Miswired coil Mercruiser 140 (let the smoke out)

[Wakesilver]

While troubleshooting an ignition problem for hours on an early 70's Mercruiser 140, I "let the smoke out" by hooking up coil minus/distributor lead to the solenoid and ballast wire. Most of the damage was the insulation heating up on the tan solenoid wire. I also saw a little puff at the distributor. After I shut the starter down and re-referred to the manual I realized the error of my ways. After wiring the coil correctly, the motor started instantly (less than one 'crank') and I idled for 10 minutes on the muffs.

Lessons learned:
1) Check the points first, not last (root cause)
2) Check the schematic one last time before applying power to the ignition system
3) The "stickies" are great reference materials...thanks!

My questions:
1) What might I have damaged with my wiring mess-up? Condenser?
2) How can I tell if the ballast wire is working? Coil + has 12.4 v before starting
3) How does one make a remote start switch?

Thanks!

 

[Don S]

Re: Miswired coil Mercruiser 140 (let the smoke out)

1) What might I have damaged with my wiring mess-up? Condenser?

Hard to say, start it up and if it doesn't work, see what is wrong. The condenser is a tuneup part. if the points are over a year old, change them and the condenser.

2) How can I tell if the ballast wire is working? Coil + has 12.4 v before starting

Check the resistance with an ohm meter.

3) How does one make a remote start switch?

http://forums.iboats.com/showthread.php?t=183904

 

[lonemust]

Re: Miswired coil Mercruiser 140 (let the smoke out)

While troubleshooting an ignition problem for hours on an early 70's Mercruiser 140, I "let the smoke out" by hooking up coil minus/distributor lead to the solenoid and ballast wire. Most of the damage was the insulation heating up on the tan solenoid wire. I also saw a little puff at the distributor. After I shut the starter down and re-referred to the manual I realized the error of my ways. After wiring the coil correctly, the motor started instantly (less than one 'crank') and I idled for 10 minutes on the muffs.

Lessons learned:
1) Check the points first, not last (root cause)
2) Check the schematic one last time before applying power to the ignition system
3) The "stickies" are great reference materials...thanks!

My questions:
1) What might I have damaged with my wiring mess-up? Condenser?
2) How can I tell if the ballast wire is working? Coil + has 12.4 v before starting
3) How does one make a remote start switch?

Thanks!

Usually if the ballast goes bad you wont get power at all to the coil unless the solniod is activated. If the points were closed yes it could fry the condenser but sense it ran so far so good. As for any thing else check to make sure you did not burn the insulation off the tan wire and it has no bare spots; if it does repair it. Now the remote starter switch, yes there is such a thing and you can find them at most auto parts stores in the tool isle. I use one made by SUNTECH(I think it's a Suntech). But it will only allow you to activate the solniod. It will not put continuas power to the coil. If you have power t/t you can use the switch to activate that also, so you don't have to go back and forth from stern to helm when working on the t/t. I know AUTOZONE carries the remote starter switch.

 

[lonemust]

Re: Miswired coil Mercruiser 140 (let the smoke out)

If you cannot find the remote switch you can make one.. Two lengths of 10 or 12 guage wire (3ft each or longer), two medium to heavy duty aligater clips, and a momentary push button. Of coarse you will also need 4 eyelets for the ends of the wire. put an aligater clip on one end of each wire then hook the other end to the button one wire on one side and the other on the other side. And if you worry about possible shock tape the crap out of the button but leave about 1/8 to 1/4" at the top so not to enterfear with the button itself. GOOD LUCK.. Oh if you have extra wire and terminals liing around it would be cheaper to build a switch then to buy a prebuilt one.(approx $10 to build v. $25-$50 or more to buy a premade) And both wires can be the same color it wont matter all it does is complete the circuit when you push the button..

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

Thanks for the help, everyone. I should have searched more for the switch info.

I have a question about the coil circuit.

On the Delco starter/solenoid/relay combo, should pin "D" (hot start) be on all of the time? On mine the large stud "A" reads .1 v higher than "D", which appears to be on all the time. Shouldn't applying power to "B" activate power from "A" over to "C" and "D" ? If hot start is on all of the time, wouldn't the lower ballast voltage be useless for the coil if the hot start is not switched by the solenoid?

Thanks again!

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

btt, curious about the mysterious pin "D"...

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

btt

 

[lonemust]

Re: Miswired coil Mercruiser 140 (let the smoke out)

If you are talking about the one on the soleniod, it should only havw power when the soleniod is engaged. That terminal sends a full 12v+ to the coil for starting only. When the ing key is in "run" or "accessory" there should be NO voltage on that terminal. Only when the key is in "start" position should the be volts. At any time you get power there when you ARE NOT triing to start the engine replace the soleniod.

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

Thanks, that is what I was expecting. I will have to look at it next time the cover is off.

It is amazing how much quicker it starts with clean points.

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

I had reason to inspect the solenoid again. The casing in back is cracked and I am still at 12.4v at the coil at "run". Time for a new one...

 

[RichRab]

Re: Miswired coil Mercruiser 140 (let the smoke out)

What I remember about the point and resistor system is to avoid the points being damaged from too much voltage that is not needed while running when you crank the I term on the solonoid receives power from the ignition sw.that goes to the I side of the coil. Letting go of the key powers the R side of the coil(resistor) and the power goes through a ballast resistor that reduces voltage to the points. If the condensor is bad do not touch the terminal end. It holds a charge.(if it runs it is ok) change it when you do a tune up. If the points do not spark when cranking, discommect the condensor and if they spark the cond. is bad. Once again if it runs there is nothing to check. If the points are burned or pitted then there is a problem.Always put some grease/cam lube on dist. shaft and the grease will be on the correct side of pts. rubbing block to help the gap stay and block from wearing too soon.

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

Thanks for the info, it's aleways appreciated

I changed the starter solenoid and unhooked the "hot start" tan wire and I am still only getting about a .2 volt drop through the labelled "do not cut" ballast wire.

There is a mess of black electricians tape on the wiring harnesses...possible sign of a hack?

Should I just go get a ballast resistor from an auto parts store and put it in line with the coil until I learn this boat's secrets???

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

I got a ballast resistor. Is there a safe/customary place to mount it?

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

btt...What would be the ideal voltage at the coil at normal run? My belated research shows 6-9.5v. I still could use help in locating the new external ballast resistor (concerned about heat buildup).

 

[6meter]

Re: Miswired coil Mercruiser 140 (let the smoke out)

9v is good at the coil+. The electrical tape could be factory. Chevy did that also to the resistor wire back pre 1975.

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

Thanks. I will try to hook it all up this weekend and see what I get.

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

Hooked it up. Battery was at 12.45v, pre-ballast was 12.24v and post ballast was 12.23v - do the ballast resistors/wires need to heat up before they drop the voltage?

 

[mariner1900]

Re: Miswired coil Mercruiser 140 (let the smoke out)

Hi it is easy to check your resistor wire.

Disconnect the main plug and measure the resistance between the +ve of coil and pin 5 of the main plug. Resistance should be 1.8 to 2 ohms.

Did you make sure the points were closed when checking the voltage at the coil? Pretty sure that to get the voltage drop the points need to be closed.

The resistance of the wire is constantly changing during engine operation depending on the engine speed. At idle, as the points are closed for longer, the wire heats up and therefore the resistance changes. When the engine is operating at higher RPM, the points are closed for a shorter period, the wire cools down and the resistance drops.

 

[Wakesilver]

Re: Miswired coil Mercruiser 140 (let the smoke out)

Thanks for the info everyone, even some from all the way around the world. I took off the other ballast off and put everything back to "stock". Pin 5 to coil+ was 1.9 Ohms. When I energized the run circuit with coil - grounded I read 4 volts. So I believe it's all working about as it should. Maybe I was dealing with just the need for a tune-up versus glazed points from high coil voltage.