Description

Mercedes-benz 119, 120, 111, 104, 112 Training Manual – Fuel Supply & ME-SFI

You’re pulling a fuel pressure reading on a 1998 Mercedes 120 V12 and the gauge says 50 psi at idle. The spec? You don’t know. Aftermarket data says one thing. The guy on the forum says another. That’s where this Mercedes-benz 119, 120, 111, 104, 112 Training Manual steps in. It’s not a full service manual – it’s a 24-page OEM training document from Mercedes-Benz USA, printed 2000, that zeroes in on the fuel supply and ME-SFI engine management systems for those specific engine families. If you’re diagnosing a no-start, chasing a lean code, or swapping injectors on one of these German motors, this is the document that tells you exactly what the engineers intended.

Fuel Supply & ME-SFI: The 7-Part Breakdown

This training manual is labeled “Fuel supply (Part 7)” of a larger series. It starts with an overview of ME-SFI versions – 1.0 for engines 119 and 120, 2.1 for 111 and 104, 2.0 for 112 and 113, and so on. Then it dives into the physical fuel system: tank, sending unit, pressure sensor, screen, splash bowl, and gas cap. Each component is shown in a simple schematic on page 4. You get the flow path from tank to fuel pump (M3), through the filter, to the rail, and into the injectors. The pressure regulator (item 40) sits on the rail. That schematic alone saves you an hour of tracing lines blind.

Pressure Regulator at Idle vs Full Load: What the Manual Shows

Your pressure reading fluctuates? The manual dedicates separate sections to the pressure regulator at idle and at full load. It explains how the regulator controls return flow to maintain a constant pressure differential across the injectors. At idle, manifold vacuum pulls the diaphragm, dropping fuel pressure. At full load, no vacuum – pressure rises. The exact values aren’t listed in the table of contents, but the training material references the official Mercedes-Benz Technical Publications and WIS for current specs. Use this as your conceptual guide, then confirm with WIS for the specific model year.

Does This Manual Cover the 119, 120, 111, 104, and 112?

Yes – that’s the whole point. Page 3 lists every ME-SFI engine variant covered: 119, 120, 111, 104, 112, 113, and 137. For this training manual, focus on the first five. The 112 and 113 are included but assigned to ME-SFI 2.0 and 2.8 versions. If you’re working on a 104 inline-six or a 119 V8, the fuel system architecture is the same layout – different part numbers but same logic. The injector section covers the PO20(X) type. You’ll see how the injectors are pulsed sequentially based on crank and cam signals.

24 Pages of Factory Training Material

Let’s be honest: 24 pages sounds thin. But these are dense, instructor-level notes – not a consumer brochure. They include a review section at the end. Page 2 carries the legal warning: “These technical training materials are current as of the date noted… you must always refer to the latest Mercedes-Benz Technical Publication.” That means this manual is a starting point, not the final word. Use it to understand the system’s theory, then cross-check torque values and troubleshooting trees with the official WIS. For a DIY guy, this is better than guessing because you see exactly how the engineers intended the system to be diagnosed. For a pro, it’s a quick reference before pulling the fuel pump relay.

Get the Fuel Pressure Specs Right

You need the charge pressure? Page 73 of the full manual – not this document. But within these 24 pages, you’ll understand why pressure changes with engine load. That knowledge keeps you from replacing a good regulator. The manual also covers special tools needed for tank-mounted pump removal and the venturi siphon system used in chassis 202 and 208. Drain valves are shown. If you’re replacing a fuel tank on a 202 or 208, this saves you from ripping out the wrong components.

Fuel pump relay logic is also discussed. The relay receives a signal from the ME-SFI control unit – if the engine doesn’t crank, the pump doesn’t run. That’s basic, but knowing the exact pinout prevents you from hot-wiring something that shouldn’t be hot-wired. Check the manual for the relay location and testing procedure.

Why trust this over a generic aftermarket PDF? Because it was written by the same engineers who designed the ME-SFI system. The drawings are to scale. The terminology is correct. Aftermarket manuals frequently get the regulator location wrong or omit the venturi siphon details. I’ve seen Chilton and Haynes swap the return and pressure lines. That will turn your afternoon into a fire hazard. This OEM training manual eliminates that risk. Pair it with a current WIS subscription and you have the full picture.

Related manuals for deeper coverage: Mercedes-Benz Truck 2010 Training Manual – Air Brake & Suspension, Mercedes-benz 327 2004 Training Manual – Brake Assist System, and Mercedes-benz 212 2009 Training Manual – Factory Systems Guide. For background on transmission systems that interact with engine management, check Manual Transmission fundamentals and Manual Transmission diagnostics.

Q: Can I use this training manual to set injector timing on a 119 engine?

No. This manual covers the fuel supply architecture, not injection timing or cam timing. For timing marks and adjustment procedures, you need the factory service manual or WIS. Use this training document to understand the system layout, then move to a specific repair manual for your engine.

Q: What’s the difference between the pressure regulator at idle and at full load according to this manual?

The manual explains that at idle, manifold vacuum acts on the regulator diaphragm, lowering fuel pressure by approximately 10 psi (varies by engine). At full load, vacuum drops and pressure returns to the regulated system pressure (around 50-60 psi typical for ME-SFI). It does not list exact values for every model – that data comes from WIS. The important takeaway: if your pressure doesn’t change between idle and snap-throttle, the vacuum line or regulator is faulty. The training manual gives you the diagnostic logic in two pages of text and one schematic.

If you’re chasing fuel delivery issues on these engines, stop guessing. Access the Factory Manual now and get the OEM training reference that Mercedes-Benz used to teach their own technicians. 24 pages, direct from the source, with no aftermarket fluff.