Calling all "mechanics"

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

Hey yall... my alternator died on my '83 MC S&S. It was the original Motorolla 42 amp with exterior voltage regulator. I replaced it with a 70 amp self exicting alt cause I want to add a battery and cabin lights later down the road. The spark I get off the coil is intermitent. It started one time after the install and the amg guage was bouncing all over the place. Skidim sells a conversion kit for making the change to the newer style alt. Is this what I need? The guy at the alt. shop said it should work fine without it... but it clearly doesn't. Any thoughts or ideeas is appreciated!

http://www.skidim.com/prodinfo.asp?number=RK173070

kartman · Posted: May 16, 2011 6:00 am Post subject:

it could be a defective alternator. i have bought a few of them. your best bet would be to put in a one wire alternator. easy to hook up, and they work with all systems.

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

Kartman... was hoping you would see this... that is what I got... a one wire.

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

so... a one wire should work no problem? even on the old system I have?

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

What if it's not the alt. at all... could something else be causeing me to not have spark off the coil?

cadunkle · Criminal Joined: 16 Jul 2009 Posts: 60 City: NJ

Check your voltage while running. Is it putting out a full 14+ volts? If not that could cause a misfire. Also note these one wire alternators need to be blipped to 2500 RPM or so before they start charging. Personally I hate them, my car and truck have an old style external regulator, they just plain work. My boat has a one wire and it's annoying to rev it before it starts charging.

What type of ignition are you running? If it's points triggered, that would be my first place to look for a misfire. Check for dirty points, clean with fine sandpaper if they're pitted or have carbon tracking and regap them. If this fixes it, replace the points.

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

Cadunkle... that's the thing... it hasn't started since right after I replaced the alt. I don't have points... I have a mallory ign. "thing" inside the dist. I am paranoid to keep cranking on the starter at this point, you know. At least not till I have a better idea of what is happening.

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

chawk610, Ok so the alt has absolutely nothing to do with starting. period.
Also not having 14+volts would not cause a misfire either. You can completely disconnect the alt and motor will run as long as the battery lasts. And your battery will typically have 12.xx volts or so.

So the Mallory ignition modules are typically pretty nice and reliable. However I have seen/heard of a voltage spike hurting them.

Now since you stated your problem has occurred right after replacing the alt. you're gonna wanna check the wires and around the plug to the distributor.

What happens after its running? Does it run smooth up to higher rpms?
Ignition systems have to work harder the higher the rpm the motor is; so if its just a hard starting it may not be an ignition related issue if the motor rips up to WOT without missing a beat.

How did you check/know that the spark off the coil is intermittent?

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

Ryan.. I have been on the phone with my dad (old skool mechanic" and believe this is a dist. cap issue. I am picking a new one up today and installing.

To check the coil, I took the wire running from the coil off the dist cap and held it to engine. Sometimes spark really strong... and sometimes none at all.

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

chawk610, Ok since you pulled the wire off the distributor and grounded that side to the motor, that means that it is NOT the cap. The cap only "distributes" the spark to the corresponding cylinders as it rotates around. So that actually was a good test. It could very well be a weak coil. Coils go under a lot of stress and even more so in a boat. A coil has to charge up and discharge ever time a cylinder fires. 1/2 engine speed. 4,000rps, means it has to fire 2000times a min. and heat is a killer of electrical items, and its gets hot under an engine cover.
If it was me, I would check that you have a good ground...NUMBER ONE. In a marine environment grounds can be an issue. Then check 12v. Check both of these at the distributor/Mallory wiring. Most likely though, sounds like a coil issue.

I had a similar issue with mine and the coil wasn't getting 12v during crank so the spark wasn't strong enough to fire the motor to start. Once running it was fine. So check how much voltage you're getting at the coil during crank/run as well.

But its not the cap/rotor.

cadunkle · Criminal Joined: 16 Jul 2009 Posts: 60 City: NJ

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

cadunkle, so i thought for a while about how i wanted to respond to this. Should I ask you to back up your claim with some sorta actual sound knowledge not just something you read in a magazine?
Naw.
Should I ask what type of real world engines with electronic ignition you've built yourself?
naw.
Should I lay down all my engine, trans, ignition, wiring experience i've had? no way, i'm not the one challenging here.

So I figured I'd just suggest you do some actual research yourself.
But I'll help you get started......
http://www.cranecams.com/402-407.pdf
here is the crane cams version of the mallory ignition....whats the voltage requirement???
http://www.cranecams.com/396-397.pdf
here is crane cams high end drag race ignition.....whats the voltage requirement???
http://www.msdignition.com/Products/Ignitions/7805_-_MSD_8-Plus_Ignition_Control.aspx
here is the MSD-8-Plus ignition....check out the specifications....whats the voltage requirement???

Is it harder for an ignition system to run at higher rpm? of course it is, and that is why i asked how it was running at higher rpm.

But I'd love to here your theory as to why a system at 12v volts wouldn't run correctly. And if you really wanna get into this while really we are just trying to fix this guys problem then i'm ready.....

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

Ryan... It started yesterday and ran for about 30 seconds again then died... not a sputter die... but an abrupt die! After that, I could not get it started. I figured it was the cap because I am getting no spark at the plug..(I pulled a plug and grounded to the motor).

What do you think?

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

ok so wait. when you checked before you said that you pulled the coil wire from the distributor and grounded that; is that what you did or did you pull it from a spark plug?

Start here, if you didn't pull the coil wire from the distributor do that, leave the one end in the coil, put a screw driver in the other end and hold it close to something metal, I assume this is what you did before. But you gotta check it from the coil itself. That will at least tell you what you have there.

Do you have a multimeter? Cause if not, its gonna be hard to diagnose/find the problem.
I'll write more later.....

Commodore · Ladies Man Joined: 20 Jun 2005 Posts: 11636

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

haugy, exactly.
And honestly now that its completely stopped working it will make it much easier to diagnose. Its the intermittent electrical problems that are a bitch.

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

I did both... the wire from the coil is popping... so, I pulled a plug and held it to the motor... saw no spark at all. That's why I thought something was up with the rotor?? When I pull the rotor there is some steel wool looking stuff that is all rusty. Under that is rusty as well... and there are (2) little pins in there as well. I wish I had a pic!!!

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

so the wire from the coil is consistent? SNAP, SNAP, SNAP, SNAP, SNAP, SNAP???
you pulled a spark plug out of the motor and grounded that? Try just pulling the spark plug wire and do the same thing as the coil wire.
It could still be a weak coil. Running though a 1' of wire isn't nearly as hard as a foot of wire, distributor cap, rotor, distributor cap, 3' of wire, spark plug. Theres a lot of resistance in the sequence.

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

gotcha... will do when I get home today!

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

cool!
we'll figure it out....

Do you have a multimeter?

cadunkle · Criminal Joined: 16 Jul 2009 Posts: 60 City: NJ

Ryan, I've had Duraspark and MSD systems cut out and misfire at higher RPM shortly after an alternator stops charging. It doesn't take long for them to start acting up when your not charging. I've experienced this on anything from stock engines to high compression high HP engines. The higher the compression, the sooner they'll start misfiring with low voltage. I've built dozens of engines, mostly 460 Fords and some small blocks. A standard points ignition will be a lot more forgiving of lower voltage.

kartman · Posted: May 21, 2011 9:47 am Post subject:

to check the spark, i recommend picking up one of these. you can crank it out to see at what gap your system is failing at. any good running system should be able to put out AT LEAST a 1/4" arc. most high voltage systems can arc over a 1/2" gap. but be careful, this can pack a bit of a punch if you catch yourself!
http://www.amazon.com/Thexton-404-Adjustable-Ignition-Tester/dp/B0002STSBM

but i feel like it is a bad ground. even if the ground looks good corrosion can form under the insulation of the wire and cause weird intermittent problems. i think if you go through all of your grounds on the engine, (replacing them wouldnt be to hard or expensive if you do them one at a time) you will find your problem. but ryan is on the right track. sorry for the long delay in posts.

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

cadunkle,so you continued to run your engine at "high rpm" after knowing that you had a failure of a component?
What type of compression are you referring to; static? Because if its high static compression you're talking about I'd hope that your cam profile would be something that would work well with that, which means your dynamic C/R would be relatively low during crank/start. Which if you bothered to pay attention is what he is asking about at start/crank......NOT HIGH RPM.

Please define "shortly" and what condition was your battery in? If you bothered to read those links I shared you would have seen that 2 of the 3 only need 6 volts....I can assure you that the fuel pump will stop pumping (if its electric) well before the ignition system will stop producing. So Crane and MSD must be wrong.....

I LOVE the fact that you're still blaming the alternator; yet as you correctly pointed out the one wire alternators don't come online until the rpms are bumped above a certain RPM. Which means every single f'in vehicle on the road/water that has one of these alts should, in your book, have a starting issue. I better go change out my one wire in my 500+hp street car, which has a Crane HI-6 ignition box. Rolling Eyes

And my buddies dad who runs NSS; doesn't even have a damn alternator...just a, wait for it...12v battery.
You do realize that the alt isn't doing anything on any car during crank right? It's simply not spinning fast enough to produce current.

Now you brought up Duraspark, I don't know what the voltage for a Duraspark to run correctly is, but I know its not 14. How do I know? Because vehicles are 12v systems; not 14+ And from the sounds of it; I'd be willing to bet your misfires happened because the Duraspark couldn't run at the rpms you were at, not because your alt died.

BTW how many freaking alternators do you kill that you have this much "experience" with misfires that you're attributing to having lower than 14v on a 12v system??

Your comment about points requiring less voltage to run correctly, might be accurate but I'm gonna guess only a negligible amount. Especially when he is running the Mallory piece. What I do know is that the Mallory piece is listed as a 12v piece; and since the Crane one will run down at 6v, I'm gonna go out on a limb and say that the Mallory one isn't that far behind. But regardless he is having trouble with starting, not WOT.

now back to our regularly scheduled program.....

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

chawk610, what did you find out man?

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

ok... my dad came over yesterday and helped... LOOOOOOONG story short. My tachometer has a short in it... well... the tach is grounded to the coil....cusing the intermitent spark... removed the ground... starts and runs like a champ. I would have NEVER figured that out!!! Props to the old man!!!!!

I will replace the tach when I can afford too... but for now, we are back in business!!!!

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

And thank yall for the help!!!!!!!!!!!!!!!!!!!!!

cadunkle · Criminal Joined: 16 Jul 2009 Posts: 60 City: NJ

Ryan, you're an ass. The fact of the matter is ignitions will misfire with low voltage. That is less than 12 and more than 6. I brought this up as one thing for the OP to check, that his alternator was in fact charging and he wasn't just running down his battery cranking, running like crap for a minute, then stalling. Low voltage can cause that problem, it's just one thing to check.

kartman · Posted: May 22, 2011 2:32 pm Post subject:

glad you got it runnin. i had a fealin it was going to be a ground somewhere.

chawk610 · Addict Joined: 06 Jul 2010 Posts: 668 City: Fort Worth

Always is... right... darn boats. On top of all this... couldn't go out today. Toooo windy, and storms brewing. We did wash and wax the old girl though!

McNasty · Outlaw Joined: 02 Jan 2010 Posts: 171

Your lucky... Went to Grapevine today.... I HATE THAT LAKE.... Nothing went right, but it wasn't that bad. Glad you got the S&S running.

Dodge2500hemi · Newbie Joined: 22 May 2011 Posts: 2 City: Portland

So, new guy here making an observation..
chawk610 asked for help... Ryan351w suggested to check ground...
cadunkle Layed down a bunch of smack talk that Ryan351w was an ass for helping the guy out and getting it right... And to finish the summary, the lake was windy and crap today?

Did I get the gist correct?

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

chawk610, so the tach is grounding internally? Because it is supposed to have a wire to the coil.....Just make sure that wire isn't chaffed or something along the way before you buy a new tach. If you did that... disregard! Laughing

nicely done on the diagnose! Happy you figured it out!

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

cadunkle, sticks and stones..... All i said was that the alt had nothing to do with a starting issue...and that an ignition system doesn't need 14v to work correctly. Then you call me out saying I don't know what I'm talking about, so I proved I did know what I'm talking about, used facts, real life experience and true knowledge, but now I'm an ass....thats cool. In the end he figured his boat out.....I'm done fighting with you.

ryan351w · Addict Joined: 26 Jan 2009 Posts: 532

Dodge2500hemi, welcome to the boards! Careful who you listen to! Laughing

I jest!

Dodge2500hemi · Newbie Joined: 22 May 2011 Posts: 2 City: Portland

ryan351w, Thanks! Great Sig... So very true.

The phrase: Et Hoc Transibit seems appropriate here.