Ok, My '85 6.9 is making a strange noise that sounds like an exhaust leak, but when I put my hand over the air intake, the noise quiets almost completely. It sounds like an air noise, or a valve tap, but it is really loud. The engine also runs quite rough.I recently did some work on my truck and now I have this rough running engine and this loud noise. The truck ran great before all this, but was a bear to start. Here is a brief synopsis of the work I did:

1. I had to replace the left head because I broke the old one trying to get the GPC out. So I got one from the junkyard, and carefully replaced it, making sure to clean it well, and torque it down to proper sepcs. I checked the pushrods and they didn't seem bent. Actually, nothing seems bent or messed up.

2. When I as putting the injector pump back on, I was careful not to screw up the timing. I took it off and put it on. That's it. I didn't rotate it or the engine.

3. The last injector on the right side was replaced with and old one out of the junkyard head, because I started to cross thread it when I was screwing the fuel line into it. I know it is probably bad, but I needed something to use just to run the truck after the head job. This injector leaks around the head, and I going to replace it tomorrow.

So, what could it be??? I was thinking air in the lines, but that wouldn't explain the loud air noise, right? Could the timing have gotten messed up somehow? Like I said, I put it on just as I took it off. I'm puzzled and very frustrated. The truck ran great before, but the GPC was going bad, and it was becoming hard to start. Now it starts great, but runs like crap. Go figure...

I really don't want to take it to the local diesel man, because he is expensive, and won't actually find the problem, just replace parts until it works right. Like I said before, when I cover up the air intake, the noise almost goes away, and the engine sounds close to normal, but still runs kinda rough. PLEASE HELP!!

 

what kinda shape was the junk yard head in?how many miles on that junk yard head?i am a diesel,ag mechanic,and i would never install a used head on anything without having it checkede out by a good machine shop first.that head could have a bad valve or it could be just plain worn out.as far as that injector,if it is bad it should cause a miss or skip.were the rockers and such in good shape,nothing worn excessivly there is thier?

 

Well, the air noise IS air. The diesel engine devours more air than you can handle. The ticking noise I believe is an injector. They are spring loaded to develop pressure to spray the fuel so it ignites. If the spring is weak, it will allow the compression to go backwards into the injector. Running lousy, is it because of the injector or IS the timing off a tad? I really dont know, due to I dont know how you removed the injector pump - did you take it off the back of the tower or did you remove the tower and the gear? One tooth off and there is several degrees of timing. Get back with a little more info and we'll get you straightened out.

 

The head I got was in really good shape, but I don't have any milage on it. The rocker were in great shape, too. As far as the pump, I took out, and left the tower and gear alone.

 

My diesel mechanic said it is probably a stuck lifter or a bad intake valve. If it is a stuck or sticky lifter, what are the chances it could work itself loose? If it's a bad valve, well, let me say the head is NOT coming off again. At least not by me...

 

the first thing id do is run and compr. check to see if valve train is working right do you hear any uneven exaust pattern at tail pipe

 

I bet its a bad injector. wile it is running, crack open each injector line and listen for a change in rpm.No change will show suspect cylinder and help narrow diagnosis. I would also make sure that all coppers on bottom of injectors are good and there is no leakage of any sort. Even return line leakage has been know to cause rough running and hard start. I hope this helps.