The situation when the car refuses to start after a rainstorm or in conditions of high humidity is familiar to many motorists. It would seem that yesterday the car worked perfectly, and today the starter spins idle or completely silent, ignoring the attempts of the owner to start the engine. Moisture is a powerful catalyst for oxidative processes and an excellent conductor for wandering currents, which leads to short circuits in the most unexpected places of the electrical circuit.
The main problem lies in violation of the tightness of the insulation or the ingress of water into the ventilation holes of the components. Wet weather. It drastically reduces the resistance of materials that were considered dielectrics in the dry state. Water can penetrate through microcracks in rubber seals, condense inside the housings or simply flow down the body directly to open contacts.
Panic at this moment is not worth it, since in most cases the problem is temporary and is solved by drying or cleaning contacts. However, ignoring signals can lead to more serious consequences, such as failure. motor-control Or expensive sensors. Understanding the physics of the process will help quickly localize the fault and return the car to service.
Effect of moisture on the ignition system
Most often, the car does not start in wet weather due to problems in the ignition system. Water, getting on high-voltage wires or coils, creates a way for current leakage. Instead of breaking through the gap of the candle and igniting the mixture, the spark “goes into the mass”, flowing down a wet insulator or rubber tip. This phenomenon is especially characteristic of cars with high mileage, where the insulation of wires already has microcracks.
Humidity also affects the state of spark plugs. If the gap between the electrodes is increased due to burnout, it becomes more difficult to break through. In wet weather, the load on the ignition system increases, and a weak spark may simply disappear. This is especially true for engines with a ignition distributor, where moisture can fall under the trambler lid, causing chaotic sparking or complete absence of spark.
Diagnosis should begin with a visual examination. At night, you can clearly see the “tracks” of current leakage if you open the hood and try to start the engine. Blue flashes on wires or coils will indicate the breakdown site. It is important to check the status of candle-head And the candles themselves are in the presence of stain and moisture.
- ⚡ High-voltage wires with cracks in the insulation pass current to the engine body.
- ⚡ Trambler cover with microcracks or oxidized contacts inside.
- ⚡ Ignition coils with damaged rubber seal.
If visual inspection did not reveal obvious breakdowns, it is worth checking the presence of condensation inside candle wells. In some engine designs, water can flow through a loosely closed probe or ventilation, accumulating around candles. Even a small amount of water on the ceramic candle can completely paralyze the cylinder.
Problems with sensors and electronic control system
Modern cars are saturated with electronics, and moisture can cause a failure in the work of sensors, without which ECU (electronic control unit) will not give a command to start or supply fuel. A critical element is the crankshaft position sensor (CRPS). If its connector is leaky or the wiring has been rubbed, water ingress causes a signal distortion or its complete disappearance.
Without a signal from the DPCV, the control unit “does not see” that the engine is rotating, and does not supply spark and fuel. A similar situation can occur with a mass air flow sensor (MMRV) or an absolute pressure sensor if their electrical contacts have oxidized due to dampness. Moisture provokes electrochemical corrosion, which increases resistance in the circuit, which is perceived by the computer as a malfunction.
⚠️ Attention: Attempts to start the engine with a faulty crankshaft sensor can lead to a filling of candles with gasoline, since the system will continue to supply fuel without a spark.
Particular attention should be paid to the wiring connectors. Rubber seals chips over time tan and lose elasticity, no longer protecting the contacts. Water, getting inside the connector, creates a galvanic pair, accelerating the corrosion of copper and brass. This leads to the fact that even after drying, contact may not be restored without chemical treatment and cleaning.
Air system and water entering the engine
One of the most dangerous reasons why the car stalls or does not start in the rain is a hydraulic shock or simply getting water into the intake manifold through an air filter. If the filter is wet or torn, water freely enters the cylinders. Since the water is incompressible, this can cause serious mechanical damage to the piston group and rods.
Even if the hydraulic shock did not occur, a wet air filter blocks the air, creating a mixture too rich that cannot be ignited. The engine can sneeze and stop immediately after starting. In wet weather, it is also possible to freeze the throttle in winter, but in summer condensate can disrupt the mechanism.
Regular checks should be made air-filterEspecially after driving through deep waters. If the filter housing is low, the risk of water suction increases many times. Some owners install special protective screens or raise the air intake if they operate the car in difficult conditions.
| Symptoms. | Possible cause | Action. |
|---|---|---|
| Starter's spinning, but silence | No spark, BB wire break. | Dry, replace the wires. |
| The engine is catching and stalling. | Water in candles or filter | Turn candles, blow cylinders. |
| Check Engine's on fire. | Sensor failure (DPKV, DMRV) | Diagnostic scanner, drying connectors |
| Cotton in a silencer | Violation of gas distribution or ignition phases | Check the tags and ignition system |
Diagnostics of the starter and battery
In wet weather, there are often problems not only with the spark, but also with the start of the engine. The starter is a powerful electric motor that is very sensitive to the contact state. Oxidation of the battery terminals and places of attachment of mass to the body leads to a drop in starting current. In dry weather, the starter can still spin, but at high humidity, the resistance of oxidized contacts increases, and there is not enough energy.
The battery also suffers from dampness. If the battery body has cracks or leaky plugs, moisture can get inside the cans, causing a short circuit or change in the density of the electrolyte. In addition, the self-discharge of the battery on a wet and dirty body is faster due to leakage currents on the surface of the contaminants.
Check the tension of the generator and starter belt. A wet belt can slip, preventing the starter from developing the necessary revs or preventing the generator from charging the battery. A stretch roller when water is ingested can also make a whistle, indicating slippage.
Pay special attention to the retracting starter relay. If its rubber cap is damaged, water gets inside, causing corrosion of the contacts and jamming of the mechanism. As a result, the starter can buzz but not push the bendix to engage with the flywheel.
Drying and emergency start methods
If the car does not start in wet weather, the first thing to do is to localize the source of moisture. For an emergency start, a hair dryer or building hair dryer can be used (with care not to melt the plastic) to dry candle wells, coils and visible connectors. The direction of the hot air flow should be spot.
An effective folk method is the use of compressed air to blow water out of candle wells. After removing the coils or wires, it is necessary to thoroughly blow the wells, removing the accumulated water there. If there is no compressor at hand, you can use a can with a brake cleaner, which perfectly displaces moisture and quickly evaporates.
In the case where the candles are filled with water or gasoline due to frequent launch attempts, they must be twisted and dried. You can calcinate the electrodes over the gas stove or simply wipe thoroughly with dry rags. While the candles dry, it is recommended to blow out the engine cylinders by scrolling the starter with open candle holes (when the fuel supply and sparks are disabled).
⚠️ Attention: Do not use an open fire to dry the hood if there are gasoline vapors or oil. It could lead to a fire.
Prevention and protection of electrical equipment
To prevent the problem of “the car does not start after the rain” from becoming regular, it is necessary to carry out a set of preventive measures. First of all, you should check the tightness of all rubber seals on headlights, control units and wiring connectors. Old, cracked rubber must be replaced.
To protect the contacts, it is recommended to use special dielectric lubricants. They create a water-repellent film, preventing oxidation and moisture penetration. Lubrication is necessary not only for the battery terminals, but also for the connectors of sensors, ignition coils and generator. This is especially true for cars that are often operated in high humidity or washed under pressure.
Regular engine washing also requires caution. A strong jet of water under pressure should not be directed directly to electrical components, generators and air intakes. After washing, it is desirable to dry the engine with compressed air or let it work at idle speeds with an open hood until the moisture is completely evaporated.
- 🛡️ Treat the connectors with silicone lubricant to create a water-repellent layer.
- 🛡️ Replace cracked high-voltage wires and candle tips.
- 🛡️ Install additional protective casings on vulnerable sensors.
Why does the car start better if you push it?
When starting from a push (on a mechanical gearbox), the engine is unwinded to higher revolutions than when the starter is working. This creates a stronger thinning in the cylinders and quickly turns the crankshaft, which helps to skip the spark even under imperfect conditions. In addition, the factor of a weak starter or a discharged battery is excluded.
Can an alarm block a launch in the rain?
Yes, if the alarm unit or its sensors (such as the impact sensor or the hood tip) are leaky. Water entering the inside can cause a short circuit, which the system perceives as an attempt to steal or damage, blocking the start of the engine. Often, the LED alarm light flashes or the siren is triggered.
How to dry the engine control unit (ECU)?
If there is a suspicion that water got into the ECU, it must be removed, opened the case and dried at room temperature or warm air (not hot). You can not use a hair dryer at maximum mode, so as not to damage the elements of the board. After drying, the contacts should be treated with alcohol and special lubrication.