Intermittant shut downs

[dtinder]

As we all know these types of shut downs can be very frustrating. I can now report the cause---but pls let me tell the story:
While bring my "new" C/C 27' home (an 80 mile trip along Florida's West Coast) we were motoring and toying with the new autopilot. There was an IMMEDIATE shutdown -----however, while the engine was still spooling, it restarted. In approx 45min it again shut down--totally. Restart was a matter of hitting the button--but the failures continued on a very regular basis---and restarts became more difficult. Whilst maintaining my helm duties (wing/wing @6knts with no pole) I suggested that my dear wife might change the racor spin on---which she kindly did. Clean. Not the solution!

The restart after a cool down caused visions of dancing coils, condensers, points, etc. Hour after hour of running at power while tied to the dock produced further shutdowns but not on a predictable basis. The nature of the failures went from IMMEDIATE to PLEASE HELP ME I'm starving---with a few IMMEDIATES thrown in.

Of course there was plenty of advice from my marina pals---none of which were young enough or small enough to get down in THERE. Several conversations with Don M. and Ken---All new electrical stuff on the engine side. Hot wire direct from battery to + side of coil----etc.

I've gone on long enough----here's the fix.

The electric fuel pump gets its start up boost thru the soleniod when the button is pushed. After that the oil pressure exceeds 10 psi and the oil pressure safety switch closes and provides power , when needed, to the pump. One can jump across these terminals for diagnostic stuff---but not a good idea long term. This seemed to help---put the switch on the work bench. Got three guys---one to supply 12v and ground to the switch. One non-smoker to supply 10+ psi thru a 3/8 hose connected to the business end of the switch, and one to man the multimeter. The non-smoker was able to close the switch 33.3% of the time. We then used a thin phillips screw driver inserted in the opening-----this provided positive results 33.3% of the time. So, go figure---intermittant failure of an oil safety switch----indeed.

I'm sure Don can explain the fine points of the confusing shutdown messages.

I'm going sailing---thanks for all the help Don.
Dave in sunny ft Myers----77F ENE @12-15

[Don Moyer]

Dave,

Thanks for the feedback regarding your intermittent shutdowns.

It looks like if we could turn the clock back, we could have saved you a lot of thrashing around if we'd simply suggested running the jumper wire from the big battery cable directly to the fuel pump, as well as to the positive terminal of the coil. This would have fixed your problem immediately, and you could have then narrowed down the exact problem at your convenience, by removing the jumper leads one at a time.

Best regards,

Don Moyer

[tartan30cirrus]

I seem to be having an intermittent shut down. I've been troubleshooting low oil pressure. This morning I removed the OP safety switch wires and the switch to make room for a tool I was using to redress the OP valve. I performed this procedure and reinstalled the OP safety switch exactly like it was. Started engine...started just fine, sounded great and it turned off on me like a flip of a switch! Restarted just fine each time. Did this a few times. Did I do something to the OP safety switch to mess this up? How do I troubleshoot this? Part of my problem is not understanding how/why the OP safety switch, fuel pump, coil and solenoid(?) all wire together.

THANKS. I hope this isn't yet another new problem.

[tartan30cirrus]

Fixed it...blown fuse from coil to fuel pump.

Cheers,
Clint
Still can't get OP up to normal though.

[Don Moyer]

Hello,

Here's a basic guide for troubleshooting intermittent shutdowns to get you
started:

IMPORTANT NOTE: During most troubleshooting work, it's frequently necessary to turn the engine over on the starter with the engine NOT STARTING. Be sure to close the raw water thru-hull valve during these times, so as to avoid filling the exhaust system with raw water until it backs up into the exhaust manifold, and into the combustion chambers of the engine.

In troubleshooting intermittent failures, it's critically important to focus on the exact nature of the shutdown. For example, running out of fuel usually results in a rather "soft and gentle" shutdown. Small missing sensations may be noticed that gradually get worse until the engine finally stops.

On the other hand, failures within the primary ignition system (similar to what would happen if someone inadvertently turned the ignition switch off), the shutdown would be very sudden - perhaps even "startling".

Familiar causes of fuel starvation include dirt in the carburetor, clogged fuel tank vent line, faulty fuel pump (or electrical connections in the case of electric pumps), clogged filters, etc.

If the shutdown drags on long enough, you can try pulling the choke about half way on before the engine quits completely. If you can affect the engine performance (even a little bit) with the choke, it is good confirmation that you're dealing with some sort of fuel starvation.

If the shutdown feels as thought some one inadvertently turned off the ignition switch, the likely cause of the shut down is an open circuit somewhere in the primary ignition system - frequently in the boat's circuitry.

To confirm an ignition failure, remove the coil lead from the center terminal of the distributor cap AS SOON AS POSSIBLE AFTER A SHUTDOWN, and hold the end of the lead close to the block or head (about 3/8" away). Check for spark between the coil lead and head as you turn the engine over on the starter.

The reason for moving quickly in the preceding step is that many faulty connections within the primary ignition system will work after they cool - sometimes within a few seconds. Therefore, even if you do see a spark in the preceding step, don't completely abandon your first assessment that the problem may be in the ignition system.

In pinning down a loose connection in the primary ignition system, it is frequently necessary to install a "diagnostic" jumper wire between the coil (positive terminal) and the positive battery cable at the starter solenoid. If the intermittent shutdowns cease, you've confirmed that the problem is somewhere in the boat's ignition system.

NOTE: It has been very useful in several troubleshooting episodes in the past to also run the jumper wire directly to the electric fuel pump (where one is installed), to rule out a failure of the oil safety switch. If the engine runs OK with this jumper wire run to both the coil and the fuel pump, you can isolate the exact problem by removing the wires one at a time.

Another distinguishing feature of a shutdown could be that it is neither soft nor sudden, but that it hesitates (stopping and starting) sharply in an almost aggravating way. The engine may even backfire or "pop" a bit in this mode. Such an indication could mean that the coil is breaking down when it gets hot, or that the condenser may have worked loose on its mount, or that there's a very loose connection somewhere in the primary ignition circuit (possibly an intermittent short to ground).

Finally, have you performed any maintenance on the engine recently? Whenever you experience problems after performing maintenance, always go back over every step of your work to see if you overlooked something. This is one of the most fertile places to find reasons for intermittent shutdowns.

Don