1990 15 hp Johnson won’t start, sort of sounds like it’s sucking air/leaking air

[jitterbug127]

I have a 1990 15 hp Johnson that has run beautifully most of the summer. We go out fishing Sunday and it started right up on the first pull like usual, runs great, idles beautifully. My buddy hadn’t actually seen my motor since I’d tuned it up, and I was bragging about how good it had been running. I take my boat/motor out 1-3 times every week.

I’m coming back up the river and motor acts like it’s starving for fuel. I could restart on the first pull, increase the throttle and it would die. I proceed to do this a few time and then motor just decides to not start. I got it home and proceed to try to work on it. Motor won’t start and sort of sounds like it is sucking air. It’s making a bizarre sucking noise that I’ve never heard it make before.

Compression check 96/100, spark that will jump a good gap in both cylinders, I see fuel getting to the carb. I checked fuel pump no clog, I even changed it out since I had a spare. Still sucking air. I put a different tank/hose combo on the motor thinking maybe that it. Still same results. It hasn’t even coughed/barked. Completely out of left field. I’m not sure where to go from here. I checked my spark plugs not fouled. I even cleaned them and out them back. I went from a great running motor to a won’t start motor in a matter of minutes. My carb was rebuilt a month or 2 ago and it’s been running phenomenally.

 

[OptsyEagle]

Did you put any fuel directly into the cylinder holes and see what result you get when you
attempt to start it?

Also, in June when you were working on this motor I asked if you noticed that your cam roller is missing a piece to it that might make it hard to line up the link and sync properly. It is the last post on this thread. If that piece is still missing perhaps your spark timing it too far advanced.

How to get my throttle roller closer to the armature/flywheel?

I’ve finally got a running motor. I’ve been through a couple I was gonna out on my boat I had to move on from because I could not get them to start. First let me apologize if my vocabulary is off titling parts. 1990 15 hp motor. I got it to start finally increasing the throttle with my finger...

forums.iboats.com

 

[jitterbug127]

Did you put any fuel directly into the cylinder holes and see what result you get when you
attempt to start it?

Also, in June when you were working on this motor I asked if you noticed that your cam roller is missing a piece to it that might make it hard to line up the link and sync properly. It is the last post on this thread. If that piece is still missing perhaps your spark timing it too far advanced.

How to get my throttle roller closer to the armature/flywheel?

I’ve finally got a running motor. I’ve been through a couple I was gonna out on my boat I had to move on from because I could not get them to start. First let me apologize if my vocabulary is off titling parts. 1990 15 hp motor. I got it to start finally increasing the throttle with my finger...

forums.iboats.com

Cam roller piece was replaced! Thanks for advice on that.

 

[tphoyt]

Any chance you have gotten some water in your gas?

 

[jitterbug127]

Cam roller

 

[jitterbug127]

Any chance you have gotten some water in your gas?

I’ve got 3 tanks and 2 hoses. I’ve rotated all of them and put fresh gas in

 

[OptsyEagle]

Put some gas directly into the cylinders and give the starter a pull and let us know what result you get.

 

[jitterbug127]

Put some gas directly into the cylinders and give the starter a pull and let us know what result you get.

I put gas directly into the cylinders. It doesn’t fire. I do have a bunch of air coming out of the tell tail which I’ve never seen before.

 

[OptsyEagle]

When you pull on the starter the water pump impeller will rotate and that will move some water up the water tube. As the water moves up the tube the air in it must move out, so perhaps that is all you are seeing there.

When you get nothing from adding fuel directly to the cylinders it makes me think you have a spark problem of some sort or perhaps compression. I would recheck those again. Other then that I got nothing. I assume you adjusted the link and sync properly when you replaced the cam roller.

 

[OptsyEagle]

A couple other thoughts:

1) Any chance you reversed the spark plug wires after you checked your compression numbers?
2) Perhaps your spark plugs are fouled. In your case both would need to have fouled at the same time, but it would not hurt to put a couple new plugs in and give it a test.
3) Could be reed valves but very unlikely since I believe each cylinder has their own reed valves. So not only do they rarely fail but in your case both would have to have failed at the same time.

 

[jitterbug127]

When you pull on the starter the water pump impeller will rotate and that will move some water up the water tube. As the water moves up the tube the air in it must move out, so perhaps that is all you are seeing there.

When you get nothing from adding fuel directly to the cylinders it makes me think you have a spark problem of some sort or perhaps compression. I would recheck those again. Other then that I got nothing. I assume you adjusted the link and sync properly when you replaced the cam roller.

I checked spark and compression today, spark jumps 3/8 inch gap well and compression is 96/100. I have probably got 50 hours on this motor since I replaced that cam roller and it’s run great. I assume I’ve got it linked and synced properly.

 

[tphoyt]

Could check the flywheel key just for kicks

 

[jitterbug127]

Could check the flywheel key just for kicks

Checked that one out already too! Replaced my fuel adapter, only thing left for me to do is unfortunately see if my carb is cracked

 

[jitterbug127]

Could check the flywheel key just for kicks

A couple other thoughts:

1) Any chance you reversed the spark plug wires after you checked your compression numbers?
2) Perhaps your spark plugs are fouled. In your case both would need to have fouled at the same time, but it would not hurt to put a couple new plugs in and give it a test.
3) Could be reed valves but very unlikely since I believe each cylinder has their own reed valves. So not only do they rarely fail but in your case both would have to have failed at the same time.

Spark plug wires are ok. I cleaned the spark plugs really well. They weren’t particularly fouled out at all, but I will try a new set of plugs just for good measure.

 

[David wright]

I have a 1990 15 hp Johnson that has run beautifully most of the summer. We go out fishing Sunday and it started right up on the first pull like usual, runs great, idles beautifully. My buddy hadn’t actually seen my motor since I’d tuned it up, and I was bragging about how good it had been running. I take my boat/motor out 1-3 times every week.

I’m coming back up the river and motor acts like it’s starving for fuel. I could restart on the first pull, increase the throttle and it would die. I proceed to do this a few time and then motor just decides to not start. I got it home and proceed to try to work on it. Motor won’t start and sort of sounds like it is sucking air. It’s making a bizarre sucking noise that I’ve never heard it make before.

Compression check 96/100, spark that will jump a good gap in both cylinders, I see fuel getting to the carb. I checked fuel pump no clog, I even changed it out since I had a spare. Still sucking air. I put a different tank/hose combo on the motor thinking maybe that it. Still same results. It hasn’t even coughed/barked. Completely out of left field. I’m not sure where to go from here. I checked my spark plugs not fouled. I even cleaned them and out them back. I went from a great running motor to a won’t start motor in a matter of minutes. My carb was rebuilt a month or 2 ago and it’s been running phenomenally.

Does it try to start every now and then and backfire ? If so its possible you have a sheared woodruff key

 

[racerone]

Fuel in the cylinders.----Spark that jumps a 3/8" gap means the motor should at least bark / roar like a lion !!----Check that flywheel key today.----Assemble with the tapers clean and dry ??---Did you torque the flywheel nut to the correct value ?

 

[David wright]

Is the underside of the flywheel scored or worn at all if so maybe its slipping

 

[jitterbug127]

Pictures of under flywheel posted in previous post. Looked good to me

 

[jitterbug127]

Fuel in the cylinders.----Spark that jumps a 3/8" gap means the motor should at least bark / roar like a lion !!----Check that flywheel key today.----Assemble with the tapers clean and dry ??---Did you torque the flywheel nut to the correct value ?

Under fly wheel

 

[David wright]

I mean where the flywheel meets the woodruff key is that worn