Hello all, I’m new here and I’ll admit I only created this account due to the issue at hand. Promise I’ll be active lol. Anyways, rode the bike about 270 miles in a thunderstorm and at about mile 265 it had a really high idle and was bogging real bad. I shut it off and it wouldn’t restart. Was out of town with no tools so I dropped it off at a local shop and the guy said it wasnt holding fuel pressure and that I needed to replace the lines and regulator. Replaced all that, bike is building pressure and holding it but still no start. Getting spark, good compression, fuel pump primes, will run if I pour fuel into the intake. Used a noid light to check the injectors and I’m not getting any pulse. Getting the normal 12v on the positive side, and good continuity to the ECM on the ground side. Now here’s where it gets ****y. Checked both the grounds on the ecm, and the switched power and constant power and all is good. Swapped the ecm with another twin cam I have and still no start. Put that ecm back in the other bike and now that bike won’t start either. Did I cook both ecm’s? And if so any ideas what would cause it? Ive poured over the harness multiple times and cannot find anything obviously wrong with it.

 

First, I hope the local guy verified the lack of fuel pressure with a fuel pressure gauge, and that wasn't just a guess.... is he a good mechanic, or just a parts changer...?

I'm not really good with electrical stuff, plus I hate doing electrical troubleshooting, but it sounds like something may have shorted out in the rain.... Did you check for codes???

If I followed your troubleshooting correctly, you're not getting pulse to the injectors, yet the ECM is getting 12V power and has a good ground...??? That would point to the an issue between, to include, the ECM and the injector's connector....

When you swapped the ECMs, did you inspect the connector to make sure it was clean & dry...?? I'd also check the connectors to the injectors for water intrusion...

The puzzler is that you switched ECMs and now the other bike won't start with it's original ECM... I sure hope there isn't (or was) a water induced short that killed your ECM and then also damaged the other one.... I don't know how to check the ECM specifically...

I know this isn't much help, just kind of thinking out loud... like I said, electrical isn't my strong suit... There are others on this forum, with a good handle on the electrical side of these bikes, that will hopefully chime in with some good suggestions...

Please report back what you find...

 

right so following the diagram I found, we get 12v at the injectors with the system on (fuel pump running etc.) and then the ECM pulses ground to actually fire the injectors. Am definitely getting 12v where I should and I used a noid light and there is no ground pulse at either injector connector. Ive verified fuel pressure myself with a gauge, and ohm checked the ground wire for the injectors back to the ECM connector. No water or corrosion anywhere, but am about 99% confident I cooked both ECM’s. Just not sure what would cause that if not an obvious water short or ground short. Oh well, either way it’s at harley now with their master tech tearing it apart because i dont have the resources to dive any further. Gonna go up there and look at it with him tomorrow, advisor said he thinks he found the problem but the advisor didn’t understand it so he wants to talk to me directly

 

OK, I didn't realize it was a ground pulse that fired the injectors.... other than changing them for size, I never worked on an injector before....

Please post up what the Tech finds.... I am very curious to know what happened..

 

Okay a bit of an update. Talked to the tech at their shop yesterday and he went over everything with me. He started from square 1 (expected this) checking all the common stuff like fuel pressure spark and compression and got to the same conclusion I did once he tested the injector pulse. He went way farther than I did though, and pulled the tank off and actually stripped the main harness down to individual wires. What he ended up finding was a bit of corrosion in the crimp area of one of the grounds under the front of the seat. He said he cleaned the ground and got a very very dim light from the noid on the injector, so he’s confident it’s a ground problem. He said he’s gonna replace all the ground wires, and the wires between the injectors and ECM. He did throw my ECM in another deuce they had there and it fired right up so thankfully my ECM is still good and makes me more confident in his diag. I’m assuming water running off the tank must have run into the wiring and caused enough corrosion for there to be a significant current drop. Either way, now I need to figure out why the other bike won’t start now

 

If you find a local shop that has TechnoReserach Centurion Diagnostics, they can pinpoint, or narrow it down quickly.
Scott