To supply accurate metering amount of fuel with sufficient pressure to open fuel injector in correct timing.
How to fuel cut out (Individually) :
#By lifting the pump roller form cam peak and securing the pump roller guide#By making pump rack to zero position
#Reduce the engine speed
How to notice the incorrect timing ?
1.Difficult to start the engine2.Abnormal exhaust temperature reading
3.Black smoke coming out
4.Irregular running of engine.
WHY FUEL PUMP TIMING ADJUSTMENT REQUIRED?
In A Marine Diesel Engine It Is Very Important To inject Fuel Inside The Cylinder At Correct Time To Ensuring Complete Combustion. If The Injection Timing Is Alter In That Case There Might Be Early Combustion Or After Combustion In Both Case Power Developed Is Not Optimum As Required And Both Have It Own Side Effect. Therefore Fuel Pump Should Be Adjust In Such A Way That It Can Develop Pressure Sufficient Enough To Inject Fuel At Correct Time.
HOW FUEL PUMP TIMING CAN BE ALTERED?
Small Adjustment Of Fuel Pump Timing Can Be Carried Out By Adjusting The Shim Thickness On The Foot Of The Pump Body.
Larger Adjustment Is Made By Adjusting Camshaft Position In Respect To Unit At Tdc.
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SPILL TIMING METHOD (Goose Neck Method) :
1.Fuel Supply To Engine Is Stopped.
2.Discharge Valve And High Pressure Pipe Is Removed.
3.A Small Bore Pipe Is Fitted And Bucket Is Kept For Collection Of Fuel Oil.
4.Camcase Cover And Flywheel Cover Is Removed.
5.Cam Of The Respective Unit Is Turned To Base Of The Cam Follower.
6.Fuel Pump Rack Is Place To It Maximum Setting.
7.Fuel Supply To Engine Is Now Open And Oil Is Collected In Bucket Place Near Small Bore Pipe.
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| SPILL TIMING METHOD |
8.The Engine Is Turned Slowly Ahead.
9.The Plunger Will Cover The Suction Port.
10.Oil Flowing From Small Bore Pipe Will Stop.
11.The Crank Angel Should Now Be Noted As This Mark The Being Of Injection. The Reading Should Be Compared With The Manufacturer Reading.
12.The Engine Is Further Turned Until The Fuel Start Dripping From The Small Bore Pipe.This Mark The End Of Injection As Plunger Has Reached It Top And It Shorted Top Part Of Plunger To Spill Port Via Helix.
13.The Reading Should Be Noted And Compared With Manufacture Reading If Required Adjustment Can Be Done By Adjusting Shim .
By hair line method:
Turn the engine so that the unit to be check is toward the TDC of compression stroke (plunger upstroke) so that hair line on plunger & pump body are coincided. When hair lines are coincided, stopped turning and check the mark on the fly wheel whether timing is correct or not.
If hair line not given:
Take out fuel in/out pipe on pump (by removing binjo bolt). By using hand torch & mirror on each side. Turn the engine so that the unit to be check is toward the TDC of compression (at plunger upstroke) so that the light on mirror is disappearing ( ie torch light has gone on mirror ) . AT this time, stopped engine turning & check the mark on flywheel.
WHAT IS FUEL PUMP LEAD?
FUEL PUMP LEAD IS THE DISTANCE TRAVELED BY PLUNGER FROM THE POINT AT WHICH RISE OF FUEL CAM START(OR THE
FOLLOWER START LIFTING) TILL THE PISTON OF THE UNIT REACHES IT TDC.
WHY IT IS IMPORTANCE OF FUEL PUMP LEAD?
FUEL PUMP LEAD DISTANCE IS MENTION IN THE MANUFACTURER NOTE. BY MEASURING THE FUEL PUMP LEAD
ONE CAN ADJUST THE TIMING OF THE FUEL PUMP IN MAN B&W ENGINE.
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| MAN B&W MC SERIES WITHOUT VIT |
HOW TIMING IS ADJUSTED IN MAN B&W ENGINE- WITHOUT VIT?
1.Small Adjustment In Timing Can Be Done Either By Adding Or Removing The Shim
2.Removing Shim Will Increase Value Of “X” Which Will Advance The Timing And Vice versa.
3.If Timing Need To Be Adjusted Too Much Then Hydraulically Cam To Be Expanded And Adjustment Need To Be Carried Out.
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| MAN B&W MC SERIES WITH VIT SYSTEM |
If no TDC mark on flywheel, How will you check pump timing?
IN M/E
1) Make a marking between cross head and guide Shoe while they are before TDC and also mark at the flywheel.
2) Turn the crank shaft in the same direction until the crosshead and guide shoe are at the previous mark (coincide).
3) Make the second marking on the fly wheel. We got two marks on the flywheel mid point between the two points is TDC.
4) I will divide 360C around the flywheel.
IN G/E
2) Insert the rod onto the piston (mark on rod and flywheel)
3) Turn crank until the rod previous mark
4) Make the second marking on the fly wheel
5) Mid point between the two points is TDC
What points do you check on fuel pump when overhaul or how will you decide ?
1.Check plunger guide wear & tear .
2.Check spring (length & stiffness, crack) .
3.Plunger & barrel wear & tear, check clearance (5 micro for DO, 15 micro for HO) by dropping the plunger into the barrel it fall down slowly is OK .
4.Check control sleeve and rack for crack .
5.Check the Delivery valve face .
6.Check ‘O’ ring of fitted.
METERING OF FUEL
means of control valves. for effective stroke.
The quantity of fuel delivered is regulated by the vertical length of the helix where it is in line with the suction port. This setting may be altered by rotating the plunger. In stop position, the vertical slot of the plunger is in lined with the spill port where then ports are opened and thus no injection occurred.