Overview

Welcome to Your D16

The RETROL D16 is one of the rarest types of model engines in the world — a fully functional miniature diesel. Almost no model engineers have successfully miniaturized a diesel injector and gotten it to work inside a tiny combustion chamber, which is exactly what makes this engine so remarkable. The D16 is inspired by the stationary diesel engines of the early 20th century, including designs by Rudolf Diesel and engines produced by Sulzer, Maschinenfabrik Augsburg, and Krupp.

Unlike gasoline engines, the D16 uses compression ignition — there is no spark plug. Fuel ignites purely from the heat generated when air is compressed to extreme pressure inside the cylinder. This is also what makes miniaturizing one so challenging: the injector orifice is extremely small (approximately 0.07mm), and the entire fuel system operates at high pressure. Patience and careful attention to procedure are essential.

This guide combines the official manual, Stirlingkit's engineering notes, and real-world cases from our after-sales team. Please read it fully before your first start.

▶ Official D16 Complete Startup Tutorial

Technical Data

Engine Specifications

Getting Started

Before Your First Start

After shipping, always perform these checks before running the engine for the first time:

1. 1
   Check all bolts for loosenessVibration during shipping can cause bolts to loosen. Go over every visible fastener — especially the timing gear grub screws and camshaft gear — and gently snug any that have worked loose.
2. 2
   Rotate all moving parts by handTurn the flywheel slowly by hand. All gears, bearings, and the crankshaft should move freely without obvious tight spots or binding. If anything feels stiff or catches, investigate before starting.
3. 3
   Check the piston oil cupLocate the independent oil cup on the engine body. If it arrived empty or nearly empty, fill it with engine oil before the first run. Some units ship with the oil cup not immediately visible — check around the cylinder area carefully.
4. 4
   Check cooling water connectionsInspect all brass tube fittings on the cooling circuit. Gently tighten any that feel loose. If they continue to seep after tightening, wrap threads with Teflon tape before running.
5. 5
   Prime the fuel system before first startBleed all air from the high-pressure fuel line before attempting a first start. Skipping this is the most common reason for a completely non-starting engine. See the "Priming the Fuel Line" section below.

Fuel

Choosing and Using Fuel

The D16 accepts three fuel options. All must be clean and fresh — the 0.07mm injector orifice will clog if contaminated fuel is used.

Lubrication

Keeping the Engine Oiled

Lubrication is the single most important maintenance task on the D16. The D16 uses a dual lubrication system: an independent oil cup for directed lubrication to the piston and cylinder, and mixed oil splash lubrication inside the crankcase. Both must be maintained.

1. 1
   Piston oil cupThe independent oil cup supplies oil directly to the piston and cylinder bore. Check its level before every run. This is the primary lubrication for the piston — do not neglect it.
2. 2
   Crankshaft big end (conrod bearing)The most mechanically stressed point in the engine. It operates under high diesel compression loads. Keep it well oiled at all times — this is the most common point of failure when lubrication is neglected.
3. 3
   All gears and bearingsEvery gear mesh and exposed bearing should have a light coat of oil. Check after each run that nothing feels dry or gritty.
4. 4
   Side shaftThe side shaft should rotate freely but must not slide axially. Adjust the brass bearing or add washers if there is back-and-forth play. The helical gears should mesh in the middle of their tooth faces — not at the edges.

Cooling System

Water Cooling

The D16 uses a closed-loop water cooling system. Proper coolant choice protects the internal passages from corrosion and scale buildup.

Fuel System — Critical Step

Priming the Fuel Line (Bleeding Air)

This is the most important step before first start, and the most common reason the D16 fails to start. The high-pressure fuel line between the injection pump and the injector must be completely free of air before the engine will fire. Air in the line prevents the pump from building the pressure needed to open the injector needle valve.

▶ D16 Air-Bleed (排空气) Tutorial

The brass screw cup at the injector outlet (marked "Diesel") is where you loosen to bleed air. The nozzle tip at the bottom (marked "no Diesel") is the 0.07mm orifice — fuel must flow bubble-free from the outlet before the engine will start.

Air-Bleed Procedure

1. 1
   Fill the fuel tank above the pickup pipeThe pickup pipe at the bottom of the tank must be fully submerged in fuel before bleeding.
2. 2
   Locate the brass screw cup on the high-pressure injector lineThis small brass fitting sits on the line near the injection pump output. Loosening it allows air and fuel to escape, bleeding the line.
3. 3
   Loosen the screw cup slightly and pump fuel throughTurn counterclockwise just enough to allow seeping. Manually operate the pump handle or slowly crank the flywheel by hand to push fuel through the line.
4. 4
   Continue until fuel flows bubble-freeYou will likely see air bubbles mixed with fuel at first. Keep pumping patiently until the flow is a steady, bubble-free stream of diesel. This can take time — do not rush.
5. 5
   Retighten and confirm the pump feels stiffOnce primed, retighten the fitting. When you operate the pump handle, it should feel noticeably harder to push — this resistance confirms the system is pressurized and air-free. A handle that moves easily with no resistance usually means air is still present.

Starting the Engine

Cold-Start Procedure

Starting a miniature diesel requires patience. The engine relies entirely on compression heat to ignite fuel. Follow this procedure for reliable starts.

1. 1
   Verify fuel, oil, and coolantFuel above the pickup pipe. Oil cup filled. All bearings lubricated. Coolant circuit filled and fittings snug.
2. 2
   Confirm the fuel line is primed (no air)If this is the first start or the engine ran dry, complete the air-bleed procedure above before proceeding.
3. 3
   (Recommended) Preheat the cylinderUse a hair dryer or warm-air blower to warm the cylinder and head for 30–60 seconds. A warm cylinder compresses air more effectively and reduces the number of cranking turns needed. Especially important in cool environments.
4. 4
   Open the decompression leverIf equipped, open the exhaust valve decompression lever before engaging the drill. This lets the drill spin the engine up to speed before full compression engages, reducing strain on the starter clutch.
5. 5
   Position the engine just past the last compression strokeBefore engaging the drill, manually rotate the flywheel back to just after the compression stroke. This one habit dramatically reduces peak load on the starter clutch.
6. 6
   Crank with the clutch drillEngage the drill and crank the engine. On a cold, dry start it is completely normal to require 20–30 turns (approximately 5–10 seconds) before the engine fires. This is not a sign of a problem.
7. 7
   Close the decompression lever once the engine firesAs soon as the engine begins firing, close the lever to allow full compression operation.

Advanced: Engine Timing

Checking and Restoring Valve & Pump Timing

If the engine runs briefly then stops and cannot restart — or if the intake valve, exhaust valve, and injection pump plunger no longer seem synchronized with crankshaft position — a timing gear has likely slipped due to a loose grub screw. Here is the complete procedure to restore correct timing.

▶ D16 Injection Pump Timing Adjustment

Helical screw gears on the D16 side shaft. Gears must mesh in the middle of the tooth face, not at edges. Adjust the brass bearing or add washers to correct axial position.

Advanced: Fuel Injector

Injector Diagnosis and Maintenance

The D16's injector is one of the most technically challenging components in any miniature engine. The nozzle orifice is approximately 0.07mm in diameter — roughly the width of a human hair. Even a tiny particle of contamination can block it completely.

The injection pump builds pressure in the high-pressure line. When pressure is sufficient, it pushes the injector needle (oil pin) off its seat and diesel is forced through the nozzle orifice into the combustion chamber. If pressure is sufficient to move the needle but no fuel exits the orifice, the orifice itself is blocked.

FAQ & Troubleshooting

Common Questions

Ongoing Care

Maintenance Summary

Support

Need Further Help?

If you have worked through this guide and are still experiencing issues, please contact our support team at service@stirlingkit.com or visit our Contact Us page. When you reach out, providing the following information helps us assist you faster:

1. 1
   Your order numberFound in your confirmation email or Stirlingkit account.
2. 2
   A clear description of the symptomWhat happens (or does not happen) when you try to start or run the engine.
3. 3
   A short video or photosShowing the issue — this allows our engineering team to diagnose accurately and quickly.
4. 4
   What you have already triedSo our team does not repeat steps you have completed.

Purchase Spare Parts

Need to replace a component? Official D16 spare parts and accessories are available directly from Stirlingkit:

If you need a part that is not listed in the accessories page, contact us and our team will do their best to assist.