Ford Powerstroke 1999-2003 Diesel Filter Troubleshooting

Checking for Air Leaks

Step Three: Placing Vacuum cap over diesel filter input

Step Five: Connecting filter output to vacuum gun

Step Six: Vacuum testing the diesel filter housing

2nd Generation Powerstroke Troubleshooting

The 2nd Generation Powerstroke was the last generation of the 7.3l engines offered in Ford Trucks, sold from '99-'03 model years. As part of troubleshooting your fuel system, you should be comfortable using a vacuum pump. There are numerous types of vacuum guns that can be used, though a Mityvac hand pump is shown in the pictures here.

Upon completion of the installation of your Greasecar kit, it is not uncommon to discover air leaks in the system.
Even a truck in the best of conditions can leak air into the truck, as the fuel system has been changed from a pressurized
system, to one under vacuum. It is possible for a vehicle to exhibit signs of an air leak in one configuration,
but not the other.
As the change to the fuel system routing has been made, the enabling criteria for the fuel system to work properly
is simply to be free of air leaks. If an air leak is present, you may experience one, many, or all of the following
symptoms:

• Hard Start or No Start
• Low Power
• Diesel Fuel bowl draining
• White smoke
• Engine hesitation

While there are several points in the system for possible air leaks, 99% of the time these symptoms are due to an
imperfectly sealed diesel filter housing. The best way to test for an air leak, is using a Mity-vac (or similar) vacuum
pump. A quality unit will have a built in vacuum gauge as well, so you can physically see the leakdown occur
if there is an air leak in the system. To test the fuel filter, follow these steps.

Step One: Drain the diesel filter housing, if any diesel is present in the filter. The filter housing needs to be
drained if there is still fuel in it, as most vacuum guns aren't designed to pull liquid through their internals. The
drain can be identified by the yellow lever on the side of the filter housing, labeled "drain".

Step Two: Disconnect the input line from the fuel tank. This is the line connected to the input side of the diesel
filter, that connects the filter to the tank.

Step Three: Place a vacuum cap over the barb on the input side of the filter. To accurately perform this test, it
is important that the vacuum cap seals the barb. If this connection isn't sealed, the test will be inaccurate.

Step Four: Disconnect the filter from the solenoid valve. Disconnect the hose
that connects the diesel filter output from the NO port on valve "A" (the supply
valve). This is where you will connect the vacuum gun to the filter housing.

Step Five: Connect the filter housing to the vacuum gun. Most vacuum guns attach using a 1/4" line. Though
the barb on the filter may be 5/16" or 3/8", use the smallest line possible, to ensure a good connection on the filter.
Again, this connection will be crucial to the success of the test, so ensure the connection is tight.

Step Six: Apply vacuum to the filter housing. Under load, these trucks can pull up to 20" hg of vacuum on the
filter housing. Apply at least 20-25" hg to the filter housing. Keep this filter under vacuum and undisturbed for 20
minutes or so. If the filter is properly sealed, the vacuum should hold. If it doesn't, it will be necessary to find the
source of the leak. Should you discover vacuum is not holding in the filter housing, use a piece of hose as a stethoscope,
and listen for a leak at each connection. A common place for these to leak is around the cap on the diesel
filter, from the o ring underneath. If you haven't changed the filter recently, now would be a good time to do so. A
replacement filter will come with a new cap, as well as a new o ring. Following the instructions, install the new
filter, cap, and o ring. Should the leak be coming from one of the brass fittings, gently tighten the leaking fitting in
1/8-1/4 turns. If the fitting continues to leak, remove it

Priming the diesel system

Before you prime the diesel system, make sure the vegetable oil filter is primed and full of diesel fuel.

Step One: Attach the vacuum gun to the filter output. Once the filter has been sealed, you should be able to
draw a prime using the vacuum gun. Begin by attaching the vacuum to the diesel filter output. Follow the instructions
included with the vacuum gun, and attach any needed components to prevent pulling fuel directly into the
vacuum gun.

Step Two: Reattach the diesel supply line to the input of the filter housing. The diesel supply line is the larger
of the two lines coming from the tank, and bends OVER the return line.

Step Three: Apply a vacuum to the filter, until you are able to draw fuel free of air out of the filter housing.
Once you have the filter primed, remove the line connecting the vacuum gun to the filter.

Step Four: Reattach a fuel line from the diesel filter output, to the valve "A" NO (normally open) port.
Don't forget to secure the connections with hose clamps.