suzuki dt25 3 cyl, voltage check on throttle valve sensor

[sandro]

Hello,
Is there anyone familiar with the outboard above? I have it mounted on my boat and it's not working properly: below 4000 rpm it seems to misfiring at one cylinder causing rough operation and vibration; I checked a lot of components including throttle valve sensor that seems to be ok, but checking the voltage IN and OUT at its wires I had a doubt: the black and red wire that carries the + tension from CDI unit gives an alternate voltage of about 6 volts at idle, increasing as RPM increase, the green and red wire which is the OUT tension from sensor gives a direct tension of 0.9 volts, increasing (as it should do) as throttle opens... may be the CDI doesn't give a correct tension to make the sensor working properly (anyway, checking the timing with a strobe light, it varies as the throttle is opened)...
On Clymer shop manual I have, there isn't any specification about...
Anyone has worked on it?
Thanks a lot
Sandro

 

[deejaycee_2000]

Re: suzuki dt25 3 cyl, voltage check on throttle valve sensor

Have you checked the compression on the cylinder missfiring?

 

[sandro]

Re: suzuki dt25 3 cyl, voltage check on throttle valve sensor

Have you checked the compression on the cylinder missfiring?

I did: no.1 (top, with problems) 125 psi, no.2 122, no.3 123.
I think it's no.1 because when I attach the strobe light inductive probe on its sparkplug wire, the timing marks on flywheel, randomly move about a couple of degrees away, and when that occurs, vibration occurs also (using the strobe light on other 2 cyl, looking at the corresponding TDC mark on flywheel i did, they appear steady)

 

[deejaycee_2000]

Re: suzuki dt25 3 cyl, voltage check on throttle valve sensor

Your compression is fine .... before getting into the technical stuff, sometimes it is the simple things that people overlook that can cause problems .... have you replaced your spark plugs? I've had a similar problem and it turned out that i had a bad spark plug and on the others the gap wasn't set correctly so have a look at that first before taking things apart ....

 

[sandro]

Re: suzuki dt25 3 cyl, voltage check on throttle valve sensor

Your compression is fine .... before getting into the technical stuff, sometimes it is the simple things that people overlook that can cause problems .... have you replaced your spark plugs? I've had a similar problem and it turned out that i had a bad spark plug and on the others the gap wasn't set correctly so have a look at that first before taking things apart ....

You are right! I To summarize what I have checked:
spark plugs (new, NGK and Denso)
ignition coils (resistance whithin spec. and I also have rotate them on different cyl, but strobe erratic indication is always on no.1)
ignition wires and ground point ok
carburators serviced
fuel lines to each carb ok
pulser coils resistance ok(I would have rotated them, but I didn't manage to remove the flywheel...)
bye