I have therough idle and telltale pop-pop sound of a fouled or failed injector on my '79 240D. This sounds more like tick-tick-tick when you get in the car and accelerate. I ran two cans of Diesel Purge through to no avail. This happened about 4 yrs. ago after I got the car, at 80k miles, and I put all new (Bosch reman) injectors in. It now has 115k.
I couldn't pinpoint the bad injector by cracking the lines, and I don't want to keep buying 4-packs, and I plan to have the car for many years, so I bought an injector test stand (I could have made one, but don't have time). I remembered seeing page after page of injector testing, diagnosis, and even cleaning procedures in the "Combustion" section of my old microfiche factory service manual. So after the pop stand arrived, I went into my factory 123 service CD to get all those procedures. There is NOTHING about servicing injectors. Not in "Engine", not in "Fuel System", nowhere! There is only a page & 1/2 on R&R of injectors. And there is no "Combustion" section at all! What gives? Can anyone advise me on how to use my $280 pop stand to diagnose my injectors? And how about cleaning them if that's the diagnosis? Is it worth cleaning them?
Why was the microfiche manual so much more comprehensive, and cheaper, too?
Also, what is the difference between an "injector" and an "injector nozzle"? Another M-B parts website has reman "injectors" for $74.95 and reman "nozzles" for $64. Which should I get if I'm replacing?

Thanks.

Ted

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Now you're suckin' Diesel!

'88 300SEL
'92 300D 2.5 Turbo
'96 Lincoln Town Car. The Jazzmobile.

You can do a search at the bottom of this forum using boolean logic such as "injectors AND testing" and get a lot of good info. I'm pretty sure that when i was having mine tested someone posted the correct pop-off with the variance allowance.

Sorry but my memory is really bad about these kinds of specs since I never write them down... Must be getting old?

Oh, BTW - if you get the specs defined then there are a lot of folks here that would probably help you pay for that pop tester..

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'99 S420 - Mommies
'72 280SE 4.5 - looking to breathe life into it
'84 300SD Grey - Sold
'85 300SD Silver - Sold
'78 Ski Nautique

Ted:

You need to do the following to test the injectors:

Install onto stand. Purge, then rapidly operate lever to see what pressure the injector opens. Keep hands away from fuel spray!

You will have to look up the pressure, but I think its around 1800 psi.

Observe the fuel spray -- it must be a nice mist with a dense center part. No sideways sprays, no direct streams, etc.

Hold the pressure just below the opening pressure and watch for drips. Must not leak more than a drip in 20 sec or so, I think. Even that may be too much.

Operate the lever more slowly. You should be able to get the injector to "buzz" from constant opening/closing. Some won't do this, but I believe the Bosch waisted pintle types in the Benz do.

Low opening pressure can be fixed by changing the shims inside the injector -- put the body into a vise and unscrew the top half. Be carefull not to crush the bottom part!

Bad spray pattern can sometimes be fixed by removing the pintle and nozzle body from the bottom of the injector and cleaning with carb cleaner. Sometimes the problem is just carbon buildup. Re-assemble and retest.

If there is no improvement, you need a new nozzle assembly.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!