2001 Johnson 150 J150PLSIF sudden condition

[Xray4]

Why not do an old fashioned cylinder drop test? Can use a timing gun (no flash no spark). Apparently need to test at WOT, so tedious. Get a driver, and hook up the clamp to each plug wire. Run it up to max rpms and check for spark, go to idle and on to the next wire. If you want to check coils before or after the test, set multimeter to 1kohm resistance, and measure between plug boot and powerhead ground -- look for 4 or 5k on the meter, but check each coil for consistency.

(good idea, btw, to make sure all boots at the coils and plugs are securely clipped in place....)

I'll try to make it to the lake today with my neighbor to test at WOT, but it's worth noting I did find an intermittent loss of spark at idle, and it was on several of the plugs. Will try to boil it down to which ones specifically, and test at WOT, and report back.

 

[Xray4]

I just meant you cant test just the powerpack. You follow the manual. It lays it out. The ignition gets tested step by step. You'll see. Not a big deal.

Got it! Thanks for clarifying. I got the manual last night and have been reading the sections. Will get to testing ignition from start to finish

 

[jakedaawg]

As I've stated before...the warped carb bowls. You will want to address that before you spend a bunch of money on components. If they leak they are part of the problem especially since you didnt find a cylinder without spark. They can leak by allowing air in as well as fuel out. The 1st step of troubleshooting is always address everything mechanical 1st. Fuel, compression then spark.

 

[Xray4]

Thanks for the direction Jake. There are so many systems and places that could be causing this fault. I'll start with the bowls, then work the fuel system, before I work compression and spark.

Before I go pulling the bowls off the carburetors, did you think it would be all right to test for leaks by spraying something like WD-40 or even some fuel at the warped edges, or instead seal them up with some tape? Just to see if it makes any difference before I crack them open? Or would that be futile and not tell me much if the bowls have sucked up a piece of gasket? Attached are pictures of the visible parts of the bowls.

​​​​​​​Maybe I'm at a point where I just need to suck it up and pull the carburetors, and get to cleaning and replacing all the gaskets, and trying to send flat the bowl on a piece of glass. I've really been hoping to test anything else possible without tearing it apart and waiting on a complete carburetor rebuild until the winter.

 

[Xray4]

Hey guys. So now I'm very, very stumped. Pretty much at my wit's end with this thing. I followed your advise going step by step, and I haven't made a dent. No change.. at this point I really don't know what else other than cylinders and engine mechanical could be going on. I spent the last week cleaning and rebuilding the carburetors, noting apart from warped bowls they were pristine. New floats, new bowls, cleaned all orifices, Jets, and the spaghetti tunnels. None were gummed but now they're for sure clean regardless.

Since this made absolutely no difference, I bit the bullet and replaced almost the entire ignition system, skipping only the rectifier.. I did all the tests I could on the ignition system, but without a dva and second-guessing my results, I went ahead and installed all New: coils, powerpack, primary and spark wires, new stator, new optical sensor. No change. Same rough idle, don't have max rpm.

I haven't got anyone to go to the lake with me to run WOT with a timing light, but at this point, the entire ignition system has been replaced, and at idle I do get spark everywhere.

I'm really at a loss,especially since this came on suddenly. It was like somebody flipped a switch and all of a sudden I started to idle rough and lost several hundred RPM at WOT.

Each of the plugs looks equally slightly brown and oiled.

Does anyone here have some sort of advice and guidance as to what you think could have happened?

 

[Xray4]

ADMIN: can we remove this thread? My wife says it's too long, that's why I'm not getting replies from people. Suggests I should make shorter less detailed posts.

I don't want to double post so how to remove this one?