Fuel injector sticks on

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Le_Max
MS/Extra Newbie
Posts: 10
Joined: Fri Jan 26, 2024 1:53 pm

Fuel injector sticks on

Post by Le_Max »

Fuel injector is a 425CC, 9 or 10 ohms.
Engine dies after 10 to 30 seconds idling.
When engine dies, ASE and WUE has already stopped, so, it's not related.
I decided to run some injector testing to double check the injector dead time.
Test was at:
100ms intervales
4ms pusles
15 injections

I found out the injector had erratic behavior; it sticks on gradually, and then, completely.
Important: while it is stuck on at full flow, if I unplug it (electrical connector), it stops.

https://www.youtube.com/watch?v=PqtAC7HJFko&t=13s

Microsquirt on a single cylindre 620CC dual sport bike; carb to EFI conversion.
Le_Max
MS/Extra Newbie
Posts: 10
Joined: Fri Jan 26, 2024 1:53 pm

Re: Fuel injector sticks on

Post by Le_Max »

new stuff measured:

The voltage at the pole of the injector is climbing up gradually during test mode. Going from 0.1vdc to 2.8 in about 30 seconds.
At 2.8vdc: BOOM. Injector opens full stream and remains there.

What is this ghost voltage climbing up?
Got it on video:

https://www.youtube.com/watch?v=rHPYtc_EmIw
bobxyz
Helpful MS/Extra'er
Posts: 117
Joined: Tue May 23, 2023 4:30 pm

Re: Fuel injector sticks on

Post by bobxyz »

Wow, those are fascinating videos. I'd guess that the MS injector drive circuit is failing. I'm not sure how that would happen on a single cylinder with a high impedance injector. On a normal 4-cyl, MS is happy driving 4 high impedance injectors per channel, or a load of ~10ohms/4 or 2.5ohms load. Unless something was shorting out the injector, the MS should have been OK.

You might be able to switch to a different injector channel & wire, and somehow setup the MS box for dual injectors, then run the injector test on the 2nd channel.

Another check would be to see what the reported Vbattery voltage is in tuner studio when it's misbehaving. I doubt that a grounding issue could cause the injector behavior, but it's easy enough to check the Vbatt.
Le_Max
MS/Extra Newbie
Posts: 10
Joined: Fri Jan 26, 2024 1:53 pm

Re: Fuel injector sticks on

Post by Le_Max »

Case closed.

It's the MicroSquirt that has failed.
The problem kept getting worst.
At some point, whenever I would activate the fuel pump relay, the injector would start at full blast.


A new wiring was installed with everything disconnect except 12V, injector and fuel pump relay: same problem.
A new MicroSquirt was installed: problem solved!
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