Hi everyone. I am hoping someone can give me some direction. My '82 35hp Evinrude is only idling on one cylinder. The top is the only one firing. I have tried to start and run it on bottom cylinder only and will fire sporadically, but not enough to keep it running. When motor is in gear and you accelerate to 1/3 throttle both kick in and the engine runs fantastic all through the throttle range until brought back to idle or near idle then one cylinder again. Lots of spark on bottom cylinder, Carb kit has been done, fuel filter clean, just did the head gasket and that did not fix the issue, compression is great in both cylinders. I originally thought it was a bit of water leaking into bottom cylinder, however this was not the case. When i pull the plug it looks a little moist with fuel, but nothing major. Engine starts and runs perfectly, just idles on the top cylinder only. Any suggestions would be a great help.
Sounds like a low speed fuel problem, it runs ok after 1/3 speed. Try squirting a little fuel mixture in carb and see if it picks up. You have 1 carb and 2 reed plates, maybe a reed plate is not working at low speed. Just thinkin.
Sounds like a low speed fuel problem, it runs ok after 1/3 speed. Try squirting a little fuel mixture in carb and see if it picks up. You have 1 carb and 2 reed plates, maybe a reed plate is not working at low speed. Just thinkin.
If this is the issue, what would be a remedy for it? I will check in the next day or so. These motors are not that complicated I am sure it is an easy fix.
I had a similar problem with my 25. I did find on mine that the fuel pump was weak."engine vacuum not moving the diaphragm very much on low idle" I installed a kit and it started working. Do as first suggested, to spray fuel in carb. and see if it starts firing. Hope this helps
I had a similar problem with my 25. I did find on mine that the fuel pump was weak."engine vacuum not moving the diaphragm very much on low idle" I installed a kit and it started working. Do as first suggested, to spray fuel in carb. and see if it starts firing. Hope this helps
Sounds easy enough to diagnose. Let me get back to everyone with the results.
Possible low compression? Possible bad spark plug? Possible bad coil?
When was the last time that it had a good tune-up and carb rebuild?
Compression great, new carb kit, new head gasket, new spark plugs and lots of spark. Swapped out coils and pretty much ruled out anything electric. I already went after the most common things to remedy the problem, but nothing fixed it. It runs a heck of a lot better, but still not idling on two cylinders.
Thinking loud here... what i would check, here is a test:
- warm up your motor
- halve spark plug gap on lower cylinder
- Spot clean and dry spark plug (use a torch flame or a gas cooker)
- start up and observe running on first say 30 seconds
Thinking loud here... what i would check, here is a test:
- warm up your motor
- halve spark plug gap on lower cylinder
- Spot clean and dry spark plug (use a torch flame or a gas cooker)
- start up and observe running on first say 30 seconds
does it idle then ... will help to know ...
Yes it is always the lower one. I will try your diagnostic on soon and post back. plugs are the QL77J4's gapped for that engine
Thinking loud here... what i would check, here is a test:
- warm up your motor
- halve spark plug gap on lower cylinder
- Spot clean and dry spark plug (use a torch flame or a gas cooker)
- start up and observe running on first say 30 seconds
does it idle then ... will help to know ...
Also is it a champion QL???C plug ...
It seemed to almost idle ok for a few seconds, missing a little bit, then back its old ways again. I pulled the plug, cleaned and dried it then reinstalled. Any idea what the issues is?
Does your fuel pump drive off of the lower cylinder? Could diaphram be leaking into cylinder? Cylinder floods at low speed, cleans out and picks up at high speed.
Does your fuel pump drive off of the lower cylinder? Could diaphram be leaking into cylinder? Cylinder floods at low speed, cleans out and picks up at high speed.
Ah-ha! That makes sense. The plug does come out looking flooded and a bit fouled, mainly flooded though. I am heading to the cottage now and I will see if I can get a kit for the fuel pump to replace its guts and report back. I have my fingers crossed.
We have a spark that will not jump the spark plug gap at idle speeds.
As electrical potential builds across plug gap, just before it discharges through the gap giving the spark, there is always a leak current through the surface of the porcelain insulator on the plug, which slightly discharges potential built up and counteracts on spark strength.
Do the following test to ensure misfiring due to leakage current on spark plug.
- remove boot from lower lead and just touch lead end to spark plug tip.
- start engine, warm up and run at idle
- as soon as misfiring starts, pull lead end (with a pair of insulated pliers) and introduce an auxiliary gap between lead end and spark plug tip of say about 0.03"
Does it help idling ?
This auxiliary gap restricts leakage current on plug and spark jumps both gaps at max strength.
On the fuel side, this leakage current increases with wet fuel oil or dry carbon deposits on porcelain. Spark plugs are constructed so as to sustain a rated heat flow through the porcelain and self clean carbon deposits. Limitations are that a too warm spark plug will cause pre ignition top end rpm and a too cold will cause misfiring at idle.
On the electrics side, any part may be faulting.
To rule out coil faulting, swap primary connectors on coils and boots on spark plugs to see if problem moves to top cylinder.
Also test your sparks simply by unplugging and removing the boots off the lead and holding the end (with a pair of insulated pliers) about 1/2" away from head to observe a crispy blue strong spark, while keeping your engine running on one cylinder as low rpm as possible.
On the fuel side, make sure your mixture is not more than 50:1 oil (use TCW III mixture oil). Adjust a lean mixture at idle and sustain idle by advancing idle timing.
Compression is a major issue, get and post readings. Normal engine wear has such symptoms.
Decarbing your motor, hotter plugs and higher octane gas may resolve problems for quite some time !!!
I have it running, but still has a single cylinder idle. I have eliminated everything, even replacing some wires in the harness that were a little corroded. I have not been able to replace the fuel pump diaphragm yet, and I am hoping that will do the trick.
We have a spark that will not jump the spark plug gap at idle speeds.
As electrical potential builds across plug gap, just before it discharges through the gap giving the spark, there is always a leak current through the surface of the porcelain insulator on the plug, which slightly discharges potential built up and counteracts on spark strength.
Do the following test to ensure misfiring due to leakage current on spark plug.
- remove boot from lower lead and just touch lead end to spark plug tip.
- start engine, warm up and run at idle
- as soon as misfiring starts, pull lead end (with a pair of insulated pliers) and introduce an auxiliary gap between lead end and spark plug tip of say about 0.03"
Does it help idling ?
This auxiliary gap restricts leakage current on plug and spark jumps both gaps at max strength.
On the fuel side, this leakage current increases with wet fuel oil or dry carbon deposits on porcelain. Spark plugs are constructed so as to sustain a rated heat flow through the porcelain and self clean carbon deposits. Limitations are that a too warm spark plug will cause pre ignition top end rpm and a too cold will cause misfiring at idle.
On the electrics side, any part may be faulting.
To rule out coil faulting, swap primary connectors on coils and boots on spark plugs to see if problem moves to top cylinder.
Also test your sparks simply by unplugging and removing the boots off the lead and holding the end (with a pair of insulated pliers) about 1/2" away from head to observe a crispy blue strong spark, while keeping your engine running on one cylinder as low rpm as possible.
On the fuel side, make sure your mixture is not more than 50:1 oil (use TCW III mixture oil). Adjust a lean mixture at idle and sustain idle by advancing idle timing.
Compression is a major issue, get and post readings. Normal engine wear has such symptoms.
Decarbing your motor, hotter plugs and higher octane gas may resolve problems for quite some time !!!
elinminated the coil as an issues by switching them out still the bottom cylinder not firing at idle. There is lots of spark on the plug though. I have always run 50:1 mixture and the idle is adjusted so that it runs smooth. It just runs smooth on one cylinder hahaha. As soon as i pass about 1/3 throttle it picks up the bottom cylinder and runs like a dream. I will post my compression test and the results of the auxiliary gap test ASAP.
'82 Evinrude 35hp idling one cylinder only
Linear Mode
