IDI Injection Pump Tuning

How to Turn up the DB2 Injection Pump on the 6.9L & 7.3L IDI Diesel

The 6.9L and 7.3L IDI use a Stanadyne DB2 injection pump, which has fuel delivery adjustment. Before you attempt to turn up the injection pump, it is highly recommended you install a pyrometer. This is cheap insurance against melted pistons, and the only reliable means of tuning the pump. The best way to tune the pump is to find the point where performance is maximized while, smoke is minimized, and EGTs remain manageable. Turning up the pump will yield noticeable performance gains at the expense of fuel economy.

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IDI injection pump location

• The injection or injector pump is located at the front of the engine, easily recognizable by the 8 injector lines exiting the rear. Begin by removing the throttle cable, which makes it easier to get to the access cover.

IDI fuel screw cover

• The access cover of the injection pump is located on the passenger side. It's a semi-triangular plate attached to the side of the pump by two small bolts. Place a rag beneath the cover to catch the fuel that will drain out of the pump once the cover is removed.

• Carefully remove the top bolt of the access cover, and loosen the bottom. There is no need to remove the cover completely, just let it hang out of the way.

IDI fuel adjustment screw

• Once the fuel has drained, you'll need a small mirror to view into the access cover and locate the fuel adjustment screw.

• The adjustment screw is located in the far corner (towards the cab) of the pump, inside the access cover. You'll notice a small hole in one corner (see diagram below). The motor will need to be bumped (turned over) until the Allen head adjustment screw is visible through this hole.

• Position the mirror so that you can see inside the pump and through the adjustment screw access hole and bump the motor (in short bursts) until you can see the Allen head. This may take several attempts.

Stanadyne DB2 fuel screw cover diagram

Stanadyne DB2 fuel adjustment screw

•If you have a friend that can help, it's much easier with two people. One person bumps the engine while the other looks for the adjustment screw to appear. A flashlight will help significantly, as the Allen head is small and relatively deep inside the pump.

Note - an alternative method is to turn the engine by putting a socket on the crankshaft; we've found it's easier to just bump the motor with two people.

Turning up the injection pump on an IDI diesel

• Once the adjustment screw is visible through the access cover, use a 5/32" Allen wrench to adjust it - clockwise for more fuel, counter clockwise for less fuel.

• The adjustment screw is tight, so a 5/32" wrench can be used on the Allen wrench for more leverage.

• Once adjustments have been made, reinstall the access cover and gasket. The engine will be hard to start at first since the injection pump has been drained; it took us three or four tries before it ran.

• Make adjustments one "flat" at a time (there are 6 sides to an Allen head, so one "flat" is 60 degrees of a turn), then drive the truck, verify exhaust gas temperatures are within a manageable range, and make further adjustments as necessary.