New Guy..95 Johnson 15hp will not crank

LongueCarabine · Jun 16, 2011

Hi everyone:

I'm new here, inherited a 15hp Johnson (1995) from my Dad. Motor was running as of a couple years ago. My sister used it once last year and noted that it died on her when she used it.

I have changed the spark plugs, (it had 2 different plugs, neither was the specified plug) drained the gas and put in a fresh mix, soaked the carburetor in cleaner and have disassembled / reassembled it. Did not see any corrosion or badly gummed up parts, although the old fuel mix did smell like varnish.

Gas is getting into the float bowl, but from what I can tell, is not getting into the engine. At least, that is my assumption since the engine would not catch. I have pumped a little into the cylinders through the spark plug holes, and it will run for a few seconds. It sounds like it is running correctly, so I am stumped as to what could be going on.

Can anyone help?

Thanks,

LC

Monte1961 · Jun 16, 2011

Re: New Guy..95 Johnson 15hp will not crank

Just because gas is getting to the carb/s doesnt mean engine is. Take a squirt bottle of fuel mix and spray into carb/s and post back what happens!

raczekp1 · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

remember if it is 2 stroke it needs mix(oil +fuel mix 1/50).
check compresion by compresion tester.
if its low, there is not enough suction to suck fuel from carb.
compresion should be over 60 psi and equal.
new or rebuilt motor has 125 or more

also slow speed needle in carb(left side of carb body) if is screwed to far ther will be no fuel flow to start

LongueCarabine · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

OK, I've gone back in and cleaned the carb out again, and it will crank but will not stay running. There were dirt dauber nests in the air filter and that would have caused a restriction in flow easily. Compression in each cylinder is 95.

I have not done anything with any of the idle settings, and I am pretty sure they have not been touched since the motor was bought 16 years ago. More and more I am leaning towards the carb needing to be rebuilt, but was wondering if anyone else had any ideas.

LC

ETA: At first I thought I was also having a water pump problem, but the last couple times I cranked, it it was peeing water out of the hose pretty well, so I am not too worried about that at this point.

Daviet · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

If it will run by squirting fuel into the carb, it has to be a fuel delivery problem. Remove the fuel line going from the pump to the carb and pull it over a few times, is fuel pulsing out of the line? If the pump is pumping fuel, the problem is most likely in the carb.

LongueCarabine · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

Fuel is definitely making its way out of the fuel pump. I did as you instructed, and it pulses out. One thing I noticed is that when I disconnected the line from the carb, fuel kept coming out. I had to undo the cap on the tank, pump it back up, then pulled the start. Fuel would spurt out after that.

I also managed to get it to run for a couple minutes after putting the line back on. Everything seemed normal, it was would even rev up and down a bit, but would run pretty rough at higher rpms. Then it conked out, and is giving me trouble cranking and staying running.

LC

Daviet · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

It's got to be an internal carb porblem. When you overhauled the carb did you install new gaskets and seals?

LongueCarabine · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

No, just started working on this yesterday and have been calling around locally for parts. I have them on order, no one around here has anything in stock. Guess that is my next step, I hope the FedEx guy hurries.......

I am gonna guess the float valve is sticking. The float seems fine, but I am gonna replace all of it with a kit.

Thanks for the help.

LC

LC

boobie · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

Are you testing this mtr on muffs, in a barrel or in the lake??

Monte1961 · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

As I said before. The carb is going to need overhauled. Remove any and all core/welch plug pryor to soaking. Do not soak anything in carb cleaner that is plastic! All other parts are ok. Take plenty of pics during removal and disassembly. This way you will have a reference as to how it goes back together. Allow carb parts to soak for a good 24hrs, rinse with fresh water and blowdry clean with compressed air. Good luck and post back.

LongueCarabine · Jun 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

boobie said:
Are you testing this mtr on muffs, in a barrel or in the lake??

Using muffs. Won't be able to do any more work until I get the carb parts in, it's kind of pointless until then.

LC

LongueCarabine · Jul 3, 2011

Re: New Guy..95 Johnson 15hp will not crank

Well, finally got the carb kit in, rebuilt it, and still having almost the same problem. It is hard to start and doesn't run very well when it finally does start. I noticed a very heavy substance on the plugs, almost like wet graphite. It wasn't doing this the last time I cranked it, so I am wondering if it isn't just running much too rich. Going to need help diagnosing this.

Thanks,

LC

LongueCarabine · Jul 6, 2011

Re: New Guy..95 Johnson 15hp will not crank

Hi again everyone. Found out the main cause of the problem was my pickup tube. Had to drill out the welch plug and run wire into it to clean it out. Motor starts fairly easily cold, runs pretty well, but is hard to crank after warming up. I think I probably need to re-set the idle also, as it will conk out when left to idle down.

Anyone have any idea about the hard starting?

Thanks,
LC

LongueCarabine · Jul 7, 2011

Re: New Guy..95 Johnson 15hp will not crank

Still having problems. Plugs are developing significant fouling, it occurs after only 10 minutes of running. Still not cranking easily after having been run. And it was hard to crank to begin with.

Could really use some help.

LC

milliesdad · Jul 7, 2011

Re: New Guy..95 Johnson 15hp will not crank

Have you cheked the spark with a spark tester? Not just grounding out a plug and pulling it over, but a real spark tester? Should jump a 3/8"gap with a white-blue snap.

Next would be to pull flywheel and check condition of coils. When you replace the flywheel, use a torque wrench and torque the nut to the specified value in your service manual.

AlTn · Jul 7, 2011

Re: New Guy..95 Johnson 15hp will not crank

under the top secret files is a decarbing procedure...try this as well

LongueCarabine · Jul 16, 2011

Re: New Guy..95 Johnson 15hp will not crank

Checked the spark, it is good and strong, bluish-white with an audible snapping sound. I really don't think there's an electrical problem with it. Gonna go over the carb again, and probably try to get some of the carbon out of the system.

LC

milliesdad · Jul 16, 2011

Re: New Guy..95 Johnson 15hp will not crank

By "cranking" do you mean the motor starts up, or does it turn over. "Cranking" means turning over but not running.

LongueCarabine · Jul 17, 2011

Re: New Guy..95 Johnson 15hp will not crank

I mean the motor starts running.

LC

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