The Cummins PT fuel system (fig. 5-28) is exclusive to Cummins diesel engines; PT stands for “Pressure – Time”. It uses injectors that meter and injects the fuel with this metering based on a pressure-time principle. A gear-driven positive displacement low-pressure fuel pump naturally supplies fuel pressure. The time for metering is determined by the interval that the metering orifice in the injector remains open. This interval is established and controlled by the engine speed, which determines the rate of camshaft rotation and consequently the injector plunger movement.
- Cummins Pt Fuel Pump Calibration Manual Transmission
- Cummins Pt Fuel Pump Calibration Manuals
- Cummins Pt Fuel Pump Calibration Manual Pdf
- Cummins Pt Fuel Pump Service Manual
- Cummins Pt Fuel Pump Manual
- Cummins Pt Fuel Pump Adjustments
- Cummins Pt Fuel Pump Pdf
Fuel supply line restriction between the fuel pump and the injectors. PT fuel pump AFC operation is malfunctioning or pump is not operating correctly. Fuel pump code (calibration) does not match engine (CPL) build. Injector calibration is not correct or does not match (CPL) build list. Surges at Idle or Hi-Idle. Access to Documents and Materials for Your Cummins Products Cummins produces a wide variety of documents to help customers get the most from their engines, generators and components. Much of this library is available online. Check out the digital resources listed below or contact us for help with your specific needs. Used Cummins Softcover Manual in Very Good Condition This manual covers the calibration instructions for the Cummins PT (type G) fuel pump on test stands made or approved by Cummins Engine Company, Inc., and equipped with an accurate flowmeter and orifices. A binder is available for your PT (type G) manual. Get this from a library! I gravity fed it with a fuel can from up high, with the same results. The fitting with o ring that connects into the filter housing is brand new. I also put a new fuel filter on. So at this point the way I see it, either the fuel filter housing is cracked or the pump is having a problem. I do not think the housing is cracked.
Since Cummins engines are all four-cycle, the camshaft is driven from the crankshaft gear at one-half of engine speed. The fuel pump turns at engine speed. ecause of this relationship, additional governing of fuel flow is necessary in the fuel pump.
A flyball type mechanical governor controls fuel pressure and engine torque throughout the entire operating range. It also controls the idling speed of the engine and prevents engine overspeeding in the high-speed range. The throttle shaft is simply a shaft with a hole; therefore, the alignment of this hole with the fuel passages determines pressure at the injectors.
A single low-pressure fuel line from the fuel pump serves all injectors; therefore, the pressure and the amount of metered fuel to each cylinder are equal.
The fuel-metering process in the Cummins PT fuel system has three main advantages:
- The injector accomplishes all metering and injection functions.
- The injector injects a finely atomized fuel spray into the combustion chamber at spray-in-pressures exceeding 20,000 psi.
- A low-pressure common-rail system is used, with the pressure being developed in a gear-type pump. This eliminates the need for high-pressure fuel lines running from the fuel pump to each injector.
FUEL PUMP
The fuel pump (fig. 5-29) commonly used in the Cummins PT Fuel System is the PTG-AFC pump (PT pump with a governor and an air-fuel control attachment). The “P” in the name refers to the actual fuel pressure that is produced by the gear pump and maintained at the inlet to the injectors. The “T” refers to the fact that the actual “time” available for the fuel to flow into the injector assembly (cup) is determined by the engine speed as a function of the engine camshaft and injection train components.
The air-fuel control (AFC) is an acceleration exhaust smoke control device built internally into the pump body. The AFC unit is designed to restrict fuel flow in direct proportion to the air intake manifold pressure of the engine during acceleration, under load, and during lug-down conditions.
Within the pump assembly a fuel pump bypass button of varying sizes can be installed to control the maximum fuel delivery pressure of the gear-type pump before it opens and bypasses fuel back to the inlet side of the pump. In this way the horsepower setting of the engine can be altered fairly easily. The major functions of the PTG-AFC fuel pump assembly are as follows:
- To pull and transfer fuel from the tank and filter
- To develop sufficient fuel pressure to the fuel rail (common fuel passage) to all of the injectors
- To provide engine idle speed control (governing)
- To limit the maximum no-load and full-load speed of the engine (governing)
- To allow the operator to control the throttle position and therefore the power output of the engine
- To control exhaust smoke emissions to EPA specifications under all operating conditions
- To allow shutdown of the engine when desired A major feature of the PT pump system is that there is no need to time the pump to the engine. The pump is designed simply to generate and supply a given flow rate at a specified pressure setting to the rail to all injectors. The injectors themselves are timed to ensure that the start of injection will occur at the right time for each cylinder.
The basic flow of fuel into and through the PT pump assembly will vary slightly depending on the actual model. A simplified fuel flow is as follows:
- As the operator cranks the engine, fuel is drawn from the fuel tank by the gear pump through the fuel supply line to the primary filter. This filter is normally a filter/water separator.
- The filter fuel then flows through a small filter screen that is located within the PT pump assembly, and then flows down into the internal governor sleeve.
- The position of the governor plunger determines the fuel flow through various governor plunger ports.
- The position of the mechanically operated throttle determines the amount of fuel that can flow through the throttle shaft.
- Fuel from the throttle shaft is then directed to the AFC needle valve.
- The position of the AFC control plunger within the AFC barrel determines how much throttle fuel can flow into and through the AFC unit and on to the engine fuel rail, which feeds the fuel rail.
The AFC plunger position is determined by the amount of turbocharger boost pressure in the intake manifold, which is piped through the air passage from the intake manifold to the AFC unit. At engine start-up, the boost pressure is very low; therefore, flow is limited. uel under pressure flows through the electric solenoid valve, which is energized by power from the ignition switch. This fuel then flows through the fuel rail pressure line and into the injectors.
A percentage of the fuel from both the PT pump and the injectors is routed back to the fuel tank in order to carry away some of the heat that was picked up cooling and lubricating the internal components of the pump and the injectors.
INJECTORS
A PT injector is provided at each engine cylinder to spray the fuel into the combustion chambers. PT injectors are of the unit type and are operated mechanically by a plunger return spring and a rocker arm mechanism operating off the camshaft.
There are four phases of injector operation, which are as follows:
- Metering (fig. 5-30)—The plunger is just beginning to move downward and the engine is on the beginning of the compression stroke. The fuel is trapped in the cup, the check ball stops the fuel flowing backwards, and fuel begins to be pressurized. The excess fuel flows around the lower annular ring, up the barrel, and is trapped there.
- Pre-injection (fig. 5-30)—The plunger is almost all the way down, the engine is almost at the end of the compression stroke, and the fuel is being pressurized by the plunger.
- Injection (fig. 5-30)—The plunger is almost all the way down, the fuel injected out the eight orifices, and the engine is on the end of the compression stroke.
- Purging (fig. 5-30)—The plunger is all the way down, injection is complete, and the fuel is flowing into the injector, around the lower annular groove, up a drilled passageway in the barrel, around the upper annular groove, and out through the fuel drain. The cylinder is on the power stroke. During the exhaust stroke, the plunger moves up and waits to begin the cycle all over.
Injector adjustments are extremely important on PT injectors because they perform the dual functions of metering and injecting. Check the manufacturer’s manual for proper settings of injectors. On an engine where new or rebuilt injectors have been installed, initial adjustments can be made with the engine cold. lways readjust the injectors, using a torque wrench calibrated in inch-pounds after the engine has been warmed up. Engine oil temperature should read between 140°F and 160°F.
Anytime an injector is serviced, you must be certain that the correct orifices, plungers, and cups are used, as these can affect injection operation. You can also affect injection operation by any of the following actions:
- Improper timing.
- Mixing plungers and barrels during teardown (keep them together, since they are matched sets).
- Incorrect injector adjustments after installation or during tune-up adjustment.
- Installing an exchange set of injectors without taking time to check and correct other possible problems relating to injection operation. This is often overlooked.
Proper injector adjustment and maintenance will ensure a smooth running engine as long as the following factors are met:
- Adequate fuel delivery pressure from the fuel pump to the fuel manifold.
- Selection of the proper sizes of balance and metering orifices.
- The length of time that the metering orifice is uncovered by the upward moving injector plunger.
NOTE
For required adjustments and maintenance schedules of Cummins PT Fuel System, always consult the manufacturer’s service manual.
July 12, 2019In 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
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.
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.
Caution: Do not pry the actuator from the housing. This can damage the actuator shaft and make it stick.
Cummins Pt Fuel Pump Calibration Manual Transmission
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.
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.
![Cummins pt fuel pump calibration manual transmission Cummins pt fuel pump calibration manual transmission](/uploads/1/1/7/7/117795207/576487412.jpg)
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.
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.
Cummins Pt Fuel Pump Calibration Manuals
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.
Cummins Pt Fuel Pump Calibration Manual Pdf
Install the EFC gasket on the actuator. The gasket will fit only one way. The fuel pump side goes against the fuel pump.
Cummins Pt Fuel Pump Service Manual
Caution: Do not use any gasket adhesive or sealant on this gasket.
Cummins Pt Fuel Pump Manual
Check that all of the mounting holes can be aligned. Install the O-rings on the shaft.
Cummins Pt Fuel Pump Adjustments
Cummins Pt Fuel Pump Pdf
Maybe you also like this article: Cummins Engine Electric Fuel Control Governor