WTF Black Box

[SoopaGhetto]

That would suggest a problem with the main relay, fusible link, timing reference sensors, or ignition switch. The lights remaining on could be a weak alternator or ignition switch. Either could be caused by high resistance connections in the primary power circuits or a weak battery.

fusible link? would cleaning the contacts help out? im just trying to get a list of things together to check on the weekend aside from the above mentionables.

[SoopaGhetto]

well i checked the fuseable link in the trunk. I didnt peel back the plastic on the actual link, but feeling it seems to be solid. is the entire rectangular black thing a fuse? if so that thing is huge and is not broken. is there another link somewhere?

[SoopaGhetto]

so did the same thing today. after i got it started i decided to check some things since i have time now.

the cap and rotor definitely needs to be replaced. there was a build up of black stuff (carbon?) prolly 2mm thick on the cap terminals. for the rotor, the contact was blacked up as well and there wasnt a lot of strip of copper tip. like probably 0.5mm. but i cleaned up all of that. seems to be running better. idles the same, but part throttle/wot pulsation is minimal even with the o2 sensor attached.


I still dont see this as a fix to my no start. when i my car didnt start, i jumped the fuel pump and put in another relay for the main relay. still no tach reading. put everything back. cranked for another 10mins and finally started. which leads me to believe maybe a bad dme???

[SoopaGhetto]

new problem today.

Same crap, would start fine, drive, park, come back and no start.

after multiple cranks with no start, waited 3 hrs and decided to check crank sensors and for more vac leaks. put everything back together and car starts up wonderfully. at this moment im pissed and decided to look for more things to check.

i started checking relays while the car was on. I pulled the white relay (in the three relay group -> white, fuel pump, orange) i dont know what it was and it made the car immediately shut off. i think it was the main relay??

after plugging it back in, i went to restart the car and the battery doesnt have enough juice to crank any more. not even 10 mins before the battery cranked the starter over with ease.

What is that white relay, and can a battery crap out in a short time like that? the car is able to be jumped easily and the battery light is not on.

i tested voltages and the battery has a good 12.45. also at the engine bay terminal its 12.45. at the relays, when high all time its 12.45.

this doesnt mean that the amperage is good. i cant test for that or ill blow my meter. I also notice that the battery was discharging slowly (12.30, 12.29, 12.28 etc etc) when i attached the negative/ground. i dont believe i have a short...

i dont know if the hard starts and wack battery are related. i would think the starter would be fucked up from the repeated starts. Or maybe i shorted something out when i pulled that white relay...but that doesnt make sense. all i was doing was removing a necessary signal so the car should just die out not short. Maybe that final start killed the battery?

im going to get that battery tested in an hr or two. rotten egg smell means death right?

this search thing is hard, and i fuckin hate this haynes!!!!!

help!!

cliffs:
-what is that white relay to the left of the fuel pump relay and the orange relay to the right?
-could a battery completely fail within 10mins after having really good cranking/starting?
-are hard starts/pulsing and a fucked up battery related?

[jlevie]

12.45v would represent a battery at a bit better than 75% charge. That should be enough to start and run the engine, provided that the voltage doesn't drop significantly when cranking. A bad battery may show that under no load, but the voltage may drop a lot under load.

The color of the relays means nothing. If in the factory configuration the once closest to the bumper is the main relay, the one in the middle is the fuel pump relay and the once closest to the firewall is the O2 heater relay. But since the relay sockets clip into the holder thaty could have been moved around. Check the wire colors against the wiring diagrams (see http://wedophones.com/BMWManualsLead.htm) to see which is which

[SoopaGhetto]

12.45v would represent a battery at a bit better than 75% charge. That should be enough to start and run the engine, provided that the voltage doesn't drop significantly when cranking. A bad battery may show that under no load, but the voltage may drop a lot under load.

The color of the relays means nothing. If in the factory configuration the once closest to the bumper is the main relay, the one in the middle is the fuel pump relay and the once closest to the firewall is the O2 heater relay. But since the relay sockets clip into the holder thaty could have been moved around. Check the wire colors against the wiring diagrams (see http://wedophones.com/BMWManualsLead.htm) to see which is which

very good point, which was evident when starting. all lights/radio were working, but would reset once i attempted to crank.

I took the battery to advance auto, they couldnt get a good reading because the battery was so low on voltage. Waited 35mins for a charge and the battery wouldnt hold one. getting another one tomorrow.

i think this is a little far fetched...but could this cause a hard start issue? there has been times when i started the car, but all the cluster lights were still on til i reved up a little bit. Could this cause the pulsation? Higher load/rpm, the alternator shorting out cuz of the battery?

[SoopaGhetto]

replaced the battery; the two starts that happend today were flawless...we will see if it keeps up. in the mean time, still hesitation blah blah :yawn:

[SoopaGhetto]

what exactly does the front crank sensor do (b27)? Ive read detects tdc for start up and ive read also its a reference sensor for ignition...but then i have those two more sensors on the flywheel. which is responsible for what exactly?


I notice the crank sensor was gapped to about 3inches. Now ive worked with megasquirt and seen other sensors and the gap is supposed to be no larger than a few mm. could this cause a no start problem? or am i completely wrong in everything?

[SoopaGhetto]

could heat impact the functionality of the dme? today has been cooler than previous days and the car is actually running good. still stubbles with the o2 sensor but accel is awesome. coolant temps still the same...

[SoopaGhetto]

blah

[SoopaGhetto]

well after about 20 dayz and no "no start" problem, i pass the issue off to being the front crank sensor. the gap was too large; i guess the car even starting was a fluke at the time. starts up fine every time now (knock on wood)

still hitting that brick wall though; could the engine driven fan cause problems at high rpms? The clutch is locked so it's always engaged regardless of rad temp.