Electrical system question

#1

I have an 87 325is. After the 1st or 2nd cold night in Baltimore, I went out to go to work and got the very slow cranking and then the battery was dead. I put in a new battery and the car cranked up beautifully (I thought all was good). Shut the car off, tried to restart it (knowing Murphy the way I do) and there was absolutely no sound from the starter. All of the power was on (radio, lights, etc…) but no cranking.

Just wondering if there is a known problem with this before I dive in with ignorance into testing electrical things.

Any help is appreciated.

Jason

#2

Jason - I would check the connections first. The + battery lead runs inside the car down the passenger side and exits on the right side of the firewall where it connects to a distribution block. Check for good connections here. From the dist. block, you will see the feed cable to the starter (big wire - 0, 1 guage. Make sure it is connected securely to starter. Also check battery ground in trunk for good connection and the other ground staps on the engine - one goes from body to top of oil pan. Check connections on starter solenoid (on top of starter). I have not see anyone with starter problems. The Bentley manual (see links) also has other starter trouble shooting info.
Ed

#3

Hard to know for sure yet, but the following scenario is possible…
Old battery died because either it was tired or your charging system was tired. I’m sure you know that the cold is hard on batteries, that’s because chemical reactions work slower in the cold. Cold is good for battery storage, but not battery use.

Then the new battery died because it didn’t have much charge to start with, because it just came from the store. You could put a charger on it and see how it does the next day.

Is interesting that the new batt powered your lights, but the starter didn’t even click. It’s possible that the starter is having a problem too, but the odds are against two simul problems. The starter needs a lot of current. The other gear less so. So it’s not impossible for there to be radio and lights, but no starter.

You might want to check the voltage coming out of your voltage regulator. I’m not sure what the spec is, but the 12V battery is really 13.8V, so it’s going to need 14-15V to charge.

Ed’s idea about checking the grounding is good too. It takes a lot of current to run the starter, so a connection that would work for a little current, can be insufficient for the higher current load.

Are you sure that the starter produced no noise at all? Not even the click of a solenoid moving? If the battery has it’s 13.8V or thereabouts, then you might try giving the starter a good whack. The starter’s solenoid might be a little balky in the cold. You should be able to hear the solenoid’s click, even if your battery is a bit low, or a ground is imperfect.

#4

My car blinked out a code when my battery was low due to the alternator’s brushes being bad. Cheap and easy fix compared to the whole alternator. Dr Herrington had what I believe was a balky starter soleniod last year at VIR that seemed to function best when whacked. :blush:

#5

Thanks everyone.

I’ll check connections this afternoon and go from there. I’ll repost tomorrow with my positive outcome (wishful thinking).

Jason

#6

my 87 iS had a funky solenoid and needed a good whack every now and then. I kept a long enough piece of rebar and a hammer in the trunk…if you ever have to replace the starter, you will find out why it is easier to whack it.

#7

With My 88is I was having intermitten dead battery too. I replaced the battery and that didn’t help much. I found that it does not charge very well at idle. About a month ago I put the new battery on the trickle charger over night and I have not had any promlems since.

I know I also need a new Starter due to the grinding sound it makes and I am will get around to it some day. :blink:

#8

The problem on my car (87 is) was the exact same. Intermittent starting issues. First reared it’s ugly head in the cold, but got continually worse. It ended up being the + battery wires running from the back to the front of the car meeting at the junction box. The DME relay was only getting power sporadically. When the starter isn’t working, throw a voltmeter on the coil, then the correct terminal of the DME relay testing for power to the starter (can’t remember which #). Then test all of the lines coming into and out of the junction block. Mine was the smaller feed line from the back of the car wasn’t providing power. Good luck. Those issues suck.

#9

No luck yet. Time to get out the voltmeter.