6.2l Diesel question.

[roydavenport]

I have a 91 Suburban with the 6.2l diesel. I have been having some issues with the glow plugs and am looking for advise. The glow plug system on my truck (according to the Haynes manual) has a temperature inhibitor switch that supposedly tell the glow plugs not to come on if the engine temp is over 120 degrees. The problem is that even when the temp gets below 120 the glow plugs still don't come on unless the engine is completely cooled off. I only have this prblem in warmer weather. In cool weather the glow plugs always come on. I never have a problem in the morning or when the truck has been sitting for a good while. I only have problems when I've been driving around and let the truck sit for an hour or two before I try starting it again. Sometimes I have to let the engine crank a good while before the engine will start. Sometimes to the point that white smoke is coming from the exhaust before it will fire up. What I'd like to do is either locate this temperature inhibitor switch and replace it or figure out how I can bypass it altogether so that my glow plugs cycle everytime I start the engine like earlier models do. Please let me know if you have any suggestions on how to fix this. Thanks alot.

 

[noJeepshere]

try giving it some throttle when you start it up, if you don't already. my school bus is the same way, if I've been driving for a while, then shut it off, it'll take forever to start, but giving it half-throttle or so, it'll fire right up. otherwise, Id just make the glow plugs manual.

 

[6.2Blazer]

I'm not even sure you have a problem....you contradict yourself in this sentence "The problem is that even when the temp gets below 120 the glow plugs still don't come on unless the engine is completely cooled off". In warm weather I very much doubt that the engine has gone from the 200 F range down to below 120 in an hour or two.

 

[tRustyK5]

Both of my 6.2's will flash up without the glow plugs if they're even remotely warm. At this time of year if the truck has been running for more than 10 minutes it'll still fire right up without the glow plugs.

There are two critical components needed for easy starting with a 6.2. Functioning glow plugs and good cranking speed. My K5 that I swapped a 6.2 into had a rebuilt starter that worked but wasn't great by any means. Even completely warm I'd have to let the GP's glow for 5 or 6 seconds before hitting the key. I replaced the starter with a Bosch 28MT gear reduction starter and the difference was amazing. Now when it's even remotely warm it flashes up on the first crank without the glow plugs.

I'd look into your starter condition, and battery cable condition as well. I swapped to 1/0 welding cable on my K5 and I swear I picked up another 50-75 cranking rpm's.

By definition a diesel is a "compression ignition" engine. The intake air is compressed which heats it up a lot...and at the top of the stroke a bit of finely misted fuel is added and ignites. The faster the intake charge is compressed the hotter that intake charge gets by TDC. You can see how crucial good cranking speed is, and it'd be my guess that your issue is cranking speed related.

Rene

 

[roydavenport]

I'm not even sure you have a problem....you contradict yourself in this sentence "The problem is that even when the temp gets below 120 the glow plugs still don't come on unless the engine is completely cooled off". In warm weather I very much doubt that the engine has gone from the 200 F range down to below 120 in an hour or two.

What I meant is you can still feel heat coming off the engine, but the temp isn't warm enouph to register on the temp gauge. When this happens the engine usually has a hard time starting unless the glow plugs come on. The engine has never had trouble starting when the glow plugs cycle first.

 

[roydavenport]

I never really thought about the cranking speed possible being too slow. I haven't had this Suburban very long and I'm not familiar with diesels. That's part of the reason I bought this was so I could learn about them. All my windows go up and down real slow. I wonder if the problems could be related. I'm not sure how fast the engine should normally turn over. It sounds ok to me, but them again I'm not real familiar with them. Could this be a compression issue? I had the compression checked and was told that 7 cyclinders were between 400-460 and one was at 360 which the mechanic said could be due to carbon build up on the valves. The Suburban has almost 200K miles on it. I'm not sure if it's the original engine or not. Someone told me it wasn't because it had a GM Goodwrench sticker on the valve cover. I'm not sure if he knew what he was talking or not.

 

[BKinzey]

Check your connections to your starter and then check your grounds everywhere. Bad or poor connections will affect your starter and/or windows.

Do the windows run faster when the engine is running?

There is a good chance the problems with the starter and windows is unrelated though.

 

[noJeepshere]

I think your windows moving slow are because the window motor is old and tired, I've had to replace 3-4 of them, and the window became the fastest in the west after.

As to your slow cranking speed, prolly old batteries and bad connections, check them all.

 

[roydavenport]

Check your connections to your starter and then check your grounds everywhere. Bad or poor connections will affect your starter and/or windows.

Do the windows run faster when the engine is running?

There is a good chance the problems with the starter and windows is unrelated though.

Yes, the windows do run faster when the engine is running. As a matter of fact, sometimes I have to start the engine in order to operate the windows.

 

[BKinzey]

Have your batteries checked. If the windows run better when the engine is running that's a sign your batteries are pooping out.

It's still a good idea to check your connections though.