Help! Runs like crap when warm!

64stang wrote: Sorry, what would be the point of running the 12v through the "resistor" during cranking? Just curious, what marine engine uses a ballast resistor and does not bypass it when starting?

Actually, this is a subject full of wives tales and misconceptions. I'll share mine (and I can be laughed at)...

I've heard various reasons why ballast resistors (or resistance wires) were first added to automotive ignition systems:


1. "Starting Boost"

Without a ballast resistor... you turn your key to Run--your coil sees battery voltage (let's call it 12V). You turn your key to Start--your starter pulls the voltage down a lot, and now the coil sees much lower voltage and may not produce enough energy for starting spark.

So... someone got the idea to put a resistor inline with the coil, and then design the coil to work at the lower voltage (let's say 9V) seen behind that resistor, and then add a ballast resistor bypass wire so that Start skips the resistor and the coil sees more like 9V rather than 6V.

BUT... The PCM 351 doesn't use a bypass wire.

So much for that theory for our boats. BUT... it does make sense for vehicles that need to be started in very cold weather, when the lower voltage (like 6V in our example) isn't enough to get things started.


2. "Non-Running Current Limiter"

You have an oil-filled coil and no ballast resistor. You're drunk and leave the key in the Run position overnight. Your points happen to be closed so this dumps a lot of current (high amps) through the coil. The coil gets hotter and hotter. Some of the insulation on the coil wires may fail due to the heat, greatly reducing the coil's resistance and causing even more current to flow. You're lucky and find coil oil all over your engine, but at least your garage didn't burn down.

Someone smart figured out that adding a ballast resistor will limit the current enough to keep the coil temperature at an acceptable level. The resistor and coil are in series, so their resistance adds.

This one makes some sense for our application.


Now, we need to look at the name... "ballast resistor". That's not just "resistor". A BALLAST resistor changes resistance with some other variable (current or temperature, for instance):

ballast resistor Noun 1. an electrical resistor whose resistance varies with the current passing through it, and thus tends to maintain a constant current 2. a resistor inserted into a circuit to compensate for changes (as those arising from temperature fluctuations)

3. "Low Temperature Starting Boost"

When it's cold out, you need more spark energy to ignite the cold fuel. Plus your battery really sucks when it's cold out. (Remember, this is many decades ago.) A BALLAST resistor can be designed so that it's resistance is much lower when it's really cold. That effectively "bypasses" the resistor (the resistance at normal temps, that is) and the engine could start. Supposedly lots of grandpas used to jumper their (apparently defective) ballast resistor to start on cold days (sorry, I don't recall that). Obviously, using a bypass wire "bypasses" this feature entirely. And not too many use their Ski Nautiques for ice breaking.


4. "Running Current Limiter"

As the RPM's increase, the spark energy is provided faster and faster; the effective resistance of the coil-points circuit decreases, allowing more current. As that additional current flows through the ballast resistor, it heats it, and the ballast resistor's increasing resistance with increasing temperature could balance this behavior and limit the current through the coil when running.



So... for our engines, what might I believe?


Starting Boost (normal or low-temp)... nope.

Current Limiter (running or not)... I think one or both of these are the reason we need a ballast resistor if we don't have an "internal resistance coil".


And why don't we need the resistor bypass wire? Because we don't boat in very cold temperatures.


Like I said, time to laugh...

I can take it.   

Steve

64stang wrote: I did not see this, so I hope I am not repeating someone, but I learned this on this board. A ballast resistor is used to give the motor better starting performance. The ignition will bypass the resistor when the key is turned to the start position and give 12 Volts to the coil, then when running, power will go through the resistor and be reduced to 8-10 volts. Mark

Mark,
You may want to do more research before commenting and possibly confusing some. Not all marinized engines use the resister by pass during cranking.

Excellent! Glad to hear it, George.   

Aha, no I did not. I bought the "MSD Blaster 2 Coil", part no. 8202. The epoxy filled is the "MSD Blaster High Vibration Coil", part no. 8222. See page 63 of the MSD 2013 Catalog. Oh well, let's see how long it lasts. I have another coil onboard.

The new NAPA ballast resistor did the trick on correcting the voltage levels, I think. We'll see for sure when we get it out later this week. The part number for the 0.85 ohm "ignition coil resistor" is NAPA ICR5500.

Our local O'Reilly Auto had the MSD Blaster2 coil hanging on the rack.

The NAPA website shows a marine ballast resistor for Pleasurecraft engines for 18 bucks or so. They have the exact same resistor, 0.85 ohm, listed for Ford, as I recall, for 9 bucks. Our local NAPA had one for me in less than 24 hours.

If you can hold your hand on it, I think it is OK.

8222 is the coil I referred to. Sorry, I guess it is just Blaster & not Blaster 2.

I would do what the Mallory instructions say, not what a guy on the phone thinks - he most likely didn't do the circuit design.

My issue was resolved with a MSD 8222 epoxy filled blaster coil and a MSD 8124 resistor.

phatsat67 wrote: But really I was always under the impression the red wire on a Mallory was 12v (it being red). Apparently not.

It is 12V. It's too easy to misread the Mallory diagram the way they show it. The red wire to the Mallory distributor wire harness is wired to the 12V ignition switch side of the ballast resistor. The diagram shows it connected at the pole on the resistor, which is apparently confusing (I had to look twice when I first read the diagram).

jblocal wrote: Ok so I'm a little confused on the Mallory wiring. For a year I been running my Mallory distrib with no resistor. My coil that came with the Mallory distributor from ski dim says no external resistor required right on it. The wiring diagram here shows the coil + going to resistor side. So do I use resistor even though it says no external resistor required on coil?

The important question is how does it run? If it runs well and doesn't give you any problems I'd tend to leave it alone.

Ok so I'm a little confused on the Mallory wiring. For a year I been running my Mallory distrib with no resistor. My coil that came with the Mallory distributor from ski dim says no external resistor required right on it. The wiring diagram here shows the coil + going to resistor side. So do I use resistor even though it says no external resistor required on coil?

Ahhh gotcha I wasn't reading everything correctly! Good deal.

delovett wrote: UPDATE: Replaced the coil with an MSD 8222. Had to wait for the matching resistor. Ran it with just the new coil, same thing. Added the MSD 8124 resistor...ran better, but same thing. I then realized that the ignition wire was running right to the + on the coil. Moved that down to the resistor and had a great afternoon on the water today. Also some of the rng terminals were looking like they had seen better days, so I replaced those as well. I think I have this figured out!

phatsat67 wrote: As far as I am aware every electronic ignition conversion needs a full 12v feed to the distributor hot wire to operate properly.

Zach the old prestolite? only had two wires purple and black. Purple to the + side black to the - side.
If you run a resistive coil remove the ballast resistor if your coil is non-resistor you need to run the ballast resistor.

> "If I have it directly to the coil, it is getting the reduced voltage, correct?"

Yes, and that's not what the diagrams show.

You need to identify the make and model to confirm all of this, though.