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6.5L GM Diesel Fuel Filter Replacement

How to Change the Fuel Filter on a 6.5L Diesel

Applicable Models:

1992 - 2002 Chevrolet & GMC C/K series trucks, Suburban, C3500HD, etc

Applicable Engine(s):

6.5L GM diesel (turbocharged and naturally aspirated)

The filter filter on a 6.5L GM/Detroit diesel is located atop the rear of the engine in an assembly known as the Fuel Filter Manager, or FFM. While General Motors recommends replacing the filter at 30,000 mile intervals, we typically recommend 15,000 miles. More frequent filter changes takes into account the fact that the 6.5 diesels are all relatively "old" engines, many with considerable miles on the odometer and plenty of sediment accumulated in the fuel tank. Fuel filters for these engines are not particularly expense, and your engine will always appreciate more frequent service.

Parts List

Part Description

Part Number(s)


Fuel filter

ACDelco TP1256F


Fuel filter housing retainer ring

ACDelco 12511963


Fuel filter strainer/screen

Clarcor/Stanadyne 29244


Fuel pump cable



[1] Secures fuel filter assembly to the fuel filter housing (fuel filter manager).
[2] Positioned below fuel filter in bottom of fuel filter housing.
[3] Eases fuel system bleeding process by easily allowing the fuel pump to be powered on without cranking engine over.

6.5L Diesel Fuel Filter Replacement & Fuel System Bleeding Procedures

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6.5 GM diesel fuel filter location

• Disconnect both negative battery cables.

• If applicable, remove the plastic "Turbo Power" engine cover (4 bolts, 13 mm socket).

• The fuel filter itself is contained within what is known as the Fuel Filter Manager (FFM). The FFM is located behind the upper intake manifold plenum centered between the left and right cylinder head.

fuel filter retainer vs fuel filter cap

• There are two types of fuel filters - those with a retaining nut, and those with a complete cap. The ACDelco replacement filter uses a retaining nut, and therefore you will need to acquire one if switching from a molded cap style. If the current fuel filter already utilizes the retaining nut, reuse it. The retaining nut is ACDelco 12511963 for those who need one.

6.5 GM diesel fuel filter manager

• Unscrew the cap/retaining nut from the top of the fuel filter manager, then pull the filter upwards to remove. If the outer gasket did not come out with the fuel filter, remove it from the fuel filter manager.

• Use a syringe, turkey baster, or other extraction device to remove the remaining fuel and any sediment from the fuel bowl.

6.5 diesel fuel filter strainer

• Locate the fuel filter strainer, which will either be located at the end of the centrally located tube in the fuel filter manager or stuck inside the bottom of the old fuel filter. If it is attached to the fuel filter remove it. If it is missing, a new one will need to be purchased. It is common for the strainer to get thrown away with the old filter, but it is an important failsafe.

• Unless the strainer remained on the tube in the fuel filter manager, you will need to install it with the detent tabs facing downwards into the FFM. If it is tight on the tube, use a deep socket that will fit over the tube in order to gently tap it until it seats against the lip near the bottom of the tube. This does not require excessive force - be gentle.

New fuel filter installation

• Lubricate the o-ring gasket of the new fuel filter with clean engine oil or diesel fuel, then install the new filter into the fuel filter manager. The filter is labeled to help line it up in the FFM, which features a series of tabs that must align into the filter housing. The filter can only be installed in one orientation; if it does not seat, do not force it and verify the orientation is correct.

• Install the retaining nut and cinch down hand tight.

Note - If you'd like to simply the process of bleeding air from the fuel system on any 6.5L GM diesel, please see: 6.5L GM Diesel Fuel Pump Cable. This tool will eliminate the need to crank the engine or cycle the key in order to run the fuel pump with the vehicle off. We highly recommend this convenient tool to any 6.5L diesel owner; simply plug it in and power the pump using the vehicle battery.

Bleeding fuel filter manager

• Attach a section of 5/16" fuel line to the bleed valve located on the top of the fuel filter housing. Open the bleed valve by turning it counterclockwise. Place the end of the hose in a fuel safe container outside of the engine bay.

• Cycle the key to the "run" position (1996+ model years) or crank the engine over (pre-1996 model years) until a steady stream of fuel flows into your container, then close the bleed valve. It is perfectly normal for the truck to start at this stage, albeit roughly; simply close the bleed valve and turn off the engine once fuel flows steadily into your container.

Bleeding sediment/water drain valve

• Once you've bled the fuel system to the fuel filter manager, the remaining air in the system must be purged through the secondary bleed/drain valve located just behind the thermostat housing. A small section of fuel line should be attached to the T-handled valve - install 1/4" fuel line if there is not. Place the end of the hose in a fuel safe container.

• If the engine will run at this point, start and run the engine then open the T-handle valve ~ 1/4 turn until a steady stream of fuel and no air bubbles exit into the container. If the engine will not start/run yet, repeat the steps in the previous procedure (with regard to cycling the key or cranking the engine) with the T-handle valve open. Once all air has been bled, close the T-handle valve, start the engine (if not running already) and check for any fuel leaks.