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1980 15hp Johnson not starting

C

chrisr

New member
My 15hp manual start is having starting issues. As of the end of October, it ran well during a trip and did so for the 4 months of weekly use before that. In June, it was not running but I found a tear in a fuel line and after replacing it the motor ran okay. Once initially started, it would start every pull thereafter after shutting it off. On the initial startup, it would take 10-20 pulls to get a spark. Now, it will not catch. I checked the fuel tank, primer bulb, and line, all were working correctly. The motor has not run in a month, and I forgot to run it out of gas as i usually would. I would guess a clogged carb, or bad spark plug, but I'm unsure.
 
Note that the engine should always start within six pulls of the starter cord.

Regardless of the problem, always begin the trouble shooting procedure by:

1 - Checking the compression. If you do not have a compression gauge and since you've owned the engine for some time, you could pretty well tell if the compression is normal as comparing it now (by feel) with what it was in the past..... but gauges are cheap and it's best to have one on hand.

2 - Check the spark. Remove the spark plugs and inspect them for any appearance out of the ordinary. With the s/plugs still removed, the spark at cranking speed should jump a 7/16" gap with a strong blue lightning like flame... a real SNAP! Note that checking spark by using the spark plugs is a waste of time.

If the above two area are as they should be, the problem you describe is usually a fouled, gummed, clogged carburetor.... a most common problem.
 
It is a 32 year old motor so a compression test should be done , could be as simple as a blown head gasket.--------Ignition system was engineered to be able to jump a gap of up to 3/8" or more so that should be tested as well.-----------Carburetor merely responds to air being pulled through it by the motor.----If there are major internal problems with rings / seals / reed valves then even a good / clean carburetor will not work.
 
I just read that checking spark with plug in not good way, what is the best way to check spark without high priced equipment?
 
There are various way to set up something with a 3/8" gap.----For example you could get some old sparkplug wire and cut it up.----------Then fasten that to a piece of plywood with staples / screws / clamp etc so that you have that gap. Then fasten a simple aligator clip to ground one end of the wire to the block and stick the other end in the sparkplug boot.----Depends on how much time and material you have on hand I guess.-----A spark tester can be purchased from your local dealer too and not that much coin.
 
Thanks for the advice guys. I checked the spark, its snapping good. Both plugs were fouled up so I replaced them. However, this didnt not solve the issue. Next step will be to check the carburetor and hope its nothing more.
 
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