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Q: in the first two days, a 2007 1.6L Buick sail was towed into the factory, the engine type was F16D3, and the mileage was 50000km. During the first maintenance, the repairman checked that there was no high pressure fire. After changing the ignition coil, the vehicle started smoothly and the trial run was normal. But the second day in the morning, the car can not start, I first checked the battery voltage 12V, start 9V, the main iron lap contact is good, the starting machine runs forcefully. In addition, the car has no high pressure fire and no oil supply, oil pump and ignition fuse are normal, the oil pump relay will not be absorbed when opening the electric door, and do not absorb when starting, but sometimes it will suck when the key is loosened at the end of the start, and there is no fault code. Using the test function to actuate the oil pump relay will pull in, forcing it to pull in and still can't start. The measuring relay has a battery voltage on foot 25, but the resistance between the 26 foot and the grounding iron is 440 ohms. After the battery is charged, it can start. And when the relay is switched on, the 2S will be pulled and then disconnected. Sometimes it takes a long time to start, and the relay is found to be intermittently combined during startup. Measuring the resistance of the position sensor 880 is the same as the new one. Please give the answers. Answer: first of all, this is the circuit fault, one is the battery vulcanization, need to be replaced; two is the car oil pump fuse and the engine computer fuse is common, to detect the voltage of the circuit; three is also need to detect generator power. The maximum allowable voltage specifications for typical automotive circuits are as follows: (1) 0.1 V (100mV) at each connection of most circuits; (2) 0.2V (200mV) at each connection of the generator circuit; and the total voltage of the power or grounding circuit of the computer power and grounding circuit should not exceed 0.1 V (100MV). The voltage value is smaller than the maximum allowable index, indicating that the components and connection resistance of the components are low enough to be acceptable. If a high voltage is encountered, a lead line of the digital voltage - the ohm meter will be connected to the battery, the other leads back to the battery direction (refer to the corresponding circuit schematic) until the voltage value falls to the acceptable level, so that the final test of the high resistance is unacceptable in the electrical circuit. A point between the point and the unacceptable test point of the first voltage. When testing the power load circuit voltage of the rear part of the car, a digital voltage ohmmeter lead extension line can be made. Using the crocodile clip to connect the long lead of the digital voltage ohmmeter to the car battery, the digital voltage ohmmeter can be taken to the rear part of the car for voltage test. Note that the high internal resistance of the digital voltage ohmmeter does not allow a large amount of current to flow through the voltage test process. When the positive extreme voltage is tested, the extended lead should be inserted into the positive pole of the digital voltage ohm table to receive the positive pole of the battery, and when the negative extreme voltage is tested, the extension lead should be inserted into the negative pole of the digital voltage ohm meter to receive the negative electrode of the battery. If the battery voltage is 12.6V, but there is an excess voltage in the positive or negative circuit of the computer, the voltage of the computer itself is less than 9V, and the logic door in the computer will not work correctly. When the engine is trying to start the engine, the power control module may fail to control the fuel injector or the ignition coil because the battery voltage is pulled down by the start motor work, even if there is no large amount of excess voltage in the computer power or the grounding circuit to maintain the normal work of the computer. In a word, at any time the computer is not working properly (or not working at all), it is necessary to test the excess voltage in the power and grounding circuits before deciding to replace the computer. It should also be noted that the voltage test can be used to identify the occurrence of occasional fault symptoms, the excess resistance in the circuit, even if the accidental symptoms of the fault are not shown, may be because the circuit conditions change (for example, cooling), the fault symptoms may disappear, but the excess electrical resistance will not completely disappear, only to reduce to. A certain value makes the circuit work again. In short, even if there are no obvious fault symptoms, voltage tests can be used to identify extra resistances. Your description makes me a little confused. According to Buick's circuit diagram, 30 and 86 feet are two normal power sources, 87 feet are supplied to the oil pump, and No. 85 receives the control signal from the computer. It is a tie signal. What do you mean by measuring the feet 25 and 26 of the measuring relay? In addition, the relay in all general vehicle systems is the same, with 85, 86, 30, 87 feet, and no 25,26 pin.