115 optimax idle issue

[mtsaz]

HI- out of the blue my optimax 115 stopped idling and would stall, and idle rough. I went thru the fuel system- changed filters and cleaned out the vapor tank. I also rebuilt the fuel pump, changed plugs, and did other unrelated things--lower unit oil, impeller etc. Once I did the vapor tank it is a little bit better. I am wondering if I have a bad coil or (more likely) an injector. There was some goo in the center compartment (where the float is) of that vapor tank. I changed all the seals in that too. SO---is there anyway to test the injectors or coils? I know with car injectors you can hook a 9v battery to see if they click (Like car injectors), and spray carb cleaner thru them, (car injectors)---but can you do that with these injectors? Also- does anyone know what kind of ohm readings I should get on good coils? I know I can unplug one at a time to see if the motor changes how it runs---but I was looking for a simpler test to screen them----I guess if they are open- probably bad- or shorted- probably bad-

Someone suggested the reed valves. I dont know---and someone suggested the fuel rail diaphram. I would like to stick with simple and work my way up to complicated/expensive. (one can always hope).

Any help/suggestions are always welcome. Thanks

 

[mtsaz]

UPDATE---I unplugged each coil and fuel injector one by one- and it ran worse until all were plugged back in place. SO- I assume from that the coils and fuel injectors are good. I might add- that this runs perfectly WOT- 45mph- no missing, nothing just smooth sailing. However, it idles rough and stalls. I never took this motor for granted- never gave it a thought- when i turned that key- I knew it would start and idle as long as I wanted it too so this is really a shocker. I know its not right and I want to get it fixed. I am wary about getting too far from boat ramp---its hard to get back with trolling motor- or oars. Thanks

 

[racerone]

What does a compression test show ?-------What air pressure does it show from the compressor at idle ?

 

[mtsaz]

PM sent to racerone---I never checked compression- its a new motor- old but very low hours- maybe 25 hrs. I will check today. I asked you in the pM how to check the compressor- I can look in manual but it doesn't have all the details in it. Thanks

 

[mtsaz]

FYI- I bought a 3 gal gas tank- using premium gas- i get the same results. I was certain the gas was ok, but now I know for sure. Thanks

 

[mtsaz]

I guess its time to take it in for the "diagnostic"- thanks