Diesel Engine Troubleshooting

Archive for the ‘Fuel Systems’ Category

Bosch Altitude Pressure Compensator

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In naturally aspirated (non turbo charged) diesel engines such as cars or trucks that can travel through varying terrain and altitudes, a means by which the fuel delivery rate can be altered is an important function of the governor and altitude pressure compensator. Since atmospheric pressure decreases with an increase in altitude, the volumetric efficiency of the engine will be less at higher elevations than it will be at sea level. On turbocharged engines, a boost compensator performs a function similar to that of the altitude compensator on nonturbocharged engines. Bosch refers to the altitude compensator as an ADA mechanism, and it is used in conjunction with either the RQ or RQV mechanical governor models. The ADA is located on the governor cover.

Written by Ed

September 13th, 2011 at 4:52 am

Bosch Boost Compensator Operation

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Basically, the boost compensator ensures that the amount of injected fuel is in direct proportion to the quantity of air within the engine cylinder to sustain correct combustion of the fuel and therefore increase the horsepower of the engine. With the engine running, pressurized air from the cold end of the turbocharger passes through the (Figure 19-63b) connecting tube from the engine air inlet manifold to the boost compensator chamber. Inside this chamber is a diaphragm (Figure 19-63a) which is connected to a pushrod, which is in turn coupled to the compensator lever. Movement of the diaphragm is opposed by a spring, therefore for any movement to take place at the linkage,
the air pressure on the diaphragm must be higher than spring tension. As the engine rpm and load increase and the air pressure within the connecting tube becomes high enough to overcome the tension of the diaphragm spring, the diaphragm and pushrod will be pushed down.

Bosch Boost Compensator Operation 300x222 Bosch Boost Compensator Operation

This movement causes the compensator lever to pivot, forcing the fuel control rack toward an increased fuel position. The boost compensator will therefore react to engine inlet manifold air pressure regardless of the action of the governor. When the turbocharger boost air pressure reaches its maximum, the quantity of additional fuel injected will be equal to the stroke of the aneroid boost compensator linkage, in addition to the normal full-load injection amount that is determined by the governor full-load stop bolt.

Written by Ed

September 7th, 2011 at 2:23 am

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Bosch ROV Governor Diagram

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The RQV governor is a variable-speed mechanical unit that employs the governor springs assembled into the weights in the same manner as that for other RQ models. As such, it controls idle speed, maximum speed, and any speed range in between at which the operator places the throttle linkage. Figure above illustrates the pear-shaped housing of the RQV governor, which is also found on all other RQ models.

The RQV governor is used with the models M,A,MW,and P Bosch inline multiple-plunger pumps, as well as on the VA and VE models of Bosch distributor pumps. Major truck engine manufacturers that use RQV variable-speed governor are Deutz, Fiat Allis, Navistar (International Harvester), Mack, Mercedes-Benz, and Volvo.The RQVis employed on vehides with auxiliary drive, such as garbage compactor trucks, tanker trucks, and cement mixer trucks, to control the PTO (power takeoff) applications. Since the RQV is a variable-speed (all-range) governor, it operates on the same basic principle as the RSV shown and discussed earlier in this chapter, the only difference being in the internal linkage arrangement. The RSVuses a starting and main governor spring, while the RQVhas the springs assembled inside the weight carrier.

The difference between the RQ governor model and the RQV is that since the RQV is an all-range variable-speed unit, and the RQ is a minimum/maximum (limiting-speed) unit, the weights in the RQV will move out throughout the complete speed range, and will not lose control between the end of the idle speed range and the start ofhigh-speed governing such as occurs within the RQ model.

Written by Ed

September 6th, 2011 at 2:28 am

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Bosch RSV Governor Linkage Schematic

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RSV mechanical governor linkage schematic.

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September 6th, 2011 at 2:12 am

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Bosch RSV Governor Components

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Prior to describing the operation of the RSV governor, refer to Figure above which illustrates the major component parts and the associated linkage used with this governor model. Note that within the governor housing there are four springs used with this governor assembly:

• A starting aid spring
• The governor main spring
• An idle spring, sometimes referred to as a bumper spring
• A torque control spring

Written by Ed

September 6th, 2011 at 2:09 am

Bosch RSV Governor Diagram

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The RSVgovernor assembly is designed as an all-range (variable) governor which functions to control the engine idle and maximum speeds, in addition to allowing the operator to place the throttle at any position between idle and maximum where the governor will control the speed setting minus the droop The RSV governor is widely used on combination on- and off-high way truck applications, as well as farm tractors and industrial and marine units employing the M, A, MW,or P Bosch model inline multiple-plunger injection pumps. Although similar in external appearance to the RS limiting-speed (minimum/maximum) governor described in this section, the RSV does allow several adjustments at points outside the housing that are not available on the RS unit. Figure above illustrates an external view of the RSV governor housing with the various external adjustments shown. These include:

• The idle-speed screw
• The auxiliary idle-speed spring or bumper screw
• The throttle lever linkage maximum speed adjusting screw

Written by Ed

September 6th, 2011 at 2:07 am

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Bosch Governors

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Robert Bosch governors used with inline pumps (M, A, MW, and P) can look the same externally; however, they
are designed for different types of engine applications, and therefore engine speed control can be governed at different settings of the throttle. Types of governors manufactured by Robert Bosch Corporation and used on their inline injection pumps in truck applications are described below.

The letter designations used for these mechanical governors take the following forms:

R: flyweight governor
S: swivel lever action
Y: variable-speed (all-range) governor
Q: fulcrum lever action
K: torque earn control
W: leaf spring action

For example, if the nameplate on a governor read EP/RS275/1400AOB478DL, this would mean:

EP: found on older governors, no longer used
RS: R/flyweight governor with swivel lever action, minimum/maximum (limiting speed) type of governor
275: low-idle pump speed (this would be 550 rpm engine speed, four cycle)
/: also indicates mini max (limiting speed) governor
1400: full-Ioad-rated speed (this would be 2800 rpm engine speed, four cycle)
A: fits on A-size inline injection pump
0: amount of speed regulation (droop percentage)
B: execution-not used to indicate the original design on governors; A, first change;B, second change; and so on
478DL: application and engineering information only

Written by Ed

September 6th, 2011 at 2:02 am

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Bosch Secondary Fuel Filter Pressure Test Diagram

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Pressure tester gauge connected between the secondary fuel filters and the injection pump inlet: 1, fuel filter housing; 2, transfer pump; 3, tester.

Refer to Figure above and disconnect the fuel line between the outlet side of the secondary fuel filter(s) and the inlet side of the fuel injection pump. Insert a special pressure gauge or, alternatively, a fuel pressure gauge and clear plastic line between the filters and injection pump as shown in Figure above.

Written by Ed

September 5th, 2011 at 4:50 am

Bosch Vacuum Pump Restriction Test Diagram

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Vacuum tester connected between the fuel transfer pump inletside and the primary filter/fuel-water separator 1. fuel filter housing; 2, transfer pump; 3, tester

This test allows the mechanic/technician to determine if there is a high restriction to fuel flow to the suction side of the fuel transfer pump. If there is, the injection pump will not receive enough fuel. This will be accompanied
by lack of power as well as possible rough idling and stalling. Either a vacuum gauge or a mercury manometer can be use to check the restriction to fuel flow. However if a mercury manometer is teed in to the fuel system in place of the special gauge make sure that you hold or mount the manometer higher than the engine. Failure to do this can result in diesel fuel running back in to the manometer when the engine is stop. A low reading is what we are looking here , since this indicates that the fuel lines and connections are offering a minimum restriction to flow at the suction side of the fuel transfer pump.

Written by Ed

September 5th, 2011 at 4:41 am

Bosch Relief Valve and Pump Pressure Test Diagram

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Fuel pressure gauge connected between the transfer pump outlet and secondary fuel filters: 1, fuel filter housing; 2, transfer pump; 3, tester

This test is a check to ensure that the injection pump relief valve is, in fact, opening at the correct pressure and that the transfer pump is performing correctly. If the relief valve is stuck open or is opening at too low pressure, the fuel delivery pressure within the injection pump housing will be too low to sustain sufficient flow to the plunger and barrel of the individual pumping assemblies. On the other hand, if the relief valve is stuck closed or opens at too high a pressure setting, the fuel within the injection pump housing, which is also used for cooling and lubricating purposes, will run hot. This can result in a loss of horse power due the expansion of the fuel, since a less dense fuel charge will be delivered to the injectors and combustion chamber. In addition fuel that is too hot can cause internal pump pluger damage due to its instability to properly cool and lubricate the component parts. Note that only 25 to 30% of the fuel delivered to the injection pump housing is actually used for combustion purposes. The remainder cools and lubricates the injection pump components.

Written by Ed

September 5th, 2011 at 4:31 am

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