Wont start backfires

[brianwake]

Hello i have an 1979 evinrude 85995r 85 hp. I had no spark in cylinders 1 and 3 so replaced the power pack. Now it just back fires when i try to start. Does this mean the timing is out. checked the wiring dirgram no wires crossed that i could see. What would be my next step?

 

[tashasdaddy]

Re: Wont start backfires

99% means the woodruff key that lines up the crack shaft and the flywheel, has sheared. this throws everything off. you need to pull the flywheel, replace the woodruff key. bet you are back in business. you need #8 harden bolts to fit the flywheel, an harmonic balancer puller. do not hammer on the flywheel. then when you reinstall flywheel everything free of grease, spotless clean, and retorque the nut. if you don't it will do it again.

 

[ezeke]

Re: Wont start backfires

Did you replace both powerpacks? Have you had the flywheel off for some reason? Was the engine running OK before the powerpack failed?

 

[R.Johnson]

Re: Wont start backfires

Do you have the wire's from the pac to the coil's correct?

 

[HighTrim]

Re: Wont start backfires

Backfiring out of the exhaust port is caused by having the ignition system fire a particular cylinder when the exhaust port is open ( ie piston down). This would sound like a shotgun going off, and hard to mistake.

This is usually due to a sheared flywheel key, a flywheel with melted (moved) center sensor magnets if they exist, timer base leads routed incorrectly to the powerpack, or having the leads from the powerpack to the coils reversed to mention a few.

Did you try swapping power packs before buying new to see if that solved the problem, and that is why you bought new? Does seem like a sheared flywheel key, but unlikely that happened from solely changing the PP, more likely a PP wiring issue. Plugs torqued down to 18.5 to 20.5 ft/lbs?

 

[brianwake]

Re: Wont start backfires

Engine was running perfect until throttle cable broke when i replaced the cable the engine would not start, Found that there was no spark in cylinder 1 and 3 so i swapped power pack from the port side and then in had spark so go new power pack and installed it. Now the engine wont start just back fires. Going from the wiring diagrams the wire's from the pac to the coil's are correct.

 

[tashasdaddy]

Re: Wont start backfires

look at the flywheel.

 

[wavrider]

Re: Wont start backfires

Coils wire on the right plugs? If coils wires get crossed could cause this also.
Most likely flywheel key.

 

[DJ]

Re: Wont start backfires

Coils wire on the right plugs? If coils wires get crossed could cause this also.
Most likely flywheel key.

Yup. Don't ask me how I discovered this.:redface:

If not, flywheel key.

 

[brianwake]

Re: Wont start backfires

Can i see if the woodruff key is sheared with out pulling the flywheel?

 

[reeldutch]

Re: Wont start backfires

nope you got to pull the flywheel to inspect the key ,
what i would do before messing with anything is check the timing (indexing the flywheel) so you see if the motor is firing at the right time.
you can check this with the plugs out grounded to a spark tester. find top dead center and check your timing.

everyting is in your manual.

thats what i would do.

i doubt it is your key.

probebly when you installed the new throttle cable you might have accidently changed the timing.
so adjustment per manual might be needed.

good luck

 

[ezeke]

Re: Wont start backfires

Just to be sure, look up just under the starboard side of the flywheel and check to be sure that the arm off the timer base is connected to the spark advace lever(spark advance rod in the diagram).

 

[Benny1963]

Re: Wont start backfires

make sure pack is wired right qnd spark plug wires are right
before removal of flywheel
i pulled a flywheel for nothing had two plug wire cross a amphenol conn.
good luck bennyb