I've had this strange knocking sound going on for the past few months and I'm not sure what it is. It does it while idling, while driving at a steady speed, while accelerating, but NOT while coasting. It doesn't sound like piston slap or bad bearings, at least not to me. 

 

Here's a video of the sound I'm talking about:

 

 

As you can hear my idle is still set too high 

Edited June 23, 20168 yr by The_Hammer

I would start by having the injectors pop tested. Being it only knocks during fueling events that would be my first thought. Coasting the governor shuts the fuel down and doesn't pump. But idling, acceleration or constant speed it would knock because the injectors and pump is pumping. So if a injector had a problem it could be your knock.

 

Edited June 23, 20168 yr by Mopar1973Man

5 hours ago, Mopar1973Man said:

I would start by having the injectors pop tested. Being it only knocks during fueling events that would be my first thought. Coasting the governor shuts the fuel down and doesn't pump. But idling, acceleration or constant speed it would knock because the injectors and pump is pumping. So if a injector had a problem it could be your knock.

 

I had the injectors cleaned and pop tested a couple years ago by a local pump shop and they said everything was fine. I've heard since then that they do shoddy work though. 

 

I wouldn't mind upgrading to some 5x12 injectors since my trans is finally squared away but I'm not sure if I could tune them down enough to work with my HX35 for now. 

Still I would start with having them pop tested to verify. Should cost anything to get a reading... At least the shop I deal with he does pop testing for free.

1 hour ago, Mopar1973Man said:

Still I would start with having them pop tested to verify. Should cost anything to get a reading... At least the shop I deal with he does pop testing for free.

The problem is there aren't any other places around here to get them tested besides the place I took them to before, and they charge $50. I've heard entirely too many bad things about that place (such as telling people their injectors are good when they're actually wore out) to deal with them again. I would have to ship them somewhere. I also can't be without my truck for more than a few days in row, which complicate things. 

 

I've noticed that my mileage has slowly gotten worse. I used to get around 17 mpg and now the best I can do is 14.

Edited June 24, 20168 yr by The_Hammer

Option b would be loosen the injector lines until you find the bad one... or don't.  

12 hours ago, CSM said:

Option b would be loosen the injector lines until you find the bad one... or don't.  

That's a great idea. I don't know why didn't think about do that 

Very difficult typically the loosen creates it own knock sound because of low pressure. So it might be difficult. Still I would pop test all them to verify the condition then you can rule it out absolutely.

The knocking sounded like it was comming from #6 cylinder so I loosened the injector line and the knocking stopped. Tightened it back up and the knocking returned. I did this a half dozen times just to make sure and got the same results each time. I'm going to swap #6 injector with #1 later to make sure it isn't a pump issue. 

1 hour ago, Mopar1973Man said:

Very difficult typically the loosen creates it own knock sound because of low pressure. So it might be difficult. Still I would pop test all them to verify the condition then you can rule it out absolutely.

Pop testing is my last resort since I will have to ship them somewhere and be without my truck for at least a week. I really wish there was a reputable shop close by.

18 minutes ago, The_Hammer said:

Pop testing is my last resort since I will have to ship them somewhere and be without my truck for at least a week. I really wish there was a reputable shop close by

 

What??? The diesel state of the nation and there isn't a diesel shop near you??? I'm in the center of Idaho in the middle of no man's land and have a good diesel shop just 2 hours away and have them pop tested for free in the very same day. Be back home and install by evening. Just doing a quick search I've found several diesel injection shops that are near you. All we are asking for is verify the pop pressure and spray pattern. (No tuning).

 

But since you found #6 now its a choice of replace the injectors or have the one pulled and looked at and inspected. If they are low mileage yet you could still have the pop tested and retuned if there is no damage.

Edited June 24, 20168 yr by Mopar1973Man

@Mopar1973Man

 

The injectors are original and have over 300k miles on them. Do you think cleaning it would do any good?

Nope get new ones haha.

 

I think 300k means that have lived their life.   Injectors are cheap for the 12v and 24v

2 minutes ago, Me78569 said:

Nope get new ones haha.

 

I think 300k means that have lived their life.   Injectors are cheap for the 12v and 24v

Not when your short on funds from fixing your house 

 

15 minutes ago, The_Hammer said:

The injectors are original and have over 300k miles on them.

 

You looking to replace all 6 they are wore for sure.

 

Sorry I for some reason had it my head that you just replace the injectors and where low mileage so that why the pop testing angle. Now know the truth that they have 300k miles on them you pushing you luck. I've done a set of RV275 from CajFlynn for free had the pop tested at +400k miles and they lasted for another year after cleaning and pop test.

12 minutes ago, Mopar1973Man said:

 

 

You looking to replace all 6 they are wore for sure.

 

Sorry I for some reason had it my head that you just replace the injectors and where low mileage so that why the pop testing angle. Now know the truth that they have 300k miles on them you pushing you luck. I've done a set of RV275 from CajFlynn for free had the pop tested at +400k miles and they lasted for another year after cleaning and pop test.

I've personally never seen injectors completely fail, will the engine just no longer start?

I've never seen them out right fail either... I lost my RV275 at a pop pressure of 240 bar and they became very pissy and popping way early in time so that tend to knock more. When it was idling and getting pissy it would miss pretty good. Thing is about failure it could potentially fail a single injector like we both experienced and the rest are running dangerously thin. Cheapest route would be to get new nozzles but after having them pop tested and tuned now you might be at the same cost of total replacement of all injectors.

 

Common rail engine only need one bad injector and it can prevent it from starting. 12V and 24V engine one injector will impact performance but I've not heard of it preventing starting. Maybe loss of prime...

I wonder if these injectors are any count? 

 

 

http://www.dieselpowerproducts.com/p-7530-dodge-12-valve-fuel-injectors-9070-hp.aspx

Now my question is... Are the injectors pop tested and flow match before shipping? At what value of percentage range?

4 hours ago, Mopar1973Man said:

Now my question is... Are the injectors pop tested and flow match before shipping? At what value of percentage range?

Those are very good questions that will be asked before purchasing injectors from anyone. I also want to make sure I don't end up with marine injectors.

I know there is lot of vendors that just have boxes of injectors in stock and just chuck 6 is a shipping box with no testing, no matching or anything. It's just assumed everything is OK and should work OK. Thing is we both like to have the performance and everything as perfect as possible. Hence the questions. Now if the shop charges extra you know what would of happened.

my 12 valve is running a wee bit different lately and has 425,000 miles w/ originals. What should I get for a stock motor to help it a little bit?