Author Topic: why did my car take a crap? (Read 9120 times)

tom d · « **Reply #15 on:** June 12, 2009, 09:30:48 AM »

The inline fuseable link is rated at 50 amps

DesktopDave · « **Reply #16 on:** June 12, 2009, 09:37:08 AM »

Wow, 50 amps to run that DME. Who knew? That's a max rating of 600 watts...my file servers don't need that much power!!

Blip Bavarian · « **Reply #17 on:** June 12, 2009, 10:18:53 AM »

Quote from: DesktopDave;73510

I'd also clean the wires with some flux & solder that sucker in with a setup like that one above. Or just use a nut & bolt with some electrical tape...idle it for a while and see if it melts. What's the worst that could happen?:rolleyes:

What are you talking about melting? The electric tape around the nut and bolt?? I have no idea what the worst that can happen is...

i've never soldered before. How easy is it? would it be worth it to buy a cheap radio shack soldering iron and do it myself???

is this the type of fusible link i need to get??
http://www.bmaparts.com/item.wws?sku=VWW004082&itempk=73400&mfr=CRP&weight=0.01

here is a 50 amp, but im not sure if this is what i need. Can someone confirm... Part # 1241-1706111
http://www.pelicanparts.com/cgi-bin/smart/more_info.cgi?pn=12-41-1-706-111-BOE&catalog_description=Genuine%20BMW%20Part%3A%20FUSE%20%2A
I would think that i just need the strip, but this second product from pelican looks like more than just the strip in the picture...

DesktopDave · « **Reply #18 on:** June 12, 2009, 12:20:14 PM »

You won't have to solder the wires right away...just strip & twist them temporarily to see if the car will start. It's just a good idea for a permanent repair. Loose wires, connectors and grounds will make you tear out your hair...if you work on old Japanese bikes, you'll understand the wisdom of this statement.

Get a cheap inline holder like this one:
http://www.tti-plus.com/8-Gauge-MAXI-Fuse-Holder-W-Weather-Cap-50-AMP-Fuse-p/tti-maxi-f8g-50.htm They're probably for sale at Advance Auto, Pep Boys, etc. Get some spare 50-amp fuses too.

Check the wire for shorts/shot insulation, etc. FIRST. Then go check for other blown fuses. Then start on replacing the link.

Pull the positive cable off the battery, cut the fusible link out, strip some wire, twist those leads together with the fuse holder, temporarily tape them up, reconnect the battery and try to start the car. Go back and check the wire to see if it's abnormally hot or the fuse is blown.

Soldering is pretty easy...there are lots of tutorials out there. It makes a really nice electrical contact, so you don't have to worry about high resistance in the wire melting or burning stuff. Flux is an acidic cleaner that provides a path for the solder to flow.

After you've fixed the problem, disconnect the battery again, pull the tape off, brush some flux on the exposed copper, heat the wire with the iron until you can melt solder into the copper, wrap it up with electric tape (or fabric tape, plastic split conduit, heat shrink), enjoy your now-running car. Double check the holder after a short test drive, carry spare fuses just in case.

I use the 15/25watt radio shack switched iron. Fine electronics need small irons. Those 50watt solder guns are a little overkill but they melt the solder quickly! Don't hold the wire for too long, copper transfers heat really well.

Finally, don't worry about getting it wrong. Just try. Sometimes you'll make expensive mistakes, but sometimes it'll work and you'll save a bunch of money. I was a kid trying to make a too-old car work with crap tools and no experience once too...old SAABs are far more difficult than old Bimmers!

Blip Bavarian · « **Reply #19 on:** June 12, 2009, 03:17:30 PM »

so i went by Pep Boys on my lunch break and picked up an inline fuse holder. Rigged it up with some electric tape, and connected the battery. Pop! the fuse popped. So i inspected the main wire, didnt see anything exposed. My car is gutted, so it is pretty easy to inspect.
I then put another fuse in, and connected the battery. This fuse didnt break. so i got in the drivers seat, turned the key to half position, and no CEL. THen i went ahead and tried to crank the car. There was a pop sound from the engine bay, and all of the lights on the dash went out.

I went to the trunk and checked the fuse. It is still in tact. got back in the drivers seat, and turned the key to half position. Still no lights at all on dash, but the light in the trunk was on. I tried to start it and it did absolutely nothing.

I guess the next step is to check the fuses and relays, to see if they are okay buyt i had to get back to work.... Any ideas on what might have happened? Or what to do next...

ps. i dont know of any way to check the main relay.. the method i used on all other relays as described above doesnt work on the main relay.

tom d · « **Reply #20 on:** June 12, 2009, 08:00:24 PM »

Quote from: DesktopDave;73516

Wow, 50 amps to run that DME. Who knew?

it fires more than just the DME. acording to the electrical troubleshooting manual it also runs the fuel pump, o2 sensor heater, fuel injectors, crank and cam position sensors, thottle position switch, idle speed actuator, and the evaporative purge valve among others.

DesktopDave · « **Reply #21 on:** June 12, 2009, 08:25:07 PM »

That's a lot of problems for the car to have. You have some big short in the harness somewhere. You might also have a bad starter...something is drawing a huge amount of power to blow those fuses. I'd start checking every inch of that wire.

twright · « **Reply #22 on:** June 13, 2009, 05:36:11 AM »

Disconnect the big wire at the starter and turn the key to start. If the fuse doesn't pop, you know where to start looking.

DesktopDave · « **Reply #23 on:** June 13, 2009, 09:47:51 AM »

I'm still trying to figure out what would have happened to cause this. The hoses you deleted are all pretty much separate from the electrical system. I'm stumped...I can't even guess at what happened.

I'd go get the e30 electrical troubleshooting manual and start from scratch. The ETM has loads of great info...and it systematically breaks the car down into systems that you can eliminate gradually. I hate that I don't have an easy answer for you here...we found the symptom but not the root cause.

Anyway, fuses blowing like that are only from overloads, right? So you only have two possible causes. Either there is a short in a wire, or an electrical component is internally shorted. That manual is around here somewhere...

After checking for any shorts, the starter is a good place to begin...you could likely take it out for testing just to be sure it's good.

Blip Bavarian · « **Reply #24 on:** June 13, 2009, 05:11:17 PM »

so, i have some new info. went through the and checked the small wire that runs from the battery positive terminal to the engine bay, and then to the main relay.

the short/problem occurs after the main relay. when i hook everything up with the main relay disconnected, the fuse doesnt blow. the second i plug the relay in, the fuse blows. the leads me to believe that the short or issue is between the main relay, and the DME/ECU.

i dont know of any way to check the ECU. Can i take the ecu to the dealer and have them check it somehow, or do i need to get a replacement and try that??

If the issue is the starter and not the ECU, wouldnt my CEL work? Also, I would think that the starter is okay since the car cranks, it just doesnt turn over. Is mine line of thinking correct??

-no fuel pump buzz
-no CEL
-no ICV buzz

DesktopDave · « **Reply #25 on:** June 13, 2009, 06:41:56 PM »

Your line of thinking sounds correct, but that wire powers more than the DME. Might not be the DME...could be any of the other components. You already tested the main relay, so I'd assume it's OK. I'd guess the old relay had an over voltage kill it, then that blew the fusible link? So I'd go check out all this stuff tom d suggested next...

Quote from: tom d;73548

it fires more than just the DME. acording to the electrical troubleshooting manual it also runs the fuel pump, o2 sensor heater, fuel injectors, crank and cam position sensors, thottle position switch, idle speed actuator, and the evaporative purge valve among others.

I'm thinking I'd pull those connections except the DME, then short the main relay socket with an inline fused wire from 30 to 87. The car won't pump fuel without a signal from the CPS, but if the fuse is good, re-connect them one by one. You'll be able to find out where your trouble is that way.

I went out to look at that wiring harness going from the small positive wire...looks like it goes to a lot of places. The electrical troubleshooting manual is your friend...

Blip Bavarian · « **Reply #26 on:** June 13, 2009, 08:47:01 PM »

i dont know how to test the main relay. I attempted to test it by applying 12v to it, and then checking continuity from 30 and 87. For some reason it doesnt work. The relay doesnt click or show continuity. I tried this on a brand new relay that had never been plugged in. It didnt click or show continuity.

can someone point me in the direction of the electrical troubleshooting manual. This is the first i heard of it. i did a search, and didnt get much..

so i now realize that that cable controls more than just the DME, but, i think i read somewhere on here that the only thing that would keep the CEL from lighting up is if the DME is not getting power. if the issue was not the DME, and was one of the other parts such as the fuel pump, wouldnt the CEL would work, and wouldnt i be able to perform the stomp test..

thanks for the help DD

DesktopDave · « **Reply #27 on:** June 13, 2009, 10:13:19 PM »

http://www.m42club.com/forums/showthread.php?t=7748 That page points to the hosted page http://www.mediafire.com/?kyzmz0yedr0

Yeah, you're right...if you apply 12v to 85-86 you should have a click and continuity from 30-87. Some relays need large (>0.5amp) current to close, so small batteries won't work. Alternately, you can just jump 30-87 on the relay plug to remove the relay as a problem.

You're right about the CEL too. Unless the bulb is burned out, the light will come on every time the system initializes. In your case, I suspect the relay is burned out, or carrying too much current, and the DME never gets a chance to start. So no CEL.

It remains to be seen if we're really helping...but we're here for you.

Blip Bavarian · « **Reply #28 on:** June 15, 2009, 10:32:36 AM »

thanks for the help DD,

i am going to try an eliminate the different options that the main relay connects to. To do this do i simply unplug all of the sensors that relate to the main relay (fuel pump, o2, ICV, etc..) then connect power to the battery. If the fuse blows, then it is definitely the DME. If it doesnt, then it is one of the other accessories that relates to the main fuse. Then i would plug a sensor back in one by one, and when the fuse blow, then that accessory is the problem?

Is the the correct way to disconect each of the accessories just to unplug the sensor that relates to it? Or is there another way that i disconnect them?

DesktopDave · « **Reply #29 on:** June 15, 2009, 10:58:49 AM »

It's not that easy, but you have the right idea. You can eliminate the sensors systematically that way. It's not perfect because it won't allow for the wiring runs, but it'll let you narrow things down to one misbehaving component. That's how I'd go at it anyway.

So, like you said, find out everything that gets power from that wire and unplug those components. If the fuse blows it's either the DME or the wiring harness. If not, plug things in one at a time until you blow the fuse.