Would low voltage cause this problem?

[blykins]

I've been sitting thinking about this....wanted to see your all's opinions....

I've doing a lot of tinkering with the carb lately.....and I figured out that my alternator wouldn't charge with the engine idling because of the underdrive pulleys.

Anyway, I put a fuel pressure regulator on, fired it up, and the thing was harder to start than usual and it seemed like it had a miss to it.

I noticed that when I was blipping the throttle trying to get it to warm up that I could hear the fuel pump getting louder and the ignition indicator light would get brighter....that's what tuned me on to the alternator and battery.

I stuck one of those chargers on the battery that tells you what percentage the battery is at....it showed 58%. I proceeded to go ahead and charge the battery....it took about 5 minutes to charge to 100%.

I pulled a plug out of each cylinder bank and looked at it. Sure enough, they were sooty and a little gassy.

My thought is that the low battery voltage has caused all of this....not a full charge....so my MSD 6AL couldn't get a good spark off to each cylinder....which caused the soot, gassiness, and the missing.

After the battery was charged, it started quicker and seemed to run smoother, but still had a very slight miss in it. (As detected by the seat-of-the-pants meter.) I would chalk that up to the plugs being sooty.....

So does this sound like a logical explanation to my dilemma?

Again, I only get to work on the car usually on the weekends....I live 2.5 hours away from the car.....so if something isn't quite right, I have to lay awake thinking about what all could be wrong at night....

Next plan of action is to go ahead and swap the plugs out for some new ones....make sure the battery is at 100% and fire it up.....

Signed,

Worried in Louisville

[slithering]

Brent,

What is your voltmeter reading at idle? If your charging it should be 14 vdc or so. Check your voltage output at the regulator, this might be your culprit. Does the car run on after the key is off? Could be a resistor problem, sounds like a regulator though.

Chris

[blykins]

I don't have my ammeter hooked up yet....and I haven't got a chance to put a voltmeter across the terminals.

I've had several members tell me that they've had the same problems with underdrive pulleys...it just won't spin the alternator fast enough to charge the system. I'm not really concerned about that part...

I was just trying to back up my suspicions that a low battery voltage will not alllow the MSD box to put out a good fire....thus causing the aforementioned plug sooting and slight misses...

[Ron61]

Brent,

I am not sure about the new MSD boxes, but on my Jacob's Pro Street, the second I turn the ignition on, the unit stores enough juice for 35 plug firings in a buffer. However I am sure that if the battery were low enough that would start to affect the performance. About 5 years ago I bought one of the little battery tenders from NAPA for $39.95 I think it was and have never had a battery problem. So if your car sits for long periods, this might be something you could think about. They can be mounted right in the car if you want and just plug in an extension cord when you park. I have them on both of my cars and love them as I don't have to worry about the battery during the long Winter breaks.

Ron

[lineslinger]

Hi blykins,
Your analysis makes sense to me.
I thought about your post for a bit and a couple of things come to mind.
I am assuming that if you have a fuel pressure regulator you are running an electric fuel pump.
If the voltage output (from whatever source) is not optimal your whole system after the alt. is being starved for power. The fuel pump now has to work even harder to build up enough pressure to deal with the regulator which may be why the performance suffered even more after you put it in. It can't do it, not enough volts for its design.
Without optimal/proper voltage at idle it cannot make the desired fuel delivery, thus you need/tried/considered enriching the idle.
With low voltage the entire ignition system is "starving" for enough juice to create a spark that is big enough and hot enough for its designed delivery, even if your ignition has a capacitor, that "stored" electricity is used up very quickly once you fire the beast up, the combustion within the chamber is not sparking/burning the fuel properly or completely.
When you blip the throttle the fuel pump works harder and the ignition calls for more juice. The low voltage will not allow it to do so, thus, louder FP and brighter ign. light.
One other thing you might consider is before you start doing all the electonic trouble shooting necessary, try changing out the pulley or pulleys and see if the problem still remains, if it goes away thats a pretty good indicator as to whats up.
I think slithering has got it right about the voltage regulator.
Low voltage at the source of electricity is producing a trickle down effect that is affecting efficiency on both sides of the system.
Sorry to be so long winded but I hope this makes sense.
Just some things to think about, good luck.

Mark

[blykins]

I didn't have a problem with it two weeks ago...that was the last time I was home and was fooling around with the car. I had the car out on the road and was driving a little bit...which would have kept the alternator spinning quick enough. I don't know what has happened since then....maybe Dad fired the motor for someone or something...I don't know....but when I went back to work on it this past weekend, that's when I saw the problem.

I really hope there's nothing wrong with the alternator....it's a brand new piece.

I think I'm gonna go home this weekend and try some things.....I'm gonna change plugs, make sure the battery is at 100%....and fire it up. The battery charger has an option where you can see what the alternator is putting out.....I'll switch it on that and check it out....along with using a voltmeter.

I had noticed before when using the charger with this selection that it would show the alternator wasn't doing crap while idling. When above 2000 revs, it would start to show up.

Other members have posted that their underdrive pulleys have caused the same problem....I just hope that it is indeed logical to say that the low voltage has caused a lack of ignition fire...therefore sooting the plugs up.

The only other reason I can think of why the engine was acting up is that when I first put the regulator on, it was apparently set high. Dad was adjusting the pressure while I was in the car......The pressure may have been so high to float the needle off the seat and flood it a little bit....

It seems awfully coincidental though that the battery was only at 58% charge.....

Alternator is not grounded either....probably need to fix that little detail.

[trularin]

Okay. I think there are several factors that could be causing problems.

1. The alternator MUST be grounded to the engine and the engine MUST be grounded to the battery.
2. Proper voltages should be read to determine if the regulator is doing it's job.
3. The case of the regulator MUST be grounded.
4. If this is a Ford regulator ( non self exciting ), the IGN on the regulator should be connected to the Ignition key ( unless you have an idiot light ).

These are the most common mistakes in wiring a charging system I have run into.

Brent, you should charge the battery and make sure these are all covered before you do ANY thing else.

Just my opinion.

[blykins]

It's an AC Delco alternator....I can't remember....is there a stud on there to hook a ground wire to?

[trularin]

Single wire, self-excite? There usually a bolt hole in the back for grounding the alternator to the engine.

The stud goes to a #10 to #8 ( depends more on strands ) wire that is conneted to the battery. The little plastic plug in with the wire hanging out goes to the ignition key. That way the system isn't trying to charge while the engine is off.

You should have a strap, copper braid or big wire connecting the engine to the battery/frame. There should be a good size wire from the alternator case to the engine block. You should NOT rely on the alternator being grounded...just because it is bolted to the engine.

This is my $0.03 worth ( you get a little extra )

[blykins]

Ok....No plastic plug on the alternator. There is about a #10 stud on the back of the alternator. I have a #4 or #6 (can't remember) wire running from it to the starter post that the positive battery lead goes to.

The engine is grounded to the frame in two places with big fat honkin braided straps.

So I need to find where to ground this sucker and ground it to the engine.

The stupid thing was working a couple weeks ago....started the engine up, took it down the road a couple times and brought it back in the garage....stuck a battery charger on it just to make sure (I have only had the alternator hooked up for a couple weeks) and the charger showed 100% charge. So I figured the alternator was doing its job.

[Ron61]

Brent,

If either of your engine to frame grounds are near the alternator, run a wire from it to one of them. The straps should be fastened at both ends with bolts.

Ron

[lineslinger]

Blykins,
At the time of your early "shakedown" it(alternator) probably was grounded because you had metal to metal contact from initial mounting, but as fasteners vibrate and settle in it may very well have shifted in just such a way as to not be visible to you but just enough to insulate itself from what was a working ground. Are your brackets painted (insulated)? Is the housing on your alternator painted or chromed, these factors act in the same principal as insulation on a wire.
This haunted me more than once on a big healy I restored.
You have to have solid grounds before proceeding. One step at a time, you'll get it figured out.
Good Luck.

Mark

[blykins]

Brackets are March brackets....polished aluminum. Alternator doesn't have a finish on it....just natural aluminum.

Straps are bolted on each end.

One thing I can't understand.....I honestly think the alternator is working guys....when it's at rpm that is. Otherwise it wouldn't have shown 100% charge after a couple of drives the other week.

I truly think the pulleys are too large...and fooling around with the fuel pump, ignition, etc...while the engine wasn't running drained the battery....then when I started the engine up and let it idle, it just wasn't spinning the alternator fast enough to charge it. Thus let to the rest of my sooty problems.

I will however do the following this weekend:

Ground the alternator...
Make sure the battery is at 100%...
Change plugs...
Fire the thing up and go crazy with a voltmeter.

I'll also use the charger I have and verify the alternator is putting back juice to the battery.

[blykins]

Update.....

I changed plugs. I charged the battery to 100%, stuck a voltmeter on it and started the engine.

The battery showed about 12.4V before I started.....After the engine started, the voltage would go up only after the engine was spinning about 1500-2000 revs...then the voltage would show about 13.5V.

Alternator works.

I messed around a little while longer, and shut the engine off. I have a master disconnect switch on the rear bulkhead. I turned it off. There was *nothing* pulling on the battery....

I stuck the charger on the battery and let it trickle charge while I was cleaning up. It showed 100%. I pulled the charger leads off the battery....and Dad interrupted me and told me just to leave them on and let it trickle charge while I was gone and he would check on it. I put the leads back on the battery, and it showed 80%. There was nothing at all putting a load on the battery, and yet a minute later it was down by 20%. It's an Optima battery....I think I have a shorted cell.

So alternator works. Battery doesn't. New plugs.

One of the highlights of the day.....I got to drive a 69/70? Boss 302 Mustang. I fell in love.

[Sydney]

Hey blykins,

If you only had 12.4 volts before you started, that battery was only about 80% charged to begin with. Typically a fully charged battery should read somewhere in the 12.75 vdc range depending on the type of battery. If I remember right, an optima will read between 12.75vdc and 12.80vdc when fully charged.

You might try a different charger first to try to get the voltage up before you fork over money for a new battery. If that charger you have now says it's at 100% charged when the battery voltage is only 12.4 vdc then I would look there first.

Sydney

[Tim Brewer]

Brent,
As far as your alternater goes, it is working correctly by not charging when you first start your car, and then showing a charge after you rev it. It is designed to start working as soon as it hits 1500 RPM, and then it will not shut off until you turn off the ignition.
Tim

[blykins]

I just can't figure out why the charger would say 100%....then when you take the leads off and put them right back on, it says 80. Doesn't make sense....especially when the main disconnect is off.....there shouldn't be anything at all putting a drain on the battery.

Would a shorted cell cause that? Or do you think I should stick another charger on it?

[Ron61]

Brent,

A bad cell in the battery could cause that as it will lose capacity. If you want to mess with checking your charger, try it on another battery that you know is good and see if it gives you the same type readings. I have had a red top Ultima in my car since 96 and have never had a problem, but I keep a cheap battery tender on all of my batteries when they are sitting for long periods.

Ron

[blykins]

This one's an orange top....I bought two of them for $100....one for my dad and one for me....his is in his Mustang Cobra and is going strong.....this one seems like it may be a handful.

[trularin]

Ron61 Makes good point. Try another battery.

It's not like the battery is eight years old and has been through six Michigan winters.

You can have the battery tested on a load master or other battery load tester. It basically tests the batteries ability to provide current.

Talk to you later.