Passat 1. What is the cylinder pressure of 8T?

A 2002 Passat B5 1.8T car (equipped with a turbocharged four-cylinder EFI engine) has traveled nearly 40,000 kilometers. There is a slight truck phenomenon when shifting gears and accelerating while driving.

In the process of maintenance, firstly, we use Jinde K8 1 car decoder produced by Weiningda Company to retrieve the fault code, and get the code 65535, which shows that there is no fault code in the electronic control system. Then the spark plug of each cylinder was checked. The model of the spark plug is PFR60, which is a platinum electrode spark plug made in Japan. Visually, the electrode of spark plug is rust-colored, indicating that each cylinder works well.

Connect the fuel pressure gauge to the fuel inlet pipe of the car with a special interface, start the engine, and the fuel pressure gauge indicates 340kPa, which is within the normal range.

No abnormal phenomena were found in the electronic control system and oil circuit detection, so it was decided to clean the injector and throttle body for daily maintenance. Remove four fuel injectors from the engine, clean them with special cleaning equipment, and test the fuel injection quantity per unit time. Results The four injectors met the standard completely. Clean the throttle body with carburetor cleaner. Reset all the removed parts, then turn on the ignition switch, select the basic setting function with Jinde K8 1 car decoder, and perform the basic setting operation on the throttle control module. The specific operation is to select group number 60 to enter the setup program, and four lines of data appear on its display screen, in which the values of item 00 in the first line and item 0 1 in the second line tend to be stable after constant changes; When ADP ok is displayed at the end of the fourth line, the setting work is completed. Then start the engine for a road test. During the road test, the car has strong power when shifting and accelerating, and there is no car jam.

However, two days later, the owner reported that the engine was not easy to start in the morning after the overhaul. I used to pick up the car as soon as I started the engine in the morning, but now I have to start the engine at least three times in the morning to stop. However, after the car was finished, the engine turned off and the normal situation of starting the starter was restored. If the vehicle is parked for more than two hours, you still have to start the machine three times before you can get on the bus.

Then use Jinde car decoder to retrieve the fault code, which is still 65535. The system is normal and trouble-free. According to the fault phenomenon described by the owner, the vehicle was verified. After two hours, the engine started again. Sure enough, it started three times before the engine started. Because the electric control system of the car is normal, the idle speed is stable and the dynamic performance is good, it is preliminarily judged as an oil circuit fault according to the fault phenomenon. Connect the fuel pressure gauge to the oil inlet pipe again. After starting the engine, the fuel pressure gauge is 340 kPa. Then the engine stopped. Observe the change of the indicated value of the fuel pressure gauge, that is, check whether the residual pressure in the fuel system is normal. 10 minutes later, the indicated value of the fuel pressure gauge drops to 200kPa, which is lower than the standard allowable value. At this time, clamp the oil hose with pliers, and the indicated value of the fuel pressure gauge will rebound to 220kPa, and the pressure drop will slow down. At that time, it was suspected that the one-way valve at the outlet of the fuel pump was not closed tightly and leaked. After replacing the fuel pump of the same model, test the residual pressure change of the fuel system. Start the engine first, and the indicated value of the fuel pressure gauge rises to 350kPa. Ten minutes later, the indicated value of the fuel pressure gauge dropped to 200 kPa. After observing for 45 minutes, the fuel system pressure value drops to 0. At this time, before starting the engine, start the engine three times. Looks like there's still a leak in the fuel system That's all the fuel pipes, fuel pressure regulators and injectors. First, all the fuel pipelines were carefully checked and no abnormal phenomena were found; Check whether the fuel pressure regulator is normal by replacement method. Finally, we can only suspect that the syringe is leaking. Remove the four fuel injectors from the engine, but install them on the oil pipe, and the fuel pressure gauge is still connected to the oil inlet pipe. After starting the engine again and raising the fuel pressure to 350 kPa, observe the nozzle hole of the fuel injector. After a while, I saw a small amount of fuel leaking from the spray holes of three injectors, and two of them arched small bubbles from time to time. Ten minutes later, not only did the fuel pressure drop to 200kPa, but two seriously leaking injectors also dropped a drop of oil. After checking this, the reason for the failure is very clear. Due to the leakage of the fuel injector, it not only accelerates the pressure drop of the fuel system, but also sucks in air, prompting the fuel to flow back to the fuel tank. Therefore, the longer the time, the more air there is in the fuel system, and the fuel pump needs to work for a long time to remove air from the fuel system and establish oil pressure. Therefore, it is inevitable that vehicles will not be easy to get on the bus for a long time (such as overnight). After cleaning these three injectors again and testing, there are still leaks, so we have to replace them with three new injectors of the same model and do the injector leakage testing again. After the engine is started, the indicated value of the fuel pressure gauge rises to 350kPa, and the pressure value of 10min drops to 300kPa. Observe the spray hole of each injector for signs of oil leakage. Replace all removed parts, start the engine and deliver it to the owner. The next day, the main phone call told him to start the engine once in the morning, and the engine was running smoothly. The fault has been completely eliminated.

Maintenance skills:

1. Simple test method on idle motor vehicles: When the vehicle is in a cold state, the engine should have a high idle speed after stopping. As the engine temperature rises, the engine speed drops to idle smoothly. When the hot car is idling, after the air conditioner is turned on, the engine speed drops first and then rises; And that rotate speed is higher than the normal idle speed; When the air conditioner is turned off, the engine speed will first increase and then decrease to the normal idle speed. If the above three tests are described, it can be preliminarily judged that the idle motor works normally.

2. The residual pressure value of fuel system provided in the data of EFI vehicle indicates the rate of fuel pressure drop, not the absolute value. For example, the residual pressure of Passat B5 fuel system is not less than 250kPa after 10 minutes. With the passage of time, its residual pressure value will continue to decline. What is the absolute value of the final residual pressure? Different models have different values. This kind of test needs time support, and interested colleagues can connect the fuel pressure gauge for a long time. However, it is necessary to maintain a certain residual pressure in the fuel system for a long time to ensure the smooth start of the engine at any time.

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