Datalogged my "run on" problem - car wont turn off

Jon k · Post by **Jon k** » Sun Jul 09, 2006 11:15 am

I datalogged the car today with both just the ignition on, and then with the motor running.

With just the ignition on, the unit comes on and when I remove the key "connected" goes out in MegaTune instantly and that's that. The datalog shows that there is no weird voltage fluctuation or anything.

With the motor running, the car runs and when I pull the key out right around 21 seconds of running. The RPM goes form a nice 700/800 idle reading on the datalog to 600, 500, 400, 300, 400, 300, 400, 200, etc etc etc... and it idles BADLY at that low RPM. The battery voltage drops off too from 13.5v idling around 700/800, to 12.9 as soon as I remove the key, all the way down to 12.4 when it FINALLY shuts off.

Does this look like the alternator feedback issue people are having? I cannot get to the wire that feeds the "charge indicator" on the cluster so i want to avoid removing the cluster if it may be somehting else?

I have MS connected to the main relay as well as the coil packs and wideband controller connected to the main relay.

Post by **jsmcortina** » Sun Jul 09, 2006 12:57 pm

Either remove the thin wire to the alternator (not the thick one that goes straight to the battery) or if it is a single multi-plug then remove the plug and drop the belt too. All of my manuals say "never run the alternator unplugged"

James

Jon k · Post by **Jon k** » Sun Jul 09, 2006 2:39 pm

jsmcortina wrote:Either remove the thin wire to the alternator (not the thick one that goes straight to the battery) or if it is a single multi-plug then remove the plug and drop the belt too. All of my manuals say "never run the alternator unplugged"

James

Checking the alternator out to see what the wire situation is - the battery is under the rear seat on this BMW so its hard to tell exactly which is going ot the battery. Also, what do you mean by drop the belt? I think you mean run the car without the alternator to see if I have the same prob with the alternator not generating, am I correct in thinking this?

Post by **jsmcortina** » Sun Jul 09, 2006 3:25 pm

It should be pretty obvious at the alternator. One wire carries say 60A the other less than 1A.
Drop the belt means take it off. You can drop it on the floor if you like.

James

Jon k · Post by **Jon k** » Sun Jul 09, 2006 5:17 pm

jsmcortina wrote:It should be pretty obvious at the alternator. One wire carries say 60A the other less than 1A.
Drop the belt means take it off. You can drop it on the floor if you like.

James

Its an S-belt so I'd have no water pump so I think I will avoid that for now.

Post by **jsmcortina** » Mon Jul 10, 2006 2:15 am

What's the worry? An engine will run safely (for a few minutes) with no water.

James