roger 04 rt
New member
Test #2 eliminates voltage drop in the connections and cable from bike Battery(+) to the starter.
As well, it adds a huge secondary current source, yet we still see a 3.99V drop.
For that reason, I say the starter is drawing too much current.
PS: I love the way you go about collecting data.
I'm on track with you except that I know I've been undercharging the battery for a year and a half according to the info from GSAddict. So I'm going to get a proper charger later this week, cycle the battery according to the Odyssey specs and see how it does. Since I've already serviced the starter twice, once with the planetary gear cover arcing on the armature, I will likely get a new starter anyway. But I've remained curious about why the voltage dip leads to the slow, lean start.
I ran another test this morning to see if I could out why the dip causes the problem: lights bright, starter turning over quickly but slow-start and lean afterstart condition. Yesterday I separately powered the the Motronic with no improvement.
This morning I separately powered the injectors and fuel pump from a second source (not hard, just pull the relay and plug in a jumper which I recommend carrying in case you lose a relay). BINGO! With only the fuel pump and injectors powered from a second source, the bike started right up. So low injector voltage is the issue with low-battery, hard-starting.
I should have known this because last year when I noticed my alternator taking time to come on-line after starting (about a minute) I also noticed that the mixture got much richer when the battery voltage stepped up due to the alternator starting to charge. This is easy to see with an LC-1 because it's always measuring the exhaust, and the Motronic is always in Open Loop until the engine is warm so the O2 sensor doesn't adapt to the low voltage.
So my theory is this: the voltage dip is coming at a time, on first cold start, that the Motronic usually adds a lot of fuel, perhaps for as little as the first few revolutions. At that time, the voltage dip keeps the injectors from squirting enough fuel to adequately wet the TP and injection track. From then on, it is behind the eight-ball and playing catch-up with the fueling.
The Motronic does compensate for low battery voltage but this is now the second time that I've seen its compensation to be inadequate.
Still TBD, battery or starter ...
Added:
Here's how the mixture varied when the alternator came on-line slowly. This isn't real bad but it is measureable. The start plot is much worse. The step down in AFR is the alternator coming on-line at 3 minutes 20 seconds.