Coil problems

[chiron]

I have been chasing a ghost around my A4 for a while now and have started many threads to help diagnose the problem which I now know to be electrical specifically pertaining to the ignition. The engine starts and runs great until it get good and warmed up then it sputters and dies then wont start until hours later. Since I had replaced the coil, cap and rotor this winter which seemed to take care of the problem temporarily I looked into and fixed anything fuel or exhaust related and still was getting towed back to the dock. When the engine would sputter and shut down I always checked for fuel and spark but on further looking found that the spark I got from the coil would get week or nonexistent after lots of cranking. I recently relocated the coil off the engine on a bulkhead hoping it would not get as hot as right next to the exhaust but the problem persisted. I replaced the new coil, which tested out at 3.5 ohm with the old one which tested out at 3.8 ohm and it ran great for an hour. There was one thing that I disconnected which I don't know what it does. There was a pink wire 16 gauge or so leading from the back of the alternator to the positive of the coil which was delivering 1.3 volts on top of the 13.3 volts coming from the ignition switch. For the first time I was able to hold my hand on the coil without getting burned. What does this wire do and do I need it?

[Kelly]

Hello Chiron,

I'm not the expert but I believe a coil/alternator connection serves as the "exciter" for the alternator. This wire sends the signal to an otherwise dormant alternator to start charging. Does the alternator post with this wire have a "EXC" label?

Hope this helps.

[hanleyclifford]

I get the impression that the coil is running cooler because you disconected the pink wire and not because you relocated the coil. Is this correct? The next question is - how long will it do so, that is, run cooler with the pink wire disconnected. This needs to be tested underway. While underway you should test voltages at 1) the alternator output post (big orange or red wire possibly #8), 2) the + terminal on the coil, and 3) the pink wire coming out of the alternator. Please post those results. The alternator or regulator is now suspect but I think we can zero in on it.

[Kelly]

Three posts from the Herreshoff sub-group!

[hanleyclifford]

Three posts from the Herreshoff sub-group!
Does this mean we have enough boats to form a sub-forum?

[chiron]

Three Herreshoff owners and counting. I'm feeling more confidant now than ever. Luck will have it that today's job takes me right past the boat on the way home so guess where I will be before dinner. I was thinking that the pink wire was an external voltage regulator so disconnecting it would simply make the alternator not charge, I just replaced the batteries so I think I have some time to leave it disconnected. While testing voltage I was getting 13.38 volts at the positive of the coil and the pink wire, disconnected, was fluctuating but I was getting readings of up to 1.3 volts on that wire alone. The new coil I had installed this winter that was failing was getting hot with the ignition switch on and the engine not running. I replaced it with the old coil and disconnected the pink wire and it barely got warm. I was plugged into shore power during all this so tonight I will disconnect the shore power while I do more voltage testing, maybe even take the boat out for a spin. I may place a call to Ted the tow guy and warn him that I am giving it another try, just so he knows to stay in my area. We are getting to be friends Ted and I.

Thanks guys I know with your input I will get this gremlin once and for all.

[Administrator]

Does this mean we have enough boats to form a sub-forum?

Done.

Bill

[chiron]

Well I made it out to the boat last night and did some testing. Of course the engine decided to run great the entire time. Yes the pink wire from the back of the alternator is labeled EXC meaning, I guess, that it is responsible for turning the alternator on and off, and confirmed that when disconnected that the voltage at the starter solenoid would drop. I also unplugged the shore power this time during testing. The voltage at the coil was 14.14 as well as the alternator output and the positive on the alternator. If I disconnect the pink wire the voltage would very slowly drop until reconnected.

I did recently replace both batteries, could bad batteries cause a coil to fail?

Is 14.14 volts on a 12 volt system high or is it in the normal range?

I run the engine with the battery selector set to both is this typical?

[sastanley]

14.1 - 14.2 is great. There is much debate on this, but I consider that an acceptable charge voltage. A 'charged' 12v battery at rest is 12.6v. I added an adjustable regulator and charge at 14.2 volts under normal conditions. FYI - A 12v battery that reads 12 volts is not in good shape. Each of the 6 cells should read 2.1v fully charged, hence 12.6v, at rest.

If you disconnected that pink wire, the slow voltage drop would indicate the (now not charging) battery(ies) are supplying the voltage to the coil for the engine to run. 13.3v is typical of a good battery that has been recently disconnected from its charging source, in this case yanking the exciter to kill the alternator. After resting for several hours, it should settle between 12.6-13.1v

So, do we still have it dying after 60 minutes? :confused:

[chiron]

Yes the engine ran for a couple hours last night except for a panicked overheating problem, a bit of debris in the water pickup thank god for wire coat hangers. I am still not sure what caused the new coil I installed months ago to have problems but the old one I had taken out seems to be working. Tonight I will take it out of the slip for some real testing and hopefully bypass the entire engine and put up the sails.

Thanks everyone

[sastanley]

chiron, I don't know about you, but I am pretty far up my creek (last sailboat as a matter of fact), and I've never had trouble running the boat under load at the dock (i.e., the prop keeps clean water flowing under the boat, I have about 6' of depth so no sediment getting stirred up, etc.). Once the docklines are loaded up, the strain is steady and I can run her wide open or whatever I want..it allows close inspection of the engine without worrying about the next crab pot off the bow. :rolleyes:

[hanleyclifford]

So you put the old coil back into service and disconnected the exciter wire. The question is: which change caused the engine to get working again?

[chiron]

I put the old coil back in after the new coil stopped giving me good spark. I have left the exciter wire connected for now, just played with connecting and disconnecting while testing voltage. The new coil had worked just fine after installing it but at the time I had been having a grounding issue in the distributor cap due to condensation building up inside the cap and shorting out. At the time I replaced the cap plugs rotor and coil. The old one may have been just fine the whole time.

The good news is that I ran the engine long enough to get me out of the slip and had one of the best sail days yet. 80 degrees and 15 knot winds are a rarity in Portland Oregon.