Description

Detroit Diesel 50G, 60G Training Manual – 146 Pages of OEM Factory Training

You are standing in a shop with a natural gas engine that won’t fire. The customer is breathing down your neck. The aftermarket PDF you obtained says “consult factory” for the fuel pressure spec. That’s the kind of junk that costs you a Saturday and a tow truck. Detroit Diesel 50G, 60G Training Manual is not that junk. It’s the actual training material Detroit Diesel used to teach technicians how to diagnose and repair these engines. 146 pages of OEM-level content, straight from the source.

This manual came from the days when DDC was putting serious R&D into alternate fuel. The Series 50G and 60G natural gas engines were built on the same block as the diesel versions, but the fuel system, ignition, and controls are a different animal. If you try to treat them like a diesel, you’ll blow the mixer, flood the crankcase with methane, or melt the spark plugs. I’ve seen it happen. This manual keeps you from making those mistakes.

Engine Components and Cylinder Kit – What the 50G/60G Shares with Diesel

The section on Basic Engine Unique Parts covers exactly what changed from the diesel architecture. The cylinder kit, connecting rod, liner cooling, and cylinder head are all documented with OEM tolerances. Page 54 shows the Series 50G transit bus engine layout – if you’re swapping a gas head onto a diesel block, you need those deck heights and liner protrusion numbers. The manual also covers the balance shaft on the 50G, which is something a lot of aftermarket sources skip. That shaft has a specific torque sequence; miss it and you get vibration that wrecks the crank sensor.

Fuel Control Systems – Closed Loop vs. Open Loop

Natural gas engines need a fuel control system that meters gas precisely. This manual devotes multiple slides to the Series 50G/60G Fuel Control System, including the DDC Pulsewidth Stepper Valve, the low-pressure regulator, and the electronic throttle. It explains the difference between the coach fuel system (closed loop with oxygen sensor feedback) and the generator set fuel system (open loop with fixed maps). The OCR excerpt shows slide 68-78 cover the transit bus closed loop system. If you are working on a bus, you need to understand the fuel trim strategy – or the engine will run lean at idle and rich under load. The manual shows how to use a DDR reader to check fuel trims.

Ignition System – Coil Over Plug and Spark Plug Tube Secrets

The Series 50G/60G Coil Over Plug Ignition System is different from the older distributor setups. This manual details the spark plug tube seals, both upper and lower, and the spark plug gap specs. It also covers cylinder cut-out diagnostic mode – a feature that lets you shut off individual cylinders to find a misfire without swapping parts. The section on the Spark Igniter Module includes the pin-out for the controller. If you are troubleshooting a no-spark condition, you trace the 12V supply through the ignition relay back to the DDEC. The manual includes the wiring logic.

Handling and Safety – CNG/LNG Fuel Systems

Natural gas is under high pressure – up to 3,600 psi for CNG. The manual has a dedicated section on Handling and Safety starting on slide 26. It covers the boiling point of LNG, ignition limits, and proper vent line routing. If you ever have to replace a CNG tank or service the LNG vaporizer, you need to understand the high-pressure fuel control solenoid and the low-pressure solenoid. The manual shows the regulator locations and the purge procedures. I’ve seen shops blow the seals on the high-pressure regulator because they didn’t follow the depressurization sequence. That’s a $700 mistake. This manual stops those errors.

OEM Interfaces and Unique Requirements – Why This Manual Matters

This isn’t a reprint of a third-party guide. It’s a Detroit Diesel training document – the same slides and notes used in the factory training program. It covers oil requirements (use the correct CNG-specific oil – 5W-30 for cold climates), coolant requirements (SCA levels are critical), and power requirements for the throttle relay. The manual also explains the DDEC system and the DDR reader interface. If you need to calibrate the wastegate on a turbocharged 60G genset, the procedure is here. The manual is 146 pages, slide by slide, with speaker notes that give you the real-world context. I trust it more than any aftermarket document because it came from the people who built the engine.

Need to know what sensors the MPSI reader shows that are unique to the gas engine? That’s in the “Gas Engine Unique MPSI Reader Parameters” section. The manual walks through all the engine sensors: MAP, exhaust temperature, barometric pressure, and fuel temperature. If you’re diagnosing a lean condition, you check the air and fuel temperature sensor first – it affects the fuel calculations. The manual tells you the correct thermistor curve. this Wikipedia article on diesel engines gives you background on the combustion cycle, but this manual gives you the actual production data.

For shops that also work with the diesel versions, check out the related manuals: Detroit Diesel DD13 2010 Training Manual – OEM Factory Specs, Detroit Diesel Series 60 Technical Manual – OEM Factory Specs (38 Pages), and Detroit Diesel DDEC 6.3 User Manual – 68 Pages OEM. Each one is an original factory document, not a composite. And if you want a quick primer on how four-stroke natural gas engines differ from diesels, this Wikipedia article on diesel engines is a starting point, but the torque specs and part numbers are only in the factory manual.

FAQ

Does this manual cover the Series 50G generator set?

Yes. The manual includes separate sections for the coach (transit bus) and genset versions. You’ll find the mixer inlet and PSV for the genset, plus the specific fuel system diagrams for the generator set.

Are torque specs included?

Yes, but the focus is training, not a full service manual. Torque values are given for critical fasteners like the cylinder head, connecting rod, and balance shaft. Page 54 references the engine component assembly. Use this alongside a factory service manual for complete rebuild specs.

What kind of fuel system does the 60G use?

Closed loop with an oxygen sensor on the coach version; open loop with a fixed map on the genset. The manual explains both systems, including the DDC Pulsewidth Stepper Valve and the low-pressure regulator. It also covers CNG and LNG fuel system components, including the high-pressure solenoid and vent lines.

Can I use this manual to flash the DDEC?

No. This is a training manual, not a programming guide. It explains how the DDEC interacts with the ignition and fuel systems, but it does not contain calibration files or ECM programming procedures. For that, you need the proper Detroit Diesel diagnostic software and a DDR reader.

If you work on natural gas engines from Detroit Diesel, you need the real thing. Access the Factory Manual – 146 pages of OEM training that shows you the systems, the sensors, and the safety procedures that keep you from torching a bus or a genset. It’s the same material the factory used to train its techs. Don’t guess. Use the source.