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

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.

Re: Fuel guage prob 49 gmc
 

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

Re: Fuel guage prob 49 gmc
 

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

Re: Fuel guage prob 49 gmc
 

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

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 ?

Re: Fuel guage prob 49 gmc
 

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...

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.

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 .