Marine Engineering Study Materials

Function of fuel injection pumps

• To supply accurate metered amount of fuel with sufficient pressure to open fuel injector in correct timing.

How to cut out fuel pump

1. Reduce the engine speed
2. By lifting the pump roller form cam peak and securing the pump roller guide
3. By making pump rack to zero position

How to notice the incorrect timing ?

• Difficult to start the engine
• Abnormal exhaust temperature reading 
• Black smoke coming out
• Irregular running of engine.

How to check the fuel injection pump timing ?

• Lock off the starring mechanism
• Start L.O pump
• Open all indicator cock

By hair line method

1. Turn the engine so that the unit to be checked is toward the TDC of compression stroke (plunger upstroke) so that hair line marking on plunger and pump body are coincided.
2. When hair lines are coincided, stop turning and check the mark on the fly wheel whether timing is correct or not.

By removing deflector from fuel pump

• Take out deflector on both sides of the fuel pump
• Put hand torch on one side of pump and mirror on the other side
• The light from torch will be visible on the mirror
• Turn the engine so that the unit to be check is toward the TDC of compression (at plunger upstroke)
• At one instant the light on mirror disappears. (When plunger covers the deflector port)
• At this time, stop engine turning & check the mark on flywheel.

Adjustment of Fuel Pump Timing

Small engine

Slightly different variation can be adjusted:

• By adding or reduction shims on the pump base, or 
• By turning the plunger up and down adjustment screw on the pump roller guide, or 
• By shifting the coupling flange between the pump and the drive side of the engine in case of combined unit system, (for small engine)

Large engine

• The timing can be altered by shifting the camshaft to the position relative to the crankshaft
• For adjustable cam type engines timing can be altered by individual cams of the fuel pumps.
• Individual unit timing checking up & adjustment required for movable cam type engine
• For solid camshaft type, it is only required for checking on No. 1 unit.

How will you check pump timing if no TDC mark given on flywheel ?

In Main Engine

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. Now 360º can be divided around the flywheel.

In Auxiliary Engine

1. Remove the fuel valve
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 ?

• Check plunger guide wear & tear
• Check spring (length & stiffness, crack)
• Plunger & barrel wear & tear, check clearance (5 microns for DO, 15 microns for HO) by dropping the plunger into the barrel it fall down slowly is OK
• Check control sleeve and rack teeth for crack
• Check the Delivery valve face 
• Check ‘O’ ring of fitted.

Metering of Fuel

• Controlling the fuel amount in two ways, by means of a helix groove on the plunger or by means of control valves. 
• 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.

Reference:

Oral Guide by – MIN ZAR TAR