Methods of finding TDC (top dead centre) of a diesel engine.
It is very important to knw the top dead centre of a unit to :
1. set the tappet clearence ,
2. to check the fuel pump timing,
3. To check the misalignment of engine if new crankshaft fitted or if slippage of crankshaft happens.
4. To fit the timing gears also.
HOW TO FIND OR CHECK THE TDC OF A UNIT.
We can find the TDC by using following methods:
1. THROUGH THE FLYWHEEL MARKINGS.
It is the best method to find the position of particular unit at TDC and BDC as there are markings on flywheel for TDC andBDC and a few degrees like 5,10,15 of that particular unit and so on or as IO ,EC and IS as inlet valve opens , exhaust valve closes. And injection starts. There is a arrow or a stationary marking attached to fixd plate or frame anf pointed towards the flywheel markings , the pointer and markings on flywheel shows the unit number and its poaition at TDC. As if all the markings are gone then in some type of engines there is marking on crankweb of number one unit or is given in manual and the other mark is on bed plate inside the crankcase when these two match means number one unit is on TDC . But it is difficult to say by checking flywheel markings that the unit is on firing or non firing TDC.
In fig TDC is marked as TC
2. DIAL GAUGE METHOD.
In this method there are two ways
A. Using dial gauge.
B. Some engine manufacturer gives template on which TDC and fuel injection point is marked .
In both we have to take the fuel injector out and put the
A. Dial gauge end from it and fix the dial the dial gauge and slowly turn the flywheel and check dail guage reading also when the reading starts going towards negative then stop and move the flywheel in other direction till it become stabilize means the point where it is in middle not going to negative or positive side.
B. Put Template from injection opening and there is marking on cyclinder head turn the flywheel untill both markings match.
3. FUEL PUMP MARKING OR HAIR LINE METHOD.
In some engines there is a window on fuel pump and on pump body there are three marking and on the plunger there is also one marking . The marking on pump body shows the start of injection and other shows the end of injection the middle one shows the unit is at TDC when the plunger marking matches with the respective one (as i found on diahatsu engine). But on some fuel pump only two marking are there
For start and end of injection.
4. THROUGH CAMSHAFT OR CAMCASE.
AS in camcase there are three cams for a particular unit one for inlet valve ,one for exhaust valve and other one for fuel pump.
As to chk the unit at TDC The follower for valves should be on base circle and the follower for fuel pump should be on lobe of cam. This method with markings on flywheel shows the unit is on firing or non firing TDC.
5. Fuel pump oil spill or spill method.
In this method the delivery valve of fuel pump is removed and pump is filled with oil and start rotating flywheel when the oil starts coming out means unit is on firing TDC.
6. THROUGH CRANKCASE
open the crankcase doors and rotate the flywheel till the connecting rod lower or big end bearing is at highest position.
LAYMAN METHOD.
7. VALVE SPRING METHOD.
Open the cyclindee head cover and chech the position of spring of valve , all of them should not be pressed by the valve bridge or rocker arm or there is some clearance between the rockerarm and valve stem.
8. PUSH ROD METHOD.
Rotate the flywheel and check both push rods should be free to rotatebut this method doesnot tell u exactly that piston is on TDC. But it is near to TDC.
None of the layman method to tell to surveyour these are only for reference.
1. set the tappet clearence ,
2. to check the fuel pump timing,
3. To check the misalignment of engine if new crankshaft fitted or if slippage of crankshaft happens.
4. To fit the timing gears also.
HOW TO FIND OR CHECK THE TDC OF A UNIT.
We can find the TDC by using following methods:
1. THROUGH THE FLYWHEEL MARKINGS.
It is the best method to find the position of particular unit at TDC and BDC as there are markings on flywheel for TDC andBDC and a few degrees like 5,10,15 of that particular unit and so on or as IO ,EC and IS as inlet valve opens , exhaust valve closes. And injection starts. There is a arrow or a stationary marking attached to fixd plate or frame anf pointed towards the flywheel markings , the pointer and markings on flywheel shows the unit number and its poaition at TDC. As if all the markings are gone then in some type of engines there is marking on crankweb of number one unit or is given in manual and the other mark is on bed plate inside the crankcase when these two match means number one unit is on TDC . But it is difficult to say by checking flywheel markings that the unit is on firing or non firing TDC.
In fig TDC is marked as TC
2. DIAL GAUGE METHOD.
In this method there are two ways
A. Using dial gauge.
B. Some engine manufacturer gives template on which TDC and fuel injection point is marked .
In both we have to take the fuel injector out and put the
A. Dial gauge end from it and fix the dial the dial gauge and slowly turn the flywheel and check dail guage reading also when the reading starts going towards negative then stop and move the flywheel in other direction till it become stabilize means the point where it is in middle not going to negative or positive side.
B. Put Template from injection opening and there is marking on cyclinder head turn the flywheel untill both markings match.
3. FUEL PUMP MARKING OR HAIR LINE METHOD.
In some engines there is a window on fuel pump and on pump body there are three marking and on the plunger there is also one marking . The marking on pump body shows the start of injection and other shows the end of injection the middle one shows the unit is at TDC when the plunger marking matches with the respective one (as i found on diahatsu engine). But on some fuel pump only two marking are there
For start and end of injection.
4. THROUGH CAMSHAFT OR CAMCASE.
AS in camcase there are three cams for a particular unit one for inlet valve ,one for exhaust valve and other one for fuel pump.
As to chk the unit at TDC The follower for valves should be on base circle and the follower for fuel pump should be on lobe of cam. This method with markings on flywheel shows the unit is on firing or non firing TDC.
5. Fuel pump oil spill or spill method.
In this method the delivery valve of fuel pump is removed and pump is filled with oil and start rotating flywheel when the oil starts coming out means unit is on firing TDC.
6. THROUGH CRANKCASE
open the crankcase doors and rotate the flywheel till the connecting rod lower or big end bearing is at highest position.
LAYMAN METHOD.
7. VALVE SPRING METHOD.
Open the cyclindee head cover and chech the position of spring of valve , all of them should not be pressed by the valve bridge or rocker arm or there is some clearance between the rockerarm and valve stem.
8. PUSH ROD METHOD.
Rotate the flywheel and check both push rods should be free to rotatebut this method doesnot tell u exactly that piston is on TDC. But it is near to TDC.
None of the layman method to tell to surveyour these are only for reference.
Comments
Post a Comment