6 Cyl 603 DIY Fuel Injector Rebuild Kit

Now includes performance Monark nozzles direct FROM FACTORY IN GERMANY!!!

For 1986 to 1993 with OM 603 6-cylinder 300D 300TD 300SD 300SDL 350SD and 350SDL. Also fits 1994-1995 S350. This kit includes Kent's new version 3 pressure tester. Watch the first video below to learn more about its key features. You will receive written instructions for disassembling and rebuilding your injectors, but the video instructions will give you the specifics of setting up and using this new bench tester. This kit will only work on specific 6-cylinder models. Please read carefully. If you have been reluctant to overhaul your worn and inefficient Bosch fuel injector nozzles because the job is too difficult or too costly then think again! For approximately the same cost as rebuilt Bosch fuel injectors, you can purchase this kit to rebuild them yourself in your garage and get better performance to boot! Works on 1986 to 1993 6 cylinder 300D 300TD 300SD 300SDL 350SD and 350SDL.Also fits 1994-1995 S350 ONLY. NOTE: Does not work on 1995 E300D!

6 Cyl 603 DIY Fuel Injector Rebuild Kit
Free Add-Ons Included:

Version 3 Injector Pressure Tester Full Function and Setup - On Demand Video

Product Details

Reasons behind my version 3 upgrade

Must watch Instructional video: Injector tester service, maintenance and repair

Our German-made Monark injector nozzles are manufactured with new technology and they outperform the original Bosch design. They just downright atomize the fuel better for more complete combustion. When these high-performance nozzles are installed and balanced-tuned properly you will not believe the difference it makes in how your diesel engine runs. Here is what one customer recently wrote in to report:

"Hi Kent, I had the Monark nozzles sitting in my garage for more than a year and I was balancing them lately within the tolerance of plus 2 or 3 bars and installed them in my 300SDL replacing my old Bosch nozzles with only 30K miles on (old nozzles were balanced at 140bar by a shop when installed but turned out having 130 - 135 bar when I  tested them after removal). Wow, what a difference Monark makes! I have heard a lot of good things about the Monark nozzles back from Germany but now I realize the big difference at idle and all operating conditions. The engine is so much quieter and smoother. Also, the torque and willingness to go at higher RPMs are improved. I think the engine is running better than ever it would easily go beyond 100 mph on the highway if it was allowed. No smoke.Great that you picked the Monark products and offer them to all Diesel enthusiasts! Many thanks for all your support. Have a great day. Martin W."

The kit we ship you will include the following items at cost savings:  Use the search box to look up each item to read more detail or purchase separately.

  • Set of 6 new Monark High-Performance Nozzles with GOLD Heat Shields included
  • Bench Mount Fuel Injector Pressure and Balance Tester that you can use at home (new flow through and capture bottle upgrade)
  • Kent's detailed pictorial manual on everything you will need to know to remove, rebuild and tune your injectors
  • 24 piece CUSTOM shim washer kit - required to adjust injector release pressure
  • 3 pairs of nitrile gloves
  • Video instructions on setting up and using our version 3 pressure tester

We are not including any tools with this kit as we know some of you may already have the tools needed to work on your fuel injectors. You will need a dial caliper to measure the thickness of your shims, a torque wrench, and the correct injector deep socket. We carry all these tools individually, or in a complete kit as pictured below.  Just type those names into the search box to view.

Please Note: We also offer a brass tool cleaning kit that is recommended, but not required, to rebuild your injectors. Look below to view and read more about the brass tool kit.

Still not sure you can do this yourself? Here is what one of our customers recently wrote about this rebuild kit:

Dear Kaia and Kent-

Kent has done it again! Another great DIY Kit...What a great package - The DIY Fuel Injector Rebuild Kit. The booklet covers everything in detail with good photos and diagrams. Being able to bench test and bench balance the injectors was a delight with Kent's test pump. The job went very smoothly and I think anyone with the right tools and this complete kit can do this job over the weekend.

By the way, the results are fantastic. My old bosh injector tips were coked over- I don't know how the car even ran with those! The new Monarch tips are working very very smoothly with no banging (I am running 100% WVO- one tank system). The cost was insignificant compared with the results...

Thanks again for supporting us "car-crazy"  DIYers with another great rebuild-it kit.

Diesel Don

Diesel Dons 300TD

Our diesel injector anti-leak kit is included at no extra cost. This kit will make sure your injector halves don't leak when installing your new Monark nozzles. Instructions and tips are included.  

Note: If you would like to order this kit to solve a pesky leak on your existing injectors

Only one set of these instructions will be included when ordering more than one item that includes this specific instruction sheet.

Available - Gasoline Injector Pressure Tester Conversion!!!

If you own an older gasoline Mercedes you can use this basic tester to test your CIS fuel Injectors. BUT ...... you will need a conversion kit with a smaller gauge. Look below to view our new Diesel to Gasoline Tester Conversion kit

WARNING:The health and longevity of your new Monark injector nozzles with be directly affected by the cleanliness of your diesel fuel and its lubricity. Any gunk or crude in your filters or injection pump could travel to the new nozzles and cause scoring leading to premature failure (our warranty does not cover nozzle tip scoring). The following procedures are a MUST with installing new nozzles:

1. Diesel Purge

Run at least one can (two if you have never done it) of diesel purge through your fuel injection system before removing your old injectors.

2. Change Filters

Change both your pre and main fuel filter. Use the search box to view all filters.


3. Use Fuel Additive

The new ultra low-sulfur  (ULSD) diesel fuel available at the pumps is not kind to mechanical fuel injectors. The sulfur was the key ingredient used to keep your fuel pump and fuel injectors lubricated. To protect your new nozzles we recommend you add a high grade fuel additive to your fuel (such as Lubro-Moly Diesel Hi-Test)


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