(video) CAm slap or Injector knock?
 

1992 300D 2.5 Turbo.

Injector 4 was bunged up so I replaced it and balanced it, but I had to use a DNSOD261 as I didnt have any DNSOD265s left.

It is knocking now (see video). I plan to get the proper injector and put it in, but for now, this 261 is better than the bunged up 265 I had in there.

HOwever, Im not sure if it is the injector or the cams slapping. I dont know the difference in sound. Can you tell from this video if it's injector knock cam/lifter slap? I took the oil cap off and didn't hear anything like the knock, but I don't know if you can hear the cam slapping better by taking the oil cap off or not. Seems you would, but Im' not sure. HELP! Thanks.

The video is here - http://www.pauldrayton.com/uploadfiles/bd/jadeinjector.html

Might be a bad lifter changing your oil to synthetic will remedy that. And it could be that your injector is still messed up and causing it to nail.

I was ASSuMEing that I would hear the cam slap louder when I took off the oil cap. Since it wasn't any louder with the oil cap off, I thought it wasnt the lifter.

I did just put synthetic (mobil 1) in to try fix it. I guess it's a wait and see. I've got the spare lifters to put in, but I don't want to pull the camshaft if theres no point to it.

Could it be leaky prechambers? There is some air puffing out of them - if I spray oil on them you can see there is air leak. NOt a big problem I thought, but I don't know.

Get a mechanics stethoscope and listen at each injector and see which one could be nailing.

I don't think it is a injector because it is such a high pitch sound, usually nailling injectors have a low pitch knock.

I have listened with a stethoscope. That injector does sound louder.

I don't see how it could be knocking though. I've ordered new injectors, so I guess I'll find out....

If it was the cam, would I hear it louder when I removed the oil cap?

I'm not grasping on the reason to suspect the cam? The entire problem has been with the single injector.........nothing in the process suggests the cam is the issue in any way.

The engine offers a very light injector knock at idle...........sounds more like a 617...........rather then the typical sewing machine sound of a 60X engine. Above idle, the problem is eliminated.

Sometimes these engines do exhibit lifter noise which will be characterized as a noticeable "ticking" sound, most easily heard behind the wheels in the fenderwells.

Thanks Brian. I guess part of the problem is I don't know what a perfect 602 sounds like.

The reason I suspect the cams is it had some bad cams, and I replaced only the bad ones, so I'm suspicious of the ones I left in that weren't acting up at the time.

There is an intermittent ticking noise - you're saying that's the cams. I have the spares, I think I should just get in there and replace them.

I guess occam's razor says it is the injector knocking - either becuase it is not the exact same type as the others, or it is the wrong pressure (it is at 2050psi = 141bar).

I wonder why it doesn't knock at high revs?

I'll have the new injectors soon and put them in and see. But for now, I don't suppose its going to cause any major engine damage knocking like that for a week is it?

How many "cams" does that thing have???

10 cams. plus 2 on each tire equals er.... (counts fingers) ....17 cams.

Oops, I meant cam LIFTERS. My bad. Only joking about the cams on the tires.

lol, i was like... i thought that it was a DOHC design but.. 17 cams?.. Ah lifters. Since its a six cylinder there should be 24 of them. 4 per cylinder. This is what it should sound like http://www.youtube.com/watch?v=aukYna3q9rA&feature=related Lol.

Let's get the terminology straight. You've got one camshaft and it has 10 lobes.

You cannot replace "only the bad cams". Either you replace the entire camshaft, or you don't.

The intermittent ticking noise is the lifters. It's got nothing to do with the camshaft.

The knock disappears at higher revs because there is more fuel from the injector and it burns closer to the ideal. At idle, any slight deviation from a perfect spray pattern can cause a slight knock. It's not an issue to drive it this way, indefinitely. Hell, the 617 lives with such noise........practically forever.

No the 2.5L motor in question is a single-cam, 2-valve, 5-cylinder design. The OM606 video you linked to is a different engine and that one sounds like it has a bad belt tensioner shock.

pdrayton, I'd bet it's the injector. Sometimes they need some time to settle in or clean out the combustion chambers if the previous injectors were spraying poorly. You can try cracking each injector line to see if the noise goes away. If it does, then it's a combustion knock instead of a mechanical one. Or you can try running the engine on Diesel Purge which has extremely high cetane and it will at least temporarily quiet down any combustion knocks.

I thought the 6ox series has DOHC? I guess i am wrong sorry. dang i need to look this up on the fsm.

thanks guys. Yes it is SOHC (602 2.5 liter) with 10 lobes and 10 lifters. I replaced 5 of them last time I pulled one of the cams (only joking - THE cam).

I think you're right - it is probably the injector not spraying exactly right, or the PC being carboned up - the car was spewing black smoke when I floored it at high revs.

If it settles down I'll leave it in, especially if it's not a damage to the engine issue. But it is the wife's car, and the quieter it is the happier she is, and the happier I am. You know how it goes....:)

At least I can now sleep easy knowing I've got the right number of cams and that they're not the problem.

However, if it ticks again I'll replace the rest of the lifters.

Here's what a 602 SHOULD sound like. Starts at 51seconds in the video. Mine sounds like that except for the other noises... like knocking, and ticking.

http://youtube.com/watch?v=MXwP6FMnl4Y