2001 90hp Johnson fuel supply problems

[Christofr1]

Hi-

I have a 2001 90hp 2 stroke Johnson motor that is used in saltwater. I tried starting the motor after about 2 weeks of non use and found it would not start and stay running.

The motor turns over fine and seems to get plenty of gas / oil. It is firing up, running for about a second or two at most and then cutting out. After starting up and doing this three or four times, the water temp / coolant indicator light came on. I tried running the engine tilted up out of the water with the hose connected as I always do to flush it, and I also tried running it lowered down into the water to draw through the impeller. Neither worked. The impeller was replaced about a year ago.

Are there any common low engine speed cooling problems? Is there an automatic kill sensor on the motor if its overheating? Cooling system clogs? Bad Thermostats? Bad Impeller? etc. that I should check? Any direction on how to troubleshoot this would be appreciated!

Chris

[Chris1956]

Chris, That motor would cut spark to 1/2 it's cylinders, if it thinks it is overheating. Did you run it 5 min or so? If not, it isn't overheating. Overheating will not kill all the spark.

You can check the temp sensers to see if they are shorting to ground. If they are shorting, and the motor is cool, they are defective. You can test the thermostats. They should open at 143*F or thereabouts.

[Christofr1]

I did some further testing this morning on the engine and determined it is not at all a cooling problem, but is in fact a fuel problem. The engine is running for just a couple of seconds off of the prime from starting and cutting out immediately after. I can get the boat to run for up to 30 seconds or so if I continuously prime it.

When I engage the primer solenoid and direct injects fuel / bypass the components of the fuel system, I run rich, but continuous. When gas is running through the whole system, I have a flow problem. Could be the OMS pump perhaps? Could be a vapor problem? Also of note, inside of the engine case there was a fair bit of engine oil. As the boat is new to me, Im not sure if this is standard, or could be related, and maybe points to the OMS pump being bad.

Does anyone know what components of the fuel system are bypassed when engaging the primer solenoid?

[Chris1956]

Only the carbs are bypassed when using the primer. It therefore sounds like your carb idle circuits are dirty.

[Christofr1]

Thanks for the insight. Even studying the engine manual it was a bit unclear to me what was bypassed. Any idea as to how to check the function of the carb idle circuits and what the remedy to this may be? Thanks again for the help!

[Chris1956]

It is hard to check the function of the carb circuits. Normally we just clean the carbs and rebuild them with new carb kits.