W124 E500 M119 LH Jetronic Open Loop Duty Cycle Measurement
10-20-2022, 05:43 PM
#1
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W124 E500 Limited
W124 E500 M119 LH Jetronic Open Loop Duty Cycle Measurement
Hi Guys,
Have a hot running issue on my W124 E500 which has the EFI LH Jetronic. Today we have performed a duty cycle measurement (on/off ratio) with a scanner.
The values we got are as follows. When cold with ignition on reading is at 30%. On cold start on idle closed loop the reading is at 50%. As far as we are aware these are
as per spec.
However the open loop duty cycle measurement at idle once engine is hot fluctuates/oscillates between a min. of 12% and a peak of 18%. What should this measurement be at for the M119/E500
once warmed up at idle? Does it point to a lean mixture which would explain the hot running?
We are also suspecting the MAF as the reading has stayed on -0.10 kg/h when the car was running.
We are not getting any faults with the scanner.
Any inputs would be appreciated. Thanks!
Have a hot running issue on my W124 E500 which has the EFI LH Jetronic. Today we have performed a duty cycle measurement (on/off ratio) with a scanner.
The values we got are as follows. When cold with ignition on reading is at 30%. On cold start on idle closed loop the reading is at 50%. As far as we are aware these are
as per spec.
However the open loop duty cycle measurement at idle once engine is hot fluctuates/oscillates between a min. of 12% and a peak of 18%. What should this measurement be at for the M119/E500
once warmed up at idle? Does it point to a lean mixture which would explain the hot running?
We are also suspecting the MAF as the reading has stayed on -0.10 kg/h when the car was running.
We are not getting any faults with the scanner.
Any inputs would be appreciated. Thanks!
10-23-2022, 06:12 AM
#2
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Join Date: Oct 2022
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W124 E500 Limited
Hi Guys,
Have a hot running issue on my W124 E500 which has the EFI LH Jetronic. Today we have performed a duty cycle measurement (on/off ratio) with a scanner.
The values we got are as follows. When cold with ignition on reading is at 30%. On cold start on idle closed loop the reading is at 50%. As far as we are aware these are
as per spec.
However the open loop duty cycle measurement at idle once engine is hot fluctuates/oscillates between a min. of 12% and a peak of 18%. What should this measurement be at for the M119/E500
once warmed up at idle? Does it point to a lean mixture which would explain the hot running?
We are also suspecting the MAF as the reading has stayed on -0.10 kg/h when the car was running.
We are not getting any faults with the scanner.
Any inputs would be appreciated. Thanks!
Have a hot running issue on my W124 E500 which has the EFI LH Jetronic. Today we have performed a duty cycle measurement (on/off ratio) with a scanner.
The values we got are as follows. When cold with ignition on reading is at 30%. On cold start on idle closed loop the reading is at 50%. As far as we are aware these are
as per spec.
However the open loop duty cycle measurement at idle once engine is hot fluctuates/oscillates between a min. of 12% and a peak of 18%. What should this measurement be at for the M119/E500
once warmed up at idle? Does it point to a lean mixture which would explain the hot running?
We are also suspecting the MAF as the reading has stayed on -0.10 kg/h when the car was running.
We are not getting any faults with the scanner.
Any inputs would be appreciated. Thanks!
Once engine is at operating temp. around 95 deg. C the on/off ratio hovers between a low of 5% and a peak of 15%. Should that not be at around 50% (+/- 10%) ?
Does anyone have any idea about this and what the cause could be?
Last edited by E500LTD; 10-23-2022 at 06:16 AM.
10-23-2022, 05:08 PM
#3
Super Member
Noticed you posted this new one, which is appropriate. One last precautionary word on this from me.
It is even possible that when the harness was replaced one of the wires were crossed. Which means the system will do the opposite of what it is trying to do and it will rail to either all the way lean or all the way rich. So I would make sure all the connections are the correct polarity in the wiring. Was the shop that conducted the replacement a reputable shop?
Good luck with this...
It is even possible that when the harness was replaced one of the wires were crossed. Which means the system will do the opposite of what it is trying to do and it will rail to either all the way lean or all the way rich. So I would make sure all the connections are the correct polarity in the wiring. Was the shop that conducted the replacement a reputable shop?
Good luck with this...
