What Causes an Engine to Inject Fuel but Not Ignite?
3 Answers
Check for faults in the ignition system, electrical circuits, electronics, and fuel system. Ignition Fault: Assuming the fuel system is intact and the battery has sufficient power, you can disconnect the main high-voltage wire, hold it with insulated pliers (to prevent electric shock), and position it 0.3mm away from the engine body. Then, start the engine and observe whether a spark jumps at the 0.3mm gap, noting its strength. If there is no spark, it indicates an ignition system fault. Electrical Circuit Fault: Possible causes include blown fuses, open circuits in the high-voltage coil, breaks in the low-voltage circuit, detached central ignition wire, leaking distributor rotor, or damaged spark plugs. Electronic faults mainly refer to the failure of the central computer control board. Fuel System Fault: Stalling caused by fuel system issues often comes with symptoms like engine weakness or a feeling of stepping on a soft accelerator pedal. Problems may include a malfunctioning fuel pump, blocked fuel lines, clogged fuel filters, a failed carburetor, or damaged injectors. Sometimes, the issue is simply an empty fuel tank that the owner is unaware of. Adding a few liters of gasoline can resolve all the problems.
When encountering a situation where the engine injects fuel but fails to ignite, the most common cause is an issue with the ignition system. I've come across this type of malfunction many times—either the spark plugs are severely carbon-fouled and can't produce a spark, the ignition coils are aged and fail to deliver high voltage, or the high-tension wires are leaking electricity, causing the current to go astray. Also, don't overlook sensor problems; if the crankshaft position sensor is damaged, the car won't know when to ignite. During a recent repair, I encountered a case where this sensor malfunctioned—the engine injected fuel but showed no ignition response at all, and the issue was only resolved after replacing the sensor. Problems with the ECU control unit can also cause chaos, sending commands to the fuel injector but no signal to the spark plugs—this requires checking the fault codes to diagnose. I recommend immediately inspecting the condition of the spark plugs and testing the resistance of the ignition coils. If that doesn’t work, take it directly to a professional repair shop to troubleshoot the entire ignition circuit.
My car had a fuel injection but no ignition issue last week. When starting, I could hear the fuel injector working but it just wouldn't fire. After disassembling it myself for inspection, I found the spark plugs were so carbon-fouled they looked like burnt rice crusts, with the gaps completely clogged. Even after replacing the spark plugs, the problem persisted. Further testing revealed one ignition coil was faulty, causing the mixture in the cylinder to be injected but not ignited. Also, pay attention to sensors - if the camshaft position sensor sends inaccurate signals, the ECU will delay ignition. Finally, while checking wiring connections, I discovered a wire whose insulation had been gnawed by rats, causing a short circuit. My DIY repair experience suggests: don't blindly replace parts. First eliminate fuel system faults, then focus on checking spark plugs, ignition modules, and the connection status of sensor wiring.
