Only 1987 - 2004 model year trucks will have one.
If your truck fits in the above range, it will be on the inside of the drivers frame rail, usually just behind the drivers door.
Unless its a diesel, in which case the 6.5 / 6.2 engines have them at the back of the intake manifold, in the lifter valley.
inside the fuel tank
The 2014 GMC Sierra-1500 runs on flex-fuel (FFV).
gmc 1500 sierra was fuel injected in '92
I own a 1990 GMC Sierra 1500 5.7L V8. My fuel filter is located along the frame rail under the cab on the driver's side of the truck. You might look there for the filter on your 1989 Sierra. It's an inline silver colored canister.
drop the fuel tank. Bummer huh. :)
The 2004 GMC Sierra-1500 runs on regular unleaded.
The 2001 GMC Sierra-1500 runs on regular unleaded.
The 2008 GMC Sierra-1500 runs on regular unleaded.
The 2002 GMC Sierra-1500 runs on regular unleaded.
The 2010 GMC Sierra-1500 runs on regular unleaded.
The 2006 GMC Sierra-1500 runs on regular unleaded.
The 2013 GMC Sierra-1500 runs on regular unleaded.