85 535i ECU/wire harness

[stewnmo]

first; this is my first post. second; i did try searching first . Here's the rub.....
bought 85 535i for first projet car (am learning as i go). it turns over, but no fire.
i have check all that i am aware of (fuses, relays, distributer, coil, position/speed sensors, etc.. now......
i have found voltage to the coil, but, no pulse from the coil (i would appreciate advice on where to go next). and i checked two pins on the ecu (18 & 35). as i understand, these should have power to them all the time. 18 does, 35 has power when the key is off and on accessory. when key is all the way to on....there is no power on pin 35. is this normal?
if yes, where to now,
if no, do i jumper main relay or trace wire for pin 35.......or something else. i am running out of searchable ideas.

[demetk]

First confirm that pin 86 of the main relay is getting power with ignition on. If not, find and fix or bypass the obc relay box.

Do you have a copy of the ETM for your car? Checkout page 120.

And I forgot to ask, your main relay doesn't have an 87a pin by chance?

[John in VA]

1985 Electrical Troubleshooting Manual:
http://wedophones.com/Manuals/BMW/1985% ... Manual.pdf

[stewnmo]

there is power at socket 30 and 86 to the main relay. the only way i know to check relay is to make sure it clicks on power (it does) and visually at the contact points which are clean.
it is a five pin relay with pin 87a
i do have the ETM
thanks so far guys

[demetk]

it is a five pin relay with pin 87a

That's your problem right there. LOL.

But let me be more clear, you have the wrong main relay. The ETM clearly shows a main relay with two 87 pins. These pins are normally open. The 87a pin is normally closed which is the reason the ecu powers up with the ignition off.

[stewnmo]

i am a little confused, this link
http://www.hiperformancestore.com/Motronic.htm
led me to believe socket 30 is always hot (it is) and 86 is hot with key on (it is). it didnt give me anything about 85,87,&87a. and this relay has the right pin numbers.
what steps should i take now? new main relay?

[demetk]

That link has accurate info. It just doesn't warn you about having the wrong relay and what the right relay looks like.

So what pin numbers do you have on your relay? If you have a 87a pin, it's the wrong relay. Where did you buy it from? A relay with a 87b will work but not 87a. Do a google search for "relay basics" to learn more.

[Brad D.]

SPDT


SPST


There is a small, but very important difference in relay types. Relays with pin 87a are also know as single pole dual throw (SPDT) and the kind you need with 87b is known as a single pole single throw (SPST).

[stewnmo]

ahhh, very intriguing. i work full time and go to school full time so i cant get to it till this weekend, but until then i will be googleing and researching and looking for an 87b relay. i will keep yall informed. thank you.

[stewnmo]

you my friend are a hero! on my lunch breaks i tried to find a different relay (on line and the phone), even the bmw service center in fort walton couldnt find one different for it than the 87a. however, i found realoem.com (oem bmw part numbers), which confirmed what you and you alone told me. i am a cautious person so i havent jumpered anything ti i got confirmation of the relay diagram. i jumpered it this morn and got spark, with the help of starting fluid it started right up. thank you very much. i will now proceed with restoration.

[demetk]

LOL. As you have found out the dealer is usually oblivious to these cars so you need to do your homework before ordering anything from them. The best place to get your information, on almost any subject for that matter, is right here.

One source for the relay is here: http://www.pelicanparts.com/cgi-bin/sma ... %2C%20Each

cheers