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97 BMW 540i - Starts only if driven every 24hours or so

Hi all,

I have a manual transmission 97 BMW 540i. It only starts normally if I drive it frequently. The more frequent I drive it, the more chances it has at starting up. If I leave it too long, it will be basically silent - no telltale battery low sounds on startup. I do hear some kind of servo type noise. If I try maybe 50X plus, it may start up randomly if I am lucky - the less time that has elapsed since last startup will increase my chances of the car starting. In this state if I hook it up to a battery to jump it, it does not change the behavior - same no start. All the cabin lights and accessories are strong and does not seem to be a battery issue. I am able to get the car pushed and can pop the clutch and the car will start.

I had the starter replaced about 6 months ago with the same problem and it seemed to fix the problem until recently and it is showing the symptoms above.
Could it be the starter again? or is it only a temporary fix for a different problem?

If I drive it very frequently - absolutely no issues - starts up immediately.

Thanks
Ray

All the cabin lights and accessories are strong and does not seem to be a battery issue.

Lights and accessories draw at most 20 amps from the battery. A starter can draw several HUNDRED amps to start a car. So it could still very well be the battery (in fact I think it is). A lot of people think because they have lights it can’t be the battery…You can run the lights with a 9v battery you buy at your local supermarket.

First thing to check is the battery connection. Remove and clean the battery cables. Make sure the clean the battery posts as well.

If that’s not the problem then I’d have the battery checked. Sounds like the battery isn’t holding it’s load. I doubt it’s the charging system because when you get the car running it continues to run. Once a car is running the electronics will run off the alternator. So it sounds like that’s working fine.

Thanks. I just took it to Advance Auto and they ran a battery and starter test. Battery came back good with 12.69V and 1048CCA. The starter however came back with Low Cranking Amps - Voltage was 11.64V and amps was .1A with time at 6 secs. The automated comment says starter amp draw is low with ok starter voltage. Check starter circuit for looks, worn or corroded wiring. The alternator checked out ok too.

So with this, I’m still confused - Should I get the more detailed battery test or start looking at the starter? Based on your comment, it seems like I should get the more detailed battery test?

The fact that the behavior is unaffected by jumping the car suggests that the problem is in the starter assembly. But before going there, check/clean/reattach all the connections including the battery cables and the engine ground strap/cable. It is ALWAYS a prudent first step.

The voltage does seem a bit low. If the battery is more than 5 years old, you’ll want to consider changing it.

The low current draw conbined with the erratic starting performance suggests an internal problem with the starter motor itself. Perhaps shorted windings or a bad armature sector. That reduces the field strength, reducing the current draw but also reducing the strength of the motor. And, of the dead winding or bad armature sector is where the motor stops, it can cause the motor not to be able to start turning at times. Once spinning it’d run, because the inertia of the armature would pull the assembly past the dead spot, but it still would not draw normal current.

The problem is finally fixed. The shop checked all of the battery connections, battery, and replaced the starter for the second time. This had no effect. They said the next step was to replace the EWS chip, but they also found that the car, (6 speed manual), could be started without the clutch pedal being pressed in. They found that the clutch master cylinder was leaking onto the clutch switch. Replacing the clutch master cylinder and clutch switch has fixed my problems and now the car starts without a problem. So ultimately the clutch switch was malfunctioning due to being leaked on. I can’t really explain why the car would start right up if it had been driven more recently than not, but it’s fixed!