Injector leaking under operation & others - PeachParts Mercedes-Benz Forum

jkubica · #1 05-11-2010, 10:30 PM

Quote:

Originally Posted by JHZR2

Here I am merely trying to put 2+2 together wrt an injector leaking INTO the engine. We were not talking about external leaks.

If I can determine somehow what injector may be leaking, Ill be that much smarter. FWIW, no black smoke at startup, and always a smooth idle on the CD. He characterized some tapping, which I couldnt really hear or isolate, as a sign of a leaking injector.

Hi
I just don't understand the idea of diagnosing a leaking injector just by hearing a tapping sound. Of course a nailing sound is common with injectors that aren't spraying right - maybe that's what he means - rather than one that is leaking.

On the other hand, I'm hear to learn. Please let us know what you find.
Joseph

JHZR2 · #2 05-12-2010, 08:04 AM

Quote:

Originally Posted by jkubica

Of course a nailing sound is common with injectors that aren't spraying right - maybe that's what he means - rather than one that is leaking.

On the other hand, I'm hear to learn. Please let us know what you find.
Joseph

Call me stupid but I dont know what a nailing sound sounds like... Therein lies half my problem, I dont know what to listen for beyond typical diesel knocking sound.

Im here to learn too, hopefully some insight can be shed as to what to listen for...

C Sean Watts · #3 05-12-2010, 10:52 AM

Quote:

Originally Posted by JHZR2

I dont know what a nailing sound sounds like...

Nailing = tapping (not slamming) two hammer heads together in time with the engine.

Normal 'clacking' = hitting the wooden handle of one of the hammers with the head of the other.

Quick test - open the hood and from a warm idle, slowly bring up the idle by hand. Do you hear an increase in a higher pitched almost metallic sound, either intermittent or exactly in time with every revolution? Does it go away at 1600-1900 rpm?

ALSO, 'internal' leaks are more likely if you consider both the needle and the bottom of the spacer disc to top of nozzle body are TWO places leaks can happen - vs - top of spacer disc to bottom of upper injector half is one place.

jkubica · #4 05-12-2010, 08:42 PM

Quote:

Originally Posted by C Sean Watts

Nailing = tapping (not slamming) two hammer heads together in time with the engine.

Normal 'clacking' = hitting the wooden handle of one of the hammers with the head of the other.

Quick test - open the hood and from a warm idle, slowly bring up the idle by hand. Do you hear an increase in a higher pitched almost metallic sound, either intermittent or exactly in time with every revolution? Does it go away at 1600-1900 rpm?

ALSO, 'internal' leaks are more likely if you consider both the needle and the bottom of the spacer disc to top of nozzle body are TWO places leaks can happen - vs - top of spacer disc to bottom of upper injector half is one place.

Hi
Thank you!

Please be so kind as to explain the "quick test" a little more. What does it mean if the sound goes away at 1600-1900 rpm? And why would that happen?

Also, does an injector with internal leaks - have a distinctive sound?

Regards,
Joseph

C Sean Watts · #5 05-14-2010, 02:05 PM

Quote:

Originally Posted by jkubica

Hi
Thank you!

Please be so kind as to explain the "quick test" a little more. What does it mean if the sound goes away at 1600-1900 rpm? And why would that happen?

Also, does an injector with internal leaks - have a distinctive sound?

Regards,
Joseph

As the RPM come up, the marginal injector(s) get more fuel - helping to quite the nailing. Idle and just above idle is where nailing will be easiest to hear.

I don't really think an internal leak/dribble will sound very different than a low pop pressure - IE: they both tend to nail BUT there might be some 'old timers' here who know how to tell them apart.....?