eta won't start

[KenC]

Spark timing is controlled by the cap/rotor and is non-adjustable. The flywheel sensor only controls fuel injector timing IIRC

It may or may not start with the CSV disconnected, depends on the ambient temp.

OK that's what I thought. I didnt think the spark timing was adjustable.

I guess it's plausible that the injectors are firing incorrectly, however, wouldn't we have had a few large backfires after all that cranking if that were the case?

[lennon]

The resistance between the two pins of the reference sensor should be 500-600ohms. The reference sensor should be a gray plug, the speed sensor a black plug.

However, usually (always?) with a failed reference sensor, you will get no spark or fuel. The ECU needs to see that signal before it sends spark/fuel signals. I suppose it's possible that the sensor is malfunctioning and making the ECU do weird things, but somehow i doubt it.

[KenC]

The resistance between the two pins of the reference sensor should be 500-600ohms. The reference sensor should be a gray plug, the speed sensor a black plug.

However, usually (always?) with a failed reference sensor, you will get no spark or fuel. The ECU needs to see that signal before it sends spark/fuel signals. I suppose it's possible that the sensor is malfunctioning and making the ECU do weird things, but somehow i doubt it.

They both read ~980ohms... but so did the other four replacements we brought with us. Are you sure about that 5-600ohms impedance?

Are they the same part? It was dark, but I think I read the same part number on both of them... and the identical impedance makes me thing that too.

[KenC]

cold compression was 150-170 on all cylinders

won't start even with a healthy dose of starter fluid in the intake... after cranking it a bunch we got one backfire out of the intake boot area

swapped ecus


still nothing... just cranks and cranks. :-/

Our next idea is to replace the coil, cap, rotor, and plugs to verify a good spark.
Is there any way to check verify correct timing of the fuel injectors???

[lennon]

i'm sorry, it was late and that was a typo.

i was reading the book, but in the motronic 1.1 section. which uses a different two pin sensor.

motronic 1, yes the sensors are the same and interchangeable. 3 pin plug. the resistance should be 860-1060 ohms between terminal 1(yellow wire) and terminal 2(black wire). between terminal 3 and 1 and 2 should be ~100,000 ohms.

your reference sensor is probably working fine. how have you tested for spark? how have you tested for fuel besides noticing the smell of fuel?

[CorvallisBMW]

motronic 1, yes the sensors are the same and interchangeable. 3 pin plug. the resistance should be 860-1060 ohms between terminal 1(yellow wire) and terminal 2(black wire). between terminal 3 and 1 and 2 should be ~100,000 ohms.

your reference sensor is probably working fine. how have you tested for spark? how have you tested for fuel besides noticing the smell of fuel?

Sounds like we're getting good numbers on the reference sensors then, good to know.

We tested for spark by pulling the plugs, setting them against the manifold to ground them and cranking the car. They did not have an even spark pattern, kind of 5 or 6 small, extremely rapid sparks and then 1 bigger one. Not at all what I'm used to seeing.

Fuel was only verified by smell and by observing fuel on the spark plugs. We didn't have a guage to test for pressure. That's the next step before doing cap/rotor/coil/plugs.

[KenC]

So we're going out there again tomorrow to replace the ignition components (coil, cap, rotor, plugs), and test the fuel pressure.

Any other ideas?

[Steven_Anderson]

http://www.youtube.com/watch?v=wHwX2wCwMq4

ITS ALIVE

[Danny]

woot

[CorvallisBMW]

No idea what was the actual culprit though.

We changed the cap, rotor, plugs and coil. Verified about 30psi of fuel pressure going in to the rail. Verified cold start injector functionality, both fuel pumps working, engine reference sensors working, AFM working, TPS working.... And it still wouldn't start. We just sat there like WTF?

Then I decided to unplug the AFM and try to start it in closed-loop mode. It got a little better, but nowhere near starting. Tried it again, and again. each time it got just a bit better. I plugged in the AFM and tried again. Still getting a little better....

After 20 or so times it cranked to life! Though it idled at 1500rpm b/c I had the ICV cranked all the way open. Oops. This engine really runs well, super smooth and pulls pretty hard for a p.o.s. eta. It helps that this car will be like 2100lbs when we're done with it :)

[M-technik-3]

So basically you threw a bunch of known parts at it and just from constantly monkeying with it it started?

[CorvallisBMW]

So basically you threw a bunch of known parts at it and just from constantly monkeying with it it started?

Ya. And this was our third trip out to try and start it. We had previously replaced the ECU and some other bits and tried for hours with no luck.

[M-technik-3]

Well it's running so that's all that matters at the moment correct. maybe the period it sat for so long that it wasn't happy and wanted to make sure you'd give it some love before it would run for you.

I had an 87 325i 4 door that did the same thing, I tossed numerous parts at it for weeks out of my spares to no avail. So I got tired of the no start and yanked the dreaded engine, tossed a warmed over M50 and sold it. Glad I didn't spend a ton of hours on it just a few here and there on it.

[KenC]

It's ALIVE! Now comes prep for 24 hours of LeMons :)

The spark quality was MUCH better after swapping in new Bosch Copper plugs and known working ignition components. I think a combination of ignition components, flushing the "old" gas out of the rail, and just cranking it a ton got it to run. I can't pinpoint anything though.