Johnson 90: "CHK ENG" alert?

timflan · Posted: Mon Jul 23, 2007 3:02 pm Post subject:

Followup: No more CH ENG alerts, but recently the engine has started stalling when I throttle down to idle after running strong. This is especially disconcerting while on final approach to a moorage. I had to "dead stick" into the float yesterday, which was not all that much fun!

So here's what happens: Cold, the engine starts fine. It runs fine. Then, when everything's hot, and you throttle down suddenly (not even all the way to idle, by the way; any sudden down-throttle might produce this), it dies. That would be bad enough, except that it won't start again! Not without playing throttle or waiting.

I'm a complete newbie at this engine diagnosis and maintenance stuff, but it seems to me that there is some problem in the delivery of fuel or the fuel/oxygen mixture. I assume my first step should be to check the fuel filter? A friend of mine suggested that CHK ENG might have meant that a sensor was not supplying appropriate data, and if so, the engine controller software may not be mixing fuel and oxygen appropriately anymore.

Anybody else have a similar story with a 4-stroke EFI engine?

dogon dory · Posted: Mon Jul 23, 2007 6:58 pm Post subject:

Sorry, Folks - Post Deleted By Author

timflan · Posted: Mon Jul 23, 2007 7:40 pm Post subject:

Thanks! I've got to start somewhere, and this sounds simple enough. Not that I've ever changed a fuel filter before, but I'm confident I'll figure it out.

Sea Wolf · Posted: Mon Jul 23, 2007 7:51 pm Post subject:

Tim-

It sound like Dan's got you onto a likely track.

If you can't figure it out, you can always take it to a Suzi or Johnson dealer and have them plug their diagnostic computer into your engine's computer and download the codes and preformance data (at least if your engine's similar to my Yamaha). AT times, these things seem to have dimensions unfamiliar to us old-time backyard mechanics!

Joe Teeth

timflan · Posted: Mon Jul 23, 2007 7:58 pm Post subject:

I'd love to do exactly that...I'm still not sure what CHK ENG meant, after all! Anybody got a recommendation for such a mechanic between Tacoma and Anacortes?

timflan · Posted: Sun Sep 02, 2007 11:48 am Post subject:

The plot thickens!

I've changed the fuel/water seperator filter element, as well as the low-pressure fuel filter in the engine. See http://www.navagear.com/2007/07/exploring-nooks-and-crannies-with-a-digital-camera/ for some pictures.

Didn't fix it.

Then I was reading in my service manual about the CTP ("closed throttle position") switch, and it said "If CTP switch has failed, engine will tend to stall when decelerating". Bingo!

Yesterday I took my multitester to the boat to check its function, and it seems to work fine: ON when the throttle is closed and OFF when it's open. Since I only experience the stalling problem when the enngine is hot, I decided to run the boat. With the cover off the engine, I let it run at the dock. Still no problem, CTP switch still functioning properly.

So I decided to take it out and run it at higher rpms for five or ten minutes, duplicating the conditions that have been consistently producing stalls. Went out, ran around outside the marina. No stalling. So the problem just fixed itself, then? Weird.

OK, this is where it gets good:

So I put the cover back on the engine, ran around a bit more, throttled back to idle, and the engine started working harder and harder until it stalled!

THE COVER! Tried it twice more, and sure enough, when hot, it won't idle with the cover on...and if you pull the cover off before it stalls, it will recover and idle just fine.

MY THEORY: exhaust that is supposed to exit the engine completely is, instead, ending up inside the engine enclosure, thus oxygen-starving the engine. When running faster, enough air is stirred around, perhaps due to the motion of the boat through the air, that the engine runs OK.

Anybody have experience with this sort of problem?

Dora~Jean · Posted: Sun Sep 02, 2007 12:13 pm Post subject:

Timflan,

If exhaust is somehow not exiting properly with the cover ON at low speeds (or exhaust being sucked into the cover's air intake port/slot) THAT would be a major design flaw -- not probable, but who knows...

Since it acts up with the cover ON, could the cover be heating the engine and components greater causing some of these anomalies?

timflan · Posted: Sun Sep 02, 2007 12:20 pm Post subject:

journey on · Posted: Sun Sep 02, 2007 1:36 pm Post subject:

Wouldn't that engine be under warranty? Take it to the dealer. It'd be a good way to find out what kind of dealer you have.

Boris

tsturm · Posted: Sun Sep 02, 2007 3:35 pm Post subject: Re: Johnson 90: "CHK ENG" alert?

timflan · Posted: Tue Sep 04, 2007 10:33 pm Post subject:

Alright, I've verified that exhaust is leaking out of the lower portion of the exhaust manifold. I can see it and feel it. I can't really do anything to fix it until I pull the boat out of the water.

Mac, it looks like I'll be over sometime soon to fetch my trailer! Smile

Island Ranger · Posted: Wed Sep 05, 2007 1:02 pm Post subject:

Doesn't sound good...

Do you know where you are going to take it for repair?

I'll start to cut back the weeds from the trailer to find it and get it ready - you can come by anytime (even if we are not here) -

Mac

timflan · Posted: Wed Sep 05, 2007 9:25 pm Post subject:

Thanks, Mac! Looks like we might come by for the trailer as early as late next week. No sooner, certainly.

timflan · Posted: Sat Sep 08, 2007 12:45 pm Post subject:

timflan · Posted: Mon Sep 17, 2007 2:51 pm Post subject: