...what part of my problem was. If some of you guys remember, about a year ago I was having problems with an abnormal rapping/knocking from the back of the engine. I replaced the fuel filter, searched for fuel leaks/air bubbles, replaced the lines from the tank to lift pump and return, replaced lift pump, had injectors cleaned and reset, pulled DV's and cleaned them, pulled tranny to check flexplate, changed rod and main bearings, checked KDP (snug as a bug), and probably a few other things I don't remember off the top of my head. But my gut said it was fuel related. Come to find out, being a bit new to diesels, changing the fuel filter is a bit more involved than a gasser. All I did the first time was put the WIF sensor on, fill it up, and screwed it on, not realizing until reading the instructions on the next filter that there are 2 o-rings that need replacing: WIF sensor and a smaller one on the bottom of where the filter screws on. Following the instructions got it running much better. It still has a bit of a rap but is slowly improving. It is a cummins after all. I'm also running about 2 qts engine oil to a tank of fuel to see if it helps, which I did a week before the filter change. Engine oil helps, but the change was noticeable after the filter was put on correctly.

I realize that air was probably getting sucked in through the old WIF o-ring, but the other little o-ring was actually missing. I think this one separates filtered fuel from unfiltered inside the filter, but I don't really know. I hope I didn't screw up the IP or injectors running it like that. I don't think I put 1000 miles total on it with it running like it did, so hopefully I'm good.

Sorry about the long post. I'm just feeling relieved to be on the right track finally (please feel free to leave my bubble alone!! ).

 

<pokes bubble>
That little o-ring is next to useless. It keeps unfiltered fuel from leaking into the filtered side - but any fuel that sneaks through between the threads is gonna be pretty well filtered! Re-use, it, change it, or leave it off - it won't make any difference in how the truck runs.

Sorry.

 

What about a broken flexplate? I recently heard a truck that had what sounded like a bad knock. I told him it's possible the flexplate is broken and he responded with "well, I had the transmission rebuilt within the last month." I told him to go straight to their shop. I never did hear the end result. I seem to recall your thread about this issue but don't recall if you had the opportunity to pull the transmission and inspect things.

 

Well I kinda figured that. But the o-ring on the WIF sensor looked pretty rough when I took it off. I'm thinking that was more of a problem than the other one. I never really noticed any leaks, though. Sucking air maybe. (bubble intact )

Yeah I pulled it. Flexplate looks fine, though I never got it magnafluxed. I did notice just the other day when poking around, I have a slight compression leak on #3 at the injector hold down nut, enough to push a couple of bubbles every now and then. I suppose if I put a little soapy water around it while running I might see more of that. I put my hand on all 6 injector lines and they all felt pretty smooth except #3 ticks and I think it's in time with the knock. I didn't have my wrenches handy to dig deeper into it and it was rainy too so I have to look into it later.

 

Tighten the #3 hold down nut to 60ft. lbs. to stop the minor compression leak. That small of a compression leak won't affect anything. To me, that doesn't seem it could be the cause of your knock though.

I changed out the stock injectors on Blackfordd's truck and #6 was spitting fuel having tightened the hold down nut to spec at 44ft. lbs. and didn't have a knock going along with it. I went back and put 80ft. lbs on it and it quit spitting fuel. I probably didn't need to double the torque but it was spitting quite a bit just at an idle.

Have you had your injectors tested? One way you can check them out is to loosen the high pressure fitting at each injector one at a time with the motor running. If the idle doesn't change, you've found a bad one.

 

Yeah they've been tested, cleaned, the tips reseated, and reinstalled to spec with all new copper. Cracking the lines creates a miss on all of them. They are all firing good, I'm just wondering if a compression leak can cause a late fire. I realize it would have to be a significant amount to cause that, but I have seen stranger things. The reason I suspect a fuel system or ignition issue is that, to me, if it were mechanical, it would be consistent no matter the conditions, given some variables would have an effect. But this thing will run great cold to hot, working hard or not, on some days, and on others I can feel a vibration in the gas pedal seemingly from something out of time, and the knock is there at all temps. Sometimes it runs great cold to warm, then after getting on the road a while, it begins to tap. It's pretty weird. Almost seems like it's related to ambient conditions. Here's a video I took after I got the tranny back in. Sounds the worst here, it's not always like this:

http://www.youtube.com/watch?v=LZ0-JkHFbQ4

All the bolts in the bell housing are torqued to spec, from adapter plate to torque converter.

I'd also like to check the valves again. Might be something with them. I want to have a look at the pushrods to see if the valves might have ever slapped the pistons. As far as clearances go, .010" for intake and .020" for exhaust is the cold setting right? If so, do you know what hot setting should be? Thanks.

 

.010" intake and .020" exhaust is the spec. Some have set them to .008" and .018" and I doubt anyone's gone tighter. I'm still baffled at the knock/ticking sound it's got. It almost sounds like a minor slap of a piston. Do you know how well the truck was maintained by the previous owner? Maybe the #6 piston got a little too warm at some point?

 

why are you running motor oil in the fuel???????

 

Too keep his IP and other related fuel system parts lubed. Since they've done away with the necessary sulfur content we require. I run 2 cycle oil in mine, and a bit of howes fuel treatment.


As for the sound. I want to suggest a rounded lobe on the cam, or a bent pushrod? Sure sounds like a valve train rattle...if I'm hear the right noise.

 

This may be the old gas mechanic in me, but that sure sounds like an exhaust leak to me...Mark

 

Well, I have it tuned more than it was when I got it and I have yet to push more than 1100* pre-turbo loaded or not. Believe me I tried. As far as maintenance, I have no records from him, but he says he learned from 2 previous trucks to run synthetic all around. But I wouldn't be surprised if it were hogwash.

Ditto. Just tried a cheap 15w40 oil this time to see what it would do. So far I like it. I usually run 2 cycle and lucas fuel tratment, sometimes a dose of tranny oil to help keep things clean.


I'm thinking a possible valve train issue my self. Don't think it's a cam lobe as it doesn't do it all the time, which might suggest something changing position now and then, like a rotating valve or pushrod. Something like that.

I already took a listen to that, but the sound comes from between the bellhousing and oil pan. It sounds like something with the rotating assembly. I might play with IP timing just to see what it does. I doubt it'll clear it up though, since it sounds like a problem with 1 cylinder, not all 6.

 

Its a really good idea because the new diesel fuel doesn't have enough Sulfur in it.

We run 10 gallons of filted WASTE motor oil to every full tank in the 93.....it LOVES it.

Just get a backdoor deal with a local shop and ask them to not mix antifreeze in with the oil which i don't think most do anyways...

 

Little smokey? Do you run a series of filters, or is that done before you put it in the tank?

 

The Sulfur is not the lubricant -- it's just that the process for removing the sulfur also reduces the lubricity of the fuel . . . and the esters that cause certain nitrile rubber compounds to swell & be compliant.

 

about the oil!
two stroke makes sence
but motor oil was never intened to be burnt!! i would be worried about deposits or some such thing????