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Discussion Starter #1
Ok, was out last night on the bike and was doing about 90-95 for a run on the interstate for about 2 miles... was running great, motor temps were under 200, then it started to breakup after a slowdown/engine braking to take the exit ramp. on the offramp is was sputtering anything over 1/8th throttle. afr's went lean then back to normal, then back to lean acting like it was out of gas...and it finally just died . luckily i made it to a gas station, my friend who was riding behind me on his triumph said there was no backfiring or flame outs.


heres what i know:

-motor still turns over, sounds fine, compression etc except it wont start. sounds like its not getting fuel, but fuel pump does pressure up
-has plenty of fuel in tank, actually its full. was when it died
-no engine light was thrown
-cam chain seems to be goo d(didnt seem to jump time) have clear cam gear cover. no odd mechanical noises were noted


im suspecting the injector died, cant think of anything else unless its the ecu or the power commander, of which neither has given any issue prior.

i'll look at it tonight but was wondering if anybody had had this happen before?

170 4v w 34mm tb and large 10 hole injector. has 4200 on it. w pcv and wb2.
 

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Most likey not your issue as it wouldn't account for your going lean, but... fouled a plug? or other plug related issue? Probably not.

pull the injector, but leave connected to the fuel line, power on the bike, let the pump prime, and connect 5v to the pins (or even 12). (check polarity) she should spray fuel everywhere. Maybe it got jammed or something made it through the filter?


Actually, screw that. Its a sign from the gods... Its time for a carb. :)
 

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Discussion Starter #4
carb was 1st thing i said lol. i'll see wat happened rechek the connectors at the pcv so forth last night all looked pretty good. going to get rain tonight so garage time!
 

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Most likey not your issue as it wouldn't account for your going lean, but... fouled a plug? or other plug related issue? Probably not.

pull the injector, but leave connected to the fuel line, power on the bike, let the pump prime, and connect 5v to the pins (or even 12). (check polarity) she should spray fuel everywhere. Maybe it got jammed or something made it through the filter?


Actually, screw that. Its a sign from the gods... Its time for a carb. :)

you will shoot the injector out of the cap by doing this with the pressure created.

Simply unbolt the 2 screws that hold the manifold to the head and crank over. does the injector spray fuel?

Or ground out the ecu side of the injector wire (this will hold it full open) and prime the fuel pump to see if she flows full while the manifold / tb is unbolted.
 

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Discussion Starter #6
i'll check all connections again, this time in in the shop, and check the map as well. also i can check the injector output and i need to look at that plug. also, the 02 sensor doesnt seem liek it was the issue. The fact it wont restart is what worries me. regardless, i'll get it sorted after work today one way or the other. more to follow.
 

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you will shoot the injector out of the cap by doing this with the pressure created.

Simply unbolt the 2 screws that hold the manifold to the head and crank over. does the injector spray fuel?

Or ground out the ecu side of the injector wire (this will hold it full open) and prime the fuel pump to see if she flows full while the manifold / tb is unbolted.
Oh lol. yeah. don't do what I said. do it that way ^^^.
 

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Could always just pull the exhaust off the head and see if fuel sprays/drips out/you can smell it. Depends which is easier to get at. The manifold or the exhaust.
 

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Discussion Starter #10
its possible have had about 3 years out of it trouble free. we'll see. if it took a shit i'll replace it, no biggie. I was pushing the hell out of the poor thing last night. could also be the ecu, i know of a few dying . my spare is actually at a shop that borrowed it to diagnose another bike. lol. like said, 'worst' case, i carb it and hit the 100 mph club. ive seen a legit 95 already.. so close...
 

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If the ecu doesn't see the proper injector resistance the ecu won't fire the ignition.. 12 ohms if I remember correctly.

Edit: also handy knowledge for keeping spark when you go carb
 

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Discussion Starter #14
yup fuel pump recall was done.

so, it isnt sparking either. changed coil: no difference. bypassed power commander: no difference. it's either the injector, (great info fox), or the ecu died. both plausible. goping to grab my spare ecu tomorrow and test, then swap injector and see. im thinking its the injector, but will ohm it out to see where its reading.

more to follow had to wire a friends vintage project bike tonight, from scratch complete harness, added led gauges/ stepper tach, etc..chewed up the majority of the evening.
 

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This is the first time I'm hearing of a factory Grom ECU potentially going bad. Seems very unlikely to me.
 

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Discussion Starter #16 (Edited)
the shop i loaned my ecu to used it to determine that it was, indeed, the ecu that died. so if mine also crapped out, thats 2 i know of. im still leaning towards injector failure though
 

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the shop i loaned my ecu to used it to determine that it was, indeed, the ecu that died. so if mine also crapped out, thats 2 i know of. im still leaning towards injector failure though
Sure. It's not impossible just first I'm hearing of it. Was your injector running at a high duty cycle? I keep thinking of going carb as well :)
 

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Discussion Starter #18
oh yeah it was. i was doing sustained 90-95 for a few miles on I-77 it was at the very end of that run where it felt like it ran out of gas, fired back up, then wouldn't take any throttle to speak of and was burping and farting. the trim table son the pcv didn't show that it was trying to enrichen anything , so as fox said, if the injector dies and it wont fire, it wont try to tune itself.

seriously wondering why it didnt throw a check engine light though.
 

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That sucks but at least it's an inexpensive fix! Glad it's sorted. Or maybe it's time to go stand alone :D

We're going to start playing with Hoedar ECU because it has a MAP sensor.

The Chicago guys have a group buy going on right now that I'm trying to get in on (I'm not a dealer, just a customer like everyone else).
 

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Discussion Starter #20
hope so. im not going to dick around with a standalone on this, that wasn't the issue if it was the injector, and not worth it if its the ecu. the powercommander did well. if it goes again its def carb time.
 
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