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scottie
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Posted - Oct 22 2004 :  14:43:17   View scottie's Photo Gallery  Show Profile  Visit scottie's Homepage  Send scottie an AOL message  Reply with Quote
hmm. good point. i'm stumped. (I'm also stumped by the same problem on my own car!)

Scottie Sharpe
San Jose CA
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88 Dinan M5
1968 2002
1987 BMW K100RT
1982 Yamaha Seca 650
1969 Honda CB350
1962 BMW R69S
1995 BMW 525i
1995 Mitsubishi Montero SR


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Rob-M545i
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27 Posts

Posted - Oct 24 2004 :  02:08:53  Show Profile  Reply with Quote
here is an update to the problem:

i first used a motronic from a M535i '86. the engine started and kept running but very bad. with the smallest touch on the gas the engine stalled.

i now use a motronic from a E23 735i '83. and the engine runs verry smooth, and revs up good when i touch the gas.

there seems to be a big difference between the E23 3.5 M30 engines en ande E28 3.5 M30 engines. i don't know yet what it is.

does the normal 3.5 motronic use the knock/overpressure ECU that is in the glovecompartment?.

the only difference i know of now is that the 745i motronic has a additional ECU program for the 4hp22EH. Could the automatic gearbox give of wrog information to the ECU so that it won't run in posiotion 2? in position 3 (starting) the ECU isn't getting any info from the 4hp22 EH or from the knock controlbox?

i just keep on searching...
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scottie
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Posted - Oct 24 2004 :  10:10:17   View scottie's Photo Gallery  Show Profile  Visit scottie's Homepage  Send scottie an AOL message  Reply with Quote
There is no difference between the e23 and e28 version as far as I know.

The M535 used the euro motor, high compression, no 02 sensor. The motor should run fine with this ecu. In fact, you can pretty much use any 3.5l Ecu and the car should run, albeit not ideal.

The symptom of dying when you put your foot on it is indicative of a bad AFM, or wiring to the AFM.

Scottie Sharpe
San Jose CA
Discussion Board SYSOP


88 Dinan M5
1968 2002
1987 BMW K100RT
1982 Yamaha Seca 650
1969 Honda CB350
1962 BMW R69S
1995 BMW 525i
1995 Mitsubishi Montero SR


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My Profile
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Rob-M545i
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27 Posts

Posted - Oct 24 2004 :  13:39:06  Show Profile  Reply with Quote
the engine will start with the E28 ECU, but runs realy bad. with the E23 ECU it runs actualy very good. the 2 motronics have different part numbers, so the could acualy be a difference between them. the E28 and E23 3.5 use different injectors. this could be because the E23 has an 4hp22 and the E28 has a manual transmission.

Now I got the 745i running with the 745i motronic!!! the problem of starting and running in key position 3, and shutting down in position 2 is bypassed. I don't now yet what causes the problem but this is how i got the motronic working (sounds a bit strange maybe):

-I pulled the black/yellow wire from the starter
-plugged a loose wire onto the black/yellow wire
-plugged a losse wire onto the starter were the black/yellow wire was
- put the ignition key in position 2
- put the 2 loose wires verry shortly onto the battery
- after the engine started i pulled the 2 loose wire of the battery and the engine kept running!

i don't know yet why it only keeps running this way and not with the black/yellow wire connected correctly.

the engine isn't running very smooth. it looks like its running on only 3 cilinders. the car hadn't run for 3 years so some parts could be not working. i put new oil and spark plugs in it, they al work .
fine. when the engine runs fine the building of my M545i can begin!

thanks everybody for the help so far!
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tihuovin
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Posted - Oct 27 2004 :  03:57:25  Show Profile  Reply with Quote
The only difference between those two ECU must be the eeprom (and the code inside it). The fuel and ignition maps must be different. The reason might be, the other is for US market, the other for EURO market. Because the compression ratio is different, the ignition/fuel maps must be different too. OR, the other motronic is slightly broken.

The black/yellow wire is the wire from ignition lock and its pin 50 (black wire from ignition lock). Maybe you have something trouble with the ignition lock, hence the strange wiring.

When the ignition key is turned to position III, it feeds +12V to starter (to its pin 50, via black/yellow wire). But simultaneously, two "power saving" relays (K5 and K7 in the schematics) start to work too, taking the mains OFF from few devices. So during the crank; blower motor, rear window defogger, A/C etc. devices do not work, so the starter gets all the power possible.

When you did the "wire trick", you basically did the same thing than using the ignition key position III except all the electrical devices were working during the crank.

It is funny though, because if I do the same and do not connect the original black/yellow wire where it supposed to be, the engine idle's badly. When I do connect it back, the idle is smooth again.

I had something troubles with my previous E23 (the starter "bush bearing's" were leaking the current to ground). So few times I was forced to "jump wire" my car, in order to get it running. I had a piece of "jump wire" under the hood, the other end has the "abiko" connector (to starter), the other one did not had it (to battery + pole). And always the case was clear, the starter original wire on its original place and the engine started to run better, MUCH better.

But of course, BE EXTRA CAREFUL when you "jump wire" your car, make sure that the gear is OFF (either P or N), otherwise your car will rush forward and possibly over your foot (instep) and capture you (please, do not ask how I know [:((])

BR,
Timo

Edited by - tihuovin on Oct 27 2004 03:58:05
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Rob-M545i
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27 Posts

Posted - Jun 26 2005 :  06:51:24  Show Profile  Reply with Quote
After a few other projects I now finished building the M106 into my 86'M535i.

i changed several parts, checked the engine and everything seemed OK.
but I still got the same problem!!??!!

with the 745i motronic the engine starts, but dies emediately, but only ignition, the injection stays on. when i do the wire trick the engine wil keep running, but very bad. there is no reaction if the TPS and AFM connectors are taken off. my gues is that the motronic things its still in start-mode sow doesn,t care about these sensors.

with a 735i 83, motronic its starts and runs fine! but the knock control doesn't work, it can be disconnected without any affect.

sow i thing the problem is in the 745i ECU, the knock control box, or in a sensor that only the 745i ECU or knock control uses.
unfortunately i do not have a spare 745i on which i can try which sensors are needed to keep the engine running.

therefore my question:

does the M106 with 745i ECU run with the cempressionvalve disconnected, the knock sensors disconnected, the AFM disconnected or the TPS disconnected? and are the temperature sensors needed to keep the engine running?


P.S.: the difference between 735i 83'motronic and 86'535i motronic has become very obvious. i blew up a 86'ECU by using 535i injectors. wich are i beleve Los impendance. also AFM is verry different, 0-5V instead of 0-10V. other thing is dat '86 535i uses automatic idle control, whereas the 735i uses a bypas valve wich can be adjusted. so don't mich te compontents of those two...[2]
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Rob-M545i
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Posted - Jul 20 2005 :  12:11:19  Show Profile  Reply with Quote
problem solved!!!

swapped the ECU with one from the junkjard. same number etc. swapped the knockcontrol and ECU. now it runs, keeps running, and runs beautifull!! nice smooth and silent.

i will try to find out wether it wat the ECU or the Knock control. and than look a bit closer to the cause of this and try to fix it, ECU aren't cheap even not on the junkjard..

only when i rev the engine for approx. 1 sec (idle to 3000-4000 rpm). black smoke comes frome the exaust. is this normal for a turbo engine?, i saw some tuned turbos running a little rich with the same "problem". Or does the 745i standart engine produce no smoke what so ever?


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RaceMe
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4 Posts

Posted - Oct 09 2005 :  17:23:57  Show Profile  Reply with Quote
HI,i have a 1984 745i when i start it in the morning it runs fine when it is cold when i drive it for couple minutes the car start running rough and alot of black smoke comes out of the exhaust.when i shut it off and try to start it up again the car wont start.Any idea?
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ra0507
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Posted - Oct 10 2005 :  09:59:14  Show Profile  Reply with Quote
As you know, black smoke is a fuel issue -- running too rich. Do you have an air/fuel gauge. I am not the most qualified but you may need to get advice on setting up the AFM spring.

Rick
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aaiello48
Grease Monkey

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50 Posts

Posted - Oct 11 2005 :  16:16:52  Show Profile  Reply with Quote
Hello
Sounds to me like your motronic has gone bad...
your are right if it were the switch it would not start with the "059" motronic
I have a 745 that a previous owner had a older transmission( non EH) replacement installed for my purposes the other half of my "013" motronic is just a dead leg, however my car runs fine,despite half the ECU is not being used!
you are on the right track.. the 745 will just barely start and idle with the "059" motronic if given any gas will stall and die...
meaning to me you will need a 745i "013" motronic,sorry
They are as rare as a hens tooth.
Try asking one of the members
Good Luck
Tony
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