View Full Version : 2.7 Liter Engine Tapping Tap Noise

05-11-2015, 01:05 PM
We have a 06 Sprinter, 2500 Series with 2.7 Liter engine inline 5 Cyl.
I am not well versed with this engine thus I have searched the forum and found much info.
My search for “tap” “tapping” did not produce much.
Search for “knock” did.
Most diagnostics I have read refer to injector issue or piston meltdown.
Here is what I am dealing with and would like to know if it sounds familiar to anyone?
Engine has a tapping noise, high in engine and at #1/vac pump/timing chain area.
Engine idles smooth and drives out smooth. Increase idle and tapping speeds up and gradually fades into other regular engine noise.
I have pulled #1 injector and taken to our well thought of Bosch repair shop, Delco Diesel, and it tested fine. There was carbon up ¾ of injector which indicates some sort of issue in this hole.
Inspected copper seal and could not make a case of leakage. Cleaned injector bore and seat areas, installed new seal, installed injector and still have noise.
When listening with a long thin screwdriver and getting on a bolt head I’m not sold or un-sold the injector is the problem.
Engine vac pump and timing chain area seem to transmit as much noise as injector.
According to vehicle tach engine idles at 800rpm. Yes there is some room for error here.
I have been able to use my long thin screwdriver and tap the metal upper core support in rhythm of tap and count taps while using a timer of 15 seconds. That times 4 is giving me, every time, 300 taps per minute at an engine revs per minute of 800.
Crankshaft rotates 2 times per camshaft once.
Seems if it were camshaft lobe/lifter/valve it would be closer to ½ of engine revs per minute.
If my count is correct, what else in this area should I be considering?
Note, I have not done CLT or compression test due to engine idle is very good, for a diesel.
Thanks for any thoughts/questions/suggestions.

05-14-2015, 08:48 PM
Thought I would throw in an update.
I failed to mention above that I had used my computer to kill the injectors and only when #1 was turned off did it make a difference in the noise, did not go away 100% but...85%.
Have pulled injectors to remove valve cover.
All the cam lobes look great.
Lifters appear fine.
Timing chain has more movement than I think it should but not seeing this cause my noise.
I have read much on this forum since first post.
I'm not thinking wrist pin, flex plate or harmonic balancer.
Injector, lifter, valve...I don't know.
Sounds like a leak down would be the next step since I do get a change dropping # 1.
Any thoughts most welcome.

05-14-2015, 11:44 PM
300 taps per 800rpm is odd
but my first thought was 1 fin of the fan is hitting something out of alignment,
second was #1 injector is worn

05-15-2015, 02:12 AM
You could swap injector #1 with #2 and see if the noise stays with the injector or the cylinder.

05-15-2015, 02:41 PM
I have the same issue. I've noticed if I cup my hand and place it over the #1 injector, the sound becomes incredibly muffled. I'm going to try the diesel purge method with some 244k this weekend. If no improvement, I'm thinking the injector is failing.

05-18-2015, 02:39 PM
I finally used my computer to identify engine RPM, bigger difference than I expected.
Looks like 800rpm on tach but actual is 675.
300rpm still not half of engine RPM but I am on the reason.
It is the hi press injection pump.
I had tunnel vision because when I killed injector #1 the noise would mostly go away making me think it was cyl #1...some how. But after removing all injectors to R&R v/c and inspected and found nothing we swapped #1 with #3 during reassembly and still no change.
So I got more diligent listening around for noise and ended up at hi press fuel injection pump.
Waiting for customer to okay removal to inspect.
I hate to do this but I "assume" there is a type of "lovejoy" connection from pump to front of intake camshaft gear.
Unless I see something there I will put a pump on it and let you all know.

05-18-2015, 02:50 PM
There is a type of floating coupler (allows for misalignment) between the pump and camshaft.

If there is excessive play between the pump and camshaft, this could possibly cause tapping?


While you have the pump off, it would be a good idea to check the rear pump bolts for security. (As you probably already know they can loosen over time).

09-28-2016, 02:53 PM
I'm pretty confident I have the same issue based on your diagnostic, and two mechanics have already been scared to help diagnose this. Did it end up being the fuel injection pump or something else?


12-26-2018, 06:09 PM
Hi Michael,
Were you ever able to solve the issue?

I have the exact same problem. Occurred after oil change and sensor cleaning. Exchanged sensor for s new one but it did not solve the issue - might have been unrelated but unlikely as it happened right after the maintenance work.

I am a little lost here and it sounds like I could spend a ton of money on mechanics that don't know more than I do