I'm wondering I'm looking to buy a another 6.2. I know the easy answer is don't buy but I love a challenge. Here is the problem it starts up smokes like a chimney - unburnt fuel. I know the injectors need to be replaced or rebuilt I pulled one out and lots of carbon deposit. Its a fairly new injection pump so I know its not that - plenty of fuel when I crack the injectors. The mark on the pump is lined up. the driver side exhaust manifold is rotted and I can see a flame shooting out. is it the timing chain as well as the injectors ?

Someone replaced the IP but didn't set the timing.

Someone replaced the IP but didn't set the timing.
The engine timing or the pump timing is this detail in the manual. Or could you supply me with the quick dry version.

Was the pump rebuilt or was it actually new?I've had cases of buying rebuilt pumps and the engine did'nt do very well after installing them.In fact it ran worse.Depends where you bought it and the care taken to rebuild it properly.What happens when you rotate the pump toward the driver side location?Does it run any better?

Was the pump rebuilt or was it actually new?I've had cases of buying rebuilt pumps and the engine did'nt do very well after installing them.In fact it ran worse.Depends where you bought it and the care taken to rebuild it properly.What happens when you rotate the pump toward the driver side location?Does it run any better?


Well it was turned all the way to the drivers side and I realigned it to the mark . It didn't seem to run any different or skip any less. another thing is when I step on the pedal it smooths right out but still smokes.

Another possiblity is a partially sheared camshaft sprocket keyway.These do shear on this engine and cause all sorts of driveability problems and the pump timing can't be sent properly.Any suction felt at the exhaust pipe while the engine is running?

I noticed you stated you need new injectors so it would be a good idea to replace them and then things might improve.After 100,000 miles they are supposed to be replaced although many times they are not.

I noticed you stated you need new injectors so it would be a good idea to replace them and then things might improve.After 100,000 miles they are supposed to be replaced although many times they are not.

I havn't ruled everything else out but I can try with that and then cross my fingers. The ones I checked were pretty bad. Another thing I noticed was the amount of rust and rot inside the return lines. The fuel is good in it new filter. He changed the pump but didn't change the injectors. He gave up after the pump didn't solve the problem. I threw a filter on it and then twisted the pump back into position and inspected the injectors. I know it needs glow plugs. Another thing my friend did as it was running was sprayed a mist of the forbidden ether over the intake and it cleared the smoke up. So I'm guessing the extra accelerant added to the fuel mix was enough to burn off any excess fuel being dumped by the bad injectors at least thats the theory. If I order the injectors they wouldn't be in till next week sometime.

Okay great.Start with replacing the fuel injectors and be sure to buy some of that braided fuel return line hose.It's found at your nearest diesel shop.The hose used nowadays eliminates the need for the tiny GM injector hose clamps.

Okay great.Start with replacing the fuel injectors and be sure to buy some of that braided fuel return line hose.It's found at your nearest diesel shop.The hose used nowadays eliminates the need for the tiny GM injector hose clamps.

Hey thanks for the advice. I'll let you know how it turns out probably late next weekend.

Sounds great.

The engine timing or the pump timing is this detail in the manual. Or could you supply me with the quick dry version.

Unfortunately, there is no way to set the correct timing without a timing tool (or maybe with a lot of experience and a clear hose connected to the IP) --- you can only get more or less close without or find the right setting by luck. Aligning the marks doesn't mean that the timing is set correctly, they are only there to give an indication sufficient to get the engine running and then to set the timing with the tool.

Replacing injectors or not, it's a very good idea to check the lift pump. If you have insufficient fuel pressure and/or flow to the IP, it'll still not run well even with a new IP, new injectors and good timing.


If you get new return lines, you'll need an injector socket if you want to cut the old lines off rather than taking them off. A straight 30mm socket doesn't fit over the injectors with the rest of the lines still on. If you want to take the lines off, have long nose pliers with a 45 degree bend at hand, that makes it way easier. You also need a torque wrench to tighten the injectors to 50ft/lbs.

Unfortunately, there is no way to set the correct timing without a timing tool (or maybe with a lot of experience and a clear hose connected to the IP) --- you can only get more or less close without or find the right setting by luck. Aligning the marks doesn't mean that the timing is set correctly, they are only there to give an indication sufficient to get the engine running and then to set the timing with the tool.

Replacing injectors or not, it's a very good idea to check the lift pump. If you have insufficient fuel pressure and/or flow to the IP, it'll still not run well even with a new IP, new injectors and good timing.


If you get new return lines, you'll need an injector socket if you want to cut the old lines off rather than taking them off. A straight 30mm socket doesn't fit over the injectors with the rest of the lines still on. If you want to take the lines off, have long nose pliers with a 45 degree bend at hand, that makes it way easier. You also need a torque wrench to tighten the injectors to 50ft/lbs.

I took all the lines off and a straight socket fit right over it. As far as the timing goes which way is more fuel the drivers side or passenger side ? If the timing chain is stretched a little that can cause some problems too wouldn't it. When it stretches out is there an a adjustment to compensate for the play or is a new timing cain in order at that point ?

Okay great.Start with replacing the fuel injectors and be sure to buy some of that braided fuel return line hose.It's found at your nearest diesel shop.The hose used nowadays eliminates the need for the tiny GM injector hose clamps.


I forgot to mention there seems to be some fuel getting into the oil I noticed. Would that also strongly suggest the injectors not fully closing ?

Timing doesn't give you more or less fuel, it's about when injecting the fuel begins (and ends) in relation to the position of the pistons within the cylinders.

The timing can be adjusted by turning the IP housing --- towards the drivers side advances, towards the passenger side retards. Advance it too far, and you can cause damage to the engine ...

When the timing chain is stretched too much, it needs to be replaced --- but I don't know how much "too much" is ...

Fuel can get in the engine oil after the engine is shut down because sometimes fuel leaks from the pintle area in the injector.This is the case with injectors that are plain worn out and in very poor condition.Also I did'nt notice if your using a mechanical or electric lift pump but if you've got a mechanical lift pump,the diaphram will sometimes rupture sending fuel into the oil.Or if your using a electric lift pump along with the mechanical lift pump,that too can cause the diaphram to tear and rupture.

If the chain is stretched badly,your pump would have to be rotated to the driver side considerabily to make up for the slack but even after doing that,the valve timing is still suffering.

Advancing the timing does increase power output and quicker cold weather starting but it also has its disadvantages too,but only if you go overboard on it.The width of the timing mark stamped upon the front cover is equal to roughly one degree.The rule of thumb is too not exceed 3 degrees past the mark stamped upon the front cover.

Fuel can get in the engine oil after the engine is shut down because sometimes fuel leaks from the pintle area in the injector.This is the case with injectors that are plain worn out and in very poor condition.Also I did'nt notice if your using a mechanical or electric lift pump but if you've got a mechanical lift pump,the diaphram will sometimes rupture sending fuel into the oil.Or if your using a electric lift pump along with the mechanical lift pump,that too can cause the diaphram to tear and rupture.

Actually its a mechanical pump. I figured it was ok cause I didn't see any leaks. It wouldn't hurt me to take it off and throw another on there just to see. If it is I wonder if it would fix any other problems I mentioned earlier.

The lift pumps seldom fail but the diapram can,which will cause the fuel to get in the oil,but as far as a driveability standpoint,yes it will affect overall engine operation if its not producing the proper pressure and volume of fuel required.

The lift pumps seldom fail but the diapram can,which will cause the fuel to get in the oil,but as far as a driveability standpoint,yes it will affect overall engine operation if its not producing the proper pressure and volume of fuel required.

It drives ok it doesn't surge or anything like its not getting enough fuel so I could probably rule the pump out. I just have to wait til the injectors come in.

The new injectors will certainly help this engine out.Once they are installed,i'm sure it'll run much better.

How do you know if the timing is too far advanced?

I advanced it a few days ago, but I'm not sure if it's too much now. It's running much stronger and smoother and starts easier, so I'm thinking I'm on the right track.

Would I notice anything when driving? Before I advanced the timing, I used to get some more power at about 75mph, but now that doesn't seem to happen. It's more like I'm losing a bit power when going faster than about 68, though there's still more than before. I'd have to drive it more and watch out for that to be sure, though.

Now I can't help thinking that picking up power before could have been an effect of the load advance. If understand it right, this would mean that I could have advanced the timing to the point where the load advance takes it too far under these conditions (driving 68mph+) and/or doesn't have the effect it's supposed to have. Turning the pump a bit back could be a good idea --- or not, I don't know how to tell.

If there only was somebody with a timing tool not too far away from here ...


BTW, the service manual (tm9-2320-289-34.pdf) describes how to check if the timing chain needs to be replaced.

The new injectors will certainly help this engine out.Once they are installed,i'm sure it'll run much better.


Well this is what happened. Instead of buying new injectors I figured I'd give it a test I got another engine that I knew ran so I took the injectors out of it and tried it in mine the truck still runs the same really rough but smooths out when I step on the pedal at least somewhat and the smoke is still unbearable. It smokes so bad it engulfs the truck and its smells like unburnt fuel. If the timing chain is that stretched out could this be the real problem. I'm at a loss. What should I do next ?

check the compression...no one else noticed that there were flames out the manifold...that tells me the exhaust valves are burnt...which would cause you to lose compression and thus get a rough running engine as well as having unburnt fuel due to incomplete burn

this incomplete burn could allow the cylinders to wet down and allow diesel into the oil...

do a compression test and a leak down test to verify

check the compression...no one else noticed that there were flames out the manifold...that tells me the exhaust valves are burnt...which would cause you to lose compression and thus get a rough running engine as well as having unburnt fuel due to incomplete burn

this incomplete burn could allow the cylinders to wet down and allow diesel into the oil...

do a compression test and a leak down test to verify

I did a compression test they were all within range. To me its seems there should be a clear answer its just driving me nuts trying to figure out what it is with out having to smash into the motor and visually inspect everything. I' d like to know whats causing it. The valves were my next guess but what else could I be missing I have another engine I could throw in it but it would be nice to know what else I can check. I've never seen an engine smoke as bad as this one.

you can set the timing
take it somewhere or get the tool...

you can set the timing
take it somewhere or get the tool...

You mean the injection timing ? Where can I get the tool ?

check the compression...no one else noticed that there were flames out the manifold...that tells me the exhaust valves are burnt...which would cause you to lose compression and thus get a rough running engine as well as having unburnt fuel due to incomplete burn

this incomplete burn could allow the cylinders to wet down and allow diesel into the oil...

do a compression test and a leak down test to verify


Could a blown head gasket be the case ? I'm going to investigate that tommorrow. It doesn't neccesarily have to have oil in the coolant for that. Maybe a good old fashioned cracked block. Dumbass never checked the coolant level and maybe its water in the oil and not so much fuel ? What do you think ?

Gee thanks to all your professional guess work guys I was able to locate the problem. Truck runs like a champion. Didn't even have to do a checklist for it.

So, what was the problem? Just asking because I'm in the same boat...

Smitty

So, what was the problem? Just asking because I'm in the same boat...

Smitty
Thats a nice truck in your pic.! Well it happened to be a partially sheared crankshaft key. I just took the timing cover off to see what was going on in there and the chain was really loose so I ordered a new one and when I slid the old timing set off the woodruff key was partially sheared. I'm glad I didn't spend a ton of money on other fuel related possibilities. Alot of work but in the end it was about an $85 dollar fix. A loose timing chain does matter. When I put the new one on I have 0 deflection and the book says to allow up to a half inch of it. Anything over replace the damn thing. I called a local diesel shop and they told me to replace the injectors with brand new ones. lol. I'm glad I don't listen to people. Then they said have the inection pump calibrated for $250.00.

I know right where to look if I ever see these symptoms again without hesitation.

Thats a nice truck in your pic.! Well it happened to be a partially sheared crankshaft key. I just took the timing cover off to see what was going on in there and the chain was really loose so I ordered a new one and when I slid the old timing set off the woodruff key was partially sheared. I'm glad I didn't spend a ton of money on other fuel related possibilities. Alot of work but in the end it was about an $85 dollar fix. A loose timing chain does matter. When I put the new one on I have 0 deflection and the book says to allow up to a half inch of it. Anything over replace the damn thing. I called a local diesel shop and they told me to replace the injectors with brand new ones. lol. I'm glad I don't listen to people. Then they said have the inection pump calibrated for $250.00.

I know right where to look if I ever see these symptoms again without hesitation.

Thanks for the info. I just picked up an 88 crew cab that starts fine and runs great. It was an Air Force truck and has less than 70K documented miles. I just need to have a starting point to find out why it has all of the white smoke under acceleration. It looks like it has been doing it for a while since both tail pipes are wet.

Smitty

Good luck Smitty