Oddball starter issue— Owned 7 E34's never had this one...

[laine34]

Rebuilt original starter (with 110K original miles) runs for 2 seconds then stops—every fresh key turn. Yep this California car only has 110K. The battery is brand new Bosch AGM as well.

Motor starts fine, except morning first starts—which now takes 2 separate key turns, thanks to the fact that the M30 is in great tune. But if it wasn't, then ooooof....

Car is a manual '91 535 which doesn't have a starter relay like automatics. The relay is just a jumper wire in the typical yellow plastic relay cube.

I pulled the fuel pump fuse to get a good taste of the cranking behavior—2 second cranking then the starter winds down.

Starter sounds strong and healthy—for 2 seconds.

Anyone know of any electrical gremlins for this, or is this just a bad starter? Perhaps the new starter solenoid is failing???

Figured I would chime in before spending precious time pulling a fresh starter.

Calling all E34 heads!

[theBMWbeast]

Did you just install the starter? Rebuilt by whom? I would tap on it and see if the starter is stuck. If it cranks for more than 2 seconds after that, there you go.

[cirrusblau]

Check the ground wire from the engine mount to the body underneath the air box. I also had a weak starter with my E32, and it turned out the ground wire was not making good contact to the body. Another sign of this is a lower alternator output (around 12.5~13V) to be seen on the OBC Test 9.

[moroza]

Bad starter is slightly more likely than a bad power or ground connection, but the latter is easier to check.

My rule with starters: ff it takes more than five minutes to install one, bench-test it first.

[ross1]

I'd be looking for loose or corroded connections, which would heat up under load and further increase resistance. The results of a load test while cranking would be interesting. EDIT: "starter winds down" it slowly loses speed? What happens if you re-try immediately? If you wait a bit? if problem is concurrent with "new" re-man starter, I'd be looking there

[TheStigg]

I had problems with a rebuilt e34 m30 starter that worked intermittently a few weeks after installing. It ran fine on the bench but was intermittent in the car under load. I could see arcing at the screws on the end plate. I removed the end plate, tapped the threads for the next oversize, cleaned the contact surfaces and coated them with Aerodag and used new larger screws with lock washers. Fixed it . . . until the solenoid died a few years later.

starter1.jpg

starter2.jpg

[zubbie]

Rebuilt starters and alternators can range from great to awful. Weird problem nonetheless. The starter draws a large current. Running for a few seconds then stopping hints at something in the circuit heating up and opening. Ground or relay or solenoid would be my guess ( or dead battery?)

[bagekko]

An E34 can have an AGM battery? Doesnt AGM need a slightly different charging system I would think the E34 pre-dated that.

[moroza]

An E34 can have an AGM battery? Doesnt AGM need a slightly different charging system I would think the E34 pre-dated that.

That's a good question. I don't know, and I'm on a quest of, so far, about an hour and a dozen browser tabs to get to an answer.

[bagekko]

That's a good question. I don't know, and I'm on a quest of, so far, about an hour and a dozen browser tabs to get to an answer.

Aside from the below there is conflicting information on if an alternator not designed for an AGM battery can cause issues or damage to the battery. Older charging mechanisms can not get accurate readings from an AGM battery supposedly. I dont think there is any benefit to having an AGM battery in an E34, only see potential negatives.

You can use your regular battery charger on AGM or gel cell batteries.
False. These batteries like to be charged slow and low. Many AGM/gel cell battery chargers have microprocessors that collect information from the battery and adjust the current and voltage accordingly. Some have different settings for charging flooded, gel and AGM batteries. Overcharging can kill these batteries. Also, alternators are not chargers. Don’t rely on an alternator to do the work of a *charger. If a battery is discharged to the point that it cannot start the vehicle, use a charger as soon as *possible to make sure the battery gets fully charged.

[moroza]

That info pertains to wall chargers, not alternators.