4-134 L Engine Service Diagnosis - MB

4-134 L Engine illustration shown for reference only - click here to shop for these parts by interactive diagram

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Service Diagnosis:
Poor Fuel Economy	Ignition timing slow or spark advance stuck
	Carburetor float high
	Accelerator Pump not properly adjusted
	High fuel pump pressure
	Fuel Leakage
	Leaky fuel pump diaphragm
	Loose engine mounting causing high fuel level in carburetor
	Low compression
	Valves sticking
	Spark plugs bad
	Spark plug cables bad
	Weak coil or condenser Improper valve tappet clearance
	Carburetor air cleaner dirty
	High oil level in air cleaner
	Dragging brakes
	Front wheels out of alignment
	Tires improperly inflated
	Inaccurate odometer
	Faulty fuel tank cap
	Clogged muffler or bent exhaust pipe
Lack of Power	Low compression
	Ignition system (Timing late)
	Improper functioning carburetor or fuel pump
	Fuel lines clogged
	Air cleaner restricted
	Engine temperature high
	Improper tappet clearance
	Sticking valves
	Valve timing late
	Leaky gaskets
	Muffler clogged
	Bent exhaust pipe
Low Compression	Leaky valves
	Poor piston ring seal
	Sticking valves
	Valve spring weak or broken
	Cylinder scored or worn
	Tappet clearance incorrect
	Piston clearance too large
	Leaky Cylinder head gasket
Burned Valve and Seats	Sticking valves or too loose in guides
	Improper timing
	Excessive carbon around valve head and seat overheating
	Valve spring weak or broken
	Valve tappet sticking
	Valve tappet clearance incorrect
	Clogged exhaust system
Valves Sticking	Warped valve
	Improper tappet clearance
	Carbonized or scored valve stems
	Insufficient clearance valve stem to guide
	Weak or broken valve spring
	Valve spring cocked
	Contaminated oil
Overheating	Inoperative cooling system
	Thermostat Inoperative
	Improper ignition timing Improper valve timing
	Excessive carbon accumulation
	Fan belt too loose
	Clogged muffler or bent exhaust pipe
	Oil system failure
	Scored or leaky piston rings
Popping-Spitting-Detonation	Improper ignition
	Improper carburetion
	Excessive carbon deposit in combustion chambers
	Poor valve seating
	Sticking valves
	Broken valve spring
	Tappets adjusted too close
	Spark plug electrodes burned
	Water or dirt in fuel
	Clogged lines
	Improper valve timing
Excessive Oil Consumption	Piston rings stuck in grooves, worn or broken
	Piston rings improperly fitted or weak
	Piston ring oil return holes clogged
	Excessive clearance, main and connecting rod bearings
	Oil leaks at gaskets or oil seals
	Excessive clearance, valve stem to valve guide (Intake)
	Cylinder bores scored, out-of-round or tapered
	Too much clearance, piston to cylinder bore
	Misaligned connecting rods
	High road speeds or temperature
	Crankcase ventilator not operating
Bearing Failure	Crankshaft bearing journal out-of-round
	Crankshaft bearing journal rough
	Lack of oil
	Oil leakage
	Dirty oil
	Low oil pressure or oil pump failure
	Drilled passages in crankcase or crankshaft clogged
	Oil screen dirty
	Connecting rod bent

Excerpt from the Service Manual for 41-45 MB, GPW