How to Clean Diesel Fuel Tanks

by TJ Hinton

Contamination in diesel fuel tanks is largely caused by petroleum-eating microorganisms. Since these microbes need water to grow, the service interval on cleaning the fuel tank varies with humidity, water contamination at the pump and water infiltration into the fuel tanks themselves. The average service interval is around five years for most applications, adjusted for conditions in marine or high-humidity regions. Properly treating your tanks with a biocide agent can extend this interval somewhat, and systems equipped with fuel-polishers have been known to eliminate the need for tank cleaning entirely. Tanks can be cleaned in-place with use of a biocide agent and a fuel-polishing rig, and they can also be cleaned mechanically using a scrubbing medium to remove stuck-on contaminants in the tank.

Cleaning a Removable Tank

Step 1

Treat the fuel, using a biocide product according to the manufacturer's instructions. Measure the dose based on the amount of fuel remaining in the tank.

Step 2

Using a positive-displacement pump rated for use with diesel fuel, pump the fuel out of the fuel tank and into a fuel container. If the fuel filler neck is fitted with an anti-siphon device, disconnect the filler and insert the hose directly into the tank.

Step 3

Remove the fuel tank and ensure that all fuel has been removed from the tank. Pour a few gallons of water and a scrubbing material, such as crumbs of safety glass or clean gravel, into the tank. Add liquid soap with petroleum-cutting properties, such as Dawn, Ajax or Palmolive, and swish the mixture around in the tank as vigorously as possible.

Step 4

Rinse the tank out thoroughly and ensure that all of the scrubbing material and loose debris is washed out. Allow the tank to dry completely before reinstalling it in the truck.

Step 5

Install an in-line, 30-micron fuel filter with a water separator in the output hose of the pump. Pump the fuel back into the tank while monitoring the filter and water trap. Change the filter and empty the trap as necessary. Hold the pickup hose above the contaminants on the bottom of the fuel container to avoid clogging the filter too quickly.

Cleaning a Captive Tank

Step 1

Treat the fuelk, using a biocide agent, according to the manufacturer's instructions. Insert the fuel pickup hose and discharge hose into the fuel tank.

Step 2

Run the pump to circulate the fuel, while monitoring the filter and water separator. Move the pickup hose around the bottom of the tank to pick up as much of the sediment as possible.