Mitsubishi K4 fuel, injection and starting
Is your Mitsubishi K4 hard to start, or do you want to properly maintain the fuel and injection system? This guide covers the complete fuel system of the four-cylinder K4 with direct injection: the injection pump, the nozzles, bleeding the system, the preheating times and the correct starting procedure.
Suitable for the entire K4 series: K4A, K4B, K4C, K4D, K4E, K4F, K4G, K4M and K4N (four-cylinder diesel). The data below is taken from the workshop manual for the direct-injection K4E, K4F, K4G and K4M; for an indirect-injection version, check your engine number and bore.
The fuel system of the Mitsubishi K4
The K4 uses a Bosch M-type injection pump (type ND-PFR4M) with a centrifugal flyweight governor. The injection plunger is φ6.5 mm on the K4E and K4F and φ7.5 mm on the K4M. Fuel passes through a paper filter (with drain cock) to the pump and from there to the multi-hole nozzles of the DLL-P type. The nozzle opening pressure is 220 kg/cm² (+10). Since this is a direct-injection engine, there is a combustion bowl in the piston crown, and the nozzles inject fuel directly into it.
| Specification | Value |
|---|---|
| Injection pump | Bosch M-type (ND-PFR4M) |
| Nozzle | Multi-hole (DLL-P) |
| Nozzle opening pressure | 220 kg/cm² (+10/0) |
| Injection timing (BTDC) | 19° agricultural / 20° industrial & export |
| Firing order | 1-3-4-2 |
Checking and replacing nozzles
A poorly atomizing nozzle causes black smoke, uneven running and loss of power. Have nozzles tested on a nozzle tester bench for opening pressure and spray pattern, or replace the tip. On the K4 with direct injection, pay close attention to the spray angle: there are two nearly identical nozzles in circulation (150° and 155°). An incorrect spray angle leads to soot formation and rough running. Always check the number stamped on your old nozzle (P72 = 150°, P15 = 155°) before ordering. Tighten the nozzle holder mounting bolt to 1.5–2.0 kgf·m and the nozzle holder lock nut to 6.0–8.0 kgf·m.
Fuel and injection parts for the K4 (direct injection)
- Nozzle DLLA155P15 (155°) – K3D/K4E/K4F DI (SKU-47003-s) — includes sealing set.
- Nozzle DLLA150P72 (150°) – K3D/K4D/K4E/K4F DI (SKU-47029-s) — note the spray angle, check your old number.
- Filter set Iseki TU/TX (SKU-10040) — includes the fuel filter.
Bleeding the fuel system
After replacing the fuel filter or if the engine has run dry, you need to bleed the system, otherwise the K4 won't start:
- Loosen the bleed screw on the fuel filter and let the fuel flow freely; open the cock.
- Pump with the hand pump (feed pump) until air-free fuel comes out, then tighten the bleed screw again.
- Then bleed the injection pump in the same way.
- Is there still air in the system? Loosen the injector lines at the nozzles slightly and let the engine turn over until fuel comes out without air.
Preheating and starting
The K4 has glow plugs that preheat the combustion chamber for smooth cold starting. Turn the ignition to the glow position ("H") and hold it there until the glow indicator light comes on properly. The required time depends on the temperature:
| Ambient temperature | Preheating time (indicative) |
|---|---|
| Above +5 °C | approx. 20 seconds |
| Around freezing point | approx. 20–40 seconds |
| Below −5 °C | up to approx. 60 seconds |
Never let the glow plugs glow continuously for more than about 2 minutes. The starting procedure after that:
- With the ignition at "ON", check that the oil pressure light/buzzer indicates there is no oil pressure yet.
- Preheat in position "H" until the light comes on.
- Open the fuel cock, set the throttle lever to full, and turn the key to the start position "S". The starter motor engages.
- If the engine doesn't start within 10 seconds, release the key and wait until the starter motor has come to a complete stop before starting again. Never run the starter motor for more than 30 seconds at a time.
- Once the engine is running: return the key to "ON", let the engine warm up at idle, and don't apply load until the temperature is up and the oil pressure light is off.
Never turn the key back to "S" while the engine is running — this damages the starter motor. Charging current comes from a 12V-40A alternator; if your battery runs down or won't charge, check the V-belt tension and the alternator.
Starting and charging system
- Glow plug Mitsubishi K4 direct injection (SKU-551012) — for smooth cold starting; replace as a set.
- Starter motor Mitsubishi K series (VAR-0027) — available in two versions; the K4 uses the 12V-2.0 kW variant (13 teeth). Check the number of teeth against your old starter motor.
- Alternator 12V Iseki TU/TX – K series (SKU-1200011) — before ordering, check the amperage (K4 version 40A) and the connection against your old alternator.
Frequently asked questions
My K4 starts poorly when cold — what could it be?
Usually weak or faulty glow plugs, a flat or weak battery, air in the fuel system, or worn nozzles. Also check the preheating time and battery voltage.
What is the nozzle opening pressure?
220 kg/cm² (+10). If in doubt, have nozzles tested and adjusted on a nozzle tester bench.
How long can I run the starter motor?
A maximum of 30 seconds at a time. If the engine doesn't start, wait until the starter motor has stopped before trying again.
