1976 Johnson 135 HP V4 - Weak Spark on One Side (2 + 4)

[CaptnKingfisher]

Picked up this old V4 for $300 cuz I had the same motor on the back of my boat (my other is a 1975, but most of the parts are the same). Old owner said it had no spark but ran when he put it away a decade ago (take that with a grain of salt, as usual). Compression was good, couple hundred bucks, I bought it. Fast forward to today:

I've got weak spark on Port side (cylinders 2 and 4) with plugs in. I can start and run the motor on muffs, but in the water when I drop to from (START- fast idle) to low idle to shift into gear, she stalls. If i throw it into gear and with some ether I can run for a minute before it quits. Presumable because the old lady is trying to run on 2 instead of 4. She's trying, but she needs help. So I got a DVA meter and tried a couple things. Here's what I found:

With the spark plugs out: Strong spark on all 4 cylinders. DVA tests according to spec. Things look perfect.
With the plugs in: Spark (on 2 and 4) will not jump 7/16's gap. DVA tests on orange coil wires are out of whack on port side of motor (the two that dont spark or spark weak)

I've swapped coils around and it doesnt matter, coils are good (brand new tested and work independently), plugs are good (also new), I've tried swapping the stator with the one from my other motor, same issue, I've swapped power packs, no change, same issue. So I'm really scratching my head here. Is this maybe not ignition system related at all? Maybe its a lack of RPMs with plugs in? I don't have a tach hooked up either though I've got one laying around from an old boat. I've done some hunting and pulled all the grounds and cleaned em and made sure theyre good. Battery is strong and tests well. I've got the manual but when I run through the manual diagnostics I arrive at Bad Powerpack or Bad Stator, but Ive tried swapping with my spares and dont see a change. Any advice is welcome, thanks guys

 

[racerone]

My usual suggestion is to take the starter apart for inspection.-----Some will argue !---Load test the battery too.----Just classic, poor starter performance means poor / no spark.

 

[CaptnKingfisher]

I actually have a new starter in box as a spare, didnt think to throw it on but might as well since the one on the motor now appears to be original. I'll load test the battery tonight and report back

 

[CaptnKingfisher]

My usual suggestion is to take the starter apart for inspection.-----Some will argue !---Load test the battery too.----Just classic, poor starter performance means poor / no spark.

Load Test was good. 12.84 V w/out load, Dropped as low as 10.3 during Cranking. My understanding is that passes (dropping below 9.6 is no good)
Replaced Starter with my spare (brand new) -> Now I have spark on 3/4 Cylinders which is an improvement. Definitely starting to think this is a cranking speed issue more so than a bad component (powerpack/stator/coil). Again, I swapped my no spark, no. 2 coil wire with another wire on the pack, and saw spark on that cylinder. Still 3/4 spark. So I know my coils and plugs are good. With the DVA adaptor I can see that the terminal on the powerpack is only getting about 50 volts whereas all the others get above 100. Again, with plugs out, all coils fire, all terminals are sent 100+ V from the powerpack.

I guess I gotta hit the manual about slow cranking issues although it sounds like its got plenty of speed..

 

[boobie]

Have you tried swapping out the timer base ??

 

[CaptnKingfisher]

Have you tried swapping out the timer base ??

I have not, but thats worth trying. I didnt look too hard at it but is the timer base just attached by those clips? Phillips screwdriver with silver metal clips holding it in place? I guess I can try that, I have my parts motor in storage but if I get my ass in gear I can get up there and get my timer base off it after work tmrw. I am getting pretty good at taking these flywheels on and off lol

 

[boobie]

With all the things you've changed it's worth a try.

 

[CaptnKingfisher]

With all the things you've changed it's worth a try.

Okay, I got the timing base from my parts motor AND my tinytach arrived. And from my tinytach I learned some valuable information.

WITH PLUGS OUT: Cranking RPM is 940 and I get spark on all 4, and spark jumps 7/16s gap. GOOD.
WITH PLUGS IN: Cranking RPM is 720ish and I only get spark on 3.

I redid my v oltage drop test from my POSITIVE cable where it connects to selenoid. Voltage drop test is good from starter (12.7 - drops as low as 10.5).. if I crank a long time goes as low as 9.9 or 9.8 but we're talking 15 seconds. So my battery is GOOD. My cables coming from battery to starter are GOOD. My starter is brand new. and my old starter is worse than the new one for cranking speed. So I am really at a loss... BATTERY = GOOD, STARTER = GOOD, CABLES = GOOD.... but slow cranking speed.. My compression isnt overly high either, its like 110 across the board. Ive had my flywheel on and off and dont see anything crazy hardly any visable wear or rust. My flywheel key looks a little beat up but I wouldnt say its 'sheared'. My flywheel key looked much better on my parts motor so I grabbed it and will swap them out but I'm really starting to scratch my head at this issue. I took a glass beer bottle (or two) and wedged them between my plug wires and the block in case them touching the block was causing a short but it didnt change anything. I feel like my issue is slow cranking and I cant seem to fiugre out whats causing it.

 

[Faztbullet]

Does it fire on all 4 when running at idle???? If not stator weak on that side or pack has a problem. Flip the brw and brw/yel with each other. Also air gap on sensors are important...

 

[CaptnKingfisher]

Air gap on the sensors? Please explain further, never heard about that before. Also, I just went back down, pulled the boat out into the driveway and hooked up the hose with the tinytach atttached and started it on the hose. Tried the tiny tach on all 4 cylinders independantly. Maybe I'm focusing on the wrong issue entirely. Sure.. it only cranks at 940ish RPMS with plugs in, but it does turn over and start... and once it starts all 4 (as I just confirmed) sparkplugs are firing during running. Low idle right now (I havent tried setting my idle speed at all yet) is about 1300 on Muffs. And it idles fine. When I shift into gear it stalls. I already started to pull my spare carbs apart and planned on cleaning and have a good looking fuel filter to put on and new hose. Maybe I'm getting hung up on the 3/4 spark on cranking when in reality its a non issue because the motor starts and then runs on all 4 (according to my tiny tach) and runs at a decent rpm.


So my new issue that I need to think about is stalling when shifting into gear or/and loss of power under load. Unless anyone has any bright ideas, I think I/we might want to abandon this discussion until I rebuild my carbs, replace my hoses and fuel filter, and this might call for a new thread if its not a spark related issue. I dont like that only 3/4 wires get spark on cranking, but maybe its not that unusual? idk, I'm still a novice..

 

[oldboat1]

Might clean up the shaft with some acetone, and switch out flywheels (use better of the two keys, and torque to spec -- 100 ft lbs).

 

[Faztbullet]

Here is tool.......to much air gap can cause spark issues..
https://www.carid.com/cdi-electronics/cdi-sensor-gap-gauge-mpn-553-9702.html

 

[racerone]

Is the wee tach set for 2 stroke or 4 stroke.----What are those " good " compression numbers ?

 

[CaptnKingfisher]

Is the wee tach set for 2 stroke or 4 stroke.----What are those " good " compression numbers ?

Compression is about 110 on all 4. Little low for this engine I believe but it was almost exactly the same on each cylinder which I like. Tiny tach is a brand and their tach displays rpm by coiling a red 12 or 14 gauge wire around a spark plug lead. The device itself is grounded and it figures rpm based on spark pulses. Making an assumption here with spark plug at 940 RPM I get Spark on my tester on All 4 cylinders and with spark plugs in and motor running idle at 1300 RPM my tiny tach shows electrical pulses on all four spark plug wires and reads the same RPM that my issue is not spark related. To confirm this I can try starting the motor and pulling the spark plug wire that wasn't firing on the tester during cranking. If I experience power loss I'll know the cylinder was firing. If there is no change then I will know that that cylinder was not firing.

As far as air gap sensor, I will look into this more after I rebuild the carburetors and replace the fuel pump.

Cleaning the shaft with acetone is a quick and easy thing to do and the key on my part motor is in much better shape so I will switch them. I will take a hard look at the flywheels before deciding which to put back on the motor. The one that's on there now has almost no visible wear that I can recall, but my parts motor shows some rust on the teeth period I will inspect the key cavity and the shuttle to see which is in better shape

 

[racerone]

Is the wee tachometer set for 2 stroke or 4 stroke ?

 

[CaptnKingfisher]

Is the wee tachometer set for 2 stroke or 4 stroke ?

2 stroke. One spark per 360. My tinytach model no is TT2B non adjustable

 

[CaptnKingfisher]

Okay time for an update.. I disconnected my rectifier and my 'stall on low idle / during shifting issue' more or less disappeared. Dropped the boat in the water to test under load and what do you know, I can kick around the lake at 5 mph with this 135 hp on my 18' vhull at 'max throttle'. So I grabbed my ignition pliers and pulled plugs with the motor running. Cylinder drop test.

No noticeable loss of power when I pulled number 4 plug.
Pulling number 2 plug was not a particularly noticeable loss of power either.
Both plugs (2 and 4) appeared to be getting a strong spark from plug boot however (I will confirm 7/16 gap tomorrow on muffs)
Pulling 1 and pulling 3 both resulted in noticeable loss and engine shutddown independently.
tmrw I'll also try changing around the spark plugs themselves just to confirm all 4 plugs are good.

I have not replaced my flywheel key yet nor have I tried changing my timer base. I'm a little miffed that I'm getting spark and compression and fuel coming in fine up to the carbs and yet two cylinders not firing. I just pulled my carbs tonight, I tore em apart and took out the jets and cleaned them with my little jet cleaner tool that has rasp like wire various gauges.. I have the rebuild kits already just gonna let the carbs themselves sit in a gallon of carb cleaner for a day or two. The carbs I pulled are from my spare motor... so I have not gotten to inspect the reeds yet but I'll do that when I put these rebuilt carbs on.

Guess I need to rewire my rectifier or switch to my spare. Also I noticed today my hot battery to engine lead has a bad crimp end where it meets the selenoid. It passed a voltage drop test while cranking, so I dont think this is causing any of my issues but I'll replace that as well.

SO to recap the issue.. 1976 135 hp Johnson appears to be running on two out of four cylinders. Compression is pretty even 105-110 psi on all 4, 7/16 spark on reaching all plugs, fresh fuel and now by the end of the weekend I'll have rebuilt carbs on there, and a new fuel pump. Maybe I'll swap the flywheel key and timer base as well depending how motivated I can get. Stator tests DVA tests are good. Any thoughts or advice welcome. I'm still a novice

 

[CaptnKingfisher]

Took a video.. still seems to be only running on 2 cylinders.. lot of misfiring on no. 2 and no 4 doesnt seem to be running much at all. Still need to swap flywheel key and timer base. my ma accidently threw out my flywheel key when she was cleaning the garage so gonna hafta wait til a new one comes in. carbs are still soaking in solvant but I might rebuild them tonight.

https://www.youtube.com/watch?v=0ZSvT6xM4Es