Damaged ECM?

[331GT]

Hi,

I managed to connect the jumper cables backwards when trying to jump my 2010 Buell XB12S (I know, I know). To make matters worse, I was key on at the time. I blew a few different fuses, but managed to get them all sorted, except the fuel pump fuse. It keeps blowing, unless I use a 15A or larger fuse (just for testing). I replaced the fuel pump, thinking that I had managed to damage it, however the issue persists.

I then probed the ECM output to the fuel pump, and measured the voltage across it while running (I can sometimes get the bike to start), here is a video of the output: https://www.youtube.com/watch?v=Vl5lViDwXy8

I am fairly certain I damaged the fuel pump output on the ECM, as it reads 6V maximum, and fluctuates to open circuit and back (I would expect to see a constant 12V). This to me would explain why the fuel pump fuse is blowing -- the fuel pump is sourcing more current because of the low voltage signal.

I have tried providing the fuel pump with a constant 12V source from the battery, and the bike fires right up and runs fine.

Does anyone have any experience with this? I think I need to replace the ECM.

Thanks,

-Alex

 

[34nineteen]

Check your relays. You may have damaged one of them in the process.

https://www.buellxb.com/forum/showthread.php?56032-09-xb12ss-electrical-issue

 

[331GT]

Check your relays. You may have damaged one of them in the process.

https://www.buellxb.com/forum/showthread.php?56032-09-xb12ss-electrical-issue

Thanks for the link. I did a bunch of research before posting, and indeed realized that I had blown a relay which I replaced. Now the ignition fuse no longer blows, just the fuel pump fuse.

I guess my question is, is the fuel pump voltage normal as indicated in the video I took? I would expect to see a constant 12V, not a fluctuating 0-6V.

 

[34nineteen]

Thanks for the link. I did a bunch of research before posting, and indeed realized that I had blown a relay which I replaced. Now the ignition fuse no longer blows, just the fuel pump fuse.

I guess my question is, is the fuel pump voltage normal as indicated in the video I took? I would expect to see a constant 12V, not a fluctuating 0-6V.

I would think you are on the right path with that, but I would have to check the FSM to be sure.

And I agree about your idea that the ~6v is causing the amperage to ramp up. Usually that causes the fuse to "melt" rather than "blow". I would examine the fuse with a magnifying glass to see if that is the case.

However, as a workaround, you could always wire in a 6v relay to turn that circuit on and off. Actually, if the voltage is fluctuating, it could cause the relay to switch on and off, which would be interesting and probably wouldnt work.

Cooter will try to convince you to install a Ford starter relay. Dont do that. He is wrong!!!!!!:eagerness:

 

[331GT]

I would think you are on the right path with that, but I would have to check the FSM to be sure.

And I agree about your idea that the ~6v is causing the amperage to ramp up. Usually that causes the fuse to "melt" rather than "blow". I would examine the fuse with a magnifying glass to see if that is the case.

However, as a workaround, you could always wire in a 6v relay to turn that circuit on and off. Actually, if the voltage is fluctuating, it could cause the relay to switch on and off, which would be interesting and probably wouldnt work.

Cooter will try to convince you to install a Ford starter relay. Dont do that. He is wrong!!!!!!:eagerness:

I was actually thinking to put the fuel pump on a switch for the time being, and look at sourcing a new ECM. I have a "Race Only" ECM in it right now, that was with it when I bought it (I suppose it is to match the Drummer SS exhaust that is on the bike).

I will check the FSM and see what it says, thanks!

 

[331GT]

I have come to the conclusion that it is my ECM that is damaged. I have a couple of questions:

1) Where is the best place to find a new ECM?

2) I have a 2010 Buell XB12s, which year ECM's work for this application, is it a 2010 ECM only?

3) I right now have a "Race Only" ECM, with the Drummer SS tune in it. Can I just get a stock ECM and flash the same tune on it?

This should work, correct? http://idspd.com/xcart/buell-xb12-2010-drummer-SS-ecm.html

Thanks!

 

[GregoXB]

If the fuel pump fuse is blowing but holds on a 15AMP you might have a damaged/frayed wire in the harness. Before buying parts I would strongly urge you to unravel the tape on your wiring harness and trace the wires to ensure eveything is intact.

 

[331GT]

If the fuel pump fuse is blowing but holds on a 15AMP you might have a damaged/frayed wire in the harness. Before buying parts I would strongly urge you to unravel the tape on your wiring harness and trace the wires to ensure eveything is intact.

How would that explain the intermittent / 6V maximum pump voltage?

 

[34nineteen]

How would that explain the intermittent / 6V maximum pump voltage?

It could be that wire is shorted (or partially) and the ECM is able to go into protection and turn off the current?

^^^^ total guess with no basis.

It wouldnt hurt to check to be sure.

 

[331GT]

It could be that wire is shorted (or partially) and the ECM is able to go into protection and turn off the current?

^^^^ total guess with no basis.

It wouldnt hurt to check to be sure.

I have done more research, and contacted the guys at IDS. As it turns out, apparently the fuel pump on the 2010 models is PWM controlled, and has a flyback diode which acts to reduce the inductive kick that occurs during the PWM process, reducing voltage and heat dissipation in the ECM output. Of course, swapping polarity would destroy the flyback diode.

The solution (I have yet to try it) is to install a new flyback diode between the pump (+) and (-). I will try it tonight and let everyone know, in case this happens to someone else in the future.

 

[34nineteen]

I have done more research, and contacted the guys at IDS. As it turns out, apparently the fuel pump on the 2010 models is PWM controlled, and has a flyback diode which acts to reduce the inductive kick that occurs during the PWM process, reducing voltage and heat dissipation in the ECM output. Of course, swapping polarity would destroy the flyback diode.

The solution (I have yet to try it) is to install a new flyback diode between the pump (+) and (-). I will try it tonight and let everyone know, in case this happens to someone else in the future.

Have you considered using a FULL BRIDGE RECTIFIER???

 

[Cooter]

I never want to see your internet history.



:upset:



Haha

 

[331GT]

Just circling back on this one for anyone who is curious, or may have this issue in the future.

I soldered in a 1N5408 diode across the (+) and (-) fuel pump wires in the harness, with the cathode connected to the (+), and the anode connected to the (-) (flyback diode). This solved the problem, and the bike runs like a top.

https://youtu.be/u3Q3AsGc0J4

 

[Cooter]

Good to know, thanks for posting the solution!

Were 2010 the only ones with PWM for the fuel pump? I wonder why that was added, and why? It doesn't seem to be necessary.

 

[mmcn49]

Just circling back on this one for anyone who is curious, or may have this issue in the future.

I soldered in a 1N5408 diode across the (+) and (-) fuel pump wires in the harness, with the cathode connected to the (+), and the anode connected to the (-) (flyback diode). This solved the problem, and the bike runs like a top.

https://youtu.be/u3Q3AsGc0J4

Is that what the little black diode in the XB's fuse box is for?