Fuel guage prob 49 gmc - The 1947 - Present Chevrolet & GMC Truck Message Board Network

dfosh · 06-29-2009, 12:26 PM

I have a friend who has just completed a 49 gmc using an S10 chassis engine ,trans . Everything works great except his fuel guage .He had the orignal guages redone telling them he was using the S10 fuel tank and fuel injected engine . Any ideas as what might be wrong ? thanks in advance

OrrieG · 06-29-2009, 01:12 PM

Most obvious cause is sending unit amperage. Older trucks used a 0-90 ohm range, newer vechicle are 75-300 ohm range. Using a newer sending unit with older guage will cause it to peg at full until you fall below 90 ohms which is when you have about 1 gallon of fuel left. When they restored the guages they may not have modifed them for the new amperage.

BlueJeep · 06-29-2009, 02:51 PM

So do AD trucks use the 0-90 ohm sending unit?

dwcsr · 06-29-2009, 05:18 PM

My first guess would be that the sender is 12 volt and the gauge is 6 volt

OrrieG · 06-29-2009, 06:49 PM

Quote:

Originally Posted by BlueJeep

So do AD trucks use the 0-90 ohm sending unit?

I believe so, although I am not sure with the 6 volt trucks. Stovebolt guys could probably tell for sure.

dfosh · 06-30-2009, 08:25 AM

Guages were completley upgraded for 12 volts and the 4.3 fuel injected engine . Somthing could have been missed but assuming it wasent anymore ideas ?

OrrieG · 06-30-2009, 11:31 AM

Quote:

Originally Posted by dfosh

Guages were completley upgraded for 12 volts and the 4.3 fuel injected engine . Somthing could have been missed but assuming it wasent anymore ideas ?

What is it doing (or not)? Not working at all, pegging to full, stops at half full, sprodic operation? Did you use the stock S-10 tank or an after market tank? Need to narrow it down to the guage or sending unit or wiring...

Kid · 06-30-2009, 10:38 PM

I'm not sure, but I don't think you can change the "Ohms" of a given gage. Your 49 GMC gage is a 0-30 Ohm gage, possibly converted to 12 volts, but I bet you'll need to use a after market 0-30 Ohm sending unit to make it work correctly.

dfosh · 07-01-2009, 06:14 PM

Thanks for all the help. Kid got it right .Ohms sending unit problem . He was using S10 fuel tank .

06-29-2009, 12:26 PM	#1
dfosh Registered User Join Date: Oct 2007 Location: greeneville tn Posts: 237	Fuel guage prob 49 gmc I have a friend who has just completed a 49 gmc using an S10 chassis engine ,trans . Everything works great except his fuel guage .He had the orignal guages redone telling them he was using the S10 fuel tank and fuel injected engine . Any ideas as what might be wrong ? thanks in advance

06-29-2009, 01:12 PM	#2
OrrieG Registered User Join Date: Jun 2006 Location: Idaho Posts: 8,800	Re: Fuel guage prob 49 gmc Most obvious cause is sending unit amperage. Older trucks used a 0-90 ohm range, newer vechicle are 75-300 ohm range. Using a newer sending unit with older guage will cause it to peg at full until you fall below 90 ohms which is when you have about 1 gallon of fuel left. When they restored the guages they may not have modifed them for the new amperage. __________________ 1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project

06-29-2009, 02:51 PM	#3
BlueJeep Registered User Join Date: Mar 2008 Location: Waukee, Iowa Posts: 1,608	Re: Fuel guage prob 49 gmc So do AD trucks use the 0-90 ohm sending unit? __________________ build threads: 86 Suburban 88 Jeep 6.0 swap 49 Chevy truck 54 Chevy wagon 86 Suburban lowered 4/6 54 Chevy wagon 49 Chevy/s10 mix 88 Jeep Wrangler rockcrawler

06-29-2009, 05:18 PM	#4
dwcsr Hollister Road Co. Join Date: Apr 2005 Location: Houston Posts: 6,131	Re: Fuel guage prob 49 gmc My first guess would be that the sender is 12 volt and the gauge is 6 volt

06-30-2009, 08:25 AM	#6
dfosh Registered User Join Date: Oct 2007 Location: greeneville tn Posts: 237	Re: Fuel guage prob 49 gmc Guages were completley upgraded for 12 volts and the 4.3 fuel injected engine . Somthing could have been missed but assuming it wasent anymore ideas ?

06-30-2009, 10:38 PM	#8
Kid Senior Member Join Date: Jun 2002 Location: Kansas Posts: 702	Re: Fuel guage prob 49 gmc I'm not sure, but I don't think you can change the "Ohms" of a given gage. Your 49 GMC gage is a 0-30 Ohm gage, possibly converted to 12 volts, but I bet you'll need to use a after market 0-30 Ohm sending unit to make it work correctly. __________________ The kid Build threads: 51 Jimmy http://67-72chevytrucks.com/vboard/s...d.php?t=154951 http://67-72chevytrucks.com/vboard/s...d.php?t=219902 http://www.classictrucks.com/feature...uck/index.html 68 C10 http://67-72chevytrucks.com/vboard/s...ad.php?t=50348

07-01-2009, 06:14 PM	#9
dfosh Registered User Join Date: Oct 2007 Location: greeneville tn Posts: 237	Re: Fuel guage prob 49 gmc Thanks for all the help. Kid got it right .Ohms sending unit problem . He was using S10 fuel tank .



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