Fuel System Contamination Testing

FUEL SYSTEM CONTAMINATION
Fungi and other microorganisms can survive and multiply in diesel fuel if water is present. The fungi can be present in any part of the fuel handling system. These fungi grow into long strings and will form into large globules. The growths appear slimy and are usually black, green, or brown. The fungi may grow anywhere in the fuel but are most plentiful where diesel fuel and water meet. As the fuel is agitated (when service station tanks are being filled), fungi are distributed throughout the tank and may be pumped into a vehicle.

Fungi use the fuel as their main energy supply and need only trace amounts of water and minerals. As they grow and multiply, they change fuel into water, sludge, acids, and products of metabolism. The most common symptom is fuel filter plugging; however, various metal components (fuel tank, pipes. and injection pump) can corrode.


WARNING: To avoid personal injury, do not come into physical contact with biocides.

If fungi have caused fuel system contamination, use a diesel fuel biocide to sterilize the fuel system. Do not exceed the dosage recommended on the label. Discontinue the use of a biocide when towing a trailer. It is permissible to have biocide in the fuel when starting to tow, but do not add any biocide while towing. Steam cleaning may be necessary if most of the fungus growth cannot be removed with biocides. The presence of water or gasoline in diesel fuel may also cause injection pump and nozzle damage.

CONTAMINATION TESTING PROCEDURE
This procedure checks for the presence of water and gasoline in diesel fuel that may cause injection pump and nozzle damage.

1. Remove the fuel filter element and inspect it:

- If water, gasoline or fungi/bacteria are not present, end the inspection.
- If water or fungi/bacteria are present, go to Step 2.
- If gasoline is present, go to Step 3.

2. Clean water from the fuel system in these steps:

A. Disconnect the batteries.
B. Drain the fuel tank.
C. Remove the fuel tank. Refer to Fuel Tank Service and Repair. Service and Repair
D. Remove the fuel sender unit. Refer to Fuel Tank Unit Service and Repair. Service and Repair
E. Inspect the fuel tank and fuel sender for rust, fungi or bacteria:

- If no rust is present, clean the inside of the fuel tank and fuel sender with hot water, then dry them with compressed air.
- If rust is present, replace the parts.

F. Disconnect the ends of the following lines:

- Lift pump suction.
- Lift pump feed.
- Fuel filter outlet.
- Fuel filter drain.
- Fuel return.

G. Inspect each of the pipes and replace any rusted pipes.
H. Dry the inside of each line with low pressure air.
I. Clean the inside of the fuel filter housing and dry it with compressed air.
J. Remove F/SOL fuse from fuse panel.
K. Install a new fuel filter element.
L. Install the fuel sender and fuel tank (add clean diesel fuel to 1/4 full).
M. Connect the following lines:

- Lift pump suction (both ends).
- Lift pump feed (both ends).
- Fuel filter drain.
- Fuel return (at injection pump).

N. Connect the fuel filter outlet and the fuel return line at the fuel sender to hoses that flow to metal containers.
0. Connect the batteries and crank the engine until clean fuel flows from the fuel filter outlet into a metal container.
P. Connect the hose from the fuel filter outlet to the injection pump inlet.
Q. Open each injection line at its nozzle end and crank the engine until clean fuel flows from it:

- Use two wrenches when loosening the injection line fittings.
- Allow a maximum of 15 seconds cranking time, followed by 1 minute of cranking motor cooling time.

R. Tighten each injection line fitting at its nozzle:

- Use two wrenches when tightening the injection line fittings.

S. Install F/SOL fuse in fuse panel.
T. Start and run the engine for 15 minutes while fuel flows from the fuel return line into a metal container.
U. Stop the engine.
V. Connect the fuel return hose to the fuel sender.
W. Clean the engine of fuel spillage.
X. Fill the fuel tank and add a biocide, if needed.

3. Clean gasoline from the fuel system in these steps:

A. Determine a procedure:

- If the engine runs, follow Steps B, C, J and K.
- If the engine does not run, begin at Step C.

B. Drain the fuel tank.
C. Fill the fuel tank.
D. Remove F/SOL fuse from fuse panel.
E. Remove the fuel filter outlet and connect it to a hose that flows to a metal container.
F. Crank the engine until clean fuel flows from the fuel filter outlet into a metal container.

- Allow a maximum of 15 seconds cranking time, followed by 1 minute of cranking motor cooling time.

G. Connect the hose from the fuel filter outlet to the injection pump inlet.
H. Install F/SOL fuse in fuse panel.
I. Start and run the engine for 15 minutes.
J. Stop the engine.
K. Clean the engine of fuel spillage.
L. Clear engine Diagnostic Trouble Code (DTC)(s). Testing and Inspection