voltage issue causing misfire

So I am getting everything sorted on my car was off the road for a nearly two decades. I had everything gone through in a beyond a major service by a Ferrari professionals - oh, Bambina is a 1975 GT4 with twin distributors and most parts stock. Assume the following:

Distributors were rebuilt and calibrated/tuned/matched on a distributor machine
Birdman Fuse blocks
DCNF's rebuilt by a guy who knows what he is doing.
Original points ignition - I would love to change this someday - but not right now.
New battery this summer
I believe the alternator was rebuilt but I have to check my records

I want to fix this myself so it means I have to learn car electrical. I did get a Paul's diagram, blew it up and laminated it when I first started 4 years ago but then handed the car off to get most of the work done. I do not know much about electrical systems. I have a basic digital multimeter. I do not know completely how to use it but I am coming along the more I do.

A while back, I posted about an engine flutter I am experiencing and not knowing if I have a carburetor or distributor issue. I have done a lot of reading and learning on here and other forums. I have been watching general automotive YouTube videos and realized it is probably a misfire due to an low voltage issue. I did a Google search to see if a misfire can be caused by low voltage and the results seemed to confirm my suspicions.


Symptoms:
I am very regularly charging my car due to power loss. I found that I could only really drive it for short runs, as the battery / charge would die. When it was driving I was getting a power flutter if there was any significant acceleration especially around 4K RPM - then it gets worse the more I drive it. I did realize I had the battery cable loose and it was discharging very quickly. I got stuck on the side of the road. Twice I required tows home - it sucked.

After realizing I had the loose cable and I tightened it. Though I was able to get more battery life, the power problem still persisted. Thus began a series of charges and short drives to better understand the issue and pattern. So this is typically what happens:

My testing:
I charge the battery overnight. I see that when I go to disconnect the battery it is getting 13.2-13.4 volts. If I let the car sit before I drive there is a parasitic drain that will drop the battery to 12.9 - 12.7 within a few hours. When I start the car volts drop to 12.3 (I know this is not good!). I have performed load tests with the radio and lights (gulp) it drops to 11.9.

I let it warm up for a few minutes. I go for a 20-40 minute drive. The car is good for the first 10 minutes, then the flutter kicks in. I think I am having a misfire and losing one bank because of the power loss that goes along with it. Then I keep the revs down to reduce / eliminate the misfire and get the car home safely in my garage. I stop the car and test and the batter is anywhere from 12.1 to 12.3. That will drop more with time as the car sits.

So I possibly have a parasitic draw and I have a bad charging system or perhaps too much resistance somewhere.

Can anybody suggest a next step or proper procedure as to what to test or look at next? Is there a standard order of operations when testing electrical?

It seems like I need to get a new alternator – I just want to test everything before I start throwing money at parts (this is me maturing).

Thank you!
Spencer

 

So I am updating my thread as I have finished the job and have more questions.

First off here are two sub threads that I started:

Alternator removal - My (and others) approach to the long bolt hitting the dipstick housing
https://www.ferrarichat.com/forum/308-328/439264-pulling-alternator-help.html

Installation - torque settings
https://www.ferrarichat.com/forum/308-328/443148-aternator-bracket-install.html

 

I did get my rebuilt alternator installed this past weekend and took it out for a drive. Oh what a difference! Done but I assume there is a little more vetting that has to be done on completely fixing my issue. I got it in and hooked up ok. Started the car and tested voltage and had to rebleed the coolant. previously mentioned I cut the tube from the aluminum pipe to the top of the block (replaced with Gates Green Stripe 1" 5/8).

I bought a rebuilt bosch unit that is 12v 65amp. The housing was different so I removed the necessary guts and put it in my original housing.

The car idled great and I observed it for a while. It idles at 12.5-12.7 volts. I thought it would be higher than this but at least it was not in the 11's like before. I took the car for a drive and this was really the first time I have been able to take it higher in the rev range (after warmed) with out getting my misfire, or as i called it an engine flutter as I started. It felt great. I gave it a little italian tune up. A guy in a new M3 tried to race me but I wasn't givning in to his games (i know how it would end). I really had a great time! Shift bushings next and already ordered from Verell so I can actually not have to think and shift into the proper gear.. I think a little more tuning might be in order as it was previously tuned with poor voltage (timing and perhaps some carb tuning need) though I know it is an old car and I am learning I can't just drop my foot like on my subaru and expect everything to respond like so. Some flat spots in acceleration and choking on my heavy foot.

So problem fixed, right? Kind of. As I was driving it got to be dusk and I turned on the lights. I started to experience the misfire again. AHHH I didn't load test it with lights and radio on. I do so when I get home after being gentle. I base it again and still getting 12.5-7v. I turn on the lights and it drops to 12.1ish. Radio added and it there is a couple tenths change for the worse.

So what next? Perhaps there is an old ground that needs refreshing or poor resistance in the cables that I presume are original. I have my Paul's electrical charts. Any other standard culprits here that I should be looking for?


BTW... I love working on this car. It is so rewarding, even if it takes longer. I have a plan for the car and would like to follow Ferraripilot's journey which reminds me of a more refined part Magnus Walker Urban Outlaw approach, part Black Beauty and part Singer with thoughts of producing some carbon fiber body panels to reduce significant weight. I am long term on the car and will drive it as long as the world lets me. #NeverSelling - I know, I'm lame... I like this guys vision and attitude: The Story Behind The Perfect Porsche Garage?s Porsche Sorry for all the Pcar referrals - we are just not as well known for properly modding our cars, yet.....

 

I do and it is faintly on. It seemed to get brighter with the lights on, dims when they are off. Before the alt rebuild it would start off dim and get brighter in about 15 minutes into my drive.

I will start ground hunting.

Thank you all!!!!!

 

Thank you! This could be a culprit as there is an issue. Right now Off, Ignition On and Start work. The Accessory Only setting is not working - could be something to take a closer look at.

I have an oil leak that I believe is coming off the rear bank - likely the head gasket and this braided wire is covered in oil - probably not safe and this could be degrading the continuity. I know I have to really clean the block, degrease and spray down to determine where this is coming from. if it is the head gasket then I know I have to pull the belts and a whole lot more. I was thinking about keeping my eyes on the oil level and living out this summer with the leak and obviously no crazy hard driving. I know many here would likely disagree. I am hoping this does not lead to an engine out service.

I will check all the main chassis connections then go for this as an order of operations.

 

Did some work on the car this weekend. I went under to check and clean all the grounds. Between all my last posts I went on a warpath of watching YouTube vids on different tests and got so caught up in creating a document for myself that I wasn't fixing the car. So I am building a "beginner's guide to 308 electronics" that people with no skills can use to get themselves going. I will post it and let the pro's rip it to shreds!

Jacked the car back up and put it on stands. First I did the engine to chassis ground strap. It was covered in oil so I removed degreased and cleaned it up. I put a brass brush on my dremel and cleaned off both ends, front and back. I also degreased and took the dremel to the mounting points and, sure enough they were filthy. There also seemed to be paint on the chassis. Then I went up to the starter and did that connection - turns out it though the nut was fastened down tight, there was play in the wires. There was not really any grease here but I did take the brush to all these contacts too and got everything back on and tight. While I was down there I changed the shift bushing with one of Verell's delrin pieces. Boy, the rubber in bushing that came out was pretty much gone as the inner and outer parts pulled apart by hand!

I check the voltage before heading to sleep and it was steady at 12.5 - a little low but pretty much where it should be.

I woke up and lowered the car off the stands to go for a drive. Much to my surprise as I started her up voltage went up to 12.8 - progress? Maybe... Lets go for a drive. I knew right away the acceleration felt stronger. I was just wondering if it was a matter of time. I went on a 10 minute run and it wasn't fading a bit. Time to refuel and go a for a longer drive up to highway 9 and Skyline in the south bay and see what she was made of. Much to my surprise it is holding. the drive going up the hill was great. I was hanging with Ducati most of the way and found a little flat spot in the acceleration higher up in the revs. Oh and the shifting was so spot on. I no longer had to worry about downshifting from 4th to 5th that was coming on in 3rd, or 2nd to 3rd in 1st (if that makes sense). It was the best drive yet. Its all coming together! So I think the worst is behind me and figure when I get home I will see some higher voltage.... but no. I pull in my driveway and the fans kick on after putting her through her paces. Voltage was reading 11.9?!? Still the misfire issue seems to be gone, so that's good! Now to trace the fuses, check the ignition and the generator light wiring as suggested by all here. The light is very bright as I prime the car before starting, dims as I start it and holds a dim throughout. As I turn off the car after my drive I put it back in the "on" position with out starting the car and the light is very bright again. Is it supposed to be bright the whole time or does it normally fluctuate for everybody like this. I don't know if that points to any indication of that being the culprit.

Some good news and a great drive, finally. The misfire is solved but I still need to do some hunting to improve the voltage when running. No parasitic drop still. Headed to the airport but I can't wait to come home in a couple days and go for an enjoyable drive overlooking the bay and the Pacific at the same time for sunset.

More to come - Thank you for all your help and I will post my guide in a few for some help and accuracy.

 

Fixed!!!!!! Cable from the alternator to the starter. The cable end had slid into the sheath (umbilical chord). I thought the connector on the small was the connection to the starter. Drove it - it is twice as powerful as before. Getting 14.5 volts at idle! It sounds and drives better than ever! It pulls without bogging down and the battery doesn't die. 10756 - BMBINA is OFFICIALLY back on the road after 20 years!!!!!