Series 40E Troubleshooting – Section 10.16 Fuel Pump Pressure

Figure 1. Diagnostic Form

Use the following procedure to check the fuel pump pressure. For a reproduction of the applicable portion of the diagnostic form, see Figure
“Diagnostic Form”

, above.‪

Section 10.16.1
Purpose

The purpose of this check is to determine if fuel pressure is sufficient to start and operate the engine.‪

Note: If the vehicle is equipped with an optional fuel/water separator and a water-in-fuel probe, check with the vehicle operator to determine if the water-in-fuel lamp has been illuminated during vehicle operation.

Section 10.16.2
Test Procedure

Follow this procedure to test the fuel pump pressure.‪

1. Remove the air bleed valve on the fuel filter header. See Figure
   “Air Bleeder Valve Removal”.
   

   Figure 2. Air Bleeder Valve Removal

2. Install 1/8 in. (3 mm) pipe fitting in place of the bleed valve.
3. Connect a line from the fitting to the Engine Field Test Kit, J 39257. See Figure
   “Measuring Fuel Pump Pressure with Pressure Test Kit”.
   

   Figure 3. Measuring Fuel Pump Pressure with Pressure Test Kit

4. Measure fuel pressure by cranking the engine for 20 seconds and observing maximum pressure. Record the pressure on the diagnostic form, and compare to specifications. If fuel pressure is low, replace fuel filter, clean fuel strainer and test again. If pressure is low on the test the second time, perform the following:
   1. Remove fuel return line and install the plug (to prevent fuel from exiting) into fuel return opening.
   2. Crank engine and observe fuel pressure gage. If pressure rises, replace fuel return valve and check the fuel pressure again. If there is no increase in fuel pressure while the return line is plugged, perform the Transfer Pump Restriction Test. Refer to “11.3 Transfer Pump Restriction”.

Note: It may take a number of crank cycles to purge the air out of the fuel system.

Section 10.16.3
Low Fuel Pressure Possible Causes

Possible causes for low fuel pressure include:‪

• No fuel in tank.
• A fuel filter or strainer could cause high restriction and low fuel pressure because dirt or fuel could jell in cold ambient temperatures. Replace the fuel filter clean fuel strainer and retest.
• Debris in the fuel regulator valve may be the cause of low fuel pressure.
• A kinked or severely bent fuel supply line or blockage at the pickup tube could cause restriction and, therefore, low fuel pressure.
• A loose fuel line on the suction side of the fuel system could cause air to be ingested into the system and cause low fuel pressure.
• Defective fuel transfer pump.

Section 10.16.4
Tools Required

Engine Field Test Kit, J 39257
‪