BMW E30: Gurus needed, electrical issue with 318

[Sven]

My 1984 BMW 318i will not start. Hell, when I turn the key nothing happens. No idiot lights, no fan, no radio. No juice whatsoever to anything. The battery is charged (@13V), and I’ve checked across the terminals. Not corroded, good connection. The car “circuit†is complete – positive lead on DMM to batt, negative to block/head/frame. I pulled all the fuses. Everything checked out.

 

Do the early E30’s still have fusible links? Where the hell are they? I’ve traced the positive cable and its branches yet can find nothing. Is there some sort of Über-relay on these things? Location? The manual only lists fuses, and doesn’t even tell what relays are what. Hmm, K1 is K1 relay. @#$!ing thanks, BMW manual writers. I started pulling relays and checking them, but it’s a crap shoot without knowing what does what. It’s maddening that this car ran before parked, now I have buyers coming over and it won’t start. Non-running tends to hurt resale value. I need to move, and this is holding me up.

 

The car hasn’t been started in several months before this, and it’s been parked in the garage. I haven’t found much of anything about this on das interweb, which surprises me because millions of these cars were made. I can find FSM's and wiring diagrams for any model year Z... but not this super common BMW.

 

Every time I started this car, it had to be jumped from sitting. I jump-started it with my SuperDuty, all 130a and 2 batteries of electrical fury. So…pretty much worst case scenario there. Maybe something fried. What should I be looking at? Keep in mind I want to spend as little as possible, because I’m selling this car for almost nothing.

 

Any help is greatly appreciated.

 

Another note to aid diagnosis: this car has the battery near the passenger firewall, not in the trunk.

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[mark]

I think these have an "imobilizer" on the ignition circuit, the last time I looked and its been a while. Check the fuses with a multimeter. One fuse of some incredibly small amperage controls this circuit. I can not even see the filiment in the fuse much less tell if it is blown.

 

If this fuse is blown, nothing happens when the key is turned. A screwdriver from the pos and neg terminals on the starter will still start the car if the key is in the on position.

 

Good luck, that is the total of my BMW electrical system knowledge.

[Sven]

Okay, POS is running!

 

After seeing a main relay mentioned, I searched through r3vlimited.com to find out where it was. I found and checked out the main relay. I bashed it but good. Okay, maybe not bashed. We'll call them happy, "I hate you damn car!" love taps. Ignition key turned and let the electrons loose like it's supposed to. Car started. The relay must have been stuck. Putting a relay in the K5 was immaterial, so I guess my car doesn't use this socket.

 

FYI: The main relay is the largest of an L-shaped block of three relays forward of the DS strut tower (the 3 relays are the main relay, fuel pump relay, and O2 sensor heater relay). You'd think the manual would have mentioned these slightly important relays, if any at all. It's frustrating to waste time on a beater car that you're selling for peanuts...

 

Yee friggin' haw. Crisis over.

 

Thanks for the assistance, it helped with my troubleshooting. After you posted, I started checking that circuit out, because it definitely fit the bill, and seems to be a common problem area. It just didn't turn out to be the problem.

[katman]

For future reference: http://www.bimmerforums.com

[Sven]

As kind of a follow up to my story, I sold the car the next day; to a Datsun guy! Turns out the kid just totalled his '79 ZX with 70k miles. We bored his dad while we ran on about Z's...

 

I felt good for helping out a fellow Datsun nut who was down on his luck, I turned a buck, and got rid of the car so I could move-without junking it. Win, win, win.