1968 Johnson FD-16A

[dgsmooth]

Good day all. Got a hard one to solve (aren't they all)

1968 Johnson FD-16A, 18 Hp, no start

This thing is like new, stored for 15 years, pulled carb apart, was absolutely spotless inside - whoever put this away 15 years ago knew what he was doing

Got good strong spark on both cylinders
Got good compression, about 75 on both cylinders
If I mess with the jetting and choke/throttle, I'll get lucky once in a while and it'll fire and rev up and sound great for couple seconds, then die. Sure feels like a fuel system problem. I'm trying to find a base jet setting, I've read everywhere from 1 turn on the high speed and 1.5 turns on the idle, to 3 turns out on each. No matter what combination I try, it just won't co-operate.

I'm a heavy duty mechanic by trade, so kind of embarrassing I can't get this one figured lol. Fuel, compression, and spark at the right time means it has to run. I can't confirm "spark at the right time", but it does have good spark and the way it fires and revs up smooth tells me spark is at the right time. Anybody have a base jet setting to start off with? Float was basically non-adjustable, but was flat/aligned with bowl surface as per the norm.

Thanks for any input

 

[Crosbyman]

well the bottom needle (HS) can be seated gently then openned 3/4 turn
and the top LS needle 1.5 turns out for trial. adjust later as per manual

what is important in starting is that the crankcase vacum must pull fuel from the upper fuel route (LS) needle into that small drip chamber under the dime size plug on top. if you did not remove it to FULLY clean the 3 small drip holes fuel may have difficulty making it into the crankcase to be pushed in the cyl on the next down stroke. make certain that at start position the back trottle plate in just about closed.

the upper LS circuit uses a tiny "side channel" from the bottom bowl to the top section. make certain that side passage is fully cleaned to allow fuel to be sucked up on the top section of the carb.

to fully undertstand the process incl. timing etc...and get good overall service info on all aspects of your FD the best book is the johnson " bible"

regardless of what you did as a check-up pulling the flywheel is pretty well standard procedure to check the coils for cracks, change old condensers and at least clean the points and adjust to .020 at the high point of the lobe. AT least peek inside with the inspectiion/adjustment port on top of the FW if you have one.

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com

 

[F_R]

well the bottom needle (HS) can be seated gently then openned 3/4 turn
and the top LS needle 1.5 turns out for trial. adjust later as per manual

what is important in starting is that the crankcase vacum must pull fuel from the upper fuel route (LS) needle into that small drip chamber under the dime size plug on top. if you did not remove it to FULLY clean the 3 small drip holes fuel may have difficulty making it into the crankcase to be pushed in the cyl on the next down stroke. make certain that at start position the back trottle plate in just about closed.

the upper LS circuit uses a tiny "side channel" from the bottom bowl to the top section. make certain that side passage is fully cleaned to allow fuel to be sucked up on the top section of the carb.

to fully undertstand the process incl. timing etc...and get good overall service info on all aspects of your FD the best book is the johnson " bible"

regardless of what you did as a check-up pulling the flywheel is pretty well standard procedure to check the coils for cracks, change old condensers and at least clean the points and adjust to .020 at the high point of the lobe. AT least peek inside with the inspectiion/adjustment port on top of the FW if you have one.

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com

AA++++ on above. It most likely has bad coils, as will most all 1960,s vintage Johnson twins unless they have already been replaced. Yeah, I know, has good strong spark, blah, blah, etc. You aren't the first pro (or otherwise) mechanic to be fooled by this and won't be the last.

 

[racerone]

The motor is a 1962 model !----Does spark jump a gap of 1/4" or more with a " snap" you can hear , yes or no ?

 

[dgsmooth]

AA++++ on above. It most likely has bad coils, as will most all 1960,s vintage Johnson twins unless they have already been replaced. Yeah, I know, has good strong spark, blah, blah, etc. You aren't the first pro (or otherwise) mechanic to be fooled by this and won't be the last.

I've had the flywheel off, and yes the plastic covering over the coils is all cracked, but with a strong "looking" spark, i didn't think much of it. I can't say for sure coils and stuff have ever been replaced, but the motor was used a lot well into the late 90's and 2000's, so I assume would have been replaced? You're right, I'll look into that further

 

[dgsmooth]

The motor is a 1962 model !----Does spark jump a gap of 1/4" or more with a " snap" you can hear , yes or no ?

I'll check that - 1/4"........

 

[dgsmooth]

well the bottom needle (HS) can be seated gently then openned 3/4 turn
and the top LS needle 1.5 turns out for trial. adjust later as per manual

what is important in starting is that the crankcase vacum must pull fuel from the upper fuel route (LS) needle into that small drip chamber under the dime size plug on top. if you did not remove it to FULLY clean the 3 small drip holes fuel may have difficulty making it into the crankcase to be pushed in the cyl on the next down stroke. make certain that at start position the back trottle plate in just about closed.

the upper LS circuit uses a tiny "side channel" from the bottom bowl to the top section. make certain that side passage is fully cleaned to allow fuel to be sucked up on the top section of the carb.

to fully undertstand the process incl. timing etc...and get good overall service info on all aspects of your FD the best book is the johnson " bible"

regardless of what you did as a check-up pulling the flywheel is pretty well standard procedure to check the coils for cracks, change old condensers and at least clean the points and adjust to .020 at the high point of the lobe. AT least peek inside with the inspectiion/adjustment port on top of the FW if you have one.

1922-1964 Johnson 302231 Outboard Service Manual

Johnson Outboard Motor Service and Repair Manual # 302231 Tenth Edition covers all Models 1922-1964 .pdf download

watercraftmanuals.com

No, I never pulled that plug out. It has some silicone on it, so somebody pulled it out once, but who knows when, I'll pull it out. But with the engine firing up and reving up high for a few seconds, isn't it past that "starting process", and should be running on the main jet by then?

 

[racerone]

These motors are elegantly easy to repair.

 

[Crosbyman]

No, I never pulled that plug out. It has some silicone on it, so somebody pulled it out once, but who knows when, I'll pull it out. But with the engine firing up and reving up high for a few seconds, isn't it past that "starting process", and should be running on the main jet by then?

probabaly true... unless it is just sucking up the remaining fuel in the upper chamber but you can check the center post HS throttle tube and side aeration holes if yours has any. they help vaporize fuel.

check the fat donut at the base

pump the bulb to ensure the carb bowl is full and kept fuel by the lift pump. if it helps the side lift pump may be bad. check the side filter in the glass bowl or remove the filter for trial

the wake -up process on old 50-60's engines is straight forward...did you check coils for cracks . replaced condensers etc... mesure secondary ohms value on coil HV boots & grd while you rotate the throtlle from LS to HS etc..etc..

 

[dgsmooth]

probabaly true... unless it is just sucking up the remaining fuel in the upper chamber but you can check the center post HS throttle tube and side aeration holes if yours has any. they help vaporize fuel.

check the fat donut at the base

pump the bulb to ensure the carb bowl is full and kept fuel by the lift pump. if it helps the side lift pump may be bad. check the side filter in the glass bowl or remove the filter for trial

the wake -up process on old 50-60's engines is straight forward...did you check coils for cracks . replaced condensers etc... mesure secondary ohms value on coil HV boots & grd while you rotate the throtlle from LS to HS etc..etc..

i did have flywheel off, and the clear outer "plastic" on the coils is all cracked. but with what i thought was "good spark" i didn't think much more about it, obviously i will now. how do i check resistance on the "coil HV"? and what should it be? thanks again to everyone

 

[racerone]

The coils are garbage.----New ones are cheap.----Not worth wasting time to test them.

 

[Crosbyman]

since ou will replace cracked oils ( many utubes on the subject) you can measure the new ones between the HV pin and either short primary wires and expect 4-8 KILO ohms approx..
primary to primary short wires is about 1 ohm or less

as Racerone said... don't even bother with the cracked ones. R.I.P. them out

since you will be in there ... may as well change plug wires 7mm copper solid strand wire NO CARBON!!!

plug boots.... may be good just poke the pin prick in the center of the 7mm wire

I use automotive Belden wire (metallic strand ) with boots already molded on the wire





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