Question about burnt smell

[Wisakedjack]

Ando, when the motor was running oil pressure was 40-50. No change compared to what I had before.

[Sam]

I think the comments about the coil are on target and should be followed, My boat was on the hard for two seasons due to covid w/stored and stbilized fuel. At launch it was running little rough and would die at idle or just quit. Using my stick transfer pump I drained the bottom two gallons - looked and smelled odd. Drained other 9 gallons and replaced w/fresh fuel - ran fine after that.

[Wisakedjack]

I just got back from the boat and unfortunately no progress was made. Here are things that I did:

1. Cleaned carburetor and replaced spark plug (I am attaching picture of my old ones). Unfortunately I could not get RJ12C one that I used before. I used RJ12YC instead, which seem to be a bit longer. I saw discussion on MM forums and it seems RJ12YC should still be ok.
2. Checked spark from coil, which looked ok. Since I had a new coil I replaced the old one.

So here is what was happening. Engine turns, but does not start. Its not even firing now (old coil or new). I tried to spray some starting fluid into flame arrester and all I got was a weak cough on next start. I checked voltage on coil '+' terminal when cranking. It was just below 9V on last try. I do have an extra ballast resistor before the coil. The battery got drained a bit today (12V) after all the cranking. At the end spark looked weaker, but should still be good enough. The only thing that I did not try was running from a portable tank using fresh fuel. I am planning to try it tomorrow. I don't have high hopes though since the engine did not fire on starting fluid. Even though my fuel is old due to boat staying on the hard last season it should at least fire up. May be run rough as Sam mentioned. But I suspect the problem is elsewhere. I still think its kinda odd things deteriorated to this point when at the start it seemed clear that it was just a fuel pump failure.

[JOHN COOKSON]

In order for your engine to start and run you need fuel, spark and compression delivered to the cylinders. The spark needs to be delivered at the correct time and the choke need to be functioning correctly.
Which of these are you lacking?
It would be helpful if you would start a new thread with your observations and diagnostic tests. You'll get more responses and suggestions if you start a new thread.

ex TRUE GRIT

[Dave Neptune]

Next time you check for spark do it via a plug wire to eliminate any issue with arching under the cap and a good spark path.

Do double check the wires for correct order twice! Maybe the rotor was left out?

When cleaning the carb what are you setting the float at? AND are you SURE the seal under the bowl top is absolutely sealed against the emulsion well? You should not have fuel puddling in the throat which introduces fuel not mixed with air properly and creates a bad burn leaving soot on the plugs.

Since it ran poorly before something you have done or overlooked is now amiss.

Confirm spar and firing order and try clean fuel after draining the carb and any lines left attached for the test. Gravity feed of a couple feet is sufficient for low RPM testing.

Dave Neptune

[edwardc]

... I checked voltage on coil '+' terminal when cranking. It was just below 9V on last try. ...

This seems way too low. When you checked the spark, was it a snappy blue one or a weak yellow? A weak yellow spark in open air will likely not fire under compression, as the breakdown voltage of the plug's gap goes up as the pressure goes up (Paschen's Law).

12V on the unloaded battery also sounds pretty low too.

Since you have a ballast resistor, one trick you can try is to use the normally-unused "R" terminal on the starter solenoid. This terminal has a direct connection to the battery "+" during cranking, and is open circuit at all other times. If you connect it directly to the coil's "+" terminal, it will bypass the ballast resistor during cranking (when the voltage is at its lowest) giving you a hotter spark for starting, then revert to normal while running.

[Sam]

Just a couple of comments - if the hotter rj12c plugs are not available I would default to THE RIGHT SIZED j8C which used to be the standard recommended plugs by Universal. Point two - since you changed the fuel pump you probably lost "siphon" from near bottom of tank, the fuel pump "pushes" better than it draws and the height of the fuel level in the tank may be too low for the pump rise? I would prime all the lines with fuel [I used a turkey baster] and give it a try - it worked for me. [ For kicks I would still pump out the bottom two gallons of fuel which after a couple of years is a fuel/water mix to some degree.] This all assumes you have needed good spark first which sounds like you initially had. Check all your battery/power/ground connection for tightness or visible or invisible corrosion. From your failed starting fluid diagnostic test I think you may be missing "fuel delivery" and/or "spark". After all of this and the other forum suggestions I probably would question the EI integrity. Good luck.

[Allegro]

This summer I helped a friend with his boat with some of these issues. The fuel pump is powered from 2 sources. One from the starter being activated, once the engine is running the oil pressure sensor powers the pump. My friends boat had a bad fuse from the oil sensor to the pump. Pushing the starter button filled the carb and let the engine run until the fuel ran out. It was hard to start again until activating the starter filled the carb again. Check if the fuel pump is running while the engine is running, not when using the starter?

[Wisakedjack]

When cleaning the carb what are you setting the float at? AND are you SURE the seal under the bowl top is absolutely sealed against the emulsion well? You should not have fuel puddling in the throat which introduces fuel not mixed with air properly and creates a bad burn leaving soot on the plugs.

Dave Neptune

I am not sure how I should set the float. I do check that the float assembly is parallel, but I never made any adjustments. What is the emulsion well? I can't find any mentioning of this in the manual. Dave, can you, please, clarify?

[TimBSmith]

Float...yes I was taught to eyeball and check level on both floats

Here is picture from my last maintenance..

https://photos.app.goo.gl/tM3AnVdWCrgccPan6

I had to be very careful not to displace the rod that anchors the floats. It is not peened and can slip out if held at sharp angle.

[Dave Neptune]

The emulsion well is in the middle of the float bowl. The fuel from the main jet feeds fuel into it and air is fed into it via vacuum and metered by the main air (corrector) jet. The chamber has a sealing surface that must be sealed by the bowl gasket. This seal is a must for good carb performance. This feature will not leak fuel into the throat though. Look to the float and or setting for that.

Dave Neptune

[TimBSmith]

Emulsion tube...and well...

This is the emulsion tube in our gravity fed system. In our system it is called the main nozzle.

https://photos.app.goo.gl/XU8bALZcgDRTdjZK6

Clogged emulsion tube

https://photos.app.goo.gl/ptiKSJpizGaX7Fht7

The fuel air mixing happens in the emulsion well into which our tube inserts and in the venturi.

An important seal is on top of the emulsion tube/nozzle (a little round gasket) and between the top and bottom of the carb. What our diagram shows as Bowl Cover Gasket. I actually put mine on inverted first attempt. Check your emulsion tube carefully because that was where my great blockages were.

https://photos.app.goo.gl/vdYbMDM7wex28QqKA

Lastly

From my reading....how the nozzle/emulsion tube functions...
Emulsion Immersion. You'll see references here to emulsion circuits, an important-sounding term that describes mixing fuel with air. Think of it as blowing bubbles in the fuel. All carburetors mix air with fuel in the venturi just before it enters the engine. But carburetors also mix air with fuel farther upstream inside the carburetor in the main well to make the liquid fuel easier to manage.

Last lastly really. I also remember reading and being told here to make sure the main jet gasket is seated carefully and that the main passage plug gasket is seated carefully or there can be pooling in throat from fuel pressure leak. Others can clarify. I am still learning and don't want to range to far out of my depth.

[ndutton]

Maybe I missed something but reading through this thread the only issue that's been found and resolved so far is fuel pressure. Coil input voltage is still suspect as is carburetor integrity, spark and fuel quality. The burnt smell that started this off could be attributed to the fuel pump damage but with replacement of the fuel pump that's been handled. Distributor timing is low on the list because it has not been disturbed since the engine was running properly. Firing order has been mentioned more than once and is so easy to check it should have been done long before now.

So where are we?

1. Coil input voltage @ 9 volts. Has this been resolved? What is the current input voltage?
2. Spark quality at the time of shut down. Can you describe the spark at the plugs immediately following shutdown? Snapping blue spark or wimpy yellow? Any spark at all?
3. Carburetor issues. We seem to be on this path now with float level concerns and gasket seal. The Moyer Marine carburetor video comes to mind.
4. Fuel system air leaks. You reported good fuel pressure so this is also low on the list.
5. Fuel quality. Having good fuel pressure with watered down fuel won't help. Have you tried running off an auxiliary (outboard style) fuel tank with clean, fresh fuel?
6. Have you tried running with the fuel fill cap open?

As can be seen, we haven't even determined yet if the problem is spark or fuel related and we are how many posts into the thread, 28? Until we do all we have is guessing.

[Wisakedjack]

It took me a while to act on the suggestions. I started by charging up my batteries, which is really easy now with boat sitting on the hard. I went there today to test things Neil listed in his last post. I was also planning to run tests from Don's sudden shutdown troubleshooting video. But it turned it was not needed. The engine just started and run. So, not having adequate voltage on coil was the main issue. It is possible other factors may have been in play as well to make things worse. I was wrong to assume that if the engine was turning it was sufficient to have good spark. Many thanks to everyone for all comments.

[ndutton]

As long as we're spreading around thanks

edwardc, post #21 in this thread.