ACHY LEAKY PUMP
Installing seals on a VW injection pump— in the driveway
Not long after he purchased a low-mileage non-cheater 2002 VW Jetta TDI, my son Kyle Tobin (a regular UDBG contributing editor and photographer—ed.) began to notice that he was getting reduced fuel mileage as well as a diesel fuel smell at times. After investigating, we found that the injection pump seals were beginning to leak, which is a common problem for the ALH engines. Since the pump seemed to be delivering fuel to the cylinders just fine and was not spraying fuel out from the high-pressure side we determined it was leaking on the low-pressure side.
Rather than replacing the 11mm Injection pump with a questionable used pump or expensive remanufactured or new pump we spoke with our friend Kraig Keith at Kraiger Automotive Service in Lima, Ohio, about sending the pump up to him for new seals. He let us know that the low-pressure seals can be replaced while the pump is on the car and he would be in the area and was able to help us out. So we took Keith up on the offer and scheduled an afternoon to get together and wrench on the Jetta.
Keith replaced the seals in the ALH injection pump in about two hours, including time for our photography slowdowns, while working in the driveway. To seal the pump, he installed a Viton pump head O-ring kit from Dieselgeek along with a Quantity Adjuster seal and Pump Top seal from ID Parts. Be sure to thoroughly clean the pump and fuel lines before starting to work to prevent dirt and debris from contaminating the fuel injection system. Spray brake cleaner will typically work well unless your pump is extremely dirty.
Replacing the pump head O-ring seal required removing the fuel lines and then loosen-
ing the pump head and cutting the old O-ring to remove it, then carefully sliding the new O-ring over the head and into position. The kit includes two O-rings in case one gets messed up during the installation. The Quantity Adjuster and Pump Top seals were also replaced as a precaution while Keith was servicing the pump. He used VAGCOM or VCDS to adjust the pump IQ to his preference of 3.0 to complete the repair.
Follow along over the next several pages for an overview of the process, taking notice that we don’t have the space available to show every step—but you will get the general idea. The Dieselgeek website features a thorough set of instructions for the procedure if you need additional references. If you plan to repair a leaky injection pump on your ALH TDI yourself, plan to set aside an afternoon or evening and be sure to practice safe shop techniques and if anything you see here seems beyond your mechanical skills and abilities have your local performance diesel specialist handle the repair work for you. Just be sure to tell them your friends at Ultimate Diesel Builder’s Guide sent you. UDBG
Kyle Tobin’s little 2002 Jetta TDI is a fun daily driver that’s great for weekend blasts down the track in bracket races, but its leaky fuel pump seals needed to be repaired.
1 The 1.9L ALH TDI engine from VW is a hearty engine, but this one was a little sick with leaky injection pump seals (which can’t be seen with the engine cover in place).
4 Here is the Bosch injection pump for the ALH, since Tobin’s car is an automatic (but will soon receive a 6-speed manual transmission swap) it has the desirable high-output 11mm pump so it was much better to reseal than to replace.
3 Keith starts by disconnecting the negative terminal on the battery.
5 Keith removed the upper half of the timing belt cover to access the pump pulley to be able to manually crank it into position later on during the install.
6 He starts getting into the pump by removing the low-pressure feed and return lines from the fuel filter to the pump as well as the injector return line.
2 The seal kits from Dieselgeek and ID Parts include the seals Kraig Keith needs to do the minor pump on-the-car reseal as well as other seals for a complete off-the-car rebuild. Note that the Bosch seal kit uses a Buna rubber seal (large green O-ring)...