Shutdown after running for a while- coil, or is it?

[cdhickey]

I’d like your guidance on an issue I encountered yesterday. My engine (EI, electric fuel pump) has been running beautifully all season, including a good multi-hour run on Saturday. I headed out again yesterday to take a few friends for a sail and some fishing. We motored around fishing for a bit then headed further out the bay. At this point we had been motoring in total for about 1:15, and had been at a constant cruising speed of 5 knots for about 15 minutes. Suddenly I heard the motor stumble slightly- it wasn’t anything too big, but enough for me to perk up and one of the other guys noticed as well. It also sounded slightly mechanical in nature with a bit of a clunk to it. About 15 seconds later another similar stumble/clunk, then another, and then the engine shut down. It wouldn’t restart immediately so we closed off the water intake and got to troubleshooting.

My buddy said it sounded like we ran out of fuel. My fuel gauge was reading ½ so I didn’t think we were out of gas, but I added a couple of gallons from my spare tank just in case my gauge was way off. Still nothing on an attempted restart. I sent him below to check for spark (using one of those in-line spark testers between the wire and the plug) while I cranked. At first he said no spark on plug 1. He switched to plug 2 and said that he saw a spark at the very end of a cranking burst. Another round of cranking and he confirmed spark, but said it was hard to see because of the bright sunlight shining in the engine area and it may have been present on #1 and he just couldn’t see it. He reconnected the wire and after we thought through some scenarios, I tried again and the engine started, albeit a bit slower than she normally does but then ran just fine as we motored around for a bit. We shut down (intentionally) and restarted again at one point, then sailed back towards the dock. When it was time to take in the sails she restarted again reasonably well and we motored to the dock (about 20 minutes) without issue. At this point I was thinking maybe it was an isolated fuel issue, but as we were at the dock securing lines and cleaning up, she shut down once again at idle. Sigh. On the plus side, we got our quota of good sized fish!

So here’s the TL/DR version:
- Sudden shutdown after 1:15 running time, following a couple of quick mechanical-sounding stumbles
- Restarted reluctantly 10 minutes later, ran fine and restarted okay after that
- Shut down again after about 20-30 minutes running after docking

And about the engine:
- Electronic ignition with Moyer coil, about 2 seasons old
- Moyer electric fuel pump installed at the beginning of this season
- New plugs and wires this season
- Had been running better than ever so far this season

And here’s my troubleshooting thoughts:
- This sounds like a classic coil problem (runs fine, shuts down suddenly, restarts after cooling) BUT there are a few things that make me question this: 1) The stumble/clunk right before shutdown 2) The coil is relatively new and shouldn’t have resistance issues (it’s the Moyer version).
- Fuel delivery is a possibility. I filled up with fresh fuel last month and there have been no issues- perhaps a slightly plugged fuel filter?
- Could this be an issue with the oil pressure sensor for the fuel pump? Possible, but that wouldn’t explain the restart.
- Carb issues are possible, but I would expect performance issues first before a sudden shutdown.

Any thoughts as I work my way through this would be appreciated!

[Administrator]

MMI coil or not, I would quickly take a resistance reading.

I like troubleshooting efforts which can reasonably be associated with the problem and can be dispensed with in seconds.

Example: Loosen the fuel fill cap to eliminate a clogged vent. Check the gasket while you're at it.

Bill

[ndutton]

I like troubleshooting efforts which can reasonably be associated with the problem and can be dispensed with in seconds.

. . . tests which also help determine if the issue is fuel or spark related thereby eliminating half of the search.

MMI coil or not, I would quickly take a resistance reading.

Please read
this post from 3 years ago.

[cdhickey]

An excellent reminder! That will be my next step.

[quiesence65]

Intermittant shutdowns

I have just spent a week searching for the cause of the "Mystery Shutdown"

Now I have a new coil, new fuel lines, have pumped out the tank, new fuel, new fuel filters.....and as of today, a new Facet Electric fuel pump replacing my other Facet Fuel pump installed in 2012.

And today I discovered the cause of the sudden, intermittent shutdowns.

When I took the old Pump off the bulkhead, the lag bolt was actually a little loose......and that was the cause of the Intermittent shutdowns......that bolt was where the ground wire for the pump was attached! The vibration of the engine caused a faulty connection for the pump, and consequently, resulted in periodic shutdowns.

It just goes to show you that you have to check everything.

[ndutton]

And today I discovered the cause of the sudden, intermittent shutdowns.

When I took the old Pump off the bulkhead, the lag bolt was actually a little loose......and that was the cause of the Intermittent shutdowns......that bolt was where the ground wire for the pump was attached! The vibration of the engine caused a faulty connection for the pump, and consequently, resulted in periodic shutdowns.

The EWDS monitors fuel pressure on the fly. It would have alerted you in seconds and identified the offending system, the fuel system in your case.

[sastanley]

One more thing....With EI it is easy to forget the advance weights. They can stick open. You mentioned the EI is ~2 years old. The weights are probably something serviced with points when we would all change them every season. I've found that when the engine stumbles it is counter-intuitive to throttle up..I always throttle back out of instinct to not break something, but with the stuck weights, if you throttle up and it runs better, they might be sticking.

My motor stumbled a bit a few weekends ago after approx. 1 hour run time. I need it to not be 150°F in the boat at the dock to check the advance weights again..I have not looked at that piece of the puzzle this year. It did run for 3 hours this weekend without a hiccup.

[cdhickey]

Thanks to all for the help so far, and especially to Don who was kind enough to give me a call and walk me through some of the troubleshooting. You guys are fantastic!

I visited the boat yesterday to check a few things. The resistance readings on the coil were confusing to me. With the coil cold and the negative wire removed (but all other connections in place), the resistance read 2.8, lower than I would have expected. However, after running the engine for well over an hour (trying to reproduce the initial problem) the coil felt quite hot and resistance read 4.9. I don't know if this is a common outcome (higher resistance when hot) or the sign of a bad coil, but in any event the low initial reading makes me wonder if that is the root of my problem.

This was my first time starting the engine since the second shutdown at the dock on Sunday, and it started perfectly and ran without a hiccup for quite a while.

And as an aside, this whole experience has been enough to make me purchase the EWS to make the next troubleshooting adventure a little easier!

[ndutton]

Primary resistance does change as the coil heats up normally in use but returns to spec when it cools down. You cold resistance measurement suggests pretty strongly that your coil has internal damage.

I propose two actions: replace the coil and find out what damaged it so it never happens again. Please measure your coil input voltage between the small coil + post and a solid ground with the engine running at a little over 1000 RPM and report back. This measurement can be taken with the old coil in place.

[cdhickey]

Primary resistance does change as the coil heats up normally in use but returns to spec when it cools down. You cold resistance measurement suggests pretty strongly that your coil has internal damage.

I propose two actions: replace the coil and find out what damaged it so it never happens again. Please measure your coil input voltage between the small coil + post and a solid ground with the engine running at a little over 1000 RPM and report back. This measurement can be taken with the old coil in place.

Thanks, Neil. The voltage at the coil at a fast idle (no tach) was 13.0v. I'll take a few more measurements at higher rpm as well.

[ndutton]

The voltage at the coil at a fast idle (no tach) was 13.0v. I'll take a few more measurements at higher rpm as well.

We want to be certain the alternator is producing when the measurement is taken.

[cdhickey]

We want to be certain the alternator is producing when the measurement is taken.

Understood. I'll measure and report back.

Thanks again for your help!

[ndutton]

Chris, do you have a dwell meter? While we're at it can you please get an ohm reading on the coil secondary? It's measured with the engine off between the center large socket with the big wire removed and the small coil " - " post, ohms scale set on 20K.

[joe_db]

Lights up red if the pressure is below 1 PSI