SL/R129: 500SL runs great cold, stalls out when it gets hot or 5 miles down the road
09-21-2018, 04:28 PM
#1
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500SL runs great cold, stalls out when it gets hot or 5 miles down the road
500SL used to run great, runs great cold, but now stalls out when it gets hot after 4 or 5 miles down the road. had to have it flatbedded home.
I need ideas as to what could be wrong - all ignition parts replaced except for the ICM / ignition control module - bosch jetronic CIS fuel distributor was rebuilt 2 years ago and all new injectors and seals replaced -
I unnecessarily replaced the cam/crank sensor and over voltage protection relay, that wasnt the problem, all voltage readings of sensors are where they should be , duty cycle is set correctly, plenty of fuel pressure on the fuel rails and injectors, tranny rebuilt professionally 4 years ago.
I'm at my wits end with this car - I spend more time and money working on it than driving it .. and can no longer afford to maintain it.
I have now been trying to solve this mystery for 6 months when I went to take it out of the garage 6 months ago ..
..I'm fed up and have reached my boiling pt. and don't want to spend $4,000 on a new ICM Ignition Control Module if that's not what it needs - as everyone says there is no way to test an ICM ..
you pros, got any ideas ?
I need ideas as to what could be wrong - all ignition parts replaced except for the ICM / ignition control module - bosch jetronic CIS fuel distributor was rebuilt 2 years ago and all new injectors and seals replaced -
I unnecessarily replaced the cam/crank sensor and over voltage protection relay, that wasnt the problem, all voltage readings of sensors are where they should be , duty cycle is set correctly, plenty of fuel pressure on the fuel rails and injectors, tranny rebuilt professionally 4 years ago.
I'm at my wits end with this car - I spend more time and money working on it than driving it .. and can no longer afford to maintain it.
I have now been trying to solve this mystery for 6 months when I went to take it out of the garage 6 months ago ..
..I'm fed up and have reached my boiling pt. and don't want to spend $4,000 on a new ICM Ignition Control Module if that's not what it needs - as everyone says there is no way to test an ICM ..
you pros, got any ideas ?
09-22-2018, 01:05 PM
#2
Banned
I recall that "everyone" thought Saddam Hussein's Iraq possessed weapons of mass destruction. I believe the following is a simple way to test an EZL control module.
Disconnect one lead to the ignition coil to remove it from the ignition's primary circuit. In place of the coil substitute a resistor valued between 1K and 10K ohms. Now measure the DC voltage across the resistor while the engine is cranking.
When I performed the above test with a working system I recall getting perhaps 4 volts. With a non-working ignition I measured zero voltage.
Disconnect one lead to the ignition coil to remove it from the ignition's primary circuit. In place of the coil substitute a resistor valued between 1K and 10K ohms. Now measure the DC voltage across the resistor while the engine is cranking.
When I performed the above test with a working system I recall getting perhaps 4 volts. With a non-working ignition I measured zero voltage.
10-02-2018, 09:52 AM
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would the resistor be in series with the coil? that is, between the removed lead and the coil terminal then,?
or am I to disregard the coil completely and put the resistor between the removed lead and ground ?
not clear as to what to do ..
what I did before reading your suggestion got me 11.7v when the ignition key was turned on measuring the voltage between either terminal of the coil and ground.
measuring across the coil there was 0v . isnt one terminal supposed to be plusV and the other ground ?
I replaced the cam sensor and the crank sensor with a new ones, no difference in running problem, so figured it must be the fuel distributor when it gets hot and leaks.
I removed all of the injector fuel lines from the CIS fuel distributor, took out the MAS relay pack and jumpered pins 1 & 2 on the connector to cause the fuel pumps to continuously pump to see if their were any leaks on the distro feeds - with pumps running no leaks, then slowly depressed the air disk meter which moves the plunger on the fuel distributor and the outlets of the distro slowly filled evenly .. so the distro is working good in cold condition.
reattached the injector fuel lines, put the MAS relay pack back in, and tightened it down.
went to start the car again but no start
but then a new problem has developed -- NO SPARK-- pulled a spark plug wire and a plug - 2 different ones one from each side no spark but plug was a bit wet with gasoline.
it turned over and started, and was fine before I did the above work, that's when I rechecked voltages at the coils, and they are still the same .. trying to solve a hot running problem after a a heat soak, now I some how inadvertently created the no spark problem.. took out the MAS and reinserted it 2 times and checked the over-voltage protection relay and fuses and they are good, in fact it is a new OVPR ... so now I am really stumped. I've read the forums for days, seems that everything points to a bad EZL, but I'm only guessing.. will do the resistor test that you suggest next. once I know where to put the resistor.
or am I to disregard the coil completely and put the resistor between the removed lead and ground ?
not clear as to what to do ..
what I did before reading your suggestion got me 11.7v when the ignition key was turned on measuring the voltage between either terminal of the coil and ground.
measuring across the coil there was 0v . isnt one terminal supposed to be plusV and the other ground ?
I replaced the cam sensor and the crank sensor with a new ones, no difference in running problem, so figured it must be the fuel distributor when it gets hot and leaks.
I removed all of the injector fuel lines from the CIS fuel distributor, took out the MAS relay pack and jumpered pins 1 & 2 on the connector to cause the fuel pumps to continuously pump to see if their were any leaks on the distro feeds - with pumps running no leaks, then slowly depressed the air disk meter which moves the plunger on the fuel distributor and the outlets of the distro slowly filled evenly .. so the distro is working good in cold condition.
reattached the injector fuel lines, put the MAS relay pack back in, and tightened it down.
went to start the car again but no start
but then a new problem has developed -- NO SPARK-- pulled a spark plug wire and a plug - 2 different ones one from each side no spark but plug was a bit wet with gasoline.
it turned over and started, and was fine before I did the above work, that's when I rechecked voltages at the coils, and they are still the same .. trying to solve a hot running problem after a a heat soak, now I some how inadvertently created the no spark problem.. took out the MAS and reinserted it 2 times and checked the over-voltage protection relay and fuses and they are good, in fact it is a new OVPR ... so now I am really stumped. I've read the forums for days, seems that everything points to a bad EZL, but I'm only guessing.. will do the resistor test that you suggest next. once I know where to put the resistor.
10-03-2018, 11:04 AM
#4
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One terminal is constant 12VDC; the other terminal is switched to ground.
No. As I wrote earlier, "In place of the coil substitute a resistor..."
No. As I wrote earlier, "In place of the coil substitute a resistor..."
10-05-2018, 09:32 PM
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can you verify these parameters for me ?
On my Bosch Ignition control module, I get different readings on only one of the two 8 pin plug connectors; the second connector that is closer to the the driver, furthest from the front of the vehicle has no continuity from pin 2 to ground and has voltage on pin 5 not pin 4, and neither pin 4 has continuity to the positive side to the the coil, even if I take the wire off the coil -- but both coils are receiving 11.7 volts with the ignition switch on.
"It is very rare for the ignition control module to fail, although after all these years problems do occur. Because the module is a sealed unit, it is very difficult to check it thoroughly, but there are some basic tests you can do to ensure that it is getting voltage.
On my Bosch Ignition control module, I get different readings on only one of the two 8 pin plug connectors; the second connector that is closer to the the driver, furthest from the front of the vehicle has no continuity from pin 2 to ground and has voltage on pin 5 not pin 4, and neither pin 4 has continuity to the positive side to the the coil, even if I take the wire off the coil -- but both coils are receiving 11.7 volts with the ignition switch on.
"It is very rare for the ignition control module to fail, although after all these years problems do occur. Because the module is a sealed unit, it is very difficult to check it thoroughly, but there are some basic tests you can do to ensure that it is getting voltage.
On the Siemens unit, remove the large round 8 pin plug and check for voltage (ign on) between pins 3(+) and 6(-).
Pins should be numbered inside the plug.
On the Bosch unit, check between pins 4(+) and 2(-). If you don't get voltage, you need to check your wiring.
The negative pin ( 6/Siemens or 2/Bosch) should show continuity to ground and the positive pin (3/Siemens or 4/Bosch) should show continuity to the #15 (green wire/ positive voltage pin) on the coil."
Pins should be numbered inside the plug.
On the Bosch unit, check between pins 4(+) and 2(-). If you don't get voltage, you need to check your wiring.
The negative pin ( 6/Siemens or 2/Bosch) should show continuity to ground and the positive pin (3/Siemens or 4/Bosch) should show continuity to the #15 (green wire/ positive voltage pin) on the coil."
Last edited by 92-500SL; 10-05-2018 at 09:37 PM.
