N14 Base Engine Troubleshooting and Repair Manual – 005-999   Fuel System – Overview

General Information

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The PT fuel system is used exclusively on Cummins® diesels. The identifying letters “PT” are an abbreviation of pressure-time.

The PT fuel system consists of the fuel pump supply lines, drain lines, fuel passages, and injectors.

The STC system is used on Cummins diesels to advance the injection timing under idle or light load conditions.

The STC system includes fuel pump, supply lines, drain lines, fuel passages, oil passages, check valves, STC oil control valve, and STC injectors.

The CELECT™ and CELECT™ Plus fuel systems are used exclusively on Cummins diesels.

The CELECT™ and CELECT™ Plus fuel systems consist of the fuel pump, Electronic Control Module (ECM), ECM cooling plate, supply lines, drain lines, engine wiring harness, sensors, and injectors.

For repairs being made to the CELECT™ or CELECT™ Plus sensors, ECM, and engine wiring harness, refer to the Troubleshooting and Repair Manual CELECT™ Plus engines, Bulletin 3666130.

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PT (Type G) AFC Fuel Pump

  1. Tachometer drive
  2. AFC air supply
  3. Fuel to injectors
  4. Priming Plug
  5. Shutoff valve electric connection
  6. Gear pump cooling fitting
  7. Fuel inlet connection
  8. Idle speed screw location
  9. Fuel rate (pressure) screw.

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PT (Type G) VS AFC Fuel Pump

  1. Tachometer drive
  2. AFC air supply
  3. Fuel to injectors
  4. VS high speed screw
  5. VS low (idle) speed screw
  6. Gear pump cooling fitting
  7. Fuel inlet connection
  8. Idle speed screw location
  9. Fuel rate (pressure) screw.

Installation Recommendations

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The following publications are available to provide fuel system installation recommendations approved by Cummins Engine Inc.:

Automotive Installation Recommendations (Fuel System), Bulletin 952849.

Contact the nearest Cummins® Authorized Repair Location for engine fuel system specifications and requirements provided on the “Engine Data Sheet” for your specific engine and application.

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If an overhead fuel tank is used the following requirements must be used.

If the fuel filter is lower than the fuel pump, install a check valve in the filter outlet fuel line. Refer to the OEM Installation Recommendations.

The check valve on the outlet side of the fuel filter prevents gear pump fuel drainback during filter removal.

Install a shutoff valve between the filter and the fuel tank.

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 WARNING 

If the fuel line valve is not used, the overhead tank can drain when the fuel filter is changed. Spilled fuel is a fire hazard. Fuel is flammable, explosive and hazardous to the environment to avoid severe personally injury or death. Do not smoke or allow an flame, pilot light, sparks, or arcing switches or equipment in the area or areas sharing ventilation when working on fuel systems. contain and clean up spills immediately as required by local regulations.
 
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When using fuel system gauges:

Make sure to always remove the air from the pressure gauge line before taking a reading.

Loosen the connection at the gauge to remove the air.

Do not loosen the vacuum gauge connections when the engine is operating.

 
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Read the gauge in direct alignment with the gauge hand.

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Read the flow meter in direct alignment with the float.

Read the level of the floats where indicated.

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Portable fuel pressure gauges must be checked regularly against a reference gauge or against the gauge on the fuel pump test stand.

Adjust the valve on the gauge until the gauge needle stops vibrating.

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When measuring the fuel inlet and drain line restriction, the manometer must be on the same level as the connection point.

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Always use the same size and material of line or hoses as was originally supplied with the gauge.

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The distance from the gauge to the connection point must be as short as possible.

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 CAUTION 

Never exceed the maximum capacity of the gauge or flow meter. If the maximum is exceeded, check the gauge against a reference gauge.

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Last Modified:  30-Jul-2007