← Golf Volkswagen Golf repair manuals →
Autopapyrus · Volkswagen Golf 2.0 TDI CRLB (2016)
https://autopapyrus.com/guides/volkswagen/golf/diagnosing-hard-cold-starting/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Volkswagen Golf 2.0 TDI CRLB (2016): Diagnosing Hard Cold Starting

The CRLB engine is an electronically controlled Common Rail diesel, so poor cold starting is most often caused by one of the following: a weak battery or starter, a faulty preheating system (glow plugs, relay), air in the fuel system or low fuel pressure, or sensor faults. Start with the simple and inexpensive checks: the battery, reading fault codes, and the fuel.

DifficultyMedium Time1-3 hours (diagnostics) Steps12

Parts

5
№PartAlternatives
01 Glow plugs for 2.0 TDI CRLB (set of 4)4 pcs AlternativesBoschBeruNGK
02 Diesel fuel filter
03 Battery with sufficient cold cranking amps
04 Coolant temperature sensor
05 Fuel rail pressure sensor

Tools

5
  • VW-compatible diagnostic scanner (VCDS or equivalent)
  • multimeter
  • socket set and ratchet
  • torque wrench
  • flashlight
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 36 more. See manuals →

Step by step

12 steps
  1. Describe the symptom precisely: the starter cranks slowly, cranks briskly but the engine doesn't catch, the engine catches and then stalls, or it runs unevenly and emits white smoke after starting. Slow cranking points to the battery and terminals; brisk cranking without catching points to the fuel system or glow plugs.
  2. Check the battery: with the engine off, voltage should be at least about 12.4 V, and while cranking it should not drop below about 9.5-10 V. Inspect and tighten the terminals, and check the ground cables to the body and the engine. A battery that is old (5-6 years or more) should be checked with a load tester, especially in cold weather.
  3. Connect the scanner and read all modules: the engine control module, and the glow plug control module if it is a separate unit. Fault codes for the glow plugs, fuel rail pressure, temperature sensors, injectors and fuel delivery will narrow the search right away. Write down the codes and only then clear them.
  4. Check the temperature data: with the engine fully cold, the readings from the coolant temperature sensor and the intake air temperature sensor should be close to the outside temperature. If a sensor reads incorrectly, the control module will not activate the proper cold-start mode.
  5. Check the preheating system. Turn the ignition on: at low temperatures, the glow plug indicator on the instrument cluster should come on for a few seconds. If the light does not come on or there is a fault code, check the glow plug fuse and relay, then measure the resistance of each glow plug with a multimeter. A plug with an open circuit or noticeably different resistance must be replaced. Replace them as a set of four.
  6. To replace the glow plugs: let the engine cool, disconnect the negative battery terminal, remove the engine cover and, if necessary, any intake components that block access, then disconnect the glow plug connectors. Unscrew the plugs carefully with a socket and ratchet: plugs that were installed crooked or are coked up can easily break off in the cylinder head, so if a plug is tight, first treat the threads with penetrating oil and let it soak. Install the new plugs with a torque wrench; use the tightening torque specified by the manufacturer for this engine (it is low, and overtightening breaks the plug).
  7. Check the fuel system. Air in the line or a clogged fuel filter causes long cranking without the engine catching. Inspect the fuel lines and fittings for leaks and air ingress, check when the fuel filter is due for replacement, and check the condition of the fuel: in winter, summer-grade fuel and water in the fuel can wax up and clog the filter. If the filter has not been changed for a long time, replace it together with its seals; follow the manufacturer's service interval.
  8. Using the scanner, view the fuel rail pressure while the engine is being cranked. The value should rise quickly to a level sufficient for starting and should not fall back. Low pressure points to a weak lift pump, a clogged filter, a faulty pressure regulator or sensor, or problems with the high-pressure fuel pump. Such cases are best handed over to a specialized diesel shop: Common Rail fuel equipment requires cleanliness and special equipment.
  9. If the scanner allows it, check the injector correction values and the return flow (leak-off) rate: excessive leak-off from one or two injectors causes hard cold starting, rough running and white smoke. Injector repair is performed only on a test bench.
  10. Check the air intake path: a dirty air filter, air leaks after the turbocharger, and a sticking EGR valve or throttle body all worsen starting and cold running. Inspect the intercooler hoses and clamps.
  11. Check the starter and wiring: if the starter cranks slowly with a good battery, look for losses in the cables, the starter's power connector and the ground connection.
  12. After the repair, clear the fault codes, perform several cold starts several hours apart, and make sure that the fuel pressure, the preheating indicator and the idle speed are normal.

Common mistakes and warnings

  • The Common Rail fuel system operates at very high pressure: do not loosen high-pressure lines while the engine is running, and do not repair injectors or the high-pressure pump without experience and equipment; take the car to a repair shop
  • Disconnect the negative battery terminal before working on the glow plugs or electrical system
  • If the fault codes point to the fuel system components or the rail pressure does not build up, it is best to leave further diagnostics to a specialist
  • Check the pressure values, the glow plug resistance values and the tightening torques for this model against the manufacturer's specifications