18hp won't fire

[pedro79]

I have a 2006 18hp Tohatsu that will not fire when outside air temp is below the mid 40's. Any help greatly appreciated.

 

[pvanv]

Re: 18hp won't fire

I'm assuming you have an MFS18B2, right? Model is everything, whereas year is unimportant for servicing.

When you say "will not fire", are you saying you tested for spark and it doesn't have any? Or are you saying that it does not start? The 18B2 is equipped with an automatic enrichment solenoid, the auto-by-starter unit. If that is failing, you might not get a rich enough mixture to start when cold.

 

[Sea Rider]

Re: 18hp won't fire

I have a 2006 18hp Tohatsu that will not fire...

Is it a 2 or 4 stroke engine to start with ?

Happy Boating

 

[pedro79]

Re: 18hp won't fire

model MFS18B2
four stroke
I have pulled the plugs and tried it and had no fire at the plugs when the outside air temp is cold. If I wait until later in the day and the air temp comes up and the boat has been sitting out in the sun, it will crank right up. I have put new plug wires and plugs in it.

 

[pvanv]

Re: 18hp won't fire

I'm assuming you grounded the plugs when testing, and confirmed no spark. If not, you will need to re-test using proper procedure.

Next step would be to get a Factory service manual, Part# 003-21041-0, $27.58, from any dealer, including me, and go through the diagnostic tests for the ignition system. You will need a good analog (not digital) multimeter, preferably with DVA capability to run the tests. You need to test the ignition coil, the CD, the pulser, and the alternator, as well as confirming that the stop switch is not failing to ground when cold (rare, but possible).