Sufficient Fuel / Pressure
Figure 1. Diagnostic Form
Follow these steps to diagnose the sufficient fuel/fuel pressure problem. For a reproduction of the applicable portion of the diagnostic form, see Figure
This procedure will determine if the fuel system is getting sufficient clean fuel at the proper pressure to start and operate the engine.
Sufficient/Clean Fuel Test Procedure
Follow these steps to check for sufficient clean fuel.
- Obtain fuel sample from the fuel tank.
Note: Fuel must be of proper grade, clean and undiluted.
- Inspect fuel in the container. It must be clean and free of air, contaminants, water, icing or clouding. The fuel should be straw colored. Fuel dyed red or blue indicates an off-highway fuel.
- Check fuel odor for the presence of other fuels such as gasoline or kerosene.
If engine oil is present in the fuel, it may indicate an injector O-ring leak and subsequent loss of injection control pressure. Refer to “10.15 Low Injection Control Pressure Test”
, for Low ICP Pressure and the Leakage Test for determining the cause of oil present in the fuel. After the cause has been determined and the repair made, drain the fuel tank(s) and dispose of the contaminated fuel properly.
Fuel Pressure Test Procedure
To test fuel pressure, follow these steps:
- Remove the air bleed valve on the fuel filter header. See Figure
“Air Bleeder Valve Removal”
Figure 2. Air Bleeder Valve Removal
- Install 1/8 in. (3 mm) pipe fitting in place of the bleed valve.
- Connect a line from the fitting to the Engine Field Test Kit, J 39257
. See Figure
“Measuring Fuel Pressure with Pressure Test Kit”
Figure 3. Measuring Fuel Pressure with Pressure Test Kit
- Measure the fuel pressure at high idle. Record the pressure on the diagnostic form and compare to the specifications. If fuel pressure is low, replace fuel filter, clean fuel strainer and test again. If pressure is low on the second test, perform the following steps:
- Remove the fuel return line and install the plug (to prevent fuel from exiting) into fuel return opening.
- Crank the engine and observe fuel pressure gage. If pressure rises, replace the 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: Perform Fuel Pressure (Full Load) Test before removing the pressure test equipment.Refer to “11.11 Fuel Pressure Full Load”
Low or No Fuel Pressure Possible Causes
The following are possible causes for the low or no fuel pressure condition:
- No fuel in tank.
- If equipped with an inline fuel valve, check it is not shut off.
- The fuel supply line from the tank(s) could be broken or crimped.
- Fuel could be waxed or jelled (most likely in cold weather with No. 2 fuel); the pickup tube in the tank could be clogged or cracked. If there is excessive water in the tank, it could freeze, preventing the fuel from being drawn to the engine.
- If the vehicle is equipped with supplemental filters or water separators, check for plugged filters or leakage that could allow the fuel system to draw air.
- Cloudy fuel indicates that the fuel may not be a suitable grade for cold temperatures. Excessive water or contaminants in the fuel may indicate that the tank and fuel system may need to be flushed and cleaned.
Clear container, approximately one quart; Engine Field Test Kit J 39257
; and appropriate line with 1/8 in. NPT fitting.
|Series 40E Troubleshooting Manual – 6SE241|
|Generated on 10-13-2008|