Am I running too lean??

[neo]

I placed this in the 6.2/6.5 cause figured it was pretty applicable to both. Anyway, I recently (with overwhelming support from this community) replaced my injectors. However, even before the injector replacement I never see any black smoke. Not even on VERY hard accleration. Not now, or before the replacement. Is this possible I am running too lean and need to dump a little more fuel to the injectors by enrichening the mixture?
On another note, today when I sarted it up and let it warm up, then began to accelerate away from the house, I heard a fairly loud knock that would change frequency with the engine speed. When at idle, it was barely audable, as I sped up, much more apparent. Turned around to park it and it stopped. Did not notice any change in engine performance or idle. Is it possible one injector had a little dirt from the replacmcent and it was not shutting or somethign? Thanks!

[moondoggie]

Good Day!

You might want to click on "Quick Links", then "Edit Signature", & let us know what year, model, equipment etc. truck you are talking about. It's handy, because you don't have to remember to do it, it shows up at the bottom of all your posts automatically. ;)

Your "no smoke" symptom will depend on what year truck you have.

"Is this possible I am running too lean and need to dump a little more fuel to the injectors by enrichening the mixture?" With a diesel, you can forget the word "lean" - it really only applies to gassers. A diesel is always WAY lean until you start seeing smoke. Take a look under the hood - see a throttle plate? A diesel doesn't have one. Your diesel draws all the air it can, all the time. Power is regulated only by how much fuel is squirted. If you "dump more fuel", you go faster.

I'll have to let one of our experts answer about the knock - I've been blessed to not have this happen to me on any of the 6.2/6.5's I've owned.

Blessings!

[john8662]

Well said MD!

The knock could be air in the fuel system, or one injector not working properly, sometimes reman injectors fail, one bad nozzle in the bunch.

If this becomes an issue where it does it all the time then you can troubleshoot it by loosing one injector line at at time until the knock stops, then you'll have that injector.

Ditto on updating the signature...

see?

[neo]

Excellent advice. I have changed my signature accordingly. I honeslty never thought about the signature establishing a bearing in which to start from.

THe knock has not re-appeared yet, hopefully it won't again. I am hoping it was some particulate moving through the injector (possibly) from the re-install. If it is a bad one, I now have the ultimate injector socket and have squashed my replacement fears.

So, given the 89, which (and I'll need to remodify the signature to reflect this) had a GM Goodwrench replacement sometime early in the life of the truck (~60k from what I can tell) and the truck has 120k now, if I stomp on the go-fast pedal, should it produce a little black smoke? It is compeltely clean. It also, or at least it seems, makes a bit more engine noise since the injector replacement.

THanks again for all the help/advice, I sincerely appreciate it.

Oh, also, sorry about the nomenclature and/or my misconception on the lean thing. Yes, my background is deeply rooted in gasoline engine work and diesels are very new to me.

[john8662]

88-93 6.2's used different heads, more similar to what the 6.5's used. The injector angle was changed in the heads leading to a more complete burn (emissions friendly). They do smoke less!

The injection pump is also calibrated better on the later 6.2's leading to less smoke.

My '91 suburban is essentially the same as your '89, it doesn't smoke either, which is a good thing.

It will only smoke if you're already in 3rd gear and punch it forcing the transmission to shift down to 2nd before going back to 3rd (governor in trans reached). Mainly due to EGR, which, is disabled on mine now so I don't think it'll do it at all now.

Glad your learning Diesels!

J

[moondoggie]

Good Day!

"I honeslty never thought about the signature establishing a bearing in which to start from." Now we know you have a fully mechanical IP.

No black smoke whatsoever - you could turn your IP up a little. Personally I'd be afraid of doing this without knowing EGT's - when you begin to overfuel diesels, the EGT's can rise precipitously, which is BAD. Others can give MUCH better advice than I can - sorry! :o

Keep us informed.


Blessings!
(signature in previous post)

[neo]

Again, wonderful advice, and I appreciate it.
Would the recent injector change make the engine noise more apparent? It seems as though it has gotten a bit louder. Could the injector change alter (slightly) the timing? I have read that advanced timing can make the engine noise louder (if I recall.) I really enjoy learning about the diesel. I love driving it. Despite the way the truck looks, it is a blast to drive. Thanks again!

[moondoggie]

Good Day!

Since nobody that actually knows about this stuff hasn't answered, here goes...

"Would the recent injector change make the engine noise more apparent? It seems as though it has gotten a bit louder." Could. Even stock replacement injectors are going to pop at a higher pressure than worn factory units, which might make her rattle a little more.

"Could the injector change alter (slightly) the timing?? Could. I would have guessed that the higher pop pressure would retard timing a little, but perhaps that's swamped by the increase in rattle caused by new higher-pop injectors.

"I have read that advanced timing can make the engine noise louder (if I recall)." That's been my experience.

Keep in mind: All I do is parrot what I've read here over the years. Virtually all of my knowledge is 2nd-hand. I've been blessed with trucks that have, for the most part, been very reliable. So, take what I write with a large grain of salt; maybe wait for others to correct and/or fill-in.



Blessings!
(signature in previous post)

[john8662]

Accurate!

Better atomization of fuel due to properly working/popping injectors will lead to better combustion, in this case a little louder boom.

The injection system could increase in it's noise output because of the slight increase of load of injectors popping later.

Remember, a GREAT deal of the noise these engine makes is in that rotary fuel thingy between the block and the intake.. A.K.A. Injection Pump.

J

[belizean6.2]

I also had a knock coming from my engine. When i started it up in the mornings the knocking was really loud. Then after it would warm I could still hear the knock from inside the truck while it's idling or if I was moving in 1st gear.

In the end what happend was that one of my pistons shattered one day while i was driving it. My mechanic says that it could have been too much fuel or that the injector was squirting diesel in as a liquid and not in a mist.

Now i have all new injectors and i still hear the knocking in the moring but it goes away once warm and I cannot hear the knocking when inside the truck.

So if I were you I would have the knock checked out for sure before something major happens..