Looking for 6.2 diesel nerds

[66gmcguy]

Hello all, I made this account about 6 years ago but haven't really been on it until recently to post some square body parts for sale, and to get some technical help.

I just picked up a 1982 GMC K2500 with a 6.2 diesel engine. This is my first diesel engine, so I am still learning about them. I drove one hour with freeway, mountain, and city driving all on the way home and it seemed to be running great and make decent power. I went to go start it the evening after I got it home and lo and behold, it wouldn't even fire. I eventually got it fired the day after drove it around again (to introduce the dog to the new truck, because car rides in the back of trucks are his favorite thing, even more than eating.) I shut it off, and it started back up 2ish hours later, but the next day, I couldn't get it cranked, even after letting the batteries sit on the charger for a couple hours, and with the block heater plugged in (which I am unsure if it even works.) I decided to test the glow plugs with a test light, and sure enough, none of them worked, so I am going to replace them tomorrow. Is there anything else that might be causing this non-start issue that I should look for? When I crank it, smoke comes out of the exhaust, but it neve fires.

Also, I should mention, one of the previous owners installed a manual control for the glow plugs. Will this cause any issues? Also, what should I look out for as far as problematic components with these engines? I bought this truck with the intention of doing a gas engine swap, but I decided I liked the diesel too much to replace it just yet.

[kwmech]

If the glow plugs are dead then you will get white smoke out of the pipe (unburnt fuel). Done a lot of conversions eliminating the factory glow plug controller. Real easy to do with just a push button. Starter push button to ground the blue wire coming from the top connector of the relay. The pink wire is ign power. No need to hold the button down for more than 5-6 seconds at a time once you turn the key on. Testing the plugs--test light connected to the + side of the battery post. Touch the lamp to the spade. Lights up--good


Converting these may be a better option as getting parts for these is really difficult and having the inj pump rebuilt is a challenge in Calif as anybody who really knows how to get them correct has either moved out to another state or retired. There is a place in West Sac that seems to have a decent handle on things--cannot think of the shop name at this time. Was there about 2 years ago picking up a couple injectors after having them tested there also

[Dead Parrot]

For a good site on 6.2 info and how to repair, visit: https://www.steelsoldiers.com/

Download the CUCV Technical Manuals(TMs). They have a wealth of step by step procedures on troubleshooting and repairing almost everything about CUCVs.

CUCVs are a slightly militarized version of an 84 K series Blazer(M1009) and an 84 K30 squarebody(M1008). Both came with a 6.2 diesel. They also have 24V electrical system for compatibility with other military vehicles but even then, most of the stuff is still 12V.

[93M6Formula]

Originally Posted by 66gmcguy

Hello all, I made this account about 6 years ago but haven't really been on it until recently to post some square body parts for sale, and to get some technical help.

I just picked up a 1982 GMC K2500 with a 6.2 diesel engine. This is my first diesel engine, so I am still learning about them. I drove one hour with freeway, mountain, and city driving all on the way home and it seemed to be running great and make decent power. I went to go start it the evening after I got it home and lo and behold, it wouldn't even fire. I eventually got it fired the day after drove it around again (to introduce the dog to the new truck, because car rides in the back of trucks are his favorite thing, even more than eating.) I shut it off, and it started back up 2ish hours later, but the next day, I couldn't get it cranked, even after letting the batteries sit on the charger for a couple hours, and with the block heater plugged in (which I am unsure if it even works.) I decided to test the glow plugs with a test light, and sure enough, none of them worked, so I am going to replace them tomorrow. Is there anything else that might be causing this non-start issue that I should look for? When I crank it, smoke comes out of the exhaust, but it never fires.

Also, I should mention, one of the previous owners installed a manual control for the glow plugs. Will this cause any issues? Also, what should I look out for as far as problematic components with these engines? I bought this truck with the intention of doing a gas engine swap, but I decided I liked the diesel too much to replace it just yet.

Sounds like possibly a couple of things. The 82-84 glowplug system is junk at best which is why it is bypassed with a switch. The only problem is, if it had the older style plugs, they do not hold hold up with extended glow times they might see when on a switch. The newer Ac Delco 60G or Bosch Duraterm are self limiting and won't swell so they are okay with longer glow time. So I would replace them either way but be prepared that some may be swelled and will be a pain to remove. Double check the wiring they did for the glowplug system, it may have some issues.

Since you said it's smoking while cranking, that means it's getting fuel so it does sound like a glowplug problem more than likely. I would however make sure the fuel system is 100% tight from tanks to engine, air intrusion is the biggest thing that can cause all sorts of issues with starting and running. Also these need to crank fast to start well.

[hatzie]

If you look in the manuals thread you'll find the 6.2L bible. It's the GM technician training textbook for the 6.2L diesel engine.

DO NOT just apply power to the glow plugs. If they are the earlier 9G or 11G plugs they will swell up making them difficult to remove and sometimes they split apart dropping pieces of the abrasive hard ceramic element into the cylinder while the engine is running.
If you still have the original glow plugs get rid of them and install decent glow plugs that don't swell and break apart.
Positive Temperature Coefficient glow plugs... AC Delco 60G or Bosch dual coil glow plugs can be operated for 8 hours without burning out and swelling.

You can replace the early glow controllers with the 1985-2001 6.xL glow controllers. The wiring diagram in the 1989 RV series wiring manual should let you set one of these controllers up.

[D13]

I did the ferd solenoid and 60G glows, really helped. Block heater any time it's below 40 makes a big difference, need about 2 hours to get it warm. Search for diesel place without the space for a good 6.2 forum. They were a great help to me when I owned mine (sold it last year). 23mpg on a square body. I had no trouble finding anything I needed except CDR's (think PVC's for diesels). If you ever need to replace the water pump, realize there are bolts coming form the back....

[legendman]

Another good place for 6.2 info is Dieselplace.com.

First thing I would check is making sure there is no air in the fuel lines.
Put a clear line on the return line off the injection pump and if there is air in it when it sits for awhile, if there is then air is getting in somewhere.

[Corts60]

Originally Posted by 93M6Formula

Sounds like possibly a couple of things. The 82-84 glowplug system is junk at best which is why it is bypassed with a switch. The only problem is, if it had the older style plugs, they do not hold hold up with extended glow times they might see when on a switch. The newer Ac Delco 60G or Bosch Duraterm are self limiting and won't swell so they are okay with longer glow time. So I would replace them either way but be prepared that some may be swelled and will be a pain to remove. Double check the wiring they did for the glowplug system, it may have some issues.

Since you said it's smoking while cranking, that means it's getting fuel so it does sound like a glowplug problem more than likely. I would however make sure the fuel system is 100% tight from tanks to engine, air intrusion is the biggest thing that can cause all sorts of issues with starting and running. Also these need to crank fast to start well.

x2

[Corts60]

If you need your injection pump rebuilt in the future, send to DFIS (Diesel Fuel Injection Service). They are located in Portland, OR. Ask for Mark. He is the local grey hair who cut his teeth on the Roosamaster pumps. He knows them very well and rebuilt me several for both my 5.7 diesel and my 6.2. Very professional service and the pumps come back looking brand new and running awesome!

They will also rebuild your injectors as well.

Also, a tip for cold starting without glow plugs: Use a heat gun in the intake. It will fire right up after about 30 seconds of heat. Never use ether.

[66gmcguy]

Thank you to all who posted tips on here. Sorry I didn't respond sooner. I've been busy tinkering with this truck. Even took it four wheeling a little bit. I wish I had been patient and waited for the advice to use the AC Delco 60G plugs. The plugs that came in the truck luckily were not swollen, despite not working at all, but I made the mistake of buying the Autolite plugs and installing them. Upon first burn, they all swelled up and stopped working. The truck never even started with them, so there went $80. I had to buy a tool to remove the swollen plugs and replaced them with the 60Gs, and now, it fires right up. It even starts pretty well on a 35 degree morning.

So now that I've spent a bit of time driving it, I noticed that if it sits for more than 8 hours, it blows blue smoke pretty heavily for about 10-15 seconds when I start it. I wouldn't say it billows out, but it leaves a small cloud behind it. It seems to go completely away after running for a bit. The truck seems to make decent power so far as I can tell (good enough for a 6.2) but I've never driven one and have nothing to compare it to, so I don't know if it's fine or if it's down on power. When I see blue smoke, my first thought is it's burning oil, but after doing some reading, it seems like that's not always the case with these old turds. I've read that it could be leaky injectors, worn out timing chains, bad EPR valves, and some say "that's just what they do." I plan on doing a compression check as soon as I can to try and rule out bad rings, guides, etc. Based off my limited knowledge of diesels, I sort of think that there's probably nothing wrong internally because the truck starts pretty easily, which I think indicates it has good compression, but I'm talking out of my behind and truthfully don't know anything about these engines so I'm probably wrong. Any pointers on how to check anything else that might be causing this? Thank you all in advance!

[hatzie]

Leaky injectors are fairly easy to fix. They use the same style large body Bosch injectors as the old Mercedes and VW diesels. If you can find the Firad nozzles for your injector bodies those are the ones to use. Monark used to be pretty good but the quality has dropped off. Monark are the ones to use if you can't get Firad nozzles.
http://www.peachparts.com/shopforum/...gain-us-2.html

You can build a pop tester with a bottle jack and a 4 inch 3,000 psi oil filled pressure gauge.
http://www.peachparts.com/shopforum/...op-tester.html

BE VERY CAREFUL using a pop tester. DO NOT get your skin near the spray it will inject the diesel fuel or kerosene into your skin and you will loose the affected appendage. I'm not interested in amputations that can be avoided.
I usually put the injector in a large glass jar with the threaded top connection below the mouth. And I wear a full face mask.

[Corts60]

Originally Posted by 66gmcguy

Thank you to all who posted tips on here. Sorry I didn't respond sooner. I've been busy tinkering with this truck. Even took it four wheeling a little bit. I wish I had been patient and waited for the advice to use the AC Delco 60G plugs. The plugs that came in the truck luckily were not swollen, despite not working at all, but I made the mistake of buying the Autolite plugs and installing them. Upon first burn, they all swelled up and stopped working. The truck never even started with them, so there went $80. I had to buy a tool to remove the swollen plugs and replaced them with the 60Gs, and now, it fires right up. It even starts pretty well on a 35 degree morning.

So now that I've spent a bit of time driving it, I noticed that if it sits for more than 8 hours, it blows blue smoke pretty heavily for about 10-15 seconds when I start it. I wouldn't say it billows out, but it leaves a small cloud behind it. It seems to go completely away after running for a bit. The truck seems to make decent power so far as I can tell (good enough for a 6.2) but I've never driven one and have nothing to compare it to, so I don't know if it's fine or if it's down on power. When I see blue smoke, my first thought is it's burning oil, but after doing some reading, it seems like that's not always the case with these old turds. I've read that it could be leaky injectors, worn out timing chains, bad EPR valves, and some say "that's just what they do." I plan on doing a compression check as soon as I can to try and rule out bad rings, guides, etc. Based off my limited knowledge of diesels, I sort of think that there's probably nothing wrong internally because the truck starts pretty easily, which I think indicates it has good compression, but I'm talking out of my behind and truthfully don't know anything about these engines so I'm probably wrong. Any pointers on how to check anything else that might be causing this? Thank you all in advance!

Valve seals. If it only does it for a few seconds at start up and you are 100% sure it is blue and not white, it is valve stem seals. There is a way to change them with the heads installed. It requires putting air pressure in each cylinder while you pull the valve keepers out, but it can be done.

[hatzie]

Originally Posted by Corts60

Valve seals. If it only does it for a few seconds at start up and you are 100% sure it is blue and not white, it is valve stem seals. There is a way to change them with the heads installed. It requires putting air pressure in each cylinder while you pull the valve keepers out, but it can be done.

Take a whiff. Burning oil smells closer to a smoky burnout than excess fuel.
https://learndiesels.com/diesel-smoke-guide/

Slightly low compression can cause a partial fuel burn that gets better after a few minutes of runtime as the pistons and rings warm up.
Leaking valve stem seals usually only lasts for 30-45 seconds or less or so.

Valve stem seals will take care of the intake side.
Exhaust valves don't have seals. If the exhaust guides are loose enough that they are leaking significant amounts of oil they'll need work.