L-Jetronic: Troubleshooting Symptoms

From: Subject: L-Jetronic: Troubleshooting Symptoms Date: Sun, 2 Jan 2005 01:08:53 +0100 MIME-Version: 1.0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Content-Location: http://www.forparts.com/techbosLjetronic.htm X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 L-Jetronic: Troubleshooting Symptoms Olympus =20 Imported Auto Parts=20 Corporation &n= bsp; &nb= sp; &nbs= p;=20 Presented by Bosch=20

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L-Jetronic:=20 Troubleshooting Symptoms

L-Jetronic = is an=20 electronically controlled injection system: the quantity of air = drawn in=20 by the engine is determined in accordance with the air-flow sensor flap=20 principle with electromagnetic control of the fuel injection into the = intake=20 manifold. All changes pertaining to the engine are detected by = numerous=20 sensors and processed by the ECU. Consistently good exhaust gas = emission=20 levels and low fuel consumption are the results.

Symptoms:

Engine cranks=20 but does not start

Engine = starts=20 but then dies

Rough or = unstable=20 idle

Idle speed=20 incorrect

CO value=20 incorrect

Erratic=20 running

Engine missed=20 when driving

Fuel=20 consumption too high

No = maximum=20 power

Symptom: Engine = cranks but does=20 not start

Cause	Remedy
Defect = in ignition=20 system	Check = battery,=20 distributor plugs, coil and timing
Mechanical defect in=20 engine	Check = compression,=20 valve adj. and oil pressure
Leaks = in air intake=20 system (false air)	Check = all hoses and=20 connections; eliminate leaks
Blockage in fuel=20 system	Check = fuel tank,=20 filter and lines for free flow
Relay = defective;=20 wire to injector open	Test = relay; check=20 wiring harness
Fuel = pump not=20 operating	Check = pump fuse,=20 pump relay and pump
Fuel = system pressure=20 incorrect	Check = pressure=20 regulator
Cold = start valve not=20 operating	Test = for spray,check=20 wiring and thermo-time switch
Cold = start valve=20 leaking	Check = valve for=20 leakage
Thermo-time switch=20 defective	Test = for resistance=20 readings vs. temperature
Auxiliary air valve=20 not operating correctly	Must = be open with=20 cold engine: closed with warm
Air = flow meter=20 defective	Check = pump contacts;=20 test flap for movement
Loose = connection in=20 wiring harness or syst. ground	Check = and clean all=20 connections
Control unit=20 defective	Use = known good unit=20 to confirm defect

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Symptom: Engine = starts but then=20 dies

Cause	Remedy
Leaks in=20 air intake system (false air)	Check air=20 system for leaks
Mechanical=20 defect in engine	Check=20 compression, valve adj. and oil pressure
Defect in=20 ignition system	Check=20 battery, distributor, plugs, coil and timing
Blockage=20 in fuel system	Check fuel=20 tank, filter and lines for free flow
Cold start=20 valve not operating	Test for=20 spray,check wiring and thermo-time switch
Thermo-time switch defective	Test for=20 resistance readings vs. temperature
Air flow=20 meter defective	Check pump=20 contacts; test flap for free movement
Idle speed=20 incorrectly adjusted	Adjust=20 idle speed with bypass screw
CO=20 concentration incorrectly set	Readjust=20 CO with screw on air flow meter
Loose=20 connection in wiring harness or syst.ground	Check and=20 clean all connections
Control=20 unit defective	Use known=20 good unit to confirm defect

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Symptom: Rough or unstable=20 idle

Cause	Remedy
Defect = in ignition=20 system	Check = battery,=20 distributor, plugs, coil and timing
Mechanical defect in=20 engine	Check = compression,=20 valve adj. and oil pressure
Leaks = in air intake=20 system (false air)	Check = all hoses and=20 connections; eliminate leaks
Blockage in fuel=20 system	Check = fuel tank,=20 filter and lines for free flow
Cold = start valve not=20 operating	Test = for spray,check=20 wiring and thermo-time switch
Thermo-time switch=20 defective	Test = for resistance=20 readings vs. temperature
Auxiliary air valve=20 not operating correctly	Must = be open with=20 cold engine; closed with warm
Air = flow meter=20 defective	Check = pump contacts;=20 test flap for free movement
Throttle butterfly=20 does not completely close or open	Readjust throttle=20 stops
Throttle valve=20 switch defective	Check = with ohmmeter=20 and adjust
Idle = speed=20 incorrectly adjusted	Adjust = idle speed=20 with bypass screw
Defective injection=20 valve	Check = valves=20 individually for spray
CO = concentration=20 incorrectly set	Readjust CO with=20 screw on air flow meter
Loose = connection in=20 wiring harness or syst.ground	Check = and clean all=20 connections
Control unit=20 defective	Use = known good unit=20 to confirm defect

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Symptom: Idle = speed=20 incorrect

Cause	Remedy
Defect = in ignition=20 system	Check = battery,=20 distributor, plugs, coil and timing
Mechanical defect in=20 engine	Check = compression,=20 valve adj. and oil pressure
Leaks = in air intake=20 system (false air)	Check = all hoses and=20 connections; eliminate leaks
Thermo-time switch=20 defective	Test = for resistance=20 readings vs. temperature
Air = flow meter=20 defective	Check = pump contacts;=20 test flap for free movement
Throttle butterfly=20 does not completely close or open	Readjust throttle=20 stops
Idle = speed=20 incorrectly adjusted	Adjust = idle speed=20 with bypass screw
CO = concentration=20 incorrectly set	Readjust CO with=20 screw on air flow = meter

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Symptom: CO value = incorrect

Cause

Remedy

Leaks in air intake system (false=20 air)	Check all hoses and connections; eliminate = leaks
Cold start valve not = operating	Test for spray,check wiring and thermo-time = switch
Air flow meter defective	Check pump contacts; test flap for free = movement
Idle speed incorrectly adjusted	Adjust idle speed with bypass screw
Defective injection valve	Check valves individually for spray
CO concentration incorrectly set	Readjust CO with screw on air flow=20 meter

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Symptom: Erratic = running

Cause

Remedy

Defect in ignition = system	Check battery, distributor, plugs, = coil and=20 timing
Mechanical defect in = engine	Check compression, valve adj. and = oil=20 pressure
Leaks in air intake system (false=20 air)	Check all hoses and connections; = eliminate=20 leaks
Cold start valve not = operating	Test for spray,check wiring and = thermo-time=20 switch
Air flow meter = defective	Check pump contacts; test flap for = free=20 movement
Defective injection = valve	Check valves individually for=20 spray
CO concentration incorrectly = set	Readjust CO with screw on air flow=20 meter
Loose connection in wiring harness = or=20 syst.ground	Check and clean all=20 connections

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Symptom: Engine = missed when=20 driving

Cause

Remedy

Defect in ignition = system	Check battery, distributor, plugs, = coil and=20 timing
Mechanical defect in = engine	Check compression, valve adj. and = oil=20 pressure
Leaks in air intake system (false=20 air)	Check all hoses and connections; = eliminate=20 leaks
Defective injection = valve	Check valves individually for=20 spray
CO concentration incorrectly = set	Readjust CO with screw on air flow=20 meter
Loose connection in wiring harness = or=20 syst.ground	Check and clean all = connections
Control unit defective	Use known good unit to confirm=20 defect

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Symptom: Fuel = consumption=20 too high

Cause

Remedy

Defect in ignition = system	Check battery, distributor, plugs, = coil and=20 timing
Mechanical defect in = engine	Check compression, valve adj. and = oil=20 pressure
Blockage in fuel system	Check fuel tank, filter and lines = for free=20 flow
Cold start valve not = operating	Test for spray,check wiring and = thermo-time=20 switch
Air flow meter = defective	Check pump contacts; test flap for = free=20 movement

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Symptom: No maximum=20 power

Cause

Remedy

Defect in ignition = system	Check battery, distributor, plugs, = coil and=20 timing
Mechanical defect in = engine	Check compression, valve adj. and = oil=20 pressure
Leaks in air intake system (false=20 air)	Check all hoses and connections; = eliminate=20 leaks
Cold start valve not = operating	Test for spray,check wiring and = thermo-time=20 switch
Air flow meter = defective	Check pump contacts; test flap for = free=20 movement
Throttle butterfly does not = completely close=20 or open	Readjust throttle = stops
Throttle valve switch = defective	Check with ohmmeter and = adjust
Defective injection = valve	Check valves individually for=20 spray
CO concentration incorrectly = set	Readjust CO with screw on air flow=20 meter
Control unit defective	Use known good unit to confirm=20 defect

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