New to the E24 ! Need help with no spark and component locations !

[CALLACI]

WBAE8360XC7505092
1982 BMW 633CSI manual no spark issue

Car has been sitting for over 3 years got it in non running state.

Hi everyone im completely lost on what to do here as I am not familiar with these cars at all ! IÂ’m having an issue where the car will not spark from the coil. what I have done so far in terms of maintenance is to replace the 2 crank sensors on the bell housing (inspected the flywheel for damage on ring gear and TDC tab) everything looks fine. I replaced the battery with new one. The car cranks fine when I turn the key. The coil has 12V on terminal 15 with key on and if I give the other side (terminal 1) a good body ground it will send spark out the coil towards distributor. My issue is I believe the computer is responsible for giving the ground to the coil to send spark but itÂ’s not doing it properly. The wire responsible for grounding (terminal 1) has a constant ground which if I put my test light on the positives of the battery and touch the terminal 1 wire (disconnected from coil) I get a constant 2.8v ground. IÂ’m not sure if that ground is normal and as soon as I unplug the ECU it goes away right away. If I crank the car that 2.8v ground wonÂ’t pulse or move at all it stays constant. By bench testing the coil with power to terminal 15 and ground to terminal 1 I can get spark so I know itÂ’s something with the terminal 1 control thatÂ’s giving me and issue. IÂ’m not sure where to start

- coil resistance tests done and coil working
- car cranks
- 2 crank sensors replaced
- battery new
- grounds cleaned (ones I know of and can see)
- ECU opened and inspected for burn or damage

I would really need a hand to get a pin out of the ECU connector so I can test if power and grounds to the ECU are all there. IÂ’d also like to test if my crank sensors are producing the right voltage and if that signal voltage is getting to ECU. Also if there are any fuses or relays I should be looking at because I donÂ’t have any wiring diagrams or anything. Im have read couple posts on this matter but none helped so I wanted to start my own and see if we can find the issue.

Thanks in advance to anyone who tries to help 👍

I am a very capable mechanic with enough tools to test most stuff and a very good understanding of automotive repair. I would just need some guidance to locate this issue and maybe understand a little more how this system is working to actually create itÂ’s spark.

[1986series6]

This info may help, although I think your 82 may be a different similar system.

https://hpsimotorsports.com/blogs/te...n-tech-article

[RSheiman]

The ECU's are and are not robust. Go find a used one as it will probably come into question for many issues and knowing you have a spare to test is a plus. Opening and looking, it may still be the ECU since you cannot see the micro-fractures. You can reflow the joints if necc.

I'm gonna vote ECU.There was no water stain that you saw behind the glovebox when you pulled it? I have found the crank sensors to be bulletproof as I have never replaced one on either E24 I own over the last 25 years.

[DesktopDave]

The DME will ground the coil to fire the spark plugs. Cold solder joints on the high-power driver transistor connections are common in the older Bosch Motronics, I'd recommend solder repairs to the coil driver transistor, or swapping the DME to test by elimination. I'm not really sure what voltage readings you should be seeing on that wire, or how BMW & Bosch recommend testing it, but most consumer-level DVMs cannot measure a rapidly changing signal, they'll just average it out. An oscilloscope is typically required.

As for the early Motronic 1.0 DME, they put it into a bunch of cars. Google is your best bet. Here's a nice graphical DME pinout. I'd also get a few of BMW's electrical troubleshooting manuals, many are available here. I know your '82 E24 ETM isn't listed, but the 533 and 733 are quite similar to your car. The E28 is virtually identical to the same year E24 with the exception of the HVAC system and a few other minor differences.

Follow that HPSI link that @1986series6 posted above, it's incredibly helpful. Test your crank and speed sensors for resistance, double-check that they're plugged into the correct harness socket, safely verify those wires have continuity back to the DME harness plug.

Be aware that 1982 was a transition year for the E24. Late '81 is when the chassis switched from the E12 platform (E24/1) to the updated E28 platform (E24/2). The early & late E24 cars look nearly identical, but they have significant differences. The other major difference was the introduction of Bosch Motronic 1.0 around the same time. Those production dates aren't the same worldwide either, so there's a lot of uncertainly. I had a '82 633CSi myself, North American market model, build date was 11/81. It was an E12 chassis with a US M30B32 running Motronic 1.0 with the later one-piece manifold.

E24 information is hard to find, but it is more or less identical to the 5-series built alongside it. I had a lot of trouble finding information about the 6er, but the 5er stuff was incredibly helpful.

[1986series6]

I found a pinout for 1.0, hope this helps.

http://e28-535i.com/upload/Montronic1.0pinout.pdf

This also may help.

Bosch Motronic 1.1-1.3 BMW explained.pdf

[CALLACI]

Thanks while I’m at it I’m gonna test to make sure everything is working as it should

[CALLACI]

Very good info I have opened up OEM ECU and noticed black burnt spots on it and smelled burnt. I proceeded to replace it with a used EBay ECU and still no luck. I will go thru the ECU pinouts and literally test every single one even if it’s not related to spark issue but because the car had not ran in years and who knows what is good or not. I will double check powers and grounds at ECU because this is where I’m thinking there is an issue. I have very quickly tested for power and I only have 1 pin with power on the ECU with key on and I think there’s supposed to be more. I did this late at night before having this pin out so I will do it properly tomorrow. Gonna keep you guys posted on what happens next. Thanks for the help already better than I would have thought.

- - - Updated - - -

I have seen burnt mark inside the ECU I have replaced it already with used from eBay still same thing.

[DesktopDave]

This info may help, although I think your 82 may be a different similar system.

https://hpsimotorsports.com/blogs/te...n-tech-article

I'm not sure if you worked through this article, he has really great shortcuts. It's an excellent guide to most of the trouble spots for early Motronics. You didn't get the number of that DME, did you? There are a few variations floating around. Some have Lambda/O2 sensors, some are for catalyst motors, etc.

Also check the ignition switch (plug under the dash), they have a tendency to burn out the contacts or get misaligned, causes all sorts of odd problems. I've taken some apart to buff the contacts.
The "code box" on later cars can also burn out a fuse or a transistor, causing a no-start situation. I'm not sure if you have an early or late car though.
I'd also recommend jumping the main relay and fuel pump relay while testing, to eliminate those components as a cause.
I'd also go through the entire engine wiring harness, it's not really all that complicated. You should be able to easily unplug it from the fusebox or probe some of the plugs, testing for wires shorted to ground or unexpected 12VDC feeds. If you disconnect it at the DME it's not all that time consuming.
Also check the ignition switch, they have a tendency to wear out in the electrical section. I've taken some apart to buff the contacts.

[CALLACI]

SO little update.. from all the help I have gathered I know Know this is a 1981 production date 10/81 and this falls into an early model production. I used the Motronic 1.0 Pinout and tested most of what I can and I noticed I have 0 power at the ECU (Pin 18 continuous power and Pin 35 Ignition power) ... this is probably my issue.. My bigger problem is I cant find a good wiring diagram for an early model so I dont know where to start... I keep reading to check the main relay I also dont know where that is. Can someone help me get an early model 1981 633CSI wiring diagram and help me locate main relay? I attached a picture of my fuse box and 4 relays (bench tested all 4) that are around it. If I can get a wiring diagram im sure I can resolve the issue. Thanks again


633 fuse box.jpg

[DesktopDave]

Seems like you're making some progress!

On some of the early cars the main and fuel pump relays are actually inside the cabin, mounted to the dash support above the DME. I can confirm that my '81 was definitely built that way. I'd just find the socket with the properly colored wires. According to that ATM, the main relay will be a 5-pin. Should have a thick red wire on terminal 30, thick brown wire on term 85, green on term 86, red/white on term 87 (fuel pump enable) and a red/blue on term 87 (DME power 18 & 35)

Use the '83 633CSi ETM for the engine wiring diagrams. All the early Motronics are the same, from late '81 up to early '87 build dates, if I recall correctly. There are some variations in the Motronic 1.0 cars, like Euro spec motors, but they're fairly small differences.

[CALLACI]

I have found the main relay and this was the issue I have replaced the main relay and my problem was solved. The main really was exactly where desktopdave said it was. Right above the ECU behind glove box. Thanks to everyone who helped so far. Car has 2 dead fuel pumps because it’s been sitting so long BUT I now have power to pumps when cranking, I have spark at the coil and injector pulse ��

[1986series6]

The in tank fuel pump will be very expensive, if you can find one.
Here is a utube, using a Walbro 255. Modification is simple to do
and will feed the high pressure pump with no problem. I did this
conversion and never looked back. The replacement pump in
this video is not a Walbro so use your own measurements to
achieve the correct results.

https://www.youtube.com/watch?v=6uogNILRt40