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-   -   2002 ZL 600 EFI servo cycle issue (https://www.hardcoresledder.com/forums/317-zr-zl-forum/1683266-2002-zl-600-efi-servo-cycle-issue.html)

CentralMaineMan 01-15-2017 04:26 PM

2002 ZL 600 EFI servo cycle issue
I got a ZL 600 EFI and it was running great then backfired and quit. The servo seems to be trying to cycle at idle then dies. If I disconnect the power going into the ECU for the power valve side the engine runs great and everything works as it should except the servo motor of course. I have been through the ringer checking everything to figure out why. TSS is disconnected, all stator windings read fine, all grounds are clean. The TPS checks out almost indenticle to my buddies. The servo motor was almost identical reading as well on the position sensor and the motor works with 12 volts. What the hell would make the engine think its at 7000 rpm when it is at idle? No lights flashing on ECU and my ECU works fine on my buddies sled? Any advice or information would be appreciated.

CentralMaineMan 01-15-2017 04:47 PM

Does the ECU get its RPM signal from the timing sensor on the stator? My wiring diagram shows the timing sensor at 190ohm and mine tested out at 157 ohms? Could that be causing my issue?

stronger800 01-15-2017 10:38 PM

Power valves all clean and free with the cables adjusted? It wouldn't explain your backfire and stall issue, but a messed up valve or cable can make the servo sit there and try to cycle like that.

CentralMaineMan 01-16-2017 07:11 AM

Power valves were cleaned and are free. I checked the adjustment and it was right in the middle of the range. I only have a few miles on this season and it was running great. The servo on the EFI from what I have read is not supposed to test or clean cycle after start up but it seems like that is what mine is doing. If I unplug the yellow and browns two wire going to the ECU to power the servo circuit the sled runs fine? When I plug it in it will idle for a few seconds then the servo cycles to open and closes and engine dies. You can hear the difference in the exhaust when the valves open. Could the ECU be getting a bad RPM reading?

CentralMaineMan 01-16-2017 03:24 PM

My timing sensor ohms is 157. Is that OK? My manual says it should be 190 but others have said the twins are 90?

aglick87 01-17-2017 01:39 AM

My uncle had the exact same sled and it went through (2) timing pickups on the flywheel. His had the same symptoms as yours. Erratic power valve operation. Changing the sensor fixed his both times.

CentralMaineMan 01-17-2017 05:50 AM

I am going to try to prove it out today by checking mine against a friends. Thanks very much aglick87 for the response. I know this has to have happen to other people before.

CentralMaineMan 01-20-2017 06:44 PM

Still have not figured this out. My voltage was low on the regulated side down to 8-10 volts so I pulled the regulator plug to let it run on the output of the stator. At idle it was 12-14 volts. I plugged the brown and yellow feed back in for the power valve servo and it stayed idle for maybe 20 seconds then the actuator cycled and the engine dies. After it stopped and I was trying other stuff plugging that power in was acting just like a kill switch. It would kill the engine immediately. Where in the harness would that brown and yellow be able to screw up and act like a kill switch? I have contacted Stator Kevin and he said the numbers I am getting on the stator are correct and the output on the lighting circuit is correct also. Thanks for any advice.

ndtorque 01-20-2017 07:42 PM

when electrical starts running me in circles that do not make sense I always go back through and triple check every ground ..

Plug your voltage regulator back in as your dealing with AC voltage ....then take a look at the wiring diagram the efi/esr has a diode in the voltage regulator for the APV and a 7.5 amp fuse in line from the starter solenoid ...


here are the wiring diagrams .. look close the ohm values are there for every coil and sensor ..

CentralMaineMan 01-21-2017 05:18 PM

I have one ground from the lighting coil part of the stator to the engine right above the timing sensor. One from the front motor mount to the chassis and one from the recoil housing to the resonator mount on the exhaust. They are all 100%. Is the brown from the lighting coil on the stator what grounds the ECU? I do not see any other grounds. I downloaded the 2002 manuals to use for reference and testing. So far everything has checked out.

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