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Discussion Starter · #1 ·
Hello and thanks for reading,
I’m an automotive service technician with 42 years experience working on automobiles and I have worked on a wide variety of vehicles equipped with the Bosch CIS and Motronic systems installed, including a number of Rolls Royces and Bentleys.
This car belongs to a friend of mine and came to me as a no start which ended up being lack of fuel delivery due to a seized fuel pump. After installing a new Bosch pump the car fired and ran reasonably well. I test drove the car and it occasionally felt like it was dropping a few cylinders and was lower on power than I expected it to be (its been awhile since I’ve driven a Turbo R).
In any case I drove the car several times (about 90km total) and after parking the car I went to move it inside my shop and it started, ran for 2 seconds and quit, the cause being no spark from either ignition system.
I used my oscilloscope and checked the outputs of both the crank and engine speed sensors and both look good. I checked powers and grounds to both the spark amplifiers and motronic unit - all good. I opened the motronic unit and someone has reflowed the solder on a number of circuit board connections.
I sent the motronic unit to a test/repair facility in germany and they say that they cant find an issue. I was hoping for a more definitive diagnosis but apparently that isn’t coming.
Before I pull the trigger and purchase a new Motronic unit, can anyone confirm that I am using the correct wiring diagram for the car. The diagram I have I found on this forum but only goes up to 1989, I am concerned that some changes may have been made when the switchover to the 30,000 cars was made.
The vehicle was built 9/89 and is X31117.
Any thoughts?
 

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My first advice: check fuses and relays (sockets too). Especially for ignition and ecu module. Read as example my post that I wrote few days ago. Look for manuals for "Starting system" and "Power distribution system". As I remember they are available for 90-91 cars at rrtechnical.info page.
Hint: Did you check safety switch at fuel pump relay?
 

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Discussion Starter · #4 ·
What did the on board diagnostic indicate if anything?
There were no trouble codes present, which was also a bit of a surprise. I know that they are pretty much an analog unit, however, I would have expected something had it been a sensor failure.
Thanks
 

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Discussion Starter · #5 ·
My first advice: check fuses and relays (sockets too). Especially for ignition and ecu module. Read as example my post that I wrote few days ago. Look for manuals for "Starting system" and "Power distribution system". As I remember they are available for 90-91 cars at rrtechnical.info page.
Hint: Did you check safety switch at fuel pump relay?
Thanks for the suggestions, I want to ensure that I'm following the correct diagram. I did not check the safety switch for the fuel pump, however, I did test fuel pressure during the no start condition and fuel delivery is good while having no spark.
Thanks
 

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Discussion Starter · #6 ·
I have read the Crewe stopped printing manuals in 1990. Is there a way to obtain access to IETIS ?
 

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This car is from second half of 1989 year and is X3xxxx series, so I believe it is already facelifted MY90, anyway someone more experienced should confirm it.
 

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Jamie, no spark where? At plugs obviously but at coil leads? Have you checked that the ignition modules are switching the coils? Flashing test lamp on coil negative terminals will test if modules are switching the coils. Does it fire at all trying to start or nothing at all now? Do you get any intermittent spark at coil leads of either coil?
It would be very unusual for this to be an ECU failure. Where are you located? Is there any possibility of borrowing another ECU out of a nearby car to check if it is the fault?
I have sent you a PM.
 

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Make sure the ignition fuse is tight in the holder. They can overheat without blowing and this will melt the plastic around the fuse base causing intermittent contact.
 

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Discussion Starter · #11 ·
Jamie, no spark where? At plugs obviously but at coil leads? Have you checked that the ignition modules are switching the coils? Flashing test lamp on coil negative terminals will test if modules are switching the coils. Does it fire at all trying to start or nothing at all now? Do you get any intermittent spark at coil leads of either coil?
It would be very unusual for this to be an ECU failure. Where are you located? Is there any possibility of borrowing another ECU out of a nearby car to check if it is the fault?
I have sent you a PM.
Jim, thanks for the response.
No spark from either coil, supply voltage stays constant in both run and Cranking position. Both modules have consistent power and ground in crank and run.
It has started and quit after 2 seconds or so a couple of times and has spark from both coils when this occurs.
I agree that the Motronic units are pretty robust except for the occasional mechanical failure of the solder joints between the connector and circuit board. I did open the unit up and someone has reflowed the solder joints on a few connections. I wonder what issue they were chasing ? Lol
I found the 30000 series update info and will have a poke through it tonight.
Unfortunately, I don't know of another Turbo R whereby I could play the 'replace with known good unit" game.
I'll check it over with the later wiring diagand report what I find. I'm away for a few days but will get back at it later in the week.
 

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Hello and thanks for reading,
I’m an automotive service technician with 42 years experience working on automobiles and I have worked on a wide variety of vehicles equipped with the Bosch CIS and Motronic systems installed, including a number of Rolls Royces and Bentleys.
This car belongs to a friend of mine and came to me as a no start which ended up being lack of fuel delivery due to a seized fuel pump. After installing a new Bosch pump the car fired and ran reasonably well. I test drove the car and it occasionally felt like it was dropping a few cylinders and was lower on power than I expected it to be (its been awhile since I’ve driven a Turbo R).
In any case I drove the car several times (about 90km total) and after parking the car I went to move it inside my shop and it started, ran for 2 seconds and quit, the cause being no spark from either ignition system.
I used my oscilloscope and checked the outputs of both the crank and engine speed sensors and both look good. I checked powers and grounds to both the spark amplifiers and motronic unit - all good. I opened the motronic unit and someone has reflowed the solder on a number of circuit board connections.
I sent the motronic unit to a test/repair facility in germany and they say that they cant find an issue. I was hoping for a more definitive diagnosis but apparently that isn’t coming.
Before I pull the trigger and purchase a new Motronic unit, can anyone confirm that I am using the correct wiring diagram for the car. The diagram I have I found on this forum but only goes up to 1989, I am concerned that some changes may have been made when the switchover to the 30,000 cars was made.
The vehicle was built 9/89 and is X31117.
Any thoughts?
Jamie. Check that you are getting continuity through the button in the cap. On rare occasions these fail in sz cars. It will baffle the most experienced mechanics.
 

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Discussion Starter · #13 ·
Jamie. Check that you are getting continuity through the button in the cap. On rare occasions these fail in sz cars. It will baffle the most experienced mechanics.
Thanks, however, at this point I'm not even getting spark from either ignition coil
 

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Always check the last thing you touched. I often cause my own problems while fixing something else. Check the alternator. The internal fusable link will cause this. A hard shut off such as turning off the trunk switch can cause damage to the alternator. Check the battery connections no matter how good you think they are. These cause a waterfall of problems all the time. Check fuses, relays and body grounds. Do this early in your investigation. These are often the culprit. See if the power remains in the run position behind the starter switch. If not it may be the switch. Good motoring.
 

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Hey Jamie, I remembered something about the turbocharged cars last night. The modules are fed from the ECU through an over voltage relay, not directly from the ECU. It should be a single relay just ahead of where the coils are located and it has an attached fuse which may be blown. IIRC it's a pink wire from the ECU that feeds it, and a white/pink wire from that relay to the modules.
 

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Discussion Starter · #19 ·
Hey Jamie, I remembered something about the turbocharged cars last night. The modules are fed from the ECU through an over voltage relay, not directly from the ECU. It should be a single relay just ahead of where the coils are located and it has an attached fuse which may be blown. IIRC it's a pink wire from the ECU that feeds it, and a white/pink wire from that relay to the modules.
Jim,
Thanks for the input. I was away for a few days and just got this morning. The motoronic unit is on its back from Germany and I expect in the next couple of days. I’ll dig back in as soon as the unit is installed again. I’ll publish my findings as soon as I have some.
 

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So, you have engine with two ignition modules and two ignition distributors?

Do you have 12V at B4 & B9 fuses?
 
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