EFI Question
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Intermediate
Joined: May 2008
Posts: 26
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EFI Question
Injectors are held open at ignition switch on. This fouls out the plugs and over feeds gas when trying to start bike resulting in no start. Could there be a sensor problem or is ECM bad. Ohmed out wiring to injectors from ECM plug No shorts to ground. Gas pours out throttle body after ignition switch on when fuel pump powers on. If injectors are unplugged, then no gas pours out at ignition switch on.
Road Captain
Joined: Mar 2006
Posts: 741
Likes: 11
From: West Central WI
RE: EFI Question
Now this is \\; one I haven't heard of yet, I would start by just unplugging one injector at a time and see if gas still pours, if it only does it on one I would then swap injector wires front to back and see if it is the injector or the power going to the injector.
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Intermediate
Joined: May 2008
Posts: 26
Likes: 0
RE: EFI Question
I replaced both injectors and problem still exists. I was able to get the bike started by unplugging the rear injector only and the bike ran on front cylinder only. I believe the problem is with the rear injector which leads me to believe the ECM is bad. I will verify by doing a little more troubleshooting. The signal is definately from the ECM but I don't know if a sensor is giving wrong information to ECM.
Road Captain
Joined: Mar 2006
Posts: 741
Likes: 11
From: West Central WI
RE: EFI Question
You might also want to do a continuity test between wires coming from the ecm, first you must make sure you are not just checking continuity on two grounds but if you find contiunity between two power wires with the battery unhooked I would start tracing those wires, It makes me wonder if the injector wire could be getting voltage from another power wire to one of the sensors.
Road Master
Joined: Mar 2007
Posts: 1,177
Likes: 23
RE: EFI Question
This is really fairly simple to trouble shoot. The injectors get 12 volts power on terminal A at the injector plug any time you can hear the fuel pump. The first thing to do is check for that. Most EFI vehicles may squirt a quick pulse or two when the ECU first gets power. This is to purge the air out of the system and to pre wet the intake runner. Harley may or may not do this but donât be surprised if the injectors give a little puff of fuel on first coming up to life. They definitely not stay on for more than a few thousandths of a second if at all.
Now disconnect the battery and turn on the ignition far a few sec to drain all power out of the system. Then pull the main 36 pin connector from the ECU.
The next thing to check is if the other wire (terminal B at the injector) is going to ground somewhere in the wire harnice. Normally the injector gets grounded thru a op-amp (high speed electronic switch) in the ECU. Hhave the injectors unplugged. Now you should check is that neither of pin 21 or pin 19 goes to ground. The ohmmeter should infinite resistance from (no flow) from either of these pins to ground at the battery cable. Also from terminal B of the injector plugs to ground should be infinite.
If all this checks out the next thing too prove that the injector control wires are not shorted to some other wire what gets grounded only when the bike is turned on. This one will be somewhat difficult to prove one way or the other.
If all this checks out then the most suspect thing is the ECU itself. I would think this is somewhat remote as most ECUs are fairly tough and this part of the ECU only goes to ground a few thousandths of a sec at a time.
Hope this helps
AW
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