2002 johnson 50hp intermittent rough running lacking power and check engine light

[jakedaawg]

What is telling you it's not firing? Are you doing a spark test? Or a cylinder drop test? When I hook these to the computer I can disable whatever I want, spark or fuel injector. There is a way for the DIY type to do this. You need the manual though. It explains how to use a little light diode to check injectors and such if I recall

 

[OttawaPhil]

When I remove the plug connector from ignition coil on the top nothing changes. When I remove either the middle or bottom one it stalls. That's what tells me the top cylinder is not firing. I swapped the coil and plug with the bottom one and they are still doing the same thing on cylinder one so it's not coil or plug.
is it easy to swap injectors between cylinder one and another cylinder? Never had a fuel injected engine before

 

[OttawaPhil]

Oh I get you. I need to check spark with number one out.
is that safe to do by grounding plug and cranking it?

 

[jakedaawg]

What you did was a cylinder drop test. Yes, we need to check for spark. I like sparkies for these four strokes. They are a little diode light that goes inline between pug and wire. Available at a parts store. They are cheap. You will want the "metric" version. Verify spark 1st. A timing light using that cylinder would work also. See if it flashes. If flash then we have spark supposedly.

 

[jakedaawg]

Have you put new plugs in this? I think yours is the NGK dcpr6e. Do that, if you already did do the top one again. These plugs are famous for being bad right out of the box.

 

[OttawaPhil]

They were new about 2 months ago. Not the plug or the problem would have followed it when I moved the plug to cylinder two, and the coil to 3 and the injector to 3, it did not. Always the problem is with #1.

There must be a problem before the coil. I will confirm no spark tonight with the spark tester. Then have to figure out why no spark.

 

[OttawaPhil]

I got a new O-ring for my compression tester. Just tested compression and top cylinder is only 100 PSI. The other two are 160 to 170

what should I check? Valves?

 

[OttawaPhil]

Double checked with another o ring Got it up to 130 dry on top 160 middle and 170 bottom
how bad.is that?

 

[OttawaPhil]

Check spark and there is no spark on the top cylinder. Obviously the bottom to have spark

 

[OttawaPhil]

Trace the orange and gray wire from that cylinder coil to the main computer large plug and 0 ohms resistance on that wire from one plug to the other for both so it doesn't seem to be a wiring problem either. Any idea why I don't have spark or what I can check for?

 

[jakedaawg]

When testing compression on a 4 stroke the throttle needs to be in the wide open position....

 

[OttawaPhil]

Ok, good to know. I did not have it wide open.

Perhaps I should make a new thread - this one is now convoluted with other things? from when it was intermittent. It is not intermittent now.

At this point a better title would be 2002 Johnson 50hp has no spark in top cylinder.

I traced the two wires from the top coil back to the ECU. The gray one is shared with the other three cylinders and tests 0 ohms resistance to the ECU harness. The orange wire goes direct to the ECU and it also tests perfect with 0 ohms resistance. But there is no spark. Wire is in perfect condition. So are connectors. Why would the ECU disable spark to one cylinder? Is there a reason it would do that? If not, then it looks like the ECU has failed right? Likely not worth buying a new ECU for a 16 year old motor right?

 

[OttawaPhil]

Here we go, made a less confusing thread:
https://forums.iboats.com/forum/eng...op-cylinder-suggestions-on-what-else-to-check

Thanks a lot for your help. I am at my witts end with this as the wires check out good, so it looks like its the super expensive computer?

 

[racerone]

Hurry ---Run to an Evinrude or Suzuki dealer to run ECU through a test.-------Will save you time and frustration and $$

 

[OttawaPhil]

I want to test the trigger for cylinder one first. I think that is what is most likely causing this, but dont know how to check.
Ordered expensive factory service manual too, hope that helps.

We dont have any competent dealers here anyway - ever dealer around Ottawa has horror stories...

 

[racerone]

Phil ---Does this motor use a " trigger " ?????-----Contact folks at Hamer Bay Marine.

 

[OttawaPhil]

It must use some way to tell when to fire, and it must have a way to adjust timing, so I imagine it does.

That dealer you mentioned is over 6 hours drive each way from me, going to try and figure this out myself first.

 

[racerone]

Good luck with it.

 

[jakedaawg]

The ckp sensor determines spark along with the map and engine speed for advance.

 

[jakedaawg]

Look for 168-252 ohms between e4 and d1 connectors. That's ckp sensor 1.