Keeping dirt out of your fuel during filter changes, choosing the right zinc, and more.

More of this Feature • Part 1: Purifying your filter • Part 2: Choosing the right zinc, and more
Related Resources • Maintenance Q & A Index • Maintenance Editorial
Elsewhere on the Web • Detroit Diesel

I keep a careful maintenance schedule for my fuel-water separators but have found that dirt occasionally gets into my fuel pump. And I recently had a problem with an injector. Do you have any suggestions? V.N., via e-mail

You may be allowing dirt to enter your fuel system by improperly servicing your separators. First, have a bucket ready in which to place the old elements, place two layers of absorbent pads under your work area in case you have a spill, and make sure to properly dispose of old filters and fuel.

If you have twin engines, service both fuel systems at the same time. Check your fuel-water separators for water in the bowls and drain as necessary. Also change the separator elements if it's time. Then move onto the engine-mounted filters. Before removing the filter elements, wipe down the filter housings, especially on top, to prevent dirt from falling into the new filter when you install it. Remember, it takes only a single speck of dirt to clog an injector.

Remove the element and old gasket, and wipe down the new gasket with clean diesel fuel. Before installing the new element, inspect it for debris like metal filings, especially the threads of spin-on filters. Install the new filter, but do not prime the system by pouring unfiltered fuel into the element, as any contaminants could cause fuel-system damage. Instead, prime and bleed the system according to the instructions in your owner's manual. Start your engine, let it run for a few minutes, and check for leaks.

Other tips: Use only manufacturer-specified parts, store new filters so that they are free of dust and dirt, and occasionally cut open your old filter to see what kind of contamination it may be picking up. 

What are some pointers for drilling through aluminum and stainless steel? M.B., via e-mail

Use the right bit at the right speed with the proper lubricant. Never use a wood bit on metal, and for precision drilling, use a drill press whenever possible. Drill stainless steel as slowly as possible, and use a 1/8-inch (3mm) bit at about 1600 rpm for starter holes. Work up towards your final hole size in one-inch increments. Apply and release downward pressure in a regular, rhythmic pattern to start the bit. As you increase hole size, decrease rpm. For example, drill a 1/4-inch hole (5mm) at 950 rpm, a 1/2-inch hole (13mm) at 370 rpm, and so on. Lubricate the bit constantly with cutting oil. I've found that kerosene or a thick mixture of dishwashing detergent and water delivered through a plastic syringe will do.

Drilling through aluminum requires a higher rpm and some specialized equipment. For a 1/8-inch starter hole, you will have to drill at about 9500 rpm. For a 1/4-inch hole, use 5700 rpm, and for 1/2 inch, 2200 rpm. While you may not have this kind of high-speed drill in your toolbox, you can rent one at any large home improvement or tool-rental shop. Because of the relatively high speeds required, you will have to use cutting oil specially formulated for aluminum.

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