Bought a engine with no spark.
Checked flywheel coils, sensors, ignition coils, pulled wiring and checked all wires for continuity and all is within spec, except ignition coils have a bit high resistance ( two are new, and AL, are the same, so I guess they are OK)
Enden up buying a brand new ECM, but there is still no spark. There is no sound from the horn either...
First thing I would recommend is to check all of your fuses. Also verify that the key switch harness is functioning properly (often best to simply connect a known good harness/switch, or a transom-mounted keyswitch harness).
Also- has the CPS (Crank Position Sensor) been replaced with a known-good unit?
Havent tried another cps, but it have recistanse within spec. Key harness seems to be OK, but I cannot see where the ecm get power. The purple wire from the ignition goes nowhere, only place ecm is connected to power is via the buzzer.
I'm afraid this engine is a hybrid of different electrical harness...
It's not an adapter, I borrowed a fluke from work which have peak voltage as an option.
After som testing the voltage was gone... O.5v max.... Must be a leakage, but I don't have a insulation tester (megger), so I ordered a new stator and crossing my fingers����
New stator, New ecm, still no spark.
I can't see where ecm gets its power from, shouldn't the ecm get 12vwhen ignition is on?
Buzzer is silent as well....
seems like the Voltage regulator/rectifier is broken, but will this result in a missing spark?
Update: Found a diode from the green wires from the coils to black\ground. It was in a bad shape, and broke of when i tried to remove insulation. Turned engine over with starter, without the diode, and i had a weak spark from the sparkplug.
Cut open som christmas decorations to find a diode, but it doesnt help much. So i guess I need the correct diode for this? does anyone know the specs for the diode? A complete harness is quite expencive when i just need a new diode...
Let's get a little more detail on the diode and the wiring to it. Sometimes a picture is worth a thousand words.
And yes, the ECM would need 12V Key-Switched power, coming from the PURPLE wire that originates at the ignition switch. Without that, the PCM can't "wake up".
According to my wiring diagram the purple goes no where. It probably in use for other models. There are 4 wires from the stator which goes to the ECM. This engine comes with a manual start aswell, and no battery needed to start it then.
The green wire is the same for all 3 coils, and a diode is connected between the green wire and ground.
Not very good pictures, as the diode broke when i removed the heat shrink. But when without the diode i get a weak spark. So i tried the diode from my wifes xmas decorations without any luck.
Talked to some eletrical designers at work, and found some info at a lawmover forum, and found out the 230 v AC\DC rectefier is not enough. So i ordered a couple of 1Kv-10A diode and will try them as soon as the show up.
As best I can tell from the parts diagraghms (not particularly clear), that is Part# 858884A1.
It's purpose is to prevent backfeed to the ignition or ECM from fuel pumps or starter/solenoid operation.
The OEM regulator should work fine- though they've been upgraded over the years. The kit Part# 893640A01 is likely to become NLA in the near future, though.
I see that. Likely used to rectify current feeding the coils as well (blocking diode). Either way... probably not that hard to find and install a large enough blocking diode to get the job done.
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