 Registered User Join Date: Dec 2006 Location: lincoln ne Posts: 57	wiring fuel sending unit Hey guys got a Boyd's AL gas tank. Awesome product strongly recommend it. It came with its own sending unit and I'm trying to wire it up to the new dash I built. I have all new gauges. I wired the fuel gauge up by grounding it and hooking the other side to 12v like the directions said the third wire I assume measures resistance. I ran that wire back to my sending unit but the tank reads full and it only has 5 gallons in it. Is the other prong on the sending unit used to ground out the unit itself? Also, the two prongs on the sending unit aren't marked does it matter which is ground and which goes back to the gauge? Thanks for the help.

01-18-2011, 12:17 AM	#2
TR65 Senior Member Join Date: Nov 2007 Location: Greenville, SC Posts: 873	Re: wiring fuel sending unit impala, Check that your gage and sending unit are compatible. Our trucks used 30 ohm senders. Later trucks used 90 ohm senders. Current senders are 240 ohm and they work backwards from the old ones (high ohms when empty). Your gage has to match the sender. You can check the sender ohms with a ohmeter. It should go from zero ohms at empty to the nominal ohms when full. Your gage should say what sender ohms should be used. A 90 ohm sender with a 30 ohm gage will read full with just a little gas in it. TR __________________ 1965 C10 SWB Fleet Two owner LS2 Swap Thread http://67-72chevytrucks.com/vboard/s...d.php?t=413880

01-18-2011, 12:18 AM	#3
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,252	Re: wiring fuel sending unit Are you sure that the gauge and sender both operate within the same ohms range. There are at least 2 different ohm ranges for GM fuel gauges and sending units, 0-30 ohms and 0-90 ohms. Then there are the other auto makers with their own 16-158 ohms, 240-33 ohms and 73-10 ohms. Ordinarily the fuel sending unit is the ground for the gauge. If the sending unit has 2 connections, one should go to the gauge and the other to the frame/crossmember as a ground. You might want to verify that with Boyd. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

01-18-2011, 08:43 AM	#4
impalaboy9 Registered User Join Date: Dec 2006 Location: lincoln ne Posts: 57	Re: wiring fuel sending unit Thanks I'll break out the meter and the ....... instructions lol



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