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

L Head Engine 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