How to solve the flameout phenomenon in EFI engine operation

Analysis of flameout fault of EFI engine

Compared with the traditional carburetor engine, the electronically controlled fuel injection engine not only has excellent performance, but also greatly reduces the oil circuit failure rate. But once a fault occurs, it is more complicated to judge and eliminate it. Because the electronically controlled engine uses many control circuits, even if the engine has a single fault, there may be faults for many reasons. Grasping the basic principle of truth and the most direct fault cause will bring great help to the fault diagnosis of electronically controlled engines. As far as the abnormal flameout phenomenon of electronically controlled engine is concerned, the direct cause of the failure is nothing more than three aspects: the failure of oil supply system; High voltage electrical fault; Other mechanical failures.

1. Oil supply system failure

There are two reasons why the fuel supply system causes the engine to stall. One is that there is no fuel injection, and the other is that the fuel injection quantity is too small.

If you want to know how the fuel supply system causes the engine to stall, you must first understand the working process of the fuel supply system of the electronically controlled engine. The gasoline in the cylinder of EFI engine is directly ejected by the fuel nozzle installed on the fuel injection pipe. The fuel in the fuel injection pipe is pumped by the electric fuel pump installed in the gasoline tank and then supplied by the fuel filter (pressure regulator). In the whole fuel supply system, fuel injectors and electric fuel pumps are controlled by control computers or relays. Therefore, the fuel injector and the electric fuel pump are the first two devices to eliminate the oil supply failure of the computer engine.

At present, the electric fuel pump is generally installed in the gasoline tank, and the fuel has a good cooling effect on the fuel pump. Most cars have only one fuel pump, but there are also two fuel pumps (such as Cadillac cars). Fuel pump is divided into roller type, worm gear type, internal gear type and side groove type, but their external performance collision has its similarities. Therefore, after the EFI car is turned off, the fuel pump should be checked as follows:

Turn ON the ignition switch ("ON" position) and listen to the running sound of the fuel pump. If there is obvious running sound, it means that the fuel pump is working normally (but for the engine with wing air flowmeter, the fuel pump control switch is installed in the air flowmeter, and after turning on the ignition switch, the engine needs to be started to check the working condition of the fuel pump). When checking, besides listening to the sound, you can also hold the oil supply hose by hand, and you should be able to feel the pressure of the oil. When the clamped tubing is loosened, the tubing should be able to recover immediately. Of course, the quality of the oil pump can be further proved by loosening the oil return pipe joint and checking whether there is oil spouting in the oil pipe.

After checking the fault of the oil pump, the fault should be eliminated. If there is nothing wrong with the oil pump, the fuel injector should be checked next. The failure of fuel injector that leads to engine flameout is often caused by the blockage of fuel injector or the failure of control circuit. The failure of the injector is due to deposits and carbon deposits on the injector, which reduces the fuel injection quantity or makes the fuel injection unstable. The simple way to check the blockage of the fuel injector is to remove the fuel injector, connect the oil supply pipe, and connect the 3V power cord at the wire connector of the fuel injector (or contact the positive battery with a special resistance wire). If the oil injection is brittle, stop the oil in time and it will be normal. Once the nozzle is found to be blocked, it should be cleaned on a special cleaning machine, or the nozzle should be cleaned with mixed gasoline cleaning agent through the gasoline pipeline in the car without removing the nozzle. Whether the fuel injector control circuit is normal or not, you can also put your finger on the fuel injector when the engine starts to feel whether the fuel injector vibrates. If yes, the control circuit is working normally. Otherwise, you should check whether there is an open circuit between the wire connector and the control computer according to the wire number indicated in the instruction manual, or whether the control computer itself is faulty.

2. Ignition high voltage circuit failure

When the car is running, if the engine suddenly shuts down, the fault often lies in the high ignition voltage. The ignition system of EFI engine is to connect or disconnect the igniter circuit after the low-voltage electricity from the battery and generator is monitored and analyzed by the control computer, and send high-voltage electricity to the spark plugs of each cylinder through the ignition coil to ignite the combustible mixture. Under normal circumstances, the ignition high voltage fault that leads to engine flameout is often no high voltage output. At this point, first check whether the high-voltage line connection is normal. On this premise, we should check the igniter and ignition coil by comparing parts, so as to determine the location of the fault. This is because the igniter and ignition coil are repaired by replacing parts. If there is no problem in the above inspection, the fault is concentrated on the computer and its related signal sensors and connecting wires. This kind of fault has obvious indication when reading the fault code, and can be judged and eliminated according to different situations.

3. Other mechanical failures

In addition to fuel and high voltage electricity, other mechanical failures sometimes cause the car to stall. For example, the fuse of the electronic control circuit is poorly contacted or blown; Due to the damage of the air flow meter, the air intake monitoring is inaccurate; The vacuum hose installed on the fuel regulator leaks, etc. Here are two fault examples for your reference.

A) The hot wire of the hot-wire air flowmeter is too dirty, which causes the engine to shut down immediately after starting (Nissan VG30 engine). After the hot wire of the air flowmeter sensor becomes dirty, the air can't take away the heat normally, which makes the detected air flow rate lower than the actual air flow rate (the output voltage is 200mV lower), which leads to the decrease of the fuel injection controlled by the controller, the mixture is too thin, and the engine stalls.

B) The engine is shut down due to abrasion of the grounding line (same as Toyota). After the engine is started, it works unsteadily, emits black smoke and automatically shuts down. After inspection, the spark plug turned off normally and the fuel injector was in good condition. When the fuel injector circuit is checked with 12V test lamp, the indicator lamp only lights up but does not flash. Further inspection with a multimeter found that the white control line was grounded. Inspection along the white line found that the wear line was short-circuited with the left rear lug of the engine, indicating that the three nozzles of cylinders 2, 4 and 6 were always open when the generator was working, and there was a strong smell of gasoline in the three cylinders. Wrap the wire wear point with insulated wire, rearrange the direction of the wire, and eliminate the flameout fault.

Causes and maintenance of automobile engine flameout

Automatic transmission model:

1. Automatic transmission models will not turn off easily, while manual transmission models may turn off frequently because of low driving level. However, it is not excluded that automatic cars will not stall. The main reason is the use of inferior fuel (many gas stations sell impure oil for profiteering), which leads to carbon deposition and flameout of the engine.

2. In addition, for a new car (automatic transmission), the flameout is mainly caused by poor driving skills, and there is another possibility that the engine or oil circuit of the car is a problem, but for a new car, the problem of the engine itself is less likely, and most of the reasons are oil circuit problems.

3. Finally, for the old models, the reason of flameout is not only that the driving skills are not skilled enough, but also that the engine flameout is caused by the carbon deposition of unqualified engine oil.

Troubleshooting of automatic gear:

Usually pay attention to the place: for the phenomenon of automatic car flameout, mainly caused by the use of inferior fuel. First, go to a regular big gas station to add high-grade oil, such as 97 # gasoline. Although the price is much more expensive, it can guarantee a longer life and good driving force. But there are also car owners who are greedy for cheap and 90 # oil. Although the price is lower, problems may arise in the future. The second is to go to a large qualified gas station to refuel!

Practical operation: Hold the steering wheel firmly with your left hand (because there is no power, you must hold it firmly), brake hard with your right foot to reduce the speed as much as possible, and then quickly shift the AT gear to the N gear (note: the re-ignition must be in the N gear, not in the D/R/P gear, otherwise the car will not catch fire or the gearbox of the car will be damaged), and then return the key to one space before re-ignition.

Troubleshooting of manual gear;

1. For beginners, stalling in the middle is not a new topic, and the main elimination method is to improve driving skills after quick running-in.

2. Use high-quality qualified fuel.

3. Thoroughly clean the oil circuit, including the fuel injector, throttle valve and fuel tank. It may be that the quality of the oil you added is not up to standard, and there is too much gum, which blocks the oil circuit and leads to poor oil output.

4. The main reason for the failure of the car idling is that there is too much dust in the air. When the engine is running, a lot of dirt is deposited on the spool and throttle seat of the idle motor. When the dirt accumulates too much, the engine will have low idle speed, poor idle stability and idle flameout when driving. The solution to this problem is simple: just clean the idle motor.

5. Whether the oil circuit is smooth or not is easy to cause flameout in the middle.

6. The new car has been parked for a long time because of the rising oil price and the increase of many people who like to go back to work by bike and on foot. Actually, don't park for a long time. If it is parked for a long time, it should be thoroughly maintained, the oil and filter should be replaced, and the fuel and circuit should be checked as appropriate. Due to long-term parking, your vehicle may have lubrication or circuit problems.

In short, whether it's a new car or a classic car, whether it's an automatic transmission or a manual transmission, whether it's a veteran or a novice, you should improve the grade of oil when refueling, even if it's more expensive, so as to protect your engine from carbon deposition. In addition, regular maintenance is also very important. Always check whether the oil circuit and circuit are unblocked.