1993 70HP Johnson. Puzzled.

[James R]

Carbs clean. Sparks good. Timing and sync good. Comps 125 all.
#2 #3 running fine. #1 not running. Will not idle properly, stalls in gear. Wont come up on revs in gear.
Swapped plugs,coils and wires around, still #1. adjusting #1 carb changes nothing. Shooting fuel into intake while running, #1 no change. Blocking intake while running, no change.
Thinking upper crank seal or reed.
Really need help on this one guys.

 

[tashasdaddy]

Re: 1993 70HP Johnson. Puzzled.

you have spark on all cylinders, compression is good on all cylinders, but when you pull # 1 spark plug wire there is not change in the running of the motor. is this correct?

if it is correct, then you have a fuel delivery problem to # 1 carb. did you remove and clean all the jets in the carb, and spray out the pickup tubes?

have you open the bowl drain to be sure it carb is getting fuel?

did you check spark with a spark tester?

 

[James R]

Re: 1993 70HP Johnson. Puzzled.

Thanks for the response TD. Getting fuel to the carb. I took this carb off a second time and gave it another clean. Most meticulous about carb cleaning. So much so that I have just taken delivery of an Ultrasonic cleaner.
Shooting fuel into the carb throat whilst running usually proves fuel shortage.
Never had to check a spark before but I have an adjustable gap tester and an inline on the way. Could be a bad power pack or trigger I suppose.
Stay with me on this please. I need all the help I can get on this one.
Thanks again.

 

[James R]

Re: 1993 70HP Johnson. Puzzled.

Spark test showed good and equal sparks at 1/2 inch on all cylinders. Checking with timing light shows sparks occuring where they should. Tried different plugs. Pulled carb again and cleaned. Getting fuel and all cylinders respond to carb idle adjustments. #1 cylinder still not performing well. Motor dies when I pull #2 or #3 plug connectors. Makes no difference when I pull #1. Tightened the intake manifold bolts just a tad. No difference. Noticed we have lost 10lbs on all three cylinders. The gauge is reliable.
Will switch upper and lower carbs if possible and test again. After that the head comes off. Don't have the gear to do a blow by.
Any suggestions most welcome.

 

[James R]

Re: 1993 70HP Johnson. Puzzled.

Switching carbs, no change. Removed head, no damage, bores clean and only 0.0025" wear. Still in spec. Pistons all same deflection. Rotating the flywheel by hand provides a satisfying snap from the transfer ports on 2&3. #1 only a soft snap.
Is this a bad reed?

 

[James R]

Re: 1993 70HP Johnson. Puzzled.

Replaced Reeds and the cylinders now idle evenly. RPM comes up easily out of the water but still can't get it to idle properly and get up above 2500 in the water. I am thinking blow by so a tear down and rebuild is probably the way to go.