What's the chance I fried the ECU before my first test run?

T

tomcolitt

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I had a dead battery just before I was going to try the Motronic 1.3 conversion and in the dark, I hooked up the battery charger backwards (that ruined a few cells in the brand new battery). Now, I'm wondering if it might have fried the ...179 as well. Here's why. I have power at both relays (good relays), but they don't switch it through to the fuel pump or the injectors. It seems like that could mean that the ECU isn't providing the ground connection for the relay to switch (no clicks from either relay, even though the 5 pin main relay has power at 3 out of 5 terminals)?

Another odd thing: The ICV hums even when the ignition switch isn't on. Just from the constant 12V going to that bundle of red power supply wires in the engine harness. (possibly also something to do with the ECU, as the only other parts that can switch any power would be the relays)....

I think Don will probably be the first to answer, but I didn't want to presume that he always has time to answer every question, which is why I posted publicly (Even though I hope he does :-)...
 
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More clues

I just found a schematic that shows the 55 ECU pin allocations for the 1.3 and in particular it seems the following would be needed in order for the main and fuel pump relays to get their switch signals. There is a main relay driver at pin 36 and an OS relay driver at pin 23 (don't know what OS stands for except maybe operating system?). Then there are also these: pin 2-ignition earth driver, pin 3-earth pump relay driver, pin 14-earth injector driver. I'm not exactly sure which of these is triggered as soon as the dark green wire to ECU pin 1 gets 12V and which aren't triggered until the engine (speed sensor?) is running, but some of you guys hopefully know the answer to this.

Thanks, Tom
 
It's a bit of a mess...
Switched Power to the ICV, fuel relay, purge valve, fuel relay is shared to the injectors from pin 87 at the main relay.
Test for B+ at ICV pin 2, Fuel injectors and main relay pin 87 and fuel relay pin 86 which are all red/white wires.

As you thought, the coil, injectors, fuel relay and main relay are all controlled by grounds and not B+ for the Motronic 1.3
It's only a guess but possible you fused the brown orange shield to B+ in your harness.
You could pin it out or you could connect 110 volt house ac to the green/red and brown/orange wires and look for the puff of smoke.
Bottom line I would toss the harness- too many shields on grounds on hots to play with.
 
There is no connection at pin 23 for the motronic 1.3 55 pin connector for the 179 ecu.
You are welcome to call me tomorrow!
 
2, 14 and 24 are common ground to chassis

16, 17, 1, 3, and 36 are switched ground from the ecu
 
Thank you Don

I'll do some measuring tomorrow first and if I can't figure it out, I'll give you a call. Meanwhile, there seem to be some discrepancies in the available literature, which is why I had hoped to find a reliable wiring diagram with wire colors to help (the one you had posted was hard to read clearly, even when I completely zoomed in). I am attaching the schematic by Equiptech, that shows that pin 23 OS driver which I found on another BMW site. For that matter, why is the maximum voltage listed as 1.25V? And what does nbv mean?.... (Duh. I just figured out that OS probably means oxygen sensor relay which, as I understand was incorporated with the fuel pump relay on my 1.3 harness, so apparently there are different 1.3 configurations for different models or brands of cars and this schematic is slightly different from the others?)...

Also, remember when you said to take the tachometer signal off terminal one from the coil or pin one at the ECU? Well then, what is pin 6 in the Equiptech schematic? (I'm not being a smart ass, just pointing out another odd thing. I just always like to try understand questions that come up, so I know what's what)...
 

Attachments

sfdon said:
It's a bit of a mess...
Switched Power to the ICV, fuel relay, purge valve, fuel relay is shared to the injectors from pin 87 at the main relay.
Test for B+ at ICV pin 2, Fuel injectors and main relay pin 87 and fuel relay pin 86 which are all red/white wires.

As you thought, the coil, injectors, fuel relay and main relay are all controlled by grounds and not B+ for the Motronic 1.3
It's only a guess but possible you fused the brown orange shield to B+ in your harness.
You could pin it out or you could connect 110 volt house ac to the green/red and brown/orange wires and look for the puff of smoke.
Bottom line I would toss the harness- too many shields on grounds on hots to play with.
Click to expand...


Hey Don, do you make house calls ??...to OZ ! :)
 
Sorry- your mains are run at two forty. Too confusing!
 
#6 at the ecu is for tach- just not our kind of tach.
#51 is also engine speed - but this one is to the tranny ecu
 
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Also- send me a pm with a email addy and I will forward a higher res schematic.
 
There is a perfectly good tach wire in the 1.3 wiring harness- located in the diagnostic plug.
It is hard wired with shielding to the coil
 
Man, those things run smoothly right off the bat!

I'm still not quite sure what happened, but after getting a nice wiring diagram from Don (where we realized that I may have a wiring harness for a 150 ECU, which uses slightly different wire colors) and a few hours of checking all sorts of wire and pin connections, I found that, on the 1.3 harness, there is a second green power wire for the ignition input pin27 on the ECU, which, on the 1.0, is incorporated together with the coil terminal 15. I fixed that problem, but still every terminal of the main and fuel relays, as well as both sides of the injector connectors were hot where they weren't supposed to be even with the ignition switch off. Even the ICV was humming, even with no power from the ignition switch which is supposed to turn on the ECU! It was hard to believe. I finally had the courage to plug in another ....179 ECU but it still wouldn't switch the relay to ground triggers or turn off the ICV. I kept fiddling some more and all of a sudden, the relays did what they were supposed to and the ICV turned off and on again when I turned on the ignition switch. I connected the ignition coil to start the motor for the first time and got a huge backfire. I had the distributor 180 degrees out of phase. Fixed that and the engine started right up and ran very smoothly. Pretty impressive for a Frankenstein engine from the recycler, with an L-jet manifold and 3.0 CS distributor. I added coolant and went for a test drive. It seems like it won't rev up past about 1500 rpm when it abruptly falls flat and backfires unless I back off again. It seems like the AFM should be responsible for that rpm range. Maybe it was damaged by the backfire? To top it all off for today, I swapped the previous ECU back in and it performed exactly like the replacement, so it looks like it had been ok all along.
 
Final Words

I just wanted to make one more post to thank Don again for your quick and helpful replies and Doug DeCoupe for sending me a complete injection manifold in time so that I didn't have to use the one off of my other car.

I also wanted to share some things that may help others. Some of the following may already be known by some and maybe I can add something new as well.

Today, I found the reason for the major and instant drop in power and backfire was a timing issue. it looks like setting up the distributor in the same way as on a conventional engine isn't close enough to bring the Motronic within firing range of its respective cylinder. After a little adjustment there was still some jerking every now and then and after a few more degrees of turn on the dizzy things are running perfectly. Amazing how smoothly a Frankenstein engine, straight from the wrecking yard can run. I can't say it's nearly as powerful as my "dirty" Euro motor with 1.0 Motronic which I first installed into my Coupe in 1989 while still living in Berlin, when I don't think many others were doing these conversions yet. When I went on the internet to find information then, I found as good as nothing.... Now, get to post a question and get an answer within hours from all parts of the country and the world.

If you want your 1.3 conversion to look as stock to a CSi as possible, I found that using a "normal-looking" 1.1 ignition coil with the 1.3 harness and ...179 ECU works fine, even though I had measured a higher secondary coil resistance on the new-fangled style 1.3 coil. The harness I used just allowed for enough length to mount the coil using the stock mounting holes near the right front. Also, out of curiosity, I compared a 3 bar fuel pressure regulator with a 2.5 bar. Obviously, the reduced fuel injection amounts should result in reduced power, but simply driving them one after another, you couldn't tell. This might help someone out who doesn't have a correct 3 bar regulator handy.

Today, I took a closer look at a late model (late 80s ;-) 735i and it looked like the main and fuel pressure relays were mounted inside the computer "safe" by the firewall and it also looked like the harness could be long enough for use on a Coupe. I can't remember where the harness came from, that I just used, but the relays were close to battery tray in a Coupe and if anything the portion of the harness that goes into the glove box was too long. I kind of like the idea of having the relays inside the glove box along with the ECU. Does anybody have any experience with this or comments?.... For that matter, why did we stop at Motronic 1.3? Isn't there a Motronic with a MAF sensor off a 90s 325i that will work too? I like the idea of using BMW components...

Thanks, Tom
 
One more issue with the starter

There is one thing that I'm having trouble with, which someone hopefully has an answer for. I've been reading about trouble with starters from B35 engines not matching b34, etc. I have a flywheel out of the original M30 Coupe engine on a M30B34 engine (yes, with a 1.3 Motronic and L-jet manifold and CS distributor)...

When I go to start the engine it seems like it has trouble engaging. The starter will spin and try to engage with the flywheel, but makes quite a few metallic noises that sound worse than normal. Sometimes, when the engaging is not successful, it seems as if the pinion wants to engage just as you let off from the ignition/ start position. It seems it works best when one aggressively holds the key in the start position, I'm just not sure how long that procedure will hold up without something giving out and I'd rather not have to take the flywheel out again....

Does anyone have any ideas?.....
 
Been using b35 starters on b34 engines for years with no problems.
You might want want to disassemble the starter and clean it up.
 
If you don't mind non original then consider the Bosch SR 441 starter - more torque and less weight.

Otherwise, I have a locally rebuilt OEM starter you can have for free but then remember where I live.
 
Thanks guys. I have a bunch of starters myself. I just was not in the mood to take a look at what the issue was yet,after all sorts of things that didn't go as smoothly as I'd hoped on this job. You know how sometimes a noise just goes away and I still have a bunch of tidying up to do on this one before I look further into it.
 
Always test a starter problem with a home run wire to battery.
Ignition switches and bad connections are a lot easier to replace than
a starter
 
tomcolitt said:
I just wanted to make one more post to thank Don again for your quick and helpful replies and Doug DeCoupe for sending me a complete injection manifold in time so that I didn't have to use the one off of my other car.

I also wanted to share some things that may help others. Some of the following may already be known by some and maybe I can add something new as well.

Today, I found the reason for the major and instant drop in power and backfire was a timing issue. it looks like setting up the distributor in the same way as on a conventional engine isn't close enough to bring the Motronic within firing range of its respective cylinder. After a little adjustment there was still some jerking every now and then and after a few more degrees of turn on the dizzy things are running perfectly. Amazing how smoothly a Frankenstein engine, straight from the wrecking yard can run. I can't say it's nearly as powerful as my "dirty" Euro motor with 1.0 Motronic which I first installed into my Coupe in 1989 while still living in Berlin, when I don't think many others were doing these conversions yet. When I went on the internet to find information then, I found as good as nothing.... Now, get to post a question and get an answer within hours from all parts of the country and the world.

If you want your 1.3 conversion to look as stock to a CSi as possible, I found that using a "normal-looking" 1.1 ignition coil with the 1.3 harness and ...179 ECU works fine, even though I had measured a higher secondary coil resistance on the new-fangled style 1.3 coil. The harness I used just allowed for enough length to mount the coil using the stock mounting holes near the right front. Also, out of curiosity, I compared a 3 bar fuel pressure regulator with a 2.5 bar. Obviously, the reduced fuel injection amounts should result in reduced power, but simply driving them one after another, you couldn't tell. This might help someone out who doesn't have a correct 3 bar regulator handy.

Today, I took a closer look at a late model (late 80s ;-) 735i and it looked like the main and fuel pressure relays were mounted inside the computer "safe" by the firewall and it also looked like the harness could be long enough for use on a Coupe. I can't remember where the harness came from, that I just used, but the relays were close to battery tray in a Coupe and if anything the portion of the harness that goes into the glove box was too long. I kind of like the idea of having the relays inside the glove box along with the ECU. Does anybody have any experience with this or comments?.... For that matter, why did we stop at Motronic 1.3? Isn't there a Motronic with a MAF sensor off a 90s 325i that will work too? I like the idea of using BMW components...

Thanks, Tom
Click to expand...

I don't think any of the later Motronic systems were based on dizzy ignition systems like our cars. Everything immediately later (M50, M60, M40) went to coil-on-plug.

The only Motronic + distributor + MAF combo I can think of is with the E34 M5, which I think was Motronic 1.2. The MAF is extremely expensive in that setup. I think the E30 M3 uses the same setup, but since that is a 4-cylinder, that is a no-go.
 
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