94mx5red

iTrader: (14)

Summary:

• Need your help!!!!!!!!!!!
• Alternator failed (pretty sure)
• Replaced alternator
• Only charging at 11.5
• Concerned, nervous, paranoid, and convinced that I will continue to have issues

Car is a daily driver. I have been having intermittent issues with the car not wanting to start over the past month or so. Most often the non-start would come after running for a while, and turning it off for a few minutes. It would be fine with a jump.

Positive terminal had loosened itself up a bit. Tightened that. There is no corrosion, and I am pretty sure I have a good connection. I am also pretty sure my grounds are good. I worked over every ground I could find about 10 months ago when I blew a head gasket. Open to going over them again, if you think that could be the problem...

Poor data to follow:
Cold weather came here in Florida in the last few weeks. Fuel started leaning out, so I started searching megasquirt threads trying to figure out what I needed to change to have it compensate.

GUESS: not enough power getting to fuel pump with combination of poor settings on MS for air density change.

I want to say I remember reading the voltmeter in MS in the 9's or 10's for the days leading up to failure. *poor data


Day of failure, car started and ran to destination a couple miles away (running lean). Would not restart a few hours later, until it was jumped. While driving to the office, I was running ultra lean. Stalled out when coasting to a light in gear while in traffic! Would not restart until screwing with the positive terminal (typing this is making me think I may still have a terminal issue). Ran ultra lean even while adding 10pts of fuel across the entire map.

Leaving the office that night: Needed to get jumped. Made it less than a block, and it was running so lean that it was wanting to stall, especially nearing idle. Turned a corner, and accessories (lights, dash lights) shut off, then misfires, then thankfully a good place to park for the night.

Note: I had the alternator fail with similar symptoms a couple years ago with this car, which is making me think it is the alternator. Replaced the alternator and have been fine since.

Next day: Have battery tested at local autoparts store- checked out fine. They charged it up. Using the charged battery, made it the mile home just fine.

Today: Replaced alternator. Only charging around 11.5 per MS. Went for a drive, and made it home... Nervous, and starting this thread.


Other random issue:
Most often when the car is started for about the past year, I seem to have limited accessory power until I put a light load on the engine. That is, wipers move slow and headlights show dim, until I apply light load in first or reverse. Then at idle, they operate normally.

Not sure if it will help or not, but attached is a datalog of the idle after the alternator swap. Also attached is the msq.


Your wisdom is greatly appreciated.

94mx5red

iTrader: (14)

Not sure why the attachments did not stay on the post... Trying it again.

magnamx-5

iTrader: (7)

You have shitty grounds something is loose or broken somewhere try to run another ground from the negative of the batery to the alternator and then if that works trouble shoot the rest of your connections. Your alternator is not working at all man 11.5 is not charging its dischargeing.

Reverant

iTrader: (10)

On NAs, I've found that the MS is always reporting very low voltages, I don't know why, probably something to do with the grounds. I've never had an issue with NBs.

94mx5red

iTrader: (14)

Thanks for the responses.

I think I remember my MS always reading in the low 14's prior to this happening.

Magna, are you talking about running a wire from the negative terminal of the battery to where the large white wire connects to the alternator in the picture?

magnamx-5

iTrader: (7)

no that is the hot feed if you that do that then you will definatley not charge run it to the base of the alternator and attach it to the bottom bolt with a big circle connector this makes a solid ground link between the negative of your battery and your alternator if this does not work then you have a problem with your alternator.

94mx5red

iTrader: (14)

Thanks for clarifying.

MartinezA92

iTrader: (4)

Alt ground is the last thing I'd check. The thing is case grounded anyway. (I think.) I would check the negative cable at the battery though.

If you replaced the alternator and its not doing anything, I'd check the wires at the alt. I don't remember off the top of my head what I got, but the wire with the nut holding it on goes straight to the battery, with the car off I'm 100% sure you should have B+ there, all the time. One of the wires on the connector should also have B+ with the key on, engine off or running. I forgot what the other wire is supposed to have (this is off memory, I may be wrong.)

Has the charge light on your dash been turning on?

94mx5red

iTrader: (14)

Not sure whether the charge light on the dash was illuminating or not. The way I have my gauges set up, it completely blocks it. I will check it out on Sunday when I dig back in.

I can tell you that the water temperature gauge was reading significantly lower than normal when megaquirt was reading fully warmed up. This only happened right near the end.

MartinezA92

iTrader: (4)

I've had weird stuff like that happen when the battery is going low with the engine running. I'd ignore it until you're sure your alt is charging again.

ApexOnYou

iTrader: (10)

A few important grounds that are over looked that can cause starting and charging issues:

-Engine/trans plate (I forget what this is called) to chassis, left side of engine bay.
-Negative cable to chassis in trunk, right above the battery, should be bolted with a clean connection
-Negative cable to PPF, directly in front of the differential on the right side of the PPF (10mm or 12mm bolt)

Yes I have personally witnessed issues from these being disconnected/corroded/broken. Usually it affects starting, acting like a bad starter.

Double check all fuses with a METER, not just visual check.

Also check that the charge light comes on with key ON engine OFF. I believe that a blown charge light will also cause a no charge situation. Haven't had that one personally, but worth a check.

94mx5red

iTrader: (14)

I appreciate the responses.


Wow, it is cold outside! I park underneath my building (think stilts), so the car is shaded. We had a cold front come through yesterday with intense winds. Today it is still windy and unbearable.


Additional Data:

• Key ON, engine OFF - Charge light is on bright
• Engine ON - Charge light is off completely

Using a multimeter at the alternator:

• Key OFF - Power at the white wire
• Key OFF - Power at one terminal of the electrical connector

There are two terminals in the electrical connector. The other had no power.


I will be working on the grounds next.


I know it is a long shot, but are there any settings in the megasquirt that I could check regarding alternator control?

ApexOnYou

iTrader: (10)

Have you verified that you are only getting 11.5 volts while charging directly at the alternator? I would think that would be triggering the charge light when running.

What you described at the alternator sounds normal. Big white wire is power output to fuse block, one of the smaller wires should be 12v input from a fuse (which one specifically I don't recall), the other goes to ECU I believe.

94mx5red

iTrader: (14)

Still not charging.

With the car running, the fat white wire coming off of the alternator measures near 16.5V! Any clue what this means?


Cleaned up all of the connections at the battery, along with its ground to the chassis. I am pretty satisfied that the battery is grounded.

I did some reading on checking fuses and continuity with a multimeter, and I think I am doing it right. I settled on the 200 Ohms setting, and they all read close to zero (.003-.004). I also used the setting one click over that will beep if there is a circuit.

In the main fuse block in the engine bay (last picture) I checked the '30A FUEL INJ'.

In the fuse panel in the cabin near driver's left foot, I checked 'ENGINE 15A' and 'METER 15A'.


I did not check the 'MAIN FUSE 80A' or the 'MAIN RELAY'. I will be moving on to those next along with go over all of the grounds on the car, including trying to run an extra ground line to the alternator.

MartinezA92

iTrader: (4)

if the big wire coming off of it has 16.5, your alt is alting. That also means you should have 16.5 at the battery posts, and if you dont, there has to be an open between that fat alt wire and B+. Your alternator is functional that's for sure and 16.5 seems normal if the alt is sensing really low batt voltage. Don't know if you mentioned it but has the battery tested fine?

94mx5red

iTrader: (14)

The old battery tested fine at the parts store. They charged it up. Since then, the car was driven a couple miles, and have been cranked over a dozen times. I am actually pretty surprised it has not died.

I do have a brand new battery I was hoping I could return, so I have not hooked it up yet.

MartinezA92

iTrader: (4)

Ah, then look for an open between that alt wire and the battery. 16.5 is too high, but should go back to normal once you fix the problem.

94mx5red

iTrader: (14)

WIN!!!!






This is the fat white wire that leaves the alternator and arrives at the 'MAIN 80A' fuse.

I cut back the bubbled sleeve and replaced with electrical tape. Gave a serious scrapping to the all of the surfaces, including the wire that leaves the other side of the fuse. Put it all back together, and it works like a charm.




I let the car warm up, and it was getting about 13.65-13.75V at idle. Turned on as many accessories as I could, and still the same.

I am very happy! Bought a new alternator that I probably did not need...oh well. Big thanks to all!!

Patriarca

Dear all,
I am a new member of this forum and I found this tread interesting and possible solution to a similar problems I have with my Miata 94. Is there any place that I can get familiar with the mnemonics you are using such as MS, how to get a log, read it, etc ?

Monk

iTrader: (3)

Megasquirt (MS) is a standalone computer that you will not have if your car is stock. You also will not be able to take logs etc.
I'll try to answer your question in your intro thread.