Look on the inside door panel. probably driver's side. that gives vehicle weight and gross possible weight.
i think it's 27 gallons (for the cargo van)
A 1991 Chevy G10 Cargo van with the 4.3 V-6 engine has a 22 gallon capacity fuel tank.
2014 Chevy cargo van E-32500
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I have a 2000 Chevrolet Express G3500 cargo van and the fuel tank capacity is 119 litres. I believe that equates to just over 31 gallons.
1990 cargo van 4.3 motor without air pump belt diagram
Standard Towing - 6400 (lb.) Maximum Towing - 10000 (lb.)
The maximum cargo capacity of the 2014 Ford E-Series-VAN is 278.6 cu.ft..
The maximum cargo capacity of the 2010 Ford E-Series-VAN is 236.5 cu.ft..
The maximum cargo capacity of the 2013 Ford E-Series-VAN is 278.6 cu.ft..
The maximum cargo capacity of the 2011 Ford E-Series-VAN is 236.5 cu.ft..
The maximum cargo capacity of the 2012 Ford E-Series-VAN is 278.6 cu.ft..