CV740-3117 (Command Pro 27) Recovery - Ignition & more

rgedye

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  • / CV740-3117 (Command Pro 27) Recovery - Ignition & more
Got handed a ZTR that was 'worked on' with dismantled Ign mods, blower & housing, etc.
I guess it was originally dismantled for leak @ oil pan. ???
When checking valve timing marks later on, I found that RTV rather than Gasket was used to reassemble & camshaft shim missing. (another topic)

After ordering missing bolts from blower & ign modules, found broken bolt in ign mod mount for Cyl 1.
Repaired this issue with installing stud. Verified spark after assembly & setting air gap.
The IGN mods (#20 584 03) were new I'm told.

I noted 2 'sparks' per full 4 strokes (2 flywheel revolutions) one near point of TDC of compression stroke & one other near end of Exhaust stroke.
The motor 'wants to' start but seems to 'kick back'.
Not fully understanding the MDI, I assumed the 'second' spark during the end of exhaust was a non-issue, possibly a 'feature' design, leading me to check internal timing.
I ASSUMED it was normal for the coil to fire each time the magnet on flywheel passed it; now understanding the MDI/Capacitive Discharge better, it might not be proper to fire each time, but possibly the 'build-up' of charge releases instead after second passing. (??)

I need to know if this double-fire is proper or an error by bad modules, cross-talk, or maladjusted air gap.

Proper flywheel & ign mods installed in DSAI to MDI Ignition conversion previously; (according to part numbers).

I'm wondering if an isolation kit (diodes ) between coils is not installed & coils are cross talking; or possibly if previous 'grease monkey' hooked up 12V to mods and caused failures.
I have a wire assembly (844547) for a Briggs with diodes in line; thinking of giving it a try on the kill wires.

Current status is waiting on oil pan gasket & shim to reassemble.
(waiting to be reinstalled in Toro Zmaster G3)

I've inherited a mess, any help would be appreciated.
 
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ILENGINE

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  • / CV740-3117 (Command Pro 27) Recovery - Ignition & more
The plugs will fire every revolution of the spark plug when the magnet passes the module. All brands of engines do this, Kohler, briggs, kawasaki, honda, etc. On Kohler engines the cross talk diodes are built into the modules themselves, therefore no external diodes. 12v to the modules will damage the MDI modules, But the DSAI modules required 12v to operate but that system is eliminated with the MDI and only uses the ground/kill wire that use to go to the old modules to kill spark from the new modules.

Seems like I remember that the MDI modules are a not adjustable air gap module. So air gap shouldn't be an issue.
 

rgedye

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  • / CV740-3117 (Command Pro 27) Recovery - Ignition & more
Thanks for the response.
Is there any test for ign mods (ohm) that are a reliable indicator of failed module?
The one I noted in the service manual for the engine was a bit confusing as I couldn't relate to the 4 terminals shown in the diagram on pg. 43 (doc 24 690 07); I only have the laminations (lead 4), Spark lead (3) and kill lead (2), & what may be lead 1 bonded to laminations.
As I stated, both modules were showing spark prior to me continuing with reassembly initially.

I noted, as I was reviewing internal timing, that the magnet is a considerable distance past the ignition module by the time the piston reaches TDC. This lead me to consider the flywheel as a culprit. It appears that, if the spark occurs exactly when the magnet passes the module, the piston is not far enough in the compression stroke to fire 'forward' in the cycle, producing 'kick back'. I'm probably over-thinking things at this point

Again, thanks for the help. I'm pretty sharp sometimes, not a novice by any means; this one is puzzling.

I have an operating machine to compare with. Only difference I noted is different ign mods. Those have slightly different frame & kill connector on the same side as spark lead, where these (20-584-03) have slightly smaller frame (height) and kill connector on opposite side of spark lead (under module). I verified both machines use the same flywheel (24-152-03) but can't easily find part number of modules on working machine (which I'm hesitant to disassemble).
 
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ILENGINE

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  • / CV740-3117 (Command Pro 27) Recovery - Ignition & more
Unless the flywheel key is sheared there is no way to adjust the timing on the flywheel end as it relates to the position of the module when it fires the plug. Something to consider is, could this flywheel have come off of a different engine like the CV18-20 series, because they used a different flywheel key position due to the spark advance.

I would say if the piston is at TDC the magnet should be about 20 degrees or so past the module. And if the modules are producing spark then I would say there are good and not damaged.
 

rgedye

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  • / CV740-3117 (Command Pro 27) Recovery - Ignition & more
Woodruff key is intact; unit was disassembled (Ign mods, blower housing, etc) when I first got it.
First thing I did, upon hearing shop talk of 'timing' & seeing paint markings of where modules are located on blower cover, was to pop the flywheel & verify it was installed correctly with keyway in place. knowing that the machine's initial service problem was oil leaks at base of block internal timing was suspect as well. I mean why remove housing & mods to repair that issue? A mess I tell ya.

The installed flywheel part number doesn't match initially with service manual, but then there was the DSAI to MDI conversion.
These installed part numbers, flywheel & mods, correspond with the service procedure for this conversion.
Conversion was done by dealer on both machines, but I can't explain the difference in mods; unless previous guy ordered new ones for this machine.
Pretty sure he did but too much time has passed to know for sure.

20 degrees may be about right; I was thinking it was more (estimate on recall is 3 to 4 inches past mod, maybe more). I'll check again in the morning & take actual measurements.

Does anyone have the information regarding relative position of keyway to magnet placement for this flywheel? Even an estimate using a 'clock face' example would help.
 

rgedye

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  • / CV740-3117 (Command Pro 27) Recovery - Ignition & more
Supposing ignition or timing is not issue (verified spark before blower housing reassembly & after, so mods are most likely non-issue).
The engine cranked hard, kicked sometimes, & sometimes made me think I had it wanting to run...
Questioned starter & battery. come to think of it now, a good word might be 'binding'.

Carb was cleaned, old gas drained completely, fresh fuel, fuel pump tested, fuel solenoid changed (because the wiring at base was twisted & questionable although it tested fine, orifice was dirty/clogged) along with gaskets for carb body, float was checked, needle & seat , fuel bowl gasket inspected, etc.
Plugs show signs of fuel/air mix present when tested.

Let's add in what I realized today...
My plan was to re-install the oil pan ('original service problem') after I double checked the timing & such, then try removing kill wire from mods to eliminate cross talk issue; basically starting diagnosis again.
Then, when reviewing the reassembly contents in the service manual (torque pattern & specs etc) I realized that this spec uses a gasket (not all do) and there was nothing but a thin layer of RTV when I ' RE-Disassembled' it to check internal timing... No gasket... No camshaft shim either... crankshaft shim was present...

I verified working, same spec machine, has gasket.

Ordered gasket & default/original (white) shim today. Anyone want to lend me a camshaft end play measuring tool just in case?
 

rgedye

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  • / CV740-3117 (Command Pro 27) Recovery - Ignition & more
Received parts this morning. Up & running.
I still have to verify my throttle linkage hook up & stops, double check governor as well. It fired up without too much effort & wants to run full throttle.
The linkage didn't seem to sit right & probably is the issue, noticed a slight after cleaning carb.

Yep. Just might need a gasket & shim as designed... 'Simple' issue: Hours upon hours finding it.
 
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