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Help!! 1986 Johnson 140 Coughs and Splutters and Dies

M

MSteele

Member
I have a 1986 Johnson 140 BJ140TLCDC. It starts easily at first but has an intermittent fault, which makes it run very roughly. No real pattern to the firing sequence as if it is running on 1 cylinder with the engine jerking all over the place as it appears to stall but then kicks back to life. I have cleaned and rebuilt the carbs, bought new plugs and ensure the plug leads were not earthing, all was fine. I then purchased a timing gun as I thought it maybe the coils. I was expecting the engine to be running roughly with the gun not flashing when attached to the ignition lead for the coil on the cylinder not firing. This was not the case, all leads flashed in time to the engine kicking back to life, as if each cylinder would miss a few beats then take a turn at firing (so the light on the gun for every lead was erratic but in tune to the engine). There was no constant ignition sequence, indicating fuel starvation as the route cause (good spark but no combustion in the chamber). In summary I have an engine that fires on all cylinders it simple misses a few beats here and there and this issue is on all 4 cylinders. The engine sometimes dies and will not start again unless left for some time, or will stop spluttering and run normal and when it does run it runs great. If it is running properly (post its coughing and spluttering phase) it runs great, however you cannot tell when it will die again, it could be 20mins or it could be 1hrs or just keep running. That said on every start-up it goes through a rough patch at some point and then it may work or may not.
I was thinking about replacing the power pack, but I do not want to waste money if this is not the issue as it could equally be something else like the Timer Base & Sensor assembly or something I have not thought about. If I do a static test all checks out great, however as soon as the engine is running there is this issue. I am a newbie to boating so if I have not used the correct terminology, please go easy on me. That said I do need your expert help so however it is fed back is more than welcomed. :confused:
 
Troubleshoot the electronics and don't waste $$$$ changing out parts.

I built one of these to check the ignition circuits on outboard motors. Very easy to do. No matter what you may read the capacitor is a 2.2uf (microfarad) though I used a 3.3uf rated at 400 volts. I wouldn't go much higher in uf (microfarad) capacity because it would take too long to charge it up for a good reading.
http://forums.iboats.com/forum/engine-r ... multimeter

A very simple circuit that can save you a lot of money and grief when the outboard starts acting up.

DVA Explained:
http://www.go2marine.com/productcenters ... lained.pdf

Troubleshooting data
http://www.ebasicpower.com/downloads/cd ... INRUDE.pdf

http://www.cdielectronics.com/support/
Bill
 
Bill thank you. One quick question does my engine have a SLOW function? If it does I can follow the path below.

I have read all the information and there are a series of actions I can take:
1) Order the parts and build the Direct Voltage Adapter - I will order the components. This should be bread and butter for me I used to be an Electronic Eng, so we will see if I still have the knack :)
2) While waiting for the parts to arrive I could check the SLOW function "If the customer is complaining that the engine won’t rev up and shakes real bad, the S.L.O.W. function could be activating." When my engine starts coughing and spluttering it will not rev and shaking would put it mildly, it jumps around "like skippy the bush kangaroo." The VRO was removed before I bought the engine (I have only had the boat for 3years) hence I will check if this Tan wire has been removed and I will also check the temperature sensor Tan wire. I have an full manual but it is only for stripping and rebuilding it does not have trouble shooting, so your page shared was great.

I will let you know how I get on. I see there is a post from a member who has a Johnson 120 with exactly the same issue as mine. If I manage to get my engine running I will post my findings on his site to assist. Thanks again.

Mark..
 
Bill, thank you for the prompt reply. I will get the service manual as advised.
On the SLOW function, it is an easy test to do. I should only have one Tan wire on my Power Pack and that is the Temperature sensor. The VRO should not be present. So find the brown wire and disconnect it seems the first action to take. All being well I will try this tomorrow. I would have thought an alarm would have sounded if the engine thought it was overheating. Well that is neither here not their as it is definitely something worth pursuing.
 
I have an 86, 140 - there is no "slow" on it - no computer - nothing to restrict the ignition etc - kinda fires or doesn't.

I have generally found "phantom" ignition issues are usually a result of a bad trigger (sensor), but do get the manual and test things out. The original manual from OMC covers a range of horsepowers but is excellent (used it to rebuild my motor and found it more than sufficient).

I'm a Merc guy and that is almost exclusively what I work on, but do own a couple OMC's (one being the same one as you). I have had zero issues so can't even give you any tips/tricks, but I did replace the ignition (save the stator and sensor) at rebuild.

The power pack was relatively "cheap" compared to many other models so I didn't even play around with the original which looked a little worse for wear - ditto with the coils (which were a little out of spec).

Good luck with the motor. When they are running good these are a pretty gutsy motor - a bit of a gas hog if you are heavy on the throttle, but really get the boat moving :)
 
Graham, thank you for confirming no S.L.O.W. By "bad trigger (sensor)" are you referring to the Timer base and Sensor assembly part number 0583045? I now have the manual you speak of and the wiring diagram shows the temperature and VRO sensors only go to the alarm. The 1988 model of the 140 has the SLOW function. So no SLOW means the fault is either the Power Pack Part number 0582262 (US$126.70 + Shipping to the UK) of the Sensor assembly (US$219 +shipping). If I want to remove all chance then pay the US$345.70 and be done with it. The reason for saying this is the fault is intermittent so I can do the peak voltage tests and any other tests with the engine off and the chances are it will all check out fine. I have ordered the parts for the Direct Voltage Adapter, I still plan to go down this route however I am not holding much hope that I am going to have a "eurika" moment.
PS. I like your note about a "professional." I did have a little chuckle as I had the engine at an Outboard spe******t who changed the fuel lines and fuel filter and fuel pump and gave the boat back to me. If I didn't have an auxiliary engine on the back of my boat I would have floated out of the Clyde estuary and been halfway across the Atlantic. I took the engine back to him and he stated that to find the fault as it was intermittent (even though it is there at every start up) would be very time consuming and expensive - hence my little laugh at your note.
 
Graham - meant to add you are spot on about the engine, it certainly knows how to drink the juice at full throttle, however when you rip it full open on my boat I am cracking 60mpg on a 17 foot ski boat with three people on board and a 30kg 5hp Mariner (Sailmate) hanging off the end (out of the water). It will pull two skiers out of the water at the same time with ease. Power to weight ratio cannot be beat ever with a modern two stroke. I love it when it is working and hate it when it plays up - it reminds me of the wife ha ha.
 
As I stated, I don't do much work on OMC's, so can not verify the "quirks". Having said that it has been my experience that switchboxes/power packs (pick the term) either work or don't - you don't get an intermittent issue with them.

On the other hand the trigger (merc term)/timer base/sensor (again pick the term) - the "thingy" that tells the power pack where to send juice and when, in my experience, can kinda/sorta fail and go a little haywire -sometimes working sometimes not.

But again, not familiar enough with OMC power packs - when they go on a Merc, they are gone...
 
Thank you, your experience outweighs by far any experience I have unless I can count the Yamaha RD350LC I had in my youth, but now I am showing my age!
 
Just for general interest. I have been going through the web and located this article http://www.thehulltruth.com/boating...rd-intermittent-no-spark-all-cylinders.html#b
This post by mkantar has done everything I have done and testing the spark using a timing light determined the intermittent fault was with the power pack. As they are relatively cheap I am going to replace mine as the similarities are so alike the chances of my issue being different have reduced significantly (I could still have the issue but the chances are much reduced as I have someone who has walked the road before). The 1986 Johnson 120 is almost identical to the 140, the only physical difference I believe is the carb setup.
 
Update - as stated I ordered the PowerPack an after market unit made by CDI Electronics Part number 113-3101. Simplicity itself to fit, comes with fitting instructions and fault diagnostic tips. I simply replaced one connection at a time, unplugging one and plugging in the other. The was made easy as the cables on the new unit are quiet a bit longer than the old unit, the only issue was getting the two main wires that go to the stator and timing base to fit under the power pack, it was tight due to the amount of cable.
My units would usually start and I would leave it to warm up, as the coughing and spluttering was intermittent, I found if I left it for 10mins the chances were it would work for a while before dying. If the fault was not their on start up it could be induced by opening up the throttle very quickly, so once I had the Power Pack on I could do a driveway first test to see if the issues was still evident.
Released the fast idle lever and pulled vertical, turned the key to on, first click, pushed in for 8 seconds to prime and then turned the key all the way, started instantly. Sounded very smooth. I then went to the engine and advanced the throttle level to 3500 revs (it was cold so I was not going to throw it full throttle) not a hiccup. I have videoed the event and will post on You Tube once I have done a load test on the water and run the engine for over 1hr.
 
Had the boat out on the open water this evening, ran it for 1.5hrs at 4000rpm then thew the boat all over the place backing off to idle and opening her up fully. New Power Pack does exactly what it said it would do, rpm limiter is at 6700 showing on my tacho and would not go any quicker, stock unit was limited to 6100. Just opened her up fully as a quick test, have no intentions of pushing the boat too hard and blowing something else, usually treat 5000 rpm as top of the house. It would seem changing the Power Pack has done the trick, yahoo.

Summary - Issue Coughing with the engine almost stalling but then catching just to stall again. Engine jerks all over the place as the engine stalls and catches.
Diagnostics - Tested stator peak voltage by building a circuit that allows the peak voltage to be sustained long enough to get a reading on my voltmeter - stator was fine - thanks to Bill for the advise and circuit (listed at the start of this thread)
Used a timing light on each high tension lead, discovered each cylinder was flashing the light erratically in time with the engine kicking and stalling.
Found a forum where a member reported doing the same tests as I had completed with the same results as I reported and he changed the power pack fixing his issue.
I simply did the same and changed the power pack - decided to go for an after market unit from CDI Electronics part number 113-3101 - problem so far is solved for me too.
 
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