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Self-diagnosis
Readout specified values for injection pump
Display group 01 during idling (engine warm, coolant temperature not below +85°C)
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Read measured value block 1
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⇒
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◂ Indicated on display
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900 rpm
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5.6 mg/stroke
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1.480 V
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87.3 °C
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Coolant temperature
▪ 85...100 °C ok
▪ < 85 °C: => Run engine until warm
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Voltage from modulating piston movement sender -G149
▪ 1.250...1.700 V okay
▪ < 1.250 V: Injection pump too rich => replace
▪ > 1.700 V: Engine loaded => switch consumers off, injection pump too lean => renew injection pump
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Injection quantity
▪ 2.0...6.0 mg/stroke OK
▪ < 2.0 mg/stroke: Injection pump too rich => replace
▪ > 6.0 mg/stroke: Engine loaded => switch consumers off, injection pump too lean => renew injection pump
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Engine speed
▪ 860...940 rpm OK
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Display group 01 with attempted start (if engine does not start) 1)
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Read measured value block 1
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⇒
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◂ Indicated on display
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230 rpm
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37.4 mg/stroke
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2.780 V
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14.3 °C
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Coolant temperature
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Voltage from modulating piston movement sender -G149 (quantity adjuster returns modulating piston position to control unit)
▪ Periodic voltage increases: okay (pump is injecting)
▪ < 1.000 V: Metering control closed =>observe display zone 2, only if specified injection quantity okay =>replace injection pump
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Specified injection quantity (control unit activating metering control in injection pump)
▪ Periodic injection quantity increases: okay (pump is being activated)
▪ 0.0 mg/stroke System fault => interrogate fault memory, Page 01-6
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Engine speed
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1) If the electrical system voltage falls below 10.8 V during the attempted start, the V.A.G 1551 fault reader will abort the diagnosis.
Display group 19 with ignition on
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Read measured value block 19
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◂ Indicated on display
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0.780 V
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4.150 V
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No display
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No display
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Voltage at sensor for modulating piston movement with metering control at maximum stop
▪ 3.800...4.400 V okay
▪ If outside tolerance: Check contact resistance in wiring
▪ injection pump quantity adjuster maladjusted => replace injection pump
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Voltage at sensor for modulating piston movement with metering control at minimum stop
▪ 0.600...0.900 V okay
▪ If outside tolerance: Check contact resistance in wiring => Page 23-92
▪ injection pump quantity adjuster maladjusted => replace injection pump
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Display group 04 during idling (engine warm, coolant temperature not below +85°C)
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Read measured value block 4
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◂ Indicated on display
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900 rpm
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0.9 °BTDC
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0.9 °BTDC
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3 %
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Duty cycle (activation) of injection start valve
▪ no specification
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Current injection start
▪ 2° after TDC...4° before TDC okay.
▪ Later 2°after TDC: Injection timing control stuck
▪ Commencement of injection valve defective
▪ Injection pump excessively retarded
▪ => Check injection timing control range, Page 23-59
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Injection start specified by control unit
▪ 2° after TDC...4° before TDC OK
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Engine speed
▪ 860...940 rpm OK
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Display group 04 at full throttle (test drive in 3rd or 4th gear, coolant temperature not below +85 °C)
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Read measured value block 4
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◂ Indicated on display
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4060 rpm
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16.3 °BTDC
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16.1 °BTDC
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84 %
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Duty cycle (activation) of injection start valve
▪ No specification
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Current injection start
▪ If as specified in display group 2 (tolerance ±2°) okay.
▪ If outside tolerance: Injection pump delivery start incorrect
▪ => check commencement of injection,
▪ Page 23-59
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Injection start specified by control unit
▪ 14...18 °BTDC okay.
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Engine speed
▪ 3800...4200 rpm OK
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