Knock, Black Smoke, & misfire on 02 6.6

[pitstop190]

We have an 02 2500 GMC that came in with black smoke, what sounds like a fuel knock, and a noticeable miss. Also, hard to start. Canceling the #7 injector makes the smoke go away, as well as the knock, and the misfire feels unchanged. After the dealership told us that truck was not covered under the warranty extention, we changed the #7 injector. Starting is much easier now but the knock, smoke, and miss are all still the same.

So, we did a compression test and the results were 380 psi on all but #7 which had 320psi and on the second round had 360psi. After several tests the compression in 7 is not consistent from one test to the other.

The owner said he noticed the miss and the smoke but is hard of hearing and didn't notice the knock, so he drove it this way for a little over a month. After reading some of these posts, I need to know if anyone else has encountered this or has any advice? The balancing rate is pretty even on all cylinders but 7 & 8, which fluctuate from -4 to +6 depending on whether it is in drive or park. There is no noticeable fuel in the oil, and no white smoke.

[madmatt]

doesn't make much sense. too bad you aren't closer.

[pitstop190]

Your right about it not making sense, and in an effort to not cost the customer a lot more than is nessesary I was hoping to find someone with a similar experience to shed some light.

[madmatt]

how bout a cylinder leak down test???

[Mark Rinker]

Sounds bad for the valves in #7...pull the head? Scope that cylinder?

[Rabbler]

Maybe check the valve clearance on #7?

[madmatt]

it sounds like the start of a cracked piston but those usually smoke white and make a lot of crankcase pressure. I'd do a cylinder leakdown. if that comfirms a leak in #7, I'd probably go ahead and jerk the head. If you have a good borescope handy, you could try it but they're usually not much help and you end up pulling a head anyway. Look for washed down cylinder walls or evidence of cracks on the piston face.

[pitstop190]

Just got in to the forum and I appreciate the input, we were afraid that the owner running with the condition as such, probably did internal damage. Have not done a cylinder leak down test, and the valve train all appears to be good from the top, but it looks like we will pulling the head.

Another customer of ours just got his 3500 back from the dealer, after 7 months of fighting and waiting, they say they put two complete sets of injectors, along with all new return lines, lots of sensors and egr equip.

We will give an update on this one as soon as we pull it down.
Thanks again.

[pitstop190]

We pulled the head and every thing looks normal, checked for leaking valves and all are good. The cylinder walls still show the original honing, and the piston tops are not cracked. checked the lifters for anything abnormal and they look good. The 4 injectors on the right side are being tested, maybe one or more will show trouble.

[Mark Rinker]

Hmmmm...isn't this why GM eventually came up with the rule of changing all 8 injectors on warranty claim work?

Changing one injector is like doing a brake job on the right front corner...

[pitstop190]

It is amazing how much money diesel truck people spend on their vehicles, over and over you see posts here of putting 2 and sometimes 3 sets of injectors in a duramax. If you just buy a bigblock gas truck, you can change the engine for what these injector jobs are costing. The only reason we are looking for the problem before we throw a set of injectors in, is to try not to spend all of a good customers money at once. If the dealership had honored their extended warranty they would have changed them all out, but they didn't. So we try to take care of the customer so they will come back next time.:)

[Rabbler]

Why wouldn't the dealer cover the injectors? Mileage too high?

You might want to let the customer decide what to replace.

Sometimes you try to be a "nice guy" and it bites you in the ass.

I know a guy who tried that with a customers 01 Dmax. Replaced 2 injectors and truck was good for a month. Then replaced 1 more, lasted a week, then 2 more injectors a few weeks later.

Customers pissed cause he keeps coming back, has spent more $ than it would have cost to replace all 8 the first time.

Tech is loosing money because he feels obligated to give the guy a break on the labor 2nd and 3rd time back and his shop is tied up with this truck and can't make any real money on someone else.

The cost of doing the "Right Thing"...

[pitstop190]

this truck has 147,000, dealer said the extention on the truck was 140,000 miles. Whether its fixed or not, he has decide to get rid of it.

[madmatt]

The special policy is 7 years 200K but can be goodwilled out longer at the dealerships discrection. I did one on Friday that was 7 years 4 months old w/ 88K on the clock. Goodwilled it due to low miles, barely out by time and the truck has been VERY well maintained.

[Mark Rinker]

this truck has 147,000, dealer said the extention on the truck was 140,000 miles. Whether its fixed or not, he has decide to get rid of it.

Sounds like it should have had all eight, under warranty, the first time around. What was the in-service date for the truck? Now...who takes the hit for the first go-around, including head removal and inspection?

Not trying to bust your *&^^s, trying just to make a case for changing out all 8...especially at the miles this truck already had on it - assuming that this was this the first injector work done on the truck...if not, I can understand why the owner would have been looking for a cheaper alternative, but even MORE ammunition that GM should stand behind the warranty, of the second short-lived set.

[madmatt]

It depends on how the dealerships choses to implement the Special Coverage wether it should have been covered or not. In this case they were blatently wrong by saying 140K but if the problem is not related to high return fuel rates then it's really not covered. In my bay though, if it could be covered by the special coverage and has an injector related problem,,, it's getting all 8 paid for by GM.

[pitstop190]

You know dealerships will do whatever it takes to do what they WANT to do, if it's to be extra nice or to be a jerk. All the times we have tried to help a customer by getting recall or warranty work done, whether GM or Nissan, its always been the same, some excuse why that didn't apply. I will always hit the duramax people with the worst case senario, from the beginning, from now on. If you gonna drive one, you gotta pay the piper.( sounds like a good slogan) We'll let you know what happens in a few days.;):):confused:

[Rabbler]

Sometime it all depends on who answers the phone at the dealer.
You get one jerk service advisor who thinks he knows it all or a new guy who just doesn't Know about all the "special" coverage and it sours the whole situation.
I had to straighten out more than a few service advisers years ago when I was a Shop Foreman.

Good advisers (like techs, and parts guys) are hard to find...

Good Luck

[pitstop190]

Rabbler, you said it all!!!!!;)

[pitstop190]

Put the head back on changed all 8 injectors and the truck is good as new, i had 4 of the injectors tested when the base engine checked out good, 2 injectors had large fuel return and the spray nozzles where eroded. Wanted to say thanks to all who posted, and now we will break the bad news right from the getgo when a customer has injector problems. :):D:cool: