RWD newsletter - April 2009
Page 7: Fuel Filters and Accessories

How long has it been since the fuel filter on your Volvo was changed? If you’re not sure, it would be a good idea to replace it at your next oil change or tune-up to prevent loss of performance or related problems. Under normal conditions, it’s safe to replace the fuel filter at 30,000 miles or 2-year intervals. When changing the filter, it is very important to use safe handling procedures and be prepared for fuel spillage. Consult the appropriate workshop manual for specifics. To ensure a leak-free installation, always install new copper sealing washers (included with most of our filters). Also keep in mind that any foreign debris in the output side of the filter or fuel line could cause serious problems in the fuel system. It is very important to measure your fuel filter on 1975-80 240 series. It’s the only way to be sure to get the correct one.

Accessing the pre-pump and fuel gauge sender assembly on 240 and 260 models can be a tough job if you don’t have the right tools. The difficulty lies in safely removing the large “bung nut” where all the lines and wiring go into the top of the tank. Believe it or not, that’s the official name for that style of nut. It’s a large ring with tabs that stick up at 60-degree intervals. The problem with using a drift or punch and a hammer is that the top of the fuel tank is only 4” below the floor of the car and the access opening is so small that you can’t get much of an angle to properly engage the tabs. This causes the tabs to bend over, making it hard to reinstall. And if you ever need to open it again, it’s so mutilated that it’s even more difficult, if not impossible, to remove. Our bung nut tool has interlocking tabs that positively engage the bung nut tabs, allowing the bung nut to be removed with a 1/4 turn of a 3/8” ratchet. The right tool makes this job go much smoother and prevents the bung nut from being damaged. No cussing, no damage and, more important, no sparks from hammering steel on steel; hence, no unexpected, loud, violent explosions. Please note that any time the fuel tank sender assembly is opened, the rubber seal ring should be replaced for safety reasons.

A common failure causing a no-start situation is the fuel pump relay. The relay overheats over time, loosening solder joints internally and causing intermittent contact. It sometimes melts the circuit board. After you check for spark, consider the fuel pump relay as a possible problem area.

One of our favorite books when it comes to understanding fuel injection on Volvo models manufactured from 1970 to 1998. Packed with original Bosch diagrams and photos, this reference guide is considered required reading for anyone who is interested in understanding and working on the complex injection systems used in Volvo cars. Includes comprehensive coverage of theory and operation, troubleshooting, diagnosis, and test procedures with specifications and a large section on performance issues. Close to 200 pages.