The situation when a car with an engine ZMZ 405 refuses to start, often takes the driver by surprise, requiring immediate decisions. This engine, installed on the Gazelle and Sobol, has proven itself to be a reliable unit, but even it has malfunctions, especially if the mileage is high or maintenance was carried out irregularly. Reasons why the engine won't start, there can be many: from a banal battery discharge to serious mechanical damage to the cylinders or gas distribution mechanism.
The first thing that needs to be done in such a situation is to carry out an initial diagnosis, paying attention to the nature of the starter’s rotation and the presence or absence of “seizing”. If the starter turns sluggishly, the problem lies in the electrics or power system, and if the rotation is fast, but there are no flashes, you should look for an error in sparking or fuel supply. It is important to understand that ZMZ 405 has an injection control system that is sensitive to the quality of gasoline and the condition of the sensors, so this factor cannot be ignored.
In this article, we will analyze in detail the main scenarios of startup failure, consider the typical “diseases” of this engine and propose an action algorithm for self-repair. You'll learn how to check compression, adjust timing, and diagnose a crankshaft position sensor without fancy equipment. The correct approach to diagnostics will save you time and money, allowing you to avoid replacing working components at random.
Primary diagnostics and analysis of starter operation
Troubleshooting should begin by assessing exactly how the starter behaves when trying to start. If when you turn the key you hear only a quiet click or the starter rotates very slowly, barely turning the flywheel, then the reason almost certainly lies in a discharged battery or poor contact in the power circuit. Starter battery should provide sufficient cranking current, especially in the cold season, when the oil viscosity is increased.
In the case when the starter turns vigorously and with a characteristic sound, but the engine is silent, it is necessary to proceed to checking the fuel supply and ignition systems. The sound of the starter turning can tell a lot to an experienced mechanic: a uniform rustling noise indicates the normal condition of the bearings, while a knocking or grinding noise may indicate deeper problems. It is important to listen for any characteristic “flashes” or attempts by the engine to “grab”, even if it immediately stalls.
Don't forget about the mechanical part of the starter drive. If the Bendix slips, you will hear a characteristic cracking sound, but the flywheel will not turn. This is a common problem on engines with high mileage, where the teeth of the starter gear or flywheel ring are already worn out. In that case engine ZMZ 405 technically sound, but it is impossible to start it without replacing the starting device.
Ignition system and spark plug problems
Lack of spark is one of the most common reasons why an injection engine will not start. On ZMZ 405 The ignition system can be made in the form of two coils with two spark plugs per cylinder or individual modules, depending on the year of manufacture and environmental class. The first step is to unscrew the spark plugs and assess their condition: carbon deposits, a wet electrode or a breakdown of the insulator will immediately indicate a problem.
If the spark plugs are dry and clean, but there is no spark, check the high-voltage wires and coils. Owners often forget that the coils on this motor can fail due to overheating or moisture. Ignition module requires reliable contact and correct clearance between the spark plug and the ground when checking. It is also worth inspecting the connectors for oxidation, which often occurs due to condensation in the engine compartment.
⚠️ Attention: When checking the spark on an injection engine ZMZ 405 Never leave a spark plug just lying on the valve cover or cylinder head. High voltage can damage the ECU controller, so you need to press the spark plug tightly to the ground through an insulated tip or a special tester.
Particular attention should be paid to the crankshaft position sensor (CPS). These are the “eyes” of the engine management system, and if a signal is not received from it, the ECU simply will not give the command for spark and injection. Dirt on the end of the sensor or a cut crankshaft pulley (where the timing teeth are installed) will prevent the engine from starting, even if all other systems are working properly.
Use dielectric grease to treat spark plug tip contacts and coil connectors. This will prevent current leakage along a wet surface and protect against oxidation of contacts in wet weather.
Fuel system and pressure diagnostics
If the spark is ok, the next step is to check the fuel supply. Engine ZMZ 405 demanding on rail pressure, which should be about 3 atmospheres (300 kPa) at idle and increase when the throttle is opened. Insufficient pressure will not allow the injectors to spray the fuel in the required volume, and the mixture will be too lean to ignite.
A common cause of pressure drop is a clogged fuel filter or fuel pump failure. On Gazelles, the tank is often not sealed, and water and dirt get into it, which accelerates wear on the pump. It is also worth checking the fuel pressure regulator: if it “pours” gasoline back into the tank, the ramp will not reach the required pressure and the engine will not start.
☑️ Checking the fuel system
The quality of the fuel itself should not be ignored. Low-octane gasoline or the presence of water in it may cause the engine to “not see” the flashes. Water that gets into the cylinder does not burn and can cause water hammer, so if you suspect bad gasoline, it is better to drain the fuel from the rail through a special fitting and inspect it for the presence of emulsion.
Mechanical failure and compression
When the electrics and fuel are normal, but the engine is silent, you should think about mechanical problems. Lack of compression is a sure sign that the engine will not start. The reasons can be different: from stuck piston rings to burnt-out valves or broken timing belt. On ZMZ 405 when the belt breaks, the valve often bends, which requires serious repairs to the cylinder head.
To check the mechanical part, it is necessary to measure the compression in the cylinders. A normal indicator for this engine is considered to be a pressure in the range of 10–12 atmospheres. If the pressure in one or more cylinders is significantly lower or equal to zero, it is necessary to pour oil into the spark plug hole and repeat the measurement. An increase in compression will indicate wear on the rings; no change will indicate problems with the valves or cylinder head gasket.
| Symptom | Probable Cause | Test method | Solution |
|---|---|---|---|
| No compression in all cylinders | Broken timing belt | Visual inspection of the timing drive | Replacing the belt, checking the cylinder head |
| Low compression in one cylinder | Valve burnout | Compression test with oil | Block head repair |
| Low compression in all cylinders | Wear of rings/sleeves | Compression test with oil | Engine overhaul |
| Pops in the muffler | Incorrect timing | Checking marks on pulleys | Setting marks at TDC |
The correct installation of valve timing deserves special attention. If, when replacing the timing belt, the marks were set incorrectly, the engine may not start or may be extremely unstable. Timing phases on ZMZ 405 they are set strictly according to the marks on the crankshaft and camshaft pulleys relative to the top dead center (TDC) of the first cylinder.
How to set timing marks on ZMZ 405
For correct installation, it is necessary to align the mark on the crankshaft pulley with the mark on the chain cover (TDC of the 1st cylinder). The marks on the camshafts should face each other and be on the same horizontal line.
Influence of sensors and ECU on startup
A modern injection engine is controlled by an electronic unit, which relies on the readings of many sensors. If ZMZ 405 does not start, the cause may be a malfunction of the mass air flow sensor (MAF) or the throttle position sensor (TPS), although most often the engine is able to start even with the sensors disabled, going into emergency mode.
The coolant temperature sensor (CTS) remains critical. If it “lies” and shows the ECU that the engine is warm when in fact it is cold, the control unit will not enrich the mixture and starting will not occur. It is also worth checking the integrity of the wiring to the ECU: breaks, ground loops or oxidation of contacts in the brain connector can completely paralyze the operation of the system.
It is best to diagnose the ECU using a scanner by connecting to the diagnostic connector. Errors stored in the controller's memory will indicate the direction of the search. For example, the error “Loss of DPKV signal” will immediately narrow the search to the sensor circuit or the sensor itself, and the error “Injector short circuit” will indicate a problem in the on-board network or the injector itself.
The absence of a signal from the DPKV (crankshaft sensor) blocks the engine from starting 100%, while the malfunction of most other sensors only worsens engine performance, but does not always prevent starting.
Seasonal problems and operating conditions
In winter, a list of reasons why ZMZ 405 It won't start and has problems related to low temperatures. Frozen condensate in the fuel line, thickened oil and a battery discharged in the cold are a classic triad of winter problems. In addition, condensation may form on the spark plugs, causing a spark to break through to the housing.
In summer, on the contrary, the problem of overheating and vapor locks in the fuel system is often encountered. If the fuel pump is located inside the tank, it is cooled by fuel, but in extreme heat and low gasoline levels in the tank, it may overheat and fail. Also, in hot weather, detonation combustion of fuel is possible if the octane number does not correspond to the compression ratio.
⚠️ Attention: When trying to “light” a car in winter, do not let the starter turn the engine for more than 5–7 seconds continuously. This can lead to overheating of the starter wiring and melting of the contacts, which will create a new problem to replace the unsolved one.
Wet weather also makes its own adjustments. A spark breakdown on a wet surface of spark plug wells or a cracked distributor cap (if there is a contact system on older versions) is a common occurrence after a car wash or rain. In such cases, drying the engine and treating high-voltage elements with moisture-protective compounds helps.
Frequently asked questions (FAQ)
Why does the ZMZ 405 start and immediately stall?
Most often, this indicates a malfunction of the idle air regulator (IAC) or the leakage of unaccounted air. The problem may also be low fuel pressure or a malfunction of the mass air flow sensor. Try to lightly apply gas when starting - if the engine runs while you hold the pedal, then the problem is in the idle system.
Is it possible to start the ZMZ 405 from a pusher?
Yes, an injection engine with working sensors and a working fuel pump can be started from a pusher or towed. However, this must be done carefully so as not to damage the catalytic converter with unburned fuel, which may already burn out in the exhaust system.
What spark plug gap should be on ZMZ 405?
The optimal gap between the spark plug electrodes for the ZMZ 405 engine is 0.7–0.8 mm. Too much clearance can result in misfire under load, while too little clearance can result in rough idle.
What should I do if the engine does not start after replacing the timing belt?
Most likely, the valve timing marks were set incorrectly. It is necessary to remove the belt and re-set the crankshaft to TDC of the first cylinder, and then set the marks on the camshafts according to the instructions. Also check to see if the valves were bent during previous assembly.
How to check the performance of a fuel pump without a pressure gauge?
When you turn on the ignition (before turning on the starter), you should hear the characteristic hum of the pump in the tank area for 2-3 seconds. If there is no sound, check the pump fuse and relay. You can also remove the fuel supply hose from the ramp (observing safety precautions) and briefly turn on the ignition - gasoline should flow out in a powerful stream.