So, a mechanic was working on a friends car and put a screw drive on the injector (of her 300sdl) and put the plastic end up to his ear.

She tells me that he was able to diagnose 3 "bad" injectors this way. My question is what was he hearing and does this trick actually work.

I would love to do this with my 300d to check and see if I should replace the injectors (without going to the trouble of popping them out and pop testing them).

Any thoughts on what to listen for?

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Thanks,
Will

1985 300D- 222k- (bad transmission)
1980 300D- (parts car)
1982 300SD- 242k

This is the same as using an engine stethoscope; just listen for the sound of the injector popping open. If you have an injector that is not working properly you will be able to hear the difference; all the others will sound pretty well the same.

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'98 E300 DT
'87 190D 2.5 turbo RIP
'92 S500 Sold
'03 3.2TL-S A-Spec

I used a cheap stethoscope from Harbor Freight to listen to my valves after an adjustment. At least I thought I was listening to the valves, I put the tip on each of the injectors.

I didn't really know what I was hoping to hear, but all cylinders sounded similar, so I thought that was good.

If you listen carefully you can hear the sound of the injectors separate from all the other clanking without any instruments.

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1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42