I apologize for this post being long. I have been watching forums for information about cold start issues with Power Commanders. I myself have a 2005 Harley Dyna with a Power Commander 3 that will not start in the cold. But the forums are full of posts with these same issues with Yamaha, Suzuki, and Honda motorcycles. Some folks indicate they do not have any cold start issues with Power Commanders, but I thought there might be enough interest to investigate further. There are a number of questions that have not been answered previously as far as I can tell. But first some basics. This post is specifically for Harley, but I think it pretty much applies to all EFI bikes.


On my bike (2005 FXDX) the fuel pump, fuel injectors, and ignition coils are all on the same circuit, although there is a fuse that is specific to the fuel pump. There is no sensor to measure fuel pressure.


The purpose of the System Relay is to energize the circuit for the fuel pump, fuel injectors, and ignition coils. From now on when I state the System Relay is PICKED (or is ON, or is UP) it is assumed there is power to fuel pump, fuel injectors, and ignition coils. If the System Relay is DROPPED (or is OFF, or is DOWN) it is assumed there is no power for fuel pump, fuel injectors, or ignition coils.


NORMALLY, when the bike powered on, and the the Run Switch set to Run from the Off position, the System Relay is picked. The System Relay stays picked for 3-4 seconds (from here on I will just say 3 seconds) and then drops. When the Start Button is pushed, the starter fires up, the crankshaft starts spinning, the Crankshaft Position Sensor (CPS) starts pulsing in response to the crankshaft rotation, and the Engine Control Module (ECM) notes the pulses from the CPS. With the ECM knowing the crankshaft is spinning, the ECM picks the System Relay again and the engine starts. Should you push the Start Button before the initial 3 seconds is up, no problem; the System Relay is already picked.


Now, from what I have seen, the magic number for POWER COMMANDER seems to be about 40-45 degrees Fahrenheit (4-7 degrees Celsius). Above that temperature the engines starts normally. You can power up the bike before, or after, the initial 3 seconds and the System Relay picks and all is good.


Below that temperature things go wrong. The Power Commander (from what I have been told and read) receives its power from the same circuit as the fuel pump, fuel injectors, and ignition coils. The standard Dynojet response is “push the Start Button while the fuel pump is running.” So you are to push the Start Button to engage the starter motor during the initial 3 seconds the fuel pump is running.


Here's where it gets interesting. The Power Commander is installed BETWEEN the ECM and the motorcycle wiring harness. So ALL signals pass thru the Power Commander before they get to the ECM from the bike, or to the bike from the ECM. The Power Commander has total control.


If you do not push the Start Button until after the initial 3 seconds, the System Relay drops and there is no power available for the Power Commander. ABOVE 40-45 degrees no problem. The CPS notices the crankshaft is turning, the System Relay picks, and the bike starts. BELOW 40-45 degrees, once the initial 3 seconds is up, the System Relay does not pick again once the crankshaft starts turning. So, no System Relay picking and no start. You can tell the engine, even though the starter is turning the engine, doesn't even try to start. BELOW 40-45 degrees if you push the Start Button, before the 3 seconds is up, the engine tries to start, but it doesn't quite “catch.”


So here are some observations.....
For those who say “For diagnostic purposes just use a 0 map. That is just as good as not having the Power Commander installed.” I don't believe that is correct. My map has all 0's for 0% throttle. That should be as good as a 0 map for starting. Nevertheless I tried a zero map and it still did not start. And remember...the Power Commander is installed between the ECM and bike harness. It has total control.


At 40 degrees last week my bike would not start with Power Commander. I removed it. Today, at 32 degrees, with no Power Commander, it fired right up with no issues.




And questions......
A) Dynojet says if the bike will not start it may be the CPS. But if that is the case, without doing a thing with the CPS, why would the engine start without the Power Commander, but not start with the Power Commander?


B) Why does the Power Commander not pick the System Relay, below 40-45 degrees, after the initial 3 seconds?


C) Why does the engine not start, below 40-45 degrees, even if the Start Button is pressed before the initial 3 seconds and the System Relay has picked?


Like I said at the beginning, there are lots of hits for this issue. But mostly the forum questions just fade away with no answers. For me, I have replaced the Power Commander with a Dobek product and my Dyna starts at any temperature. It would be nice to know if there is an actual Power Commander fix for this issue.



PS Firmware on my PCIII was the latest. 2.2.5.0.


Sorry for the long post. But I thought the detail might help generate a conversation that will provide answers.
Thank you very much.

 

Damn! Here on this Forum you will be lucky to to get someone to read the whole thing you wrote. I use an old SERT and I have no probs at all starting my bike with all it's engine modifications, and I'm a Texas man as well. This may help you a lot more than I can https://www.hdforums.com/forum/ignit...-injection-55/ Welcome aboard fellow Texan.

 

Sounds like the additional amp draw added in with the cold temps on the battery is just a little too much for the bike to fire up. I ran the pc3 for 5 years without any problems hot, cold, rain or shine. What I do maintain is the battery. Agm battery don't perform nearly as well in cold weather and high heat will shorten their life. After Amy battery gets 2 years old I notice the amps begin to drop and the bike cranks a little slower. I run a cheap yulsa battery so I replace it after 2 years to eliminate battery problems. Another issue is check all areas for corrosion on main power wire and the power commander. The pc3 is not sealed up well and is easily effected by moisture.

 

I have no detailed answer, but my bike with a PCIII has fired right up down to 20* with out fail. I just think I need more gas in choke mode as it stumbles a bit at first when I take off.

 

SERT is the way to go. I have a bud who had a Power Commander. It was crap, so he went to the SERT. He's never been happier.

 

I know for a fact if your voltage drops below 9 when trying to start the bike.....the PC3 will not fire the bike. The PC3 is powered from the Fuel Injector circuit. I had an issue with low power from a battery..the bike would turn over..be it a little slow and it would not start. The bike did start with the same low battery and the PC3 removed.

I did some research and found the voltage issue and replaced the battery and all is well.

 

My wife's '05 Dyna has a carb. Always starts.
(See how short and uncomplicated this post was?)