Specific Diagnostic W124 Query
- Thread starter Andrzej
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- diagnostic query specific w124
grober
MB Master
check out the HT CIRCUITS.
w124coupe has offered some sound advice. If its ignition problem then first thing is to CHECK OUT THE HIGH TENSION SIDE OF THINGS, COIL, HT LEADS, DISTRIBUTER CAP, ROTOR ARM. See if you can induce a spark from the coil HT LEAD alone before it gets to the distributor. temporarily
connect the coil ht lead to an earthed spark plug to give it a load and look for a healthy spark between the electrodes as you turn the engine over. If you have a spark there then your problem is in the distributer cap/ rotor arm. I once had a rotor arm go bad on me so it continually earthed the ht supply for example . Then check the rotor arm is rotating with the cap off, the drive might be sheared UNLIKELY but worth a quick visual inspection. then examine the distributor cap for tracking to earth. If you dont get a spark at all from the coil then time to check it with a temporary supply from the battery and then collapse the field by earthing the other side of the primary coil as suggested by dieselman on the previous thread. http://mbclub.co.uk/forums/showthread.php?t=29100
after that its down to the low tension side.
ps DONT ELECTROCUTE YOURSELF IN THE PROCESS THESE HT SYSTEMS CAN GIVE YOU A FEARFUL "BELT"
w124coupe has offered some sound advice. If its ignition problem then first thing is to CHECK OUT THE HIGH TENSION SIDE OF THINGS, COIL, HT LEADS, DISTRIBUTER CAP, ROTOR ARM. See if you can induce a spark from the coil HT LEAD alone before it gets to the distributor. temporarily
connect the coil ht lead to an earthed spark plug to give it a load and look for a healthy spark between the electrodes as you turn the engine over. If you have a spark there then your problem is in the distributer cap/ rotor arm. I once had a rotor arm go bad on me so it continually earthed the ht supply for example . Then check the rotor arm is rotating with the cap off, the drive might be sheared UNLIKELY but worth a quick visual inspection. then examine the distributor cap for tracking to earth. If you dont get a spark at all from the coil then time to check it with a temporary supply from the battery and then collapse the field by earthing the other side of the primary coil as suggested by dieselman on the previous thread. http://mbclub.co.uk/forums/showthread.php?t=29100
after that its down to the low tension side.
ps DONT ELECTROCUTE YOURSELF IN THE PROCESS THESE HT SYSTEMS CAN GIVE YOU A FEARFUL "BELT"
Andrzej
Member
- Joined
- Oct 29, 2005
- Messages
- 42
- Location
- Amersham, Bucks
- Car
- 1997 W140 S600, 1980 Porsche 928 4.7 Manual
Grober / w124coupe I really appreciate all your help. I'll follow through this advice. Some of it I have tried, but I think it makes sense to start at the beginning and go through it all systematically, and keeping notes too. The coil switching test especially could help me determine where things are going wrong... Anyway I'll let you know how I get on. Thanks again guys...!
I've looked on Alldata and it lists these codes for your car (as always, Alldata lists US model codes for bits we didn't get fitted as well as the standard stuff).
Suggests code 17 on the 300 EZL is the CPS?
This conflicts with the earlier answer (although I have known Alldata to be wrong) but makes testing of the CPS and its connectivity a priority as the EZL will not ground the coil if it can't sense crank position.
DTC Possible Cause 1 No Faults in System 2 Maximum retard setting on at least one cylinder has been reached 4 Load Sensor in ignition control module (N1/3) defective 5 Knock Sensor (A16) 1 and/or 2 defective 6 Camshaft position sensor (L5/1) defective 7 Knock control output switch in ignition control module (N1/3) defective 8 Transmission overload switch (S65) does not close 9 Transmission overload switch (S65) does not open 11 Reference resistor (R16/2) in ignition control module (N1/3) defective 12 TN-Signal (engine RPM) is outside of tolerance range 15 Ignition coil 1 output from ignition control module (N1/3) defective or primary winding of ignition coil has open circuit 16 Ignition coil 2 output from ignition control module (N1/3) defective or primary winding of ignition coil has open circuit 17 Crankshaft position sensor defective (L5) 18 Magnets for crankshaft position sensor (L5) not recognized 19 Not used 20 Ignition control module (N1/3) DTC memory defective 21 Load sensor in ignition control module (N1/3) defective (recognized with engine running) 26 Ignition control module (N1/3) data exchange fault 27 LH Control Unit (N3/1) data exchange fault 28 Electronic accelerator control module/idle speed control data exchange fault 34 Ignition misfire cylinder 1 35 Ignition misfire cylinder 2 36 Ignition misfire cylinder 3 37 Ignition misfire cylinder 4 38 Ignition misfire cylinder 5 39 Ignition misfire cylinder 6
Sorry re the formatting!
Good luck.....
Suggests code 17 on the 300 EZL is the CPS?
This conflicts with the earlier answer (although I have known Alldata to be wrong) but makes testing of the CPS and its connectivity a priority as the EZL will not ground the coil if it can't sense crank position.
DTC Possible Cause 1 No Faults in System 2 Maximum retard setting on at least one cylinder has been reached 4 Load Sensor in ignition control module (N1/3) defective 5 Knock Sensor (A16) 1 and/or 2 defective 6 Camshaft position sensor (L5/1) defective 7 Knock control output switch in ignition control module (N1/3) defective 8 Transmission overload switch (S65) does not close 9 Transmission overload switch (S65) does not open 11 Reference resistor (R16/2) in ignition control module (N1/3) defective 12 TN-Signal (engine RPM) is outside of tolerance range 15 Ignition coil 1 output from ignition control module (N1/3) defective or primary winding of ignition coil has open circuit 16 Ignition coil 2 output from ignition control module (N1/3) defective or primary winding of ignition coil has open circuit 17 Crankshaft position sensor defective (L5) 18 Magnets for crankshaft position sensor (L5) not recognized 19 Not used 20 Ignition control module (N1/3) DTC memory defective 21 Load sensor in ignition control module (N1/3) defective (recognized with engine running) 26 Ignition control module (N1/3) data exchange fault 27 LH Control Unit (N3/1) data exchange fault 28 Electronic accelerator control module/idle speed control data exchange fault 34 Ignition misfire cylinder 1 35 Ignition misfire cylinder 2 36 Ignition misfire cylinder 3 37 Ignition misfire cylinder 4 38 Ignition misfire cylinder 5 39 Ignition misfire cylinder 6
Sorry re the formatting!
Good luck.....
Andrzej
Member
- Joined
- Oct 29, 2005
- Messages
- 42
- Location
- Amersham, Bucks
- Car
- 1997 W140 S600, 1980 Porsche 928 4.7 Manual
Hello, me again. OK carried out some tests. First of all thought I'd test the CPS sensor. Got a resistenance of 850ohms which is within range. Centre pin to ground resistance was infinite, and AC voltage across it was measured at 0.5V whilst cranking. So concluded that all is well with the CPS. Next checked the high tension side, checked the resistance of the distributor to plug end caps and rotor itself. All within range and clean. Then tested voltages as at contacts 1 & 15 when ignition on. Both at battery level. Then checked for grounding activity between contact 1 by connecting a test lamp (led & resistor between +12v and contact 1). No blinking...
The EZL is getting voltage in & is supplying voltage to the coil, but is not performing the grounding for contact 1 on the coil, hence no spark on the HT side. So, is the conclusion as I'd feared, that the EZL is dead... I certainly think that this is the case now....
The EZL is getting voltage in & is supplying voltage to the coil, but is not performing the grounding for contact 1 on the coil, hence no spark on the HT side. So, is the conclusion as I'd feared, that the EZL is dead... I certainly think that this is the case now....
