I'm replacing injectors on my '81 300TD turbo, and I noticed that the current injectors on the car have a different part number than the ones I bought for it. The current injectors are NA31X, the new ones are NA34X. I bought injectors specifically for a 617 turbo, like my motor.

Does this mean I've had the wrong injectors on the car all along? (I've only had it 18 months).

What's the difference between NA31X and NA34X?

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'81 300TD turbo <<sold 12/05 to another diesel nut

When you bought the new injector's (if they were bought off internet site), did the online catalogue give an engine # range of value's to ensure getting the correct injector? Second thought, perhaps MB re-designed better injector's after the fact to replace the original na31x. For example on my 69 220d a replacement pre-combustion chamber is available that is different in design and part #. I imagine there'll be someone on this forum who will clear the matter up for you.

I bought them from ***************, which specified NA31X for the 617.912 motor, and NA34X for the 617.952. Because my car is an '81, the first year of the turbo wagons, there's sometimes confusion when ordering parts as to whether the parts are for a turbo car or not.

The ******** website order forms show the 617.912 engine in the '81 wagon, and specify the NA31X injectors, which I assumed was a mistake. For an '82 wagon, they show the 617.952 motor and specify NA34X injectors, so that's what I bought.

Oddly, here at mercedesshop.com, the parts section specifies NA33X injectors, yet another variant, for the 617.912, and NA31X for the 617.952. What's going on? Should I install the NA34X in my car or not?

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'81 300TD turbo <<sold 12/05 to another diesel nut

Bosch has redesigned its nozzles several times and some parts have been superseded. While I'm not familiar with the NA* numbers, I do know that the OM617 turbo needs 135 bar pop pressure so if this is stamped on the injectors that's a good sign. Before you install these injectors you should do a seach on this board about testing and balancing injectors. Frequently these rebuilts are not pop pressure matched and some have poor spray pattern. It's always a good idea to test your existing injectors as usually they don't need replacing.

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2004 VW Jetta TDI (manual)

Past MB's: '96 E300D, '83 240D, '82 300D, '87 300D, '87 420SEL

The turbo are different from the non-turbo.
The turbo are set to a higher pop pressure, and I believe there is a minor design difference. I'm going by memory, but I think the 34x are for NA engines and the 31x are turbo. I've never heard of the 33x injector.

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'79 300SD W116
'86 190E 2.3-16V W201
'92 300D 2.5 W124
'99 E320 4MATIC S210

Well I went ahead and installed the NA34X injectors and everything seems fine. The car has more power, runs smoother, and smokes less (it looked like one of the old injectors was a leaker).

But the engine seems louder -- more 'diesel clatter.' What would cause this?

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'81 300TD turbo <<sold 12/05 to another diesel nut

Pop pressure degrades over time, so new injectors will build more pressure and inject more suddenly than the worn-out ones. Result is steeper increase in cylinder pressure and louder "klatta". If you like klatta, have somebody shim a set of injectors to 160 bar.

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'79 300SD W116
'86 190E 2.3-16V W201
'92 300D 2.5 W124
'99 E320 4MATIC S210

say that some clatter indicates proper adjustment on the fuel supply for best economy and power.

tom w

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[SIGPIC] Diesel loving autocrossing grandpa Architect. 08 Dodge 3/4 ton with Cummins & six speed; I have had about 35 benzes. I have a 39 Studebaker Coupe Express pickup in which I have had installed a 617 turbo and a five speed manual.[SIGPIC]

..I also have a 427 Cobra replica with an aluminum chassis.

All new injectors will be loud for a time. Klatta is good as long as its not a rod knock.

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1981 300D 147k
1998 VW Jetta Tdi 320k
2001 Dodge Ram 2500 141k
1979 300D 234k (sold)
1984 300D "Astor" 262k(sold)
Mercedes How-To and Repair Pictorials
I love the smell of diesel smoke in my hair

Cool. I like the klatta. I'm sure my neighbors won't, except the guy with the big Ford Powerstroke truck.

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'81 300TD turbo <<sold 12/05 to another diesel nut

I don't care what my neighbors think.......I pay too many taxes to care.

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Proud owner of ....
1971 280SE W108
1979 300SD W116
1983 300D W123
1975 Ironhead Sportster chopper
1987 GMC 3/4 ton 4X4 Diesel
1989 Honda Civic (Heavily modified)
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Section 609 MVAC Certified
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