A leaking injector pump is a common problem with vehicles over 150,000 miles. The injector pump itself has a good reputation, and if you are experiencing leaking from around the injector pump it is most likely caused by broken O-rings. These O-rings are very inexpensive and will more than likely fix your issue. You will also need to purchase a special socket that is splined on the inside in order to remove the valves from the top of the injector pump. Bosch sells these sockets for about $50.
Step 1 - Clean the Engine
Before you get started on the injector pump, the day before you need to completely clean and degrease your engine. Washing it the day before will give the engine plenty of time to dry. Everything needs to be degreased before you begin, so that you do not get any dirt or debris into the pump or delivery valves. When you are working, you need to keep your hands clean as well, it is a good idea to use disposable gloves. They sell disposable gloves that are specially made for mechanics, you should be able to find them at any auto parts store. Make sure you change the gloves frequently.
Step 2 - Access the Injector Pump
These steps may not all apply to your vehicle, but you can use them as a general guide to help you find your way. Your injector pump may be easier or more difficult to access. If you get stuck, a great reference is to search for forums for your specific car model. There are plenty of DIYers willing to offer advice and suggestions. You will need to remove the intake manifold, and disconnect any vacuum lines connected to the manifold.
Step 3 - Remove the Injection Lines
You need to remove the injection lines from the valves using as flare nut wrench. If you have steel injection lines, you will need to bend them to get them out of the way. Take care not to bend them too much, because you will reuse them and they will have to bend back to their original position. Once the lines are removed, you need to remove the locks on top of the valves. Now that the locks are removed, you will find that there is dirt in the area. Using carb cleaner and a toothbrush, clean the area completely. Carb cleaner dries quickly, and you should never use water, it could end up in your fuel system.
Step 4 - Replace Copper Seats and O-Rings
In the materials it mentions that you should purchase 10 of each copper seats and O-rings. You will not need this many, but it is good to have extra in case you mess up. Now, working with just one valve at a time, unscrew the valve very slowly. Use the special splined socket to remove the valves from the pump. There is a small spring inside the valve that you can lose if you aren't careful. The copper seat sits under this spring, you can use your tweezers to put it in place. Then you need to remove the O-ring from around the valve and replace that as well. Now you can reassemble everything in the reverse order that you took it apart.