The situation when Renault Logan does not start well when cold, is familiar to many owners of this popular car. Problems especially often arise in winter or after a long period of parking, when the engine has completely cooled down. Instead of a confident start, the driver hears long cranking of the starter, “sneezing” of the engine, or a complete failure of the ignition system to respond to turning the key. This is not only annoying, but can also signal serious problems that require immediate attention.
The reasons for unstable starting lie in the imbalance of the air-fuel mixture or a weak spark. Modern engine management systems such as Siemens or Megatroninstalled on Logans are sensitive to the quality of components. If the on-board computer does not receive correct temperature or pressure data, it cannot generate the correct command for fuel injection. As a result, the mixture is either too lean or, conversely, flooded with gasoline.
Diagnosing such problems requires a consistent approach. You cannot randomly change spark plugs or sensors in the hope of luck. It is necessary to understand the physics of the cold start process: at this moment, the rich mixture mode operates, for which specific components are responsible. Ignoring the first symptoms can lead to failure of the catalyst or an expensive fuel pump. Let's look at the main culprits of this malfunction in detail.
Ignition system and glow plugs
The first thing that comes to mind when starting problems is spark plugs. On Renault Logan gasoline engines, they form the spark that ignites the mixture. Over time, the gap between the electrodes increases, and carbon deposits on the insulator impair the quality of sparking. On a cold engine, when fuel volatility is low, a weak spark is simply not able to ignite the mixture the first time.
In addition to spark plugs, attention should be paid to ignition coils and high-voltage wires (if your modification has them). Breakdown of wire insulation often occurs precisely at high humidity or low temperatures. The current begins to flow to ground, not reaching the spark plug. It is difficult to check the wires visually, but at night you can notice “electricians dancing” - sparks shooting under the hood.
It is important to remember the condition of the battery, which is the source of energy for the ignition system. A weak charge will result in a sluggish spark, even if the spark plugs are new.
- 🔌 Checking the gap: Measure the distance between the spark plug electrodes, it should correspond to the manufacturer's specifications (usually 0.7-0.8 mm).
- 🔋 Load test: Check the voltage at the battery terminals when cranking the starter; it should not fall below 10 volts.
- 🔥 Visual inspection: Look for cracks in the spark plug insulators and coils, as well as signs of oxidation on the contacts.
⚠️ Attention: When replacing spark plugs on a Logan with an 8-valve engine, be careful not to drop the spark plug into the well. Removing fragments or a whole spark plug from the depths of the cylinder will require removing the cylinder head or using a complex tool.
Buy candles only from original production or proven brands (NGK, Bosch, Champion). Cheap analogues often fail after 5-10 thousand kilometers, returning the cold start problem.
Fuel system and gasoline pressure
The second most important group of reasons why Renault Logan It turns the starter for a long time, it is connected with the fuel supply. For a reliable start, the engine requires a certain pressure in the ramp. If after stopping the car the pressure in the system drops (“goes away”), then the next time you start the pump it takes time to pump up the line again. At this point you hear long scrolling sounds.
Most often the culprit is fuel pressure regulator, which is located on the fuel rail or built into the fuel pump module (depending on the year of manufacture and engine type). Its valve may not hold pressure, allowing gasoline to flow back into the tank. It is also worth checking the fuel pump grid: if it is clogged with dirt, the performance of the pump when cold drops sharply due to thickened fuel.
Injectors also play a key role. If they “pour” or, conversely, have a poor spray pattern due to carbon deposits, the mixture will not ignite. The condition of injectors is especially critical for 1.6 16V engines, where the requirements for ecology and injection accuracy are higher.
To diagnose pressure, you will need a pressure gauge. It is connected to the fitting on the fuel rail (after releasing the pressure through the pump fuse).
Normal pressure in the Renault Logan ramp: 3.8 - 4.0 bar (with the engine running).If, after turning off the ignition, the pressure gauge needle quickly creeps down, it means there is a leak somewhere or the check valve is not holding.
Engine control sensors and electronics
A modern car is a computer on wheels. If Logan doesn't start well when cold, the reason may lie in incorrect sensor readings. The electronic control unit (ECU) makes decisions based on their signals. Incorrect data leads to incorrect mixture composition.
The key element here is Coolant Temperature Sensor (Coolant Temperature Sensor). It is he who tells the “brains” of the car that the engine is cold. If the data gauge shows that the engine is hot (for example, due to an open circuit), the ECU will not give the command to enrich the mixture, and the car will not start. Often the problem lies in oxidized contacts of the sensor connector.
Also important Crankshaft Position Sensor (CPS). If it malfunctions, a spark may not form at all or form late. The magnetic tip of the sensor may become covered with metal shavings, which distorts the signal.
| Sensor | Problem Symptom | Effect on cold start |
|---|---|---|
| DTOZH (Temperatures) | RPM fluctuates, high consumption | No mixture enrichment, difficult starting |
| DPKV (Crankshaft position) | Stalls while driving, no spark | The engine won't start at all |
| MAF (Mass Air) | The craving is gone, it twitches | Incorrect mixture calculation at start |
| Oxygen sensor | Check Engine light on | Has little effect, works after warming up |
⚠️ Attention: When diagnosing DTOZH, do not rely only on the arrow readings on the dashboard. It often shows the average value. The real temperature is seen only by a scanner or multimeter connected to the sensor itself.
Suction of unaccounted air
Another common reason why Renault Logan is capricious in the morning - this is the leakage of foreign air into the intake manifold. Excess air depletes the mixture, making it impossible to ignite without prolonged cranking. The control system does not have time to adjust the fuel supply in the first seconds.
First of all, inspect the pipes leading from the air filter to the throttle valve. Rubber dries out and cracks over time. Pay special attention to the idle air control (IAC) o-ring and throttle valve gasket. On 1.4 and 1.6 8V engines, these places often become a source of problems.
There are several ways to check for suction. The simplest is to spray “Quick Start” (an aerosol for starting the engine) at the joints of the pipes and the manifold while the engine is running. If the rpm changes, then you have found the leak.
☑️ Checking the intake tract
It is also worth checking the adsorber valve. If it is stuck in the open position, gasoline vapors from the tank can constantly enter the inlet, re-enriching the mixture when parked, which also interferes with normal starting.
Influence of fuel and oil quality
The quality of fuels and lubricants directly affects how your car starts. Low-octane gasoline or fuel with a high content of water and alcohol does not evaporate easily in the cold. Water may freeze in the fuel lines or filter, cutting off the supply completely.
Motor oil also plays a role. If you are using oil with a viscosity that does not suit the climatic conditions (for example, 10W-40 in winter at -25°C), it will be extremely difficult for the starter to crank the crankshaft. Thick oil creates high resistance, and the engine simply does not reach the necessary speed to ignite the mixture.
For winter operation of Renault Logan, synthetic oils with a viscosity of 5W-30 or 5W-40 according to API SN/CF standard. They retain fluidity even in severe frosts, making it easier for the starter and lubrication system to operate.
How does water get into the tank?
Water enters the gas tank due to condensation (temperature changes), refueling at questionable gas stations, or through a loose tank cap during washing. It is recommended to regularly add a quality dehumidifier to the tank.
Mechanical problems and compression
If all the above systems are in order, but Logan still has trouble starting, it is worth thinking about the mechanical condition of the engine. Reduced compression is the main enemy of a cold start. With low compression, the mixture is not compressed to the required pressure and temperature, which makes ignition impossible.
The reasons for a drop in compression can be different: wear of the piston rings, burnt-out valves or a breakdown of the cylinder head gasket. At long mileage (more than 200 thousand km), ring jams are a common occurrence, especially if the car was operated primarily in urban mode with short trips.
The compression test is carried out using a compression gauge through the spark plug holes. You need to measure “hot” and “cold”, although a cold engine is sufficient for initial diagnostics. The spread of values between cylinders should not exceed 1 bar.
- 📉 Low compression in all cylinders: Worn rings or timing chain/belt (stretched).
- 📉 Low compression in one cylinder: Valve burnout or gasket breakdown.
- 📉 Increased oil level: Oil is thrown into the combustion chamber through the crankcase ventilation system.
⚠️ Attention: Before measuring compression, make sure the battery is fully charged. A weak starter will not be able to develop the required speed, and the compression meter readings will be underestimated, which will lead to a false diagnosis.
Regular oil changes and the use of high-quality fuel are the best prevention of decreased compression and problems with engine starting in Renault Logan.
Frequently asked questions (FAQ)
Why does Logan start and immediately stall when cold?
Most often this is a sign of a malfunction of the idle air control (IAC) or a strong air leak. It is also possible that the throttle valve is very dirty and cannot open to the desired angle to maintain speed.
How often do you need to change spark plugs on Renault Logan?
For ordinary nickel spark plugs, the limit is 15-20 thousand kilometers, for iridium or platinum spark plugs - up to 60 thousand. However, the condition of the spark plugs affects a cold start after 10 thousand mileage, so it is better to check them visually more often.
Can the timing belt affect starting?
Yes, if the timing belt has jumped a tooth or is stretched too far, the valve timing will be disrupted. This will lead to the spark not being supplied in time with the opening of the valves, and the engine will not start or will operate extremely unstably.
What to do if Logan does not start in -25 frost?
First of all, check the battery charge. If the battery is OK, try turning the ignition on several times (without cranking the starter) to increase the pressure in the fuel rail. You can use Quick Start spray, but be careful not to damage the sensors.