Injector Knock Diagnosis!!

[FPoitra]

Today I brought in my truck for the low rpm injector knock that myself and many other people have been experiencing. When hot (20 miles of driving), a loud knock, not clatter, would occur at around 900 to 1200 rpms, especially when pulling our from a standstill or driving around a parking lot. Of course it would not do it when I showed it to the shop foreman right way, so I took it for a 20 mile drive down the interstate and brought it back. Sure enough, it did it while he was driving it into the shop. He checked the cylinder temps and they were all at the 240-250 range. 6 hours later they called me and said they re-torqued the injectors, tested them and found out that 2 did not test to specs!! They said they ordered two new ones but they are on national backorder. My question is it safe for me to drive it. It runs perfect and does not lack any power and get around 18 mpg highway. I figure if they let me take it home, then it must be OK to drive.

 

[SquareDave]

I know just what you're going through. My truck needs only one injector, but the national backorder situation has put me out of commission for two weeks as of tomorrow. The mechanic told me that the truck is "driveable," but he recommended that I not drive it unless it's absolutely necessary.



I'm parked in my travel trailer only three miles from my current jobsite, so I just left the truck there on the dealer's lot until they can get the part and fix it. It's a great opportunity to get my old worn-out body back in shape by commuting on a mountain bike. There's little else of any positive nature coming out of this situation.



The truck was really good for two months, but the injector knock was accompanied by a significant drop in fuel mileage and a somewhat noticeable drop in power while pulling the travel trailer. I'm really bummed out about all this to the point that I'm starting to regret having bought the truck. The truck is great, but Daimler-Chrysler has been like the north end of a southbound horse about supporting this customer.



I hope this thing gets resolved for both of us soon. Perhaps, I'll be a less unhappy camper when I get my truck back.



Good luck





Dave

(parked in Vacaville, CA)





2001 Mobile Scout 27FKS Travel Trailer

2004 Dodge Ram 2500 SLT 4. 1 6-speed (with towing package)

2002 Klein Manitou mountain bike, 24-speed (no towing package)

 

[FPoitra]

Dave, How bad was your knock, and was it only at low rpms as well. Mine seemed to go away now that they retightened the injecotrs, but still the thought of 2 faulty injecotors. I have no choice but to drive it, so hopefully nothing worse will happen.

 

[rashwor]

Negotiate a cash settlement and get you some aftermarket injectors!!

 

[SquareDave]

The knock was loudest at low rpm after reaching operating temperature, but unnoticeable at cruising speed. As for how the knock is, well, how do you communicate "very loud"? It was loud enough that the mechanic at first suspected any of a number of problems with the engine itself. Inside the dealer's shop, the knock really echoed. The tentative shipping date for my injector via DC distribution channels is June 28. I hope they overnight it, but with my luck they'll send it by three-legged mule train.



After market injectors??? Is anybody making them for the 600?



Dave

(parked in Vacaville, CA)

 

[ButchJ]

I have a 2004. 5 with 350 miles and have had the knock twice, the first time low rpm and only did it for a few seconds, today engine was hot just came off freeway and a mile later began to knock, let off accelerator no change and then tried stepping on it with no change and no power, finely costed to side of road and shutdown. After a minute re-started and "NO" knock. Went staight to dealer and they checked for codes and there were "None" Engine light never came on. Any Ideas?

 

[FPoitra]

Just talked to a friend tonight who had the same thing happen to him. He said it sounded like someone was operating a jack hammer in his engine, thats how loud it was. Then it just quit and never did it again. My knock is getting louder and more annoying. I am getting a little upset that an engine with 12,000 miles is already having what I consider major problems. I hope the injectors arrive soon and hopfully they are whats causing the knock. I hope it is safe to drive, if not thank god for warranty!!

 

[rbattelle]

2 days ago, after a period of about 2 months with the engine sounding like a gnome was beating the block with a hammer at low RPM, the knock all but disappeared. It has done this pattern since new: knock real bad for awhile, then quiet down for awhile. I've had the truck just about 14 months now, 27500 miles. This knock is identical to what FPoitra reports.



I've found I can make mine knock louder if I purposely lug the engine a bit at low RPM.



Given the wide disparity between solutions to this problem and my reluctance to let my dealer go "willy-nilly" tearing through the engine looking for a noise, I am quite content to drive it until it explodes! I did have the fuel filter replaced (I always make the dealer do it) 2 weeks ago, and the tech drove the truck and told me the noise is "normal". He is pretty good at what he does. I have no loss of mileage or power.



Thanks for the update, FP! Keep us posted!

 

[amsoilman]

Do any of you that have this "KNOCK" have aftermarket boxes, such as an EZ installed?

I can get mine to KNOCK, if I let the engine "LUG" the least little bit! This Knockin will show itself much more when the engine is not warmed up.

I can remove the EZ, and I can hardly get it to KNOCK at all.



Wayne

amsoilman

 

[Windscreen]

Here's another datapoint for the discussion.



My truck has developed an idle to 1000 rpm knock from about 4000 miles. I had an ex-Cummins engineer at work take a listen to it. His prognosis was it was probably an unbalanced injector at idle causing a partial misfire. The partial misfire causes a quick load reversal in the front gear train that we hear as a knock. It shouldn't hurt anything, only annoy. He suggested, if the misfire is bad enough, you can find it by shooting a non-contact IR thermometer at each exhaust runner and look for one significantly cooler than the rest (after an extended idle to stabilize the temps in the manifold).



I was considering taking it to a dealer to have them do a cylinder balance/cut-out test at idle, but I need it every weekend to tow my race car. I figured I'd wait for my season to get over with, or for the noise to get worse.



Well, anyway, my truck now has 8,500 miles on it. Yesterday, after my usual 100 mi round trip commute, the knock completely vanished! It is as quiet as new again. I did change the oil the night before (previous change at 2,500), but I still had the knock (to some degree) when I got to work yesterday, so I think the oil change was coincidental. It never seemed to affect mileage, as mine has steadily been going up... last tank all highway, unloaded at 75 mph average = 18. 5 mpg hand calc'ed and over head. Over head will show in the low 20's if I slow down to 60 - 70 mph, but I just can't drive that slow on the open highway.



Perhaps these Bosch in injectors get a needle that sticks just a little every now and then. The quantity of fuel delivered at idle is very small, especially when it is delivered in two batches (e. g. pilot injection and main). So, any stickiness results in a partial misfire, but the sticky deposit can clear it self off over time? Just a theory. Obviously lots of people are taking their trucks in for the noise and getting injector(s) replaced, if there is indeed a national backorder.



Steve

 

[rbattelle]

Wayne,



I have no fueling boxes. Never have, probably never will.

 

[FPoitra]

When they change the injectors and if it still makes the knocking sound afterwards, I will then consider the sound normal. It just may be the "lug" sound that all diesels make at low rpms, but then everyones truck has to do it, which doesnt seem to be the case. Maybe I just have super sensitive hearing????

 

[jjdiesel]

Mine developed the knock at about 7500 miles. Same as described above, just off idle when loading the engine. Dealer hooked up diagnostics, shut off cylinders one at a time with me driving. Found the #1 cylinder causing the knock. Replaced injector... . knock gone. Took about 3 days to get the injector... just happened last week. I'm happy. Mileage did suffer about 1. 5 per gallon, now its back to normal.

 

[SquareDave]

FPoitra,



I got a PM that on July 1 Cummins sent out a bunch of injectors, and one of them was specifically for my truck (V. I. N and all). On the afternoon of July 2, I got a call from the local Dodge dealer that my truck was fixed and that I could come get it before they closed for the holiday weekend at 6 o'clock. When I walked into the service department, I thought they were going to break out into a round of applause. The truck runs great, the power is back, the knock is GONE, and the local dealer has recovered a space to park something he can sell.



Kudos to several on TDR who did legwork, made phone calls, and offerred to help. None of them HAD to do it, but they took a few minutes and did it anyway. I'm convinced that a lot of it resulted in a phone call or two to the local dealer from somebody from somewhere in the system or outside the system. That's in addition to my own calls and visits. The dealer seemed to be as helpless as I was on getting an injector, since their best information indicated an earliest shipment date of July 28. However, to everybody's surprise and elation, the injector arrived July 2. Thanks, guys.



Anyway, my truck is back on the road, and I'm much happier than I was a few days ago. The sad saga with the happy ending is on the 911 section of TDR ("Injectors on National Backorder"). I hope your truck has been taken care of also.



Dave

(parked in Vacaville, CA)

 

[Vaughn MacKenzie]

Dave, great news, glad you are finally back on the road, and can enjoy your truck as intended once again



Vaughn

 

[FPoitra]

I'm glad to hear that Dave! I also got a call on July 2nd stating my injectors have arrived and am scheduled to bring it in on Wednesday the 7th. So your knock is completely gone, even when hot? I hope everything goes well for mine too. Not saying that this was a fun injector escapade, but it was nice knowing that I was not the only one who had this problem because I would of really then became woried. Dave, its been real, its been fun, but not real fun. Freddy

 

[SquareDave]

Freddy,



Sure enough, the knock is gone, even after warmup. Low RPM, High RPM -- it's gone. The only sound I can hear is that slight clatter that lets me know it's a diesel. I hope the injectors solve your problem.





Dave

 

[Jumbo Jet]

One replaced injector solved my problem. I've added over 7,500 miles to mine since they replaced the injector and the knock has not returned.



My service man was going to the lot to harvest an injector from a new truck when the UPS showed up a day late with my injector. National backorder my a$$! They have an entire lot full of spare parts as far as I'm concerned!