2.7i swap crank/start/run issues - RESOLVED

[lateracer]

DME shouldn't be humming. ICV should be, but not DME. You should try and get your hands on at least two or three good DMEs so you can eliminate it as a problem source at times like this.

Other than intake leaks, check for cracks in your CPS wire. I know you said fuel pressure was good, but did you check it while the motor was sputtering? When my high pressure pump died the car idled fine, but once the revs went much beyond 2.5K the pressure would drop as the pump struggled to keep up.

[NigelStu]

Finally got a chance to get to a local parts-yard and picked up a spare DME (525), AFM and TPS. Also installed an inline FP gauge (those little summit ones are pretty nice, especially for $18!)

Turns out my no-rev issue ended up being the AFM.



Both DME's seem to run the car about the same, although the 'buzzy' 153 has a bit of a lopey idle. FP is in spec range throughout rev range (have not driven under load yet).

Simple as plugging in the new AFM - started up quicker, sounds healthier at idle revs up like she should! Sounds sweet to my ears! The run issues are finally taken care of and the car can now go to the cage shop.


I've updated the first post with this info also, hopefully it can be of use to someone else along the way.

[nando]

you won't get power to 37 with the ECU disconnected, and you won't be able to trigger the main relay either.

this is how the start circuit on Motronic 1.1/1.3 cars works:

pin 18 is constant 12v. the ECU waits for a signal from the ignition switch (pin 27). When it sees that, it grounds the main relay (pin 36). When the main relay is energized, it powers up the ECU (pin 37).

So if you're not getting anything from pin 27, you need to start at the ignition switch.

I know you've already figured it out, but I wanted to clear that up.

[NigelStu]

Good info ad Nando - I didn't have that issue, but someone else might, and now they have a path/method to troubleshoot.

To help others on this - how DO you check for power at pin 37 with the DME connected?

[Frye]

You would be correct, if the car is wired as equipped with an OBC, it will not start if the relay box is unplugged.

Time to thank the Bavarians.



In this pic in the lower right hand corner, C104 is disconnected. Follow the body side harness to the upper left hand corner... Kinda looks like another C104 right?

It is actually that easy, thats all the OBC anti-theft harness is. Switch the plugs and you are good to go (and sell your uncut 13 button harness to recoup a little $)

Could someone explain this a little better to me please? I am trying to eliminate my OBC but do not understand what I should plug in to my C104 ECU side.

[ForcedFirebird]

You would be correct, if the car is wired as equipped with an OBC, it will not start if the relay box is unplugged.

Time to thank the Bavarians.



In this pic in the lower right hand corner, C104 is disconnected. Follow the body side harness to the upper left hand corner... Kinda looks like another C104 right?

It is actually that easy, thats all the OBC anti-theft harness is. Switch the plugs and you are good to go (and sell your uncut 13 button harness to recoup a little $)

My 10/85 2.7i swapped car has this c104 off the main DME harness unplugged and runs fine and the OBC works when those wires are connected. It's my understanding the driveway protection will not work unless the third wire is connected in the glovebox, haven't confirmed this though.

[ForcedFirebird]

Did the engine harness come off of a 88 or later car? If it did it won't have the C104 connector that routes the start signal to the DME and the tach & econometer data from the DME to the cluster.

Early cars route those signals from the body electricals to the engine harness via C104. Late I/IS cars (from 9/87) route them through C101. If you don't have a harness from a 9/86-8/87 I/IS, there are two possible fixes. One is reroute the wires to C101 and the other is to graft a C104 connector to the engine harness. You also need to make sure that the body side pin 20 of C101 isn't grounded when using a late harness. If it is the harness will smoke when the main relay closes. Grafting a C104 onto the harness is lots easier than adding those wires to C101.

I have heard of this, but yet to experience this wire. In my 10/85 car (round c101 body harness) I have tried early and late M1.3 harnesses without issue. The car even runs with the c104 left hanging even though it's OBC equipped. There are a lot of variations of wiring in the e30, they all have to be paid attention to when doing swaps.

[nando]

I have heard of this, but yet to experience this wire. In my 10/85 car (round c101 body harness) I have tried early and late M1.3 harnesses without issue. The car even runs with the c104 left hanging even though it's OBC equipped. There are a lot of variations of wiring in the e30, they all have to be paid attention to when doing swaps.

that's because early M1.3 harnesses (and M1.1 in '88 ) don't have power running to pin 20.

there really aren't many variations in the 1.1/1.3 harnesses with only a C101 either, basically the only things that change are pin 6 and pin 20.

[ForcedFirebird]

that's because early M1.3 harnesses (and M1.1 in '88 ) don't have power running to pin 20.

there really aren't many variations in the 1.1/1.3 harnesses with only a C101 either, basically the only things that change are pin 6 and pin 20.

Do you know when the dividing year was? My 10/88 325i has no pin in 20 on the body side like the 86es. The 86 has a 89 harness and 173DME, same with the 89i - both having the round injector harness splice.

[nando]

it's by build date, somewhere in '89. basically I think it changed when airbags came out.

[ForcedFirebird]

it's by build date, somewhere in '89. basically I think it changed when airbags came out.

You have me curious now. We put a 1/90 engine/DME and harness in the 2002 and only hooked up the wires needed to make it run in another chassis which were 1,6,7,13 and 18 (alternator, ignition, ignition, fuel pump and B+ start respectfully).

[nando]

pin 6 and 20 don't have anything to do with the engine. :p

[ForcedFirebird]

Right, but it was from an OBC car. Sorry, two thoughts at once lol.

[amcink]

You would be correct, if the car is wired as equipped with an OBC, it will not start if the relay box is unplugged.

Time to thank the Bavarians.



In this pic in the lower right hand corner, C104 is disconnected. Follow the body side harness to the upper left hand corner... Kinda looks like another C104 right?

It is actually that easy, thats all the OBC anti-theft harness is. Switch the plugs and you are good to go (and sell your uncut 13 button harness to recoup a little $)

If I read this right, I just need to swap both of these plugs and connect back the OBC relay and then the car should start (if the OBC relay is the problem) but then the color of the wires of both plugs (males) will nt match with their female sides but it is ok correct? See photo

[amcink]

It started !!!!

OK I swap the connectors per your directions (as per the sketch above) and it started.

Well, after all the OBC harness was the culprit I re-plugged the C104 with the recommended set up and it started I also double check my main relay and change it to one that has both 87 since i had the wrong one that is one 87 and one 87A.

Now what is happening is that you need to be maintain the ignition switch on (hold it while starting the car) and continously pump gas to have the car run but once you let the switch go it dies.

I will keep on trying and maybe it needs to have steady fuel (since the car had no fuel on the rail sicne I took the intake manifold and the rail off for a major cleanup and paint and i had done a TB replacement therefore i need to do a bleed of the system also)