Cummins Pt Fuel Pump Calibration Manual

The fuel pump can now be calibrated (Refer to the Fuel Pump Calibration Manuals or the monthly Cumulative Supplement Update). NOTE: Apply the actuator rated battery voltage to the normally closed actuator when the fuel pump is calibrated. The throttle shaft must be locked in the full open position. In this week's Tech Tip video, Brian explains how swapping the button in your Big Cam's fuel pump will change fuel pressure as well as other adjustments you.

In the previous article, we talk about Cummins engine electric fuel control governor, this article will turn to introduce Cummins generator engine actuator.


Actuator Description

The actuator is an electromagnetic rotary solenoid valve. The actuator is installed in the EFC cavity of the PT fuel pump. The actuator controls the engine speed and horsepower by controlling the fuel flow to the injectors.


The actuator shaft will turn when the current from the governor control changes.



The current from the governor control will change when the magnetic pickup senses a change in the engine speed.



Fuel Flow Through the Fuel Pump

The throttle shaft is set in the full open position. The fuel flows through the fuel pump to the actuator (EFC) cavity.



The actuator controls the fuel flow to the injectors. The fuel flows through the actuator to the shutoff valve.



Actuator Identification
Two styles of the actuator are now available.
a. Normally open
b. Normally closed



The normally open actuator is in the full fuel position when the electrical system is turned off.



The normally closed actuator will stop the fuel flow when the electrical system is turned off.



The actuators are available in low, high, and ultra high flow.


Cummins Pt Pump Fuel Pressure


The actuators are rated at 12 or 24 volts D.C.

Make sure the governor control voltage is the same as the actuator voltage rating.



EFC Fuel Pump Housing

When a new EFC fuel pump is built at Cummins, the pump will have an EFC housing.

The EFC fuel pump housing can be identified in the following areas:

The AFC no-air adjusting screw hole has been omitted.




The ASA or AFC vent hole, in the top of the housing has been omitted.

The AFC spring seat groove is not machined. A 45 chamfer is at the EFC actuator mounting surface.



Actuator Removal From an EFC Fuel Pump Housing

Remove the actuator wires and capscrews.

Pump

Caution: Do not pry the actuator from the housing. This can damage the actuator shaft and make it stick.



Twist tho actuator and pull it from the housing. Remove the three O-rings from the actuator.



Actuator Installation in an EFC Fuel Pump Housing

Install a new O-ring on the 50 mm [2 in] diameter of the actuator. Install two new O-rings on the actuator barrel.



Apply the actuator rated battery voltage across the two terminals on the actuator to test the solenoid and to observe actuator operation.The actuator will make a loud click when the actuator shaft hits the internal stop. Removing the voltage from the actuator terminals will allow the force of the springs to return the actuator shaft to its original position. A click must be heard when the voltage is removed.

NOTE: The EFC housing does not require the EFC plug in the bottom of the EFC housing bore.



Lubricate the two barrel O-rings with clean engine oil. Insert the actuator in the fuel pump housing. The actuator flange will be approximately 3/8 inch [9.5 mm] from the pump housing.



Pump

Use the palm of the hand. Firmly push and rotate the actuator approximately 30 degrees until the actuator flange contacts the fuel pump housing. Rotate the actuator until the mounting holes are aligned.



Install the three 1/4-20 x 1 1/4 inch hex head capscrews. These capscrews have captive spring washers and do not require lock-washers. Tighten the capscrews until they are finger tight.



The actuator capscrews must be tightened in the following sequence:

1. Tighten the mounting capscrews 1/8 of a turn, in the sequence shown in the figure, until they are seated.



2. Tighten the capscrews in sequence to 25 in-lb [2.8 N*m] torque.



Cummins

3.Tighten the capscrews in sequence to a torque in-lb. [5.6 N*m].



4. Loosen all three capscrews completely.



5. Tighten the capscrews again in sequence to 25 in-lb. [2.8 N*m] torque.

6. Tighten the capscrews again in sequence to 50 in.lb. [5.6 N*m] torque.

7. This procedure will make sure that the actuator is properly installed and is not binding.

A final check is to apply and remove battery voltage across the two actuator terminals. The operation of the actuator must have a similar sound as it did before installing in the fuel pump housing. If the actuator does not click, as if it is not operating, or operating slower than before, loosen all of the capscrews and tighten them again as described in the previous procedure.

Caution: This test will only verify that the actuator will go from the full open to the full closed position. A slight binding of the actuator shaft can cause a governor stability complaint. This test may not detect a slight binding.



The fuel pump can now be calibrated (Refer to the Fuel Pump Calibration Manuals or the monthly Cumulative Supplement Update).

NOTE:Apply the actuator rated battery voltage to the normally closed actuator when the fuel pump is calibrated.



The throttle shaft must be locked in the full open position. After the calibration, the fuel pump can be mounted on engine.



Actuator Installation in an AFC Fuel Pump Housing

Remove the fuel pump if it is on the engine.

Remove the ASA, if required, and the AFC fuel drain tube. Install a plug in the housing. Install a plug in the fuel tube connection.



Remove the AFC no-air plug, if the fuel pump does not have an AFC. Replace it with the no-air needle valve. The AFC no-air plug is located directly above the throttle shaft.

Tighten the AFC no-air needle valve in the housing to 25 in.lb. [2.8 N*m]. Tighten the jam nut.



Remove the AFC cover plate. Remove the AFC bellows/plunger assembly, if required. Use a pair of snap ring pliers to remove the barrel or barrel plug snap ring.



Thread one of the previously removed 1/4-20 capscrews into the AFC barrel plug. Pull out the barrel plug with a pair of pliers. Discard the three original AFC cover plate capscrews.

If the fuel pump has a functional AFC, use the AFC barrel puller. Service Tool 3375599 to remove the barrel. The AFC cannot to be used with an EFC governor. The AFC cavity is now ready for the installation of the EFC governor actuator.



Install the O-ring plug on the Governor Plug Tool, Part No. 3376457, approximately three turns. Install the O-ring on be plug.

Caution: Do not tighten the O-ring plug to the plug tool or the tool can not be removed after the plug is inserted in the pump AFC cavity.

Lubricate the O-ring with clean engine oil.

Press firmly until the O-ring plug is seated in the pump housing. Carefully unscrew the plug tool.



Install the EFC gasket on the actuator. The gasket will fit only one way. The fuel pump side goes against the fuel pump.

Caution: Do not use any gasket adhesive or sealant on this gasket.

Check that all of the mounting holes can be aligned. Install the O-rings on the shaft.


Maybe you also like this article: Cummins Engine Electric Fuel Control Governor

When it comes to Cummins generator, it is well known that the gensets have good quality, low fuel consumption, low noise, big output power and reliable performance. The reliable stability, economy, power performance, durability and environmental safety is welcomed by customers.


In last article, we talk about CCEC Cummins diesel engines operating principles. Well, in this article, you will learn what are the major components of its PT Fuel System.


Fuel System


The PT fuel system is used exclusively on Cummins Diesels. The identifying letters, “PT” are an abbreviation for “pressure-time”.

The operation of the Cummins PT Fuel System is based on the principle that the volume of liquid flow is proportionate to the fluid pressure, the time allowed to flow and the passage size through which the liquid flows. To apply this simple principle to the Cummins PT Fuel System, it is necessary to provide:

1. A fuel pump.

2. A means of controlling pressure of the fuel being delivered by the fuel pump to the injectors so individual cylinders will receive the right amount of fuel for the power required of the engine.


Fig.5-1. Fuel flow schematic N/NT-855 Engine

1). PT (TYPE G) FUEL PUMP

2). SHUT-DOWN VALVE

3). FUEL CONNECTOR

4). INJECTOR

5). INJECTOR RETURN

6). FROM TANK

7). FUEL FILTER


3. Fuel passages of the proper size and type so fuel will be distributed to all injectors and cylinders with each pressure under all speed and load conditions.

4. Injectors to receive low-pressure from the fuel pump and deliver it into the individual combustion chambers at the right time, in equal quantities and proper condition to burn.

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


Fuel Pump


The fuel pump is coupled to the fuel pump drive which is driven from the engine gear train. Fuel pump main shaft in turn drives the gear pump, governor and tachometer shaft assemblies.

Fuel injection pumps must be supplied with fuel under pressure because they have insufficient suction ability. All diesel injection systems require a supply pump transfer fuel from the supply tank through the filters and lines to the injection pump.


Gear Pump And Pulsation Damper


The gear pump is driven by the pump main shaft and contains a single set of gears to pick up and deliver fuel throughout the fuel system. Inlet is at the rear of the gear pump. A pulsation damper mounted to the gear pump contains a steel diaphragm which absorbs pulsations and smooths fuel flows through the filter screen and to the governor assemblies.


Throttle


The throttle provides a means for the operator to manually control engine speed above idle as required by varying operating conditions of speed and load.

In the fuel pump, fuel flows through the governor to the throttle shaft. At idle speed, fuel flows through the idle port in the governor barrel, past the throttle shaft. To operate above idle speed, fuel flows through the main governor barrel port to the throttling hole in the shaft.


PT(type G) VS Fuel Pump


Cummins Pt Pump Manual

The PT (type G) VS fuel pump, is made up of four main units; the gear pump, standard governor, throttle and a VS (Variable Speed) governor.


Governors


The “Standard” governor is actuated by a system of springs and weights, and has two functions:

1. The governor maintains sufficient fuel for idling with the throttle control in idle position.

2. It cuts off fuel to the injectors above maximum rated rpm.


During operation between idle and maximum speeds, fuel flows through the governor to the injectors. This fuel is controlled by the throttle and limited by the size of the idle spring plunger counter bore. When the engine reaches governed speed, the governor weights move to governor plunger, and fuel passages to the injectors are shut off. At the same time another passage opens and dumps the fuel back into the main pump body.


In this manner, engine speed is controlled and limited by the governor regardless of throttle position.

The VS governor, in the upper portion of the fuel pump housing, operates in series with the standard governor to permit operation at any desired (near constant) speed setting within the range of the standard governor. Speed can be varied with the VS speed control lever, located at top of pump. This pump gives surge free govern ring throughout the engine speed range with a speed droop smaller than the standard governor and is suited to the varying speed requirements of power take off, etc.

Note: When operating the PT(type G) VS fuel pump at any desired constant speed, the VS governor lever should be placed in operating position and the throttle locked in full open position to allow a full flow of fuel through the standard governor.



PT (tyep D) Injectors


Cummins Pt Fuel Pump Rebuilding And Calibration Instructions

The injector provides a means of introducing fuel into each combustion chamber. It combines the acts of metering, timing and injection. Principles of operation are the same for Inline and V-engines but injector size and internal design differs slightly.


Fuel supply and drain flow are accomplished through internal drillings in the cylinder heads. A radial groove around each injector mates with the drilled passages in the cylinder head and admits fuel through an adjustable orifice plug in the injector body. A fine mesh screen at each inlet groove provides final fuel filtration.


The fuel grooves around the injectors are separated by 0-rings which seal against the cylinder head injector bore. This forms a leak-proof passage between the injectors and the cylinder head injector bore surface.


Fuel flows from a connection atop the fuel pump shutdown valve through a supply line into the lower drilled passage in the cylinder head. A second drilling in the head is aligned with the upper injector radial groove to drain away excess fuel. A fuel drain allows return of the unused fuel to the fuel tank.


The injector contains a ball check valve. Ad the injector plunger moves downward to cover the feed opening, an impulse pressure wave seats the ball and at the same time traps a positive amount of fuel in the injector cup for injection. As the continuing downward plunger movement injects fuel into the combustion chamber, it also uncovers the drain opening and the ball rises from its seat. This allows free flow through the injector and out the drain for cooling purposes and purging gases from the cup.


Fuel Lines, Connections And Valves


Supply And Drain Lines - Fuel is supplied through lines to cylinder heads. A common drain line returns fuel not injected, to supply tank.

Connections - Fuel connectors are used between the Inline engine cylinder heads to bridge the gap between each supply and drain passage.

Shut-Down Valve - Either a manual or an electric shut-down valve is used on Cummins Fuel Pumps.

Fig. 5-2, Fuel pump manual override knob

Attention: With a manual valve, the control lever must be fully clockwise or open to permit fuel flow through the valve.

With the electric valve, the manual control knob must be fully counterclockwise to permit the solenoid to open the valve when the “switch key” is turned on. For emergency operation in case of electrical failure, turn manual knob clockwise to permit fuel to flow through the valve.


No matter it is engine’s fuel system or other parts, it is very necessary and important to know about the related knowledge if you want to prolong the generator set service life. Also, familiar with the operation, it is convenient to do the maintenance in the future.