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

gmc67swb · 03-29-2003, 06:03 PM

OK HERE GOES. THE GAS GAUGE READS EMPTY. I PULL THE SENDING UNIT OUT AND IT READS PAST FULL.(WITH WIRE CONNECTED) I GROUND THE SENDER, AND AT THIS POINT I CAN MANUALLY MOVE THE FLOAT ARM UP AND DOWN AND THE FUEL GAUGE READS FULL SWEEP JUST LIKE IT SHOULD. SO NOW I TAKE THE FLOAT OFF THE ARM AND THERE'S NO GAS IN IT. JUST FOR KICKS I FILL UP THE TUB AND PUT THE FLOAT AND SENDER IN AND IT FLOATS. I'VE CHECKED THE SENDER WITH A METER AT BOTTOM IT READS 1.5 OHMS AND AT THE TOP(FULL) IT READS 95 OHMS. I WOULD THINK THIS IS WITHIN RANGE. THE ONLY THING I CAN THINK OF IS THE FLOAT IS HANGING AGAINST THE TANK WALL, BUT HOW DOES IT READ EMPTY? DOES ANYONE HAVE ANY SUGGESTIONS? IF THE FLOAT FLOATS IN WATER IT SHOULD FLOAT IN GAS, RIGHT?

cdowns · 03-29-2003, 07:28 PM

sounds like a problem with your tank ground

Class of 69 · 03-29-2003, 07:38 PM

If the tank wasn't grounding, the gauge would read full, just like it did when the sender was removed, and not grounded. I would agree, it (the float) could be sticking, or the wire harness has a dead spot from corrosion or a break, that reconnected when you removed the sending unit. Have you reinstalled, and tried it again? Move the wires around by hand with the sending unit in the tank to check for a brake in the wire.

cdowns · 03-29-2003, 09:29 PM

there's supposed to be a black wire from the sending unit directly to ground on the cab is it there and hooked up???

spinning wheels · 03-29-2003, 09:58 PM

Has anyone considered that the fuel gauges aren't all that accurate?

Class of 69 · 03-29-2003, 10:03 PM

He said the gauge moved full sweep when the float was manually operated, so I skipped the gauge being at fault, but it is a possability, if nothing else is found to be wrong.

Blue Beard · 03-29-2003, 10:35 PM

Can be any of the wiring from the sending unit to the dash.......check it all.

hobby67stepside · 03-29-2003, 11:11 PM

Don't mean to stomp on your thread, but I would like to know the proper ohm rating for an aftermarket sender that will match the factory guage for a custom made tank. Thanks

Purs · 03-29-2003, 11:55 PM

90 I think.

gmc67swb · 03-30-2003, 01:12 PM

PURS IS RIGHT IT SHOULD BE 0 TO 90 OHMS..BTW GUYS, I PULLED IT BACK APART AND SHOOK IT. I COULD HEAR GAS INSIDE THE FLOAT. THE FIRST TIME I JUST STUCK IT IN WATER AND IT FLOATED. I GUESS THERE WAS ENOUGH FOR IT TO NOT FLOAT IN GAS? I'M GONNA HIT A WRECKING YARD OR TWO TODAY AND FIND A FLOAT...I MEAN I'M GOING SHOPPING FOR MY WIFES BIRTHDAY GIFT TODAY AND IF I SEE A WRECKING YARD, I MIGHT STOP IN....

MAN I CAN'T BELIEVE I DIDN'T SEE THAT THE FIRST TIME! I AM STUPID.. I AM STUPID...ETC.

Class of 69 · 03-30-2003, 05:57 PM

The surface tension of water is much higher than gas, and will support more weight, therefore the float floated in water, but not gas.... see were this is going??? The first time was practice, the second time you KNEW what you were looking for... therefore you can't be stupid, or the second time would have been practice too!!!... and the third, and the fourth...lighten up.. other people tell us we're stupid often enough. Good luck shopping for the wife's float.. I mean gift!

03-29-2003, 06:03 PM	#1
gmc67swb Registered User Join Date: Feb 2003 Location: Mesquite, Tx Posts: 396	question about fuel sending unit OK HERE GOES. THE GAS GAUGE READS EMPTY. I PULL THE SENDING UNIT OUT AND IT READS PAST FULL.(WITH WIRE CONNECTED) I GROUND THE SENDER, AND AT THIS POINT I CAN MANUALLY MOVE THE FLOAT ARM UP AND DOWN AND THE FUEL GAUGE READS FULL SWEEP JUST LIKE IT SHOULD. SO NOW I TAKE THE FLOAT OFF THE ARM AND THERE'S NO GAS IN IT. JUST FOR KICKS I FILL UP THE TUB AND PUT THE FLOAT AND SENDER IN AND IT FLOATS. I'VE CHECKED THE SENDER WITH A METER AT BOTTOM IT READS 1.5 OHMS AND AT THE TOP(FULL) IT READS 95 OHMS. I WOULD THINK THIS IS WITHIN RANGE. THE ONLY THING I CAN THINK OF IS THE FLOAT IS HANGING AGAINST THE TANK WALL, BUT HOW DOES IT READ EMPTY? DOES ANYONE HAVE ANY SUGGESTIONS? IF THE FLOAT FLOATS IN WATER IT SHOULD FLOAT IN GAS, RIGHT? __________________ GM 330HP/350, Magnuson 122HH, Tremec TKO 5spd

03-29-2003, 07:28 PM	#2
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	sounds like a problem with your tank ground __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

03-29-2003, 07:38 PM	#3
Class of 69 Registered User Join Date: Mar 2003 Location: Stillwater MN Posts: 1,166	If the tank wasn't grounding, the gauge would read full, just like it did when the sender was removed, and not grounded. I would agree, it (the float) could be sticking, or the wire harness has a dead spot from corrosion or a break, that reconnected when you removed the sending unit. Have you reinstalled, and tried it again? Move the wires around by hand with the sending unit in the tank to check for a brake in the wire. __________________ 69 GMC K10 ..some restoration required....still..

03-29-2003, 09:29 PM	#4
cdowns Senior Member Join Date: Jan 2003 Location: daytonabeach Posts: 22,956	there's supposed to be a black wire from the sending unit directly to ground on the cab is it there and hooked up??? __________________ 71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY

03-29-2003, 09:58 PM	#5
spinning wheels Registered User Join Date: Sep 2001 Location: Hacienda Heights, California USA Posts: 474	Has anyone considered that the fuel gauges aren't all that accurate? __________________ '72 GMC custom camper 350/350

03-29-2003, 10:03 PM	#6
Class of 69 Registered User Join Date: Mar 2003 Location: Stillwater MN Posts: 1,166	He said the gauge moved full sweep when the float was manually operated, so I skipped the gauge being at fault, but it is a possability, if nothing else is found to be wrong. __________________ 69 GMC K10 ..some restoration required....still..

03-29-2003, 10:35 PM	#7
Blue Beard Registered User Join Date: Jan 2003 Location: Washington State Posts: 8,831	Can be any of the wiring from the sending unit to the dash.......check it all. __________________ 1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo

03-29-2003, 11:11 PM	#8
hobby67stepside Registered User Join Date: Dec 2001 Location: NW Iowa Posts: 952	Don't mean to stomp on your thread, but I would like to know the proper ohm rating for an aftermarket sender that will match the factory guage for a custom made tank. Thanks

03-29-2003, 11:55 PM	#9
Purs Got Big Block? Join Date: Apr 2000 Location: West Texas Posts: 1,510	90 I think. __________________ "Experience is what you get when you didn't get what you wanted."

03-30-2003, 01:12 PM	#10
gmc67swb Registered User Join Date: Feb 2003 Location: Mesquite, Tx Posts: 396	PURS IS RIGHT IT SHOULD BE 0 TO 90 OHMS..BTW GUYS, I PULLED IT BACK APART AND SHOOK IT. I COULD HEAR GAS INSIDE THE FLOAT. THE FIRST TIME I JUST STUCK IT IN WATER AND IT FLOATED. I GUESS THERE WAS ENOUGH FOR IT TO NOT FLOAT IN GAS? I'M GONNA HIT A WRECKING YARD OR TWO TODAY AND FIND A FLOAT...I MEAN I'M GOING SHOPPING FOR MY WIFES BIRTHDAY GIFT TODAY AND IF I SEE A WRECKING YARD, I MIGHT STOP IN.... MAN I CAN'T BELIEVE I DIDN'T SEE THAT THE FIRST TIME! I AM STUPID.. I AM STUPID...ETC. __________________ GM 330HP/350, Magnuson 122HH, Tremec TKO 5spd

03-30-2003, 05:57 PM	#11
Class of 69 Registered User Join Date: Mar 2003 Location: Stillwater MN Posts: 1,166	The surface tension of water is much higher than gas, and will support more weight, therefore the float floated in water, but not gas.... see were this is going??? The first time was practice, the second time you KNEW what you were looking for... therefore you can't be stupid, or the second time would have been practice too!!!... and the third, and the fourth...lighten up.. other people tell us we're stupid often enough. Good luck shopping for the wife's float.. I mean gift! __________________ 69 GMC K10 ..some restoration required....still.. Last edited by Class of 69; 03-30-2003 at 05:59 PM.



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