What to look for when buying a 6.2

[gravedigger472]

hey all, im fairly new to the 6.2 Diesel scene and am considering buying one. Are there any things that I should look out for when test driving and listening to the engine? Any other ways to tell the condition of the engine?

I went to look at a 1982 K10 last night, had 6.2, 700r4, 3.73's, 6" Lift, 35's, straight 3" dual pipes (loud as hell and sounds oh so right )

while running the owner took off the oil cap after it started and said "look, there is no blow-by, no smoke coming out of the oil fill cap"

im wondering if this is correct, and weather blow back on a diesel would be a significant problem or not.

i just want to make sure im getting what i pay for

 

[apache]

There seems to be typical issues with the 6.2 and a search for "GM 6.2 diesel problems" will bring up all kinds of info. Head cracking,injection pump,glow plug things,many simple fixes and some more severe. Regarding the blowby any worn engine can produce blowby if the motor is tired which is a result of compression leaking past the rings while running. Personally Id love to find a clean K5 diesel and do what it takes to keep it goin.

 

[Russell]

The lack of smoke coming out of the oil filler neck is a very good sign! Shows that the engine's rings are in excellent shape. There are not a whole lot of external things that you can investigate, however one of them is the harmonic balancer. You'll want to crawl under the truck and take a nice close look at it. If the rubber between the inner and outer rings is deformed, cracked, or missing, the balancer needs to be replaced immediately.

When running the engine, it should have a healthy clatter to it. You'll want to test the high idle and injection timing advance circuits. Just run a wire from the battery to the injection timing advance spade on the injection pump after disconnecting it and make sure that the sound of the engine changes. To test the high idle, do the same thing and make sure that when you tap the throttle, the idle increases and remains there until you release the battery wire. The engine should idle higher and have advanced timing from a cold start, you should be able to notice a significant drop in clatter and idle speed when it shuts off.

Take a look for any major leaks, particularly around the oil cooler lines, and off the fuel system (both supply and return).

The engine should start quickly in these temperatures with just a few moments of glow time. There should not be any smoke (other than a black haze), at any time. A small amount of smoke is normal right on start up, but should clear up nearly immediately.

Take your time with the truck, and try everything out. Go for a decent test drive to get a feel for how the truck handles, and to get a good idea of the capabilities of the diesel engine before you commit to purchase. Of course, make sure you check the brakes and driveline as well.

Also, one more thought -- Next time to go to look at it, call the owner in advance and tell him you want to start the truck from dead cold. Put your hand on the heads, exhaust manifold and oil pan to confirm that everything is cool to the touch. That'll give you a good indication of how well it starts, as some owners will run the engine before you get there to mask starting problems, or smoke when the engine is cold.

 

[gravedigger472]

thanks guys very helpful.

also the glow plug relay has been converted to a push button instead of automatic, it this an issue?

 

[thedrip]

A lot of owners do that themselves anyway. Its an easier/cheaper fix than replacing the problematic controller.

 

[Ronnie4wd]

And remember to run the engine warm and shut off for a couple of minutes and start again.
A wornout injectionpump will not function when starting warm