Help me with this dumb wiring

[BrandonG]

http://www.r3vlimited.com/board/showthread.php?t=193350

^ sub link

im having trouble getting the car started and iv checked a lot of things and cant find the culprit , im using a 90 m20b25 main harness plugging into a 87 m20b27 body harness ?? < can that be reason

also wat relays go here and this is pic of pc and harness

[jlevie]

My immediate suspicion, given the car and harness, is that no START signal is being provided to the DME. The 90 harness routes that signal via c101 but an early 325is (at least) provides that signal via a pigtail connector off the engine harness near the DME connector. I'd guess that an ETA would be the same. Check pin 27 of the DME connector when the ignition is on.

[Chrisv006]

Early model body harness and late model engine harness? Not all of the pins are the same. I'd post the charts but I don't have the links on my laptop.

[NC325iC]

Those relays are fuel pump, main power, and o2 heater

Aka if you haven't had them in there start there

[BrandonG]

ill take more pics 2moro i think i see wat ur saying and u gotta pic of the relays so i know wats wat :)

[NC325iC]

My immediate suspicion, given the car and harness, is that no START signal is being provided to the DME. The 90 harness routes that signal via c101 but an early 325is (at least) provides that signal via a pigtail connector off the engine harness near the DME connector. I'd guess that an ETA would be the same. Check pin 27 of the DME connector when the ignition is on.

this could be an issue as well.

I took a look at the 86 eta ETM. The start signal for this car comes directly from the black/yellow wire that connects the key switch to the starter motor. after the c101 inside the engine harness it is spliced to signal the ecu to start.

In the late model cars this is not the case, i cannot find where the start signal comes from however it is not from this same black/yellow wire.

as i am in the midst of swapping an 89 engine into my 86 ill get back to you when i find out.

[NC325iC]

jlevie does pin 27 require voltage during starting and while the car is running?

im not finding any mention of it except possibly in the power distribution section, there is a green wire spliced after c200 that holds a start and run signal to the injection electronics. it doesnt have any other connectors shown in the diagram.

edit: i found it, it does go through c101, pin 7, this is also the connection that provides power to the primary of the ignition coil. The eta body side harness provides the same signal to pin 7 as does the 325i body harness, since the connection to the dme and the ignition coil happen on the engine side of the harness this should not be a problem. however if you wish to eliminate this as an issue you could snip the wire from pin 27 on the motronic harness and connect it to the center pin of the c104 harness which is located in the glovebox, this is the wire the eta uses to control the main relay and provides the correct switched voltage for use in the dme.

[BrandonG]

so can it be a fried computer if so how can i check ?? my Buddie does chevy harnesses and he told me pulse grounds go through the body harness which is why i came to the assumption cuz the coil has power .. just cant find a ground

[NC325iC]

Did you install those relays? Because your car can't run if the fuel pump isn't running or if the computer isn't getting power from the main relay.

[BrandonG]

main relay is good and in and i dunno wer the other ones go the main problem is ther is no ground present for the coil to spark through the computer which is why im guesing body harness or the computer

[slammin.e28]

Are all your engine grounds hooked up and clean? Just my $.02.

[NC325iC]

the two orange relays go in the two spots that are on the same level, the white one (o2 sensor) goes in the lower spot.

your car wont start if all the components arent installed

[BrandonG]

ill double check grounds but i believe i measured the resistance and there all good , and ill hok up those relays and post back results .. im goin to buddies house Friday to get a body harness and computer 2 so lets get this bitch started lol

[BrandonG]

kk relays in and grounds checked still no spark :( pics of confused wires with no mates >>

[DaveSmed]

Did you ever check pin 27 for power with the key on like jlevie said?