I had a 85 burban with the 6.2 without the EGR valve. It was a 3/4 ton. The 1/2 version has the EGR Valve. If want your getting has the EGR valve on the intake, black suttie looking thing that blocks the intake, find another intake
from a 2500. Someone mentioned head gaskets. The 5.7 diesel was famous for head gaskets, had two of them. The 6.2 never blew a head gasket the entire time I had it. 250,000 miles.

Like mentioned, check them glow plugs. If you get it and have problems with the glow plugs, you can bypass the controller using a spring loaded toggle switch that you can turn them on with. Can't hold in longer than 10 seconds.

Injection pump, as mentioned its a rotary type. The older ones have a retainer ring that wears out and will stop up the fuel return check valve located in the front of the pump. It will shut down the engine when it stops up. It has a glass, spring loaded check valve in it. Everyone thinks they need to replace the pump then. Remove the check valve and drill it out with a 3/16" drill. You will have no further problems with the pump utill it just craps. I never had one crap after the drill out. The only other thing that might happen is the cruise control may surge a little. It will also make the truck run like you just put a turbo on it compared to the way it was.

I have a complete service manual for the 85. If you have questions if you get it, let me know.

Dave

 

Ive Got An 1982 Gmc 6.2 1500 Pick Up. I Bought It When It Had About 180,000 On It. The Only Problem This Truck Has Ever Had Was A Glow Plug Controller 100 Bucks, And Back On The Raod Again. The TRUCK Has Roughly 300,000 On It Now. The Speedo Cable Broke When The Odometer Read 292,000. Great Truck, Ive Ran The Crap Out Of It. Until I Bought My Dodge! Now I Let My Dad Use It For Dump Runs, But Thats All It Does Now. Still Runs Like A Champ, Its A Pig Though. The Body Is In Terrible Shape, But Starts Every Time So Ill Keep Till It Stops Running, Or Falls All The Way Apart. Just Figured I Would Share My 6.2 Story

 

Yeah, mine was really slow, and you could stick your arm from the outside of the box, to the inside of the box, directly over the rear tire. Not over top of the box, I mean directly over the rear tire. It was that "metallic bronze" color, almost exactly the color of rust. Looked pretty good until you got to within about 50' of it, and realize how much daylight you could see through the box.