89 C2500 6.2 Knocking

[Scoutsout]

A couple of days ago my 6.2 developed a knocking sound which sounded like a rod went out. Before all that happened I noticed it started to idle rough, then the check gauges light came on, then the loud knocking sound and then it just stops. It started right up but it goes thru the same cycle.

So, I take off the valve covers and everything looks intact. Any thoughts or ideas on this one?

Thanks
Angelo

[john8662]

Could be a stuck injector, they'll make a really loud knock, similar to the rod knock.

When your check gauges light came on, were any of the gauges out of range (oil, volt, water temp)?

To check for a stuck injector, you need the engine running (and knocking), then one by one loosen an injector line at the injector, to where it starts leaking. This will cause that injector to no longer function, and cause a miss. You will do all 8 until you find the spot where the knock goes away completly, and you're left with just the miss. If the knock never goes away, it's something else. Note: the knock will get softer with each line being loosened (loss of injection presure in system throughout), but the knock won't go away, until you find your culprit (if you have a bad one).

J

[Robyn]

I assume when you say it stops, meaning by itself??

Starts right up?? after it stops??

Check gauges Hmmmmm sounds like it has lost oil pressure.

Very likely a rod or main bearing as left this world or other issues to stop oil flow.

What is the oil pressure when at idle?? Should be about 20 PSI hot and 40 running at speed 1200 and up.

Let us know

RC

[eliasl6.2]

Hello everybody, I'm new to the 6.2 diesel scene. I have the same problem that Angelo had and my blazer produces excessive white smoke also. I went ahead and checked the injectors like J sugested and found that injector no. 1 was the culprit. Changed the injector started the blazer and the knocking was still there. I understand that if the fuel return pressure coming from the injector housing differs from normal it will affect timing. I tested the pressure by pinching the line and the sound whent away, motor ran pretty good. I'm thinking timing?? Bad fuel?? I also checked everything else, like HPCA, lift pump, temp. switch, air in system, glow plug system, inj. pump housing press., and filters. The only thing I have no way of checking is the timing. How do you change the timing.

[More Power]

I recommend swapping an injector into another hole to see if the knock migrates with the injector. This way, you don't spend money on an injector when it might not be the problem.

Remove the valve cover so you can see the valve train operates correctly with the engine at idle. If the rocker arms for #1 cyl move similarly to the others, you can eliminate a cam/lifter/rocker issue....

Now, it comes to the more serious causes of a knock.... The piston may be damaged - broken, bent skirt, worn piston pin bore or loose small end bearing. You won't know till you've taken the engine apart to eliminate these possibilities. :(

Jim

[eliasl6.2]

Hello Jim,
Thanks for the reply. The knocking goes away only if I crack open the no 1 fuel line. I'll try to remove the cover next. Hopefully the problems stops there. What does the heavy white smoke mean? At idle it smokes lightly, but when I accelerate it it smokes heavily. The motor starts on the first revolution. Sounds healthy. I hope is nothing internal. Thanks for the info.

Do you know of any shops that deal with this type of motor? Machine shops, parts, aftermarket. Most of the PepBoys and similar shops have no clue about this motor. I live in Inglewood Califonia. People look at me funny when i tell them that the blazer came with a 6.2 detroit diesel. Most machine shops that I know of do not whant to deal with this motor. Thanks again for any info.

Elias