Hard starting Downtown 300i

[CROSSBOLT]

Things discovered that affect reliable starting on this model (and probably every model with the Kymco EFI):
1. Voltage while cranking must be greater than 9.5 to 10 volts or no spark.
2. Injector must produce fine mist while cranking to start.
3. There can be no vacuum in fuel tank.
4. There must be sufficient air into throttle body.
5. Compression must be within spec.

Seems also you may be dealing with an intermittent connection somewhere. These are extremely hard to find. Could be in either a plug-receptacle or a terminal lug crimp.

[CROSSBOLT]

I can make no sense of this:

The spark checker I use forces the spark to jump about 5/16s of an inch, spark plug out, no problem, spark plug in, it will not even jump the ,035 gap on the plug laying on the block. 

I re-read the whole thread and have seen nothing posted by you about checking the injector and it's spray pattern. I know you have pulled your last hair out on this "project" but no codes will show when the injector is plugged or has a crummy pattern. Ethanol fuel can produce some kind of super snot that will float around and cause all kinds of havoc.

[Ruffus]

@jaydee,
I assume ignition coils, sparkplugs, sparkplug caps and sparkplug cables are new.

 Even if I had a new coil with integrated sparkplug cable, a tiny hole in my sparkplug cable fired towards frame and caused an intermittend failure.
Maybe check upon that.

Cure for me was a new cable from ignition coil to sparkplug.

[CROSSBOLT]

Just realized you already indicated when it ran it ran flawlessly so that SHOULD get the injector off the list.
You also said something about the plug would spark when out but not when in. How did you know it did notbspark when in? Straighten me out on that one, please...

[JaydeeFL]

Just realized you already indicated when it ran it ran flawlessly so that SHOULD get the injector off the list.
You also said something about the plug would spark when out but not when in. How did you know it did notbspark when in? Straighten me out on that one, please...

Okay, here goes.  I am using a spark checker, it is a fiber ring about an inch and a half in diameter.  It has an alligator clip on one end and a stud on the other that the plug wire will grab on to.  The center of the ring is open with the two probes facing each other about a quarter inch apart.  When spark is present it will jump the quarter inch with a nice blue spark.  I have used this for the last forty years as if a spark will jump that far in free air, it will jump the thirty thousands under compression.  Now with the spark plug laying on the bench and the spark plug hole open, it jumps no problem with a beautiful blue spark.  As soon as I just plug the spark plug hole with a spark plug, and not even tight, absolutely no spark.  I am only using the spark plug to fill the hole, it is not hooked up, I could use a pipe plug it I had one that fit, I am still only using the spark checker to check spark.  And not only will it not jump the quarter inch of the spark checker, it will not jump the thirty thousands of another spark plug laying on the block.  No spark with the spark plug hole filled.  Difference is, lower voltage is available to the ECU  because the starter is now working against compression.  Solution, I have provided a completely separate battery power to just power the starter, the ECU is seeing a constant 12.5 volts.  No change.  The only other difference that I can see is a little slower RPM of the flywheel past the pulsar coil.  I have changed the stator and pulsar coil with new now twice, no difference.  I have changed the battery with another new, I have three coils, two are new, two ECUs, one new. jumped the starter with a high amp charger to get the spin up, and nothing ever changes.  I have wrung out every wire, changed connectors, used dielectric grease on about everything and a year and counting, I haven't gained a thing.  I suppose it is possible that I could have two ECUs with the exact same problem.  Hard to believe, but I am a total loss.  Hoping someone, somewhere has the hood off a Downtown and would plug these puppies in and let me know.  Hate to drop another 499 on an unknown.   

[CROSSBOLT]

Even with a SEPARATE battery to power the ECU, there is no spark with a dummy plug in the spark plug hole, right? But with the dummy plug OUT and everything else the same you get a spark, right?
The one thing in all this that is common, the one thing that has not been changed seems to be the wires from the pulsar to the ECU and the wires from the ECU to the spark coil and maybe the plug wire. The fat, high voltage wire between the coil and the plug.

[rjs987]

I skimmed over the past posts here so may have missed it.


Did you check your ground connection to the engine block? The engine block provides ground for your spark plugs. I've read many posts on other forums about a corroded ground connection causing strange electrical issues including no spark or low spark voltage/current. I've read this for cars as well and actually fixed one of mine by using a wire brush and cleaner on the ground connection and bolt.


Just a thought. Like I said, I may have missed it if already thought of.

[JaydeeFL]

Even with a SEPARATE battery to power the ECU, there is no spark with a dummy plug in the spark plug hole, right? But with the dummy plug OUT and everything else the same you get a spark, right?
The one thing in all this that is common, the one thing that has not been changed seems to be the wires from the pulsar to the ECU and the wires from the ECU to the spark coil and maybe the plug wire. The fat, high voltage wire between the coil and the plug.

I agree with you, the problem is really getting down to the three wires, the two from the pulsar and the one to the negative side of the coil, Trust me, I have wrung out these wires til I am blue in the face.  What I can't check is the connections in the ECU plug and of course what is going on inside the ECU. The plug wires on the three coils all fire with the plug out, they should not see any difference.  As near as I can figure, the connections to the ECU seem fine, no breaks in the connectors that I can see.  Dielectric grease has been used. Sure seems like the problem always wants to end up inside the ECU, and that sucks.

[JaydeeFL]

I skimmed over the past posts here so may have missed it.


Did you check your ground connection to the engine block? The engine block provides ground for your spark plugs. I've read many posts on other forums about a corroded ground connection causing strange electrical issues including no spark or low spark voltage/current. I've read this for cars as well and actually fixed one of mine by using a wire brush and cleaner on the ground connection and bolt.


Just a thought. Like I said, I may have missed it if already thought of.

Funny, for the first six months on this, I was always checking voltage to everything, totally ignoring grounds, boy I thought I had it when I figured that out.  Checked every ground and like always, nothing changed.  I am about ready to drop another 400 on another ECU, because everything else I can think of has been done.  For the life of me, I really don't see much difference in what the ECU sees different with the plug in or out.  Al little signal voltage drop going to the ECU caused by the little slower RPM of the flywheel past the pulsar coil with the engine turning over under compression.  Almost wish it had a kick starter.

Thanks

[Stig / Major Tom]

Well, before you drop another $400 on an ECU - would you be willing to buy the cyclepedia.com manual book for your scooter ($34) or a life-time manual subscription ($75) from them - either of which includes free access to technical advice from the guys who wrote the service manuals for KYMCO-USA? A purchaser starts a service ticket with a Kymco tech....and you two begin communicating as you work through the issue.
There are plenty of 'free' manuals floating around the ether-net --- but this one can talk back to you....from the USA.

just a thought....

Stig

[JaydeeFL]

Well, before you drop another $400 on an ECU - would you be willing to buy the cyclepedia.com manual book for your scooter ($34) or a life-time manual subscription ($75) from them - either of which includes free access to technical advice from the guys who wrote the service manuals for KYMCO-USA? A purchaser starts a service ticket with a Kymco tech....and you two begin communicating as you work through the issue.
There are plenty of 'free' manuals floating around the ether-net --- but this one can talk back to you....from the USA.

just a thought....

Stig

I am going to try one more thing and then I think I better go with the talk back manual, thanks!

  Last ditch effort is going to be to figure out how to release the three connectors from the ECU plug that either go to the pulsar coil or neg side of the coil.  The original pulsar coil had experienced a plastic melt down and not sure how that could even happen.  It still worked but it had gotten hot like external voltage may have been applied?  I suppose that if enough voltage had somehow been applied to that coil to melt it down, perhaps it also screwed up the connectors in the plug.  I have wrung them out, but not being able to see just how far the ECU actually engages, perhaps there is damage only to that point.  There is usually a tab that can be depressed to release the connector from the plug, but these connectors are tiny.  Perhaps the signal from the pulsar when the engine is turning over free is just strong enough to trigger the ECU, drop the speed of the flywheel by adding compression, little weaker signal, maybe, just maybe..............

Thanks
Dave