Before buying or having your pump repaired, you will need to use an obd2 to scan the codes on your vehicle. You will also have to test the fuel rail pressure with this obd2. If you have pump codes with other codes, you will need to ensure that those other codes do not disable the pump to put it in soft mode. Normal pressure should be between 650 psi and 1800 psi on a pump that is operating normally. The most frequent problem is a difficult start after a long rest without having a code. After a while, the vehicle begins to lose power until it turns on the engine light and puts the vehicle in soft mode by turning off the pump. At that time you will have a pressure reading between 70 psi and 115 psi.

The hard start is not always the pump. The difference to recognize it is a difficult start after a rest for several hours. Difficult starting after using the vehicle and the engine is hot is often a Vanos selenoid valve problem. 

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I suggest you an obd2, easy to use with several functions. You must have a smart phone. www.bluedriver.com