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6.4L Fuel System Debris Inspection

Glossary

Metal particles in the fuel drained from a 6.4L Power Stroke diesel fuel line indicating that the high pressure fuel pump has failed, or is failing.

The fuel system debris test is vitally important in diagnosing performance concerns as well as engine failures on 6.4L Power Stroke Diesel engines. The test is intended to find debris from the HPFP (high pressure fuel pump) by opening the fuel supply lines at the fuel injectors and draining fuel from the lines and the supply manifold. The debris which is typically small shiny metal particles is created in the fuel pump. In severe failures the debris may be a dark silt-like substance that can pass through the injectors and return to the secondary filter housing after passing through the fuel cooler. For this reason it is wise to take two fuel samples during the initial diagnostic pre-checks. One sample from the HFCM (the frame mounted Horizontal Fuel Conditioning Module) and a second from the test port on the fuel cooler. When taking a sample at the injectors use a black cap from an aerosol spray can. The dark color of the cap will contrast the bright metal particles nicely as seen in the photo on the right. You may then pass the sample through a light colored paper such as a paper napkin or a coffee filter to check for darker colored debris.

The test is straight forward. Remove the valve covers following the Workshop Manual, read and understand all safety warnings regarding fuel system pressure and procedures. Start with any misfiring cylinders or cylinders with high fuel trims above 10% positive or negative. Slightly loosen the feed tube at the fuel manifold enough to allow the tube to rotate when disconnected at the injector. Then disconnect the fuel supply tube at the injector and place the collection cup/cap under the fitting and move the tube away from the injector fitting. Loosen the injector tube at the manifold to allow fuel to drain into the cup. Keep in mind that the fuel lines must be replaced once the fittings are loosened. Don't drain the manifold as you will likely want to take samples from the other injectors. Set the cup down for a few minutes to allow any particles to settle then you can drain off dome of the fuel and inspect for debris.

Checking the fuel system for debris that will indicate that the high pressure fuel pump has failed, or is failing on a 6.4L Power Stroke Diesel engine

Collecting a fuel sample directly from an injector supply tube for inspection.

Regardless of whether or not you find debris in the high pressure fuel system your inspections are not complete. disconnecting the fuel lines at the HPFP, cylinder heads and the supply system will allow you to inspect the fittings, banjo bolts and the fuel lines for rust as seen below. You can easily identify rust on the HPFP inlet fittings as well as on the inside of the high pressure outlet fittings. Rust can only mean one thing. Water. At this point a complete inspection of the fuel system is necessary including the fuel tank(s), fuel water separator and the WIF indicating system. For warranty purposes a fuel sample and analysis will likely be required to test for fuel with low lubricity and, contaminants like water, gasoline and other various chemicals that do not belong in diesel fuel. The presence of alcohol which allows water to disperse for example will indicate that unapproved fuel additives are being used. Under most circumstances fuel related fuel system failures are not covered by warranty.

6.4L Power Stroke Diesel high pressure fuel pump fittings showing rust due to water contamination of the fuel

Remove the fuel lines at the high pressure fuel pump fittings and inspect for rust.

Rust on an injector at the return port area is undeniable evidence of water in the fuel. There is no question that this injector is internally damaged.	Inspect the inside of the fuel line banjo fittings for rust indicating the presence of water or dark debris that could indicate a high pressure fuel pump failure.
On the right: More undeniable evidence of water in the fuel. The fuel line fitting bolts are as rusty and corroded as they are on the outside. Inspect for rust or corrosion on and inside of the fuel line fitting bolts. These bolts also known as "banjo bolts" are used in the fitting shown above to the right.	.

Article by: Keith Browning Photographs by: Keith Browning

This article is only to provide information. It is hoped that it helps technicians in identifying possible causes and assist in the quick diagnosis of the identified concern. This is not intended to replace any official instructions, authorization or documentation of any Ford Motor Company Engineers, service manual, TSB, Service Message or recall.

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