'88 120 looper, Idle timing jumping around-UPDATE!

[walleyehed]

Got a 120 Looper I'm messing with and just checked Idle timing and it's jumping back and forth from 4 to 8 degrees ATDC, with quickstart plugged in, or unplugged, doesn't matter.<br />I'll be testing per manual specs after lunch, just thought maybe someone would have a clue...<br />timer base is against the stop too...

 

[fishnfiend]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

I wonder if the pickup sensor is loose in its' mount under the flywheel - causing it to pick up the signal at different times (or - possible defect in the sensor itself??)<br /><br />I wouldn't think a missing flywheel magnet would cause this problem. I'll be watching this thread with interest....Good luck.

 

[walleyehed]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

According to the manual, the orange/black and orange each to grnd should be open, and it is, and if Ohms reading from coils are 96+/- 10, replace the powerpack...my Ohms read 98. Manual says if results vary, replace stator too.<br />Quickstart does not work that I can see, and I don't quite understand even how it works for sure...If someone can enlighten me on that, I'd be greatful.<br />The manual makes no mention of "How the timing is advanced", just a reference to quickstart.

 

[OBJ]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

Not being the sharpest tack in the box, I can only guess at what goes on. It is possible to advance or retard the timing just by delaying or speeding up the time it takes for the pack to release it's voltage to any coil. The trigger is the engine temp. Yeah, we are talking nano sec's here but did ya ever try to get away from being shocked? <br /><br />No basically what I'm saying is, engine overheats and the temp sensor sends a voltage to the pack saying slow this thing down. So the pack trigger gets delayed from telling the pack to fire a coil. Same when cold only it speeds up the process.<br /><br />Hope I didn't confuse you with all those electronic terms.... This is all conjecture on my part....never really talked to any smart folks over at the old OMC or Bomby. Just makes sense to me.<br /><br />Maybe Mr. D or Paul or some of the other guys will tell us how it really works....

 

[walleyehed]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

Thanks, Jim...I know I need atleast a power pack, and from what I gather from the OEM sevice manual, if run long enough with the power pack giving false info, it can take the stator out too.<br />I thought a Linc-n-sync was easy until I cracked open the hood on this 90* looper.... <br />What I can't figure out, is if they had this much more torque with these loopers, why did they continue the simple crossflow for 13 more years in the V4's?????

 

[rodbolt]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

the orange/blk and orange/black wires supply power to the pack to engage both quick statrt and SLOW. in quick start cold mode the ign timing is advanced by about 10 degrees. its supposed to disengage when the correct operating temp is reached or engine speed exceeds 1100 rpm. t6he advancing is a funtion of the pack selecting the proper trigger coil voltage input.. to disable the system for checking ground the white/blk wire on the port head. timimg should stabilize. if the t-stat for the port head is leaking or stuck open the sensor will see it as a cold engine and keep quick start applied until RPM exceeds 1100 or so. so it could be a bad sensor, bad t-stat, bad pack or its remotly possible a timer or hub magnets. the timers are usually trouble free. the yellow/red wire going to the pack supplies 12v when cranking to activate quick start then the power coils take over once started.

 

[walleyehed]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

All tests according to manual, point to power pack. What kills me is it says if tests vary, replace stator too....<br />This condition exists with Blk/white sensor lead connected or disconnected, in fact, timing doesn't change at all, hot or cold, from what it's doing now.<br />I've checked yellow/red for residual voltage and none found there.

 

[rodbolt]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

do the timer tests with a CD-77. a faulty timer can do it as well.<br /> but it soundss more like a pack problem.<br /> have you indexed the flywheel and checked to see if the timing is jumping on the other 3?<br /> another trick is to ground the wht/blk wire. remove the yellow/red from the pack and restart the motor. if timing is now normal odds are its the pack. occasionally the will lock into quickstart at cranking and not release.

 

[walleyehed]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

Indexed and checked all 4....jumps the same on all.<br />I haven't grounded the Blk/wht and tried that.

 

[walleyehed]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

Pack checked bad, (timing normal, ylw/red unhooked) Replaced pack, link-n-sync done per manual..Customer just called and said engine runs great and Idles better than it ever has....That kinda stuff makes ya feel all good inside..Thanks RB and OBJ.<br />I don't want to tell everyone I replaced the NGK plugs with the correct champs for fear of a fight..

 

[Seasport]

Re: '88 120 looper, Idle timing jumping around-UPDATE!

I know how the Quickstart works on the OIS ignition system. It's simple really, the timing sensor puts out a series of square pulses - one per cylinder. The pulse width corresponds to 10 degrees of crankshaft rotation. Normally the powerpack electronics triggers the ignition pulse on the falling edge of the square pulse but it uses the leading edge (i.e. 10 degree advance) when it figures (from temp sensor and rpm's) that quickstart should be activated.<br /><br />I presume that quickstart works in a similar way for the conventional ignition system using a timer base, i.e. the trigger coils give a (roughly) square wave output which the powerpack treats in the same way.<br /><br />Now can anyone explain what happens to the ignition pulses when SLOW activates? Do the cylinders only fire once every two revolutions? Is this why the engine shakes?