M11 Series – Service Manual – 005-011   Fuel Flow

Loosen the fuel line at the shutoff valve while the engine is cranking. If fuel does

not
come out of the connection, the pump

must
be primed.

Connect a pressure gauge to the quick disconnect fitting of the fuel pump.

Start cranking the engine and observe the cranking fuel pressure.

If the fuel pressure is below the specification, check to be sure there is a fuel supply to the pump and that it is

not restricted. Refer to Procedure

006-020. Prime the fuel pump if necessary. Refer to Procedure

005-016-050.

Connect a 0-300 psi pressure gauge to the quick disconnect fitting to the fuel pump.

Start the engine and operate it at 1200 rpm with no load applied.

Record the fuel pressure.

Install an 18-inch piece of clear tubing on the suction side of the gear pump or the fuel filter head. Tygon R-3603 is the correct size for use with standard Stratoflex No. 10 hose fittings.

NOTE: Add the 18-inch piece of clear tubing to the existing fuel suction line. Do

not replace any portion of the suction line to install the 18-inch piece of clear tubing.

Start the engine and allow the air to purge from the clear tubing. No air bubbles can appear.

Shut off the engine, and observe the clear tubing.

NOTE: Generally, an air space will appear in the clear tubing that is drawn from the top of the fuel filter.

Observe the fuel in the clear tubing. It should stop moving within 1 minute if the system is leak free. If the fuel continues to move toward the fuel tank, there is a leak in the system. Observe from which direction air bubbles are coming into the clear tubing. If they are coming from the fuel tank side, then the leak is in the cooling plate, fittings, fuel line, or fuel tank.

If the fuel did

not move immediately, let the vehicle sit for about 1 hour. If there is no movement of the fuel, the system is sealed and should

not cause a hard start due to drainback of the suction lines.

Remove the clear tubing, and connect the suction line back to its original connection.