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· Premium Member
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Discussion Starter · #1 ·
2-3 weeks ago, the car started doing some strange things. It would run good for a little while, then just dies like turning off the power. Wait just a moment or two, and then it would start right up.

I finally figured out the problem by looking at a data log as the engine died. The battery voltage would cruise along at 14.5-15.0v for a while. Then it would rapidly rise to 20v and trip the breaker, killing power to the ECU.

I replaced the voltage regulator and alternator with rebuilt parts from Autozone. Parts I'v been using in a lot of vehicles for many years.

That fixed the problem. I drove the car about 600 miles without any problems. Highway and back road. Cold enough to wear a jacket, and warm enough to wish for shorts. I even drove to the top of Pikes Peak, over 14,000' ASL.

Today, it started doing it again.

It's a little warm today, but not really hot - air temp is only 84*. I drove down to the other end of town, about 30 minutes away. Mostly a gentle cruise down the highway, but I did run the speed up a little to about 95mph once or twice. On the way back, I was cruising along at 2,000 rpm's or so in 5th. Water temp was about 170* or so. I was in the left lane of the freeway, near rush hour. Suddenly the engine died. that was scary.

I did manage to get home, but it kept dying on me.

Has anybody ever heard of this before?
 

· Official OLD GUY
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3,877 Posts
Check your PIP

Bob,

Mine did that a couple of years ago . . . turned out to be the PIP sensor in the dizzy. It would heat up and then the car would just shut off, like I had turned the key or something. Let it cool for a bit and it would fire up and go another few miles till it heated up again. I changed the PIP inside the dizzy, no issues after that. It's a PITA to do, you have to disassemble the distributor to replace it, so the gear has to come off. Almost makes me want to go to a crank trigger the next time it fails . . .

Just my 2¢

Doc :beerchug:
 

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Discussion Starter · #3 ·
That might work, and had a distributor. I am running an EDIS style distributorless ignition system, managed by the ECU.

I believe this is happening, because I captured it on a data log through the ECU. It happens so quick, I can't catch it on the voltmeter.

This is pretty unusual, and I can't find any information about it.

My other thought is that it's not really happening. But the ECU believes it is, because it is losing it's 5v referance line. I'm going to try and use the LM-1 to data log the failure and see what happens.
 

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Discussion Starter · #4 ·
Nobody else? Did I stump the experts again? Man, I hate it when I do that.

Over the last couple of days, I've driven the car 3-4 hours. It ran really well, with no problems at all. Never died once. Until today.

After driving for about an hour or so, it died while cruising down a side street. Checked the data log, and it's the same. Battery voltage climbs to 20v, and the engine dies. Let it sit for a minute - and I do mean 1 minute - and it starts up again. Then it will do it again. The longer I let it sit, the longer it will go before doing it again.

I got home by shutting it off at the lights and long down hills.

What are the symptoms of an overheating alternator?
 

· Junior Charter Member
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You wouldn't be the first person to get a bad part from the part store. However, that is not exactly the most common symptom.

Do you really know that the breaker is tripping? If so, then too much current is being drawn which can be from voltage too high. If the ECU itself started drawing too much, I would expect voltage to go down. So, this could be a crazy loose ground issue.

If the breaker is not really tripping, I would look at the ECU.
 

· Registered
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You wouldn't be the first person to get a bad part from the part store. However, that is not exactly the most common symptom.

Do you really know that the breaker is tripping? If so, then too much current is being drawn which can be from voltage too high. If the ECU itself started drawing too much, I would expect voltage to go down. So, this could be a crazy loose ground issue.

If the breaker is not really tripping, I would look at the ECU.
The breaker should trip on current, not voltage. As such, it is more likely that something is overheating and shorting to ground which would cause a current spike that would pop the breaker. I would look for something that is close to heat and which could pull a pile of current. Distributor is a likely culprit but your computer could also be going bad. The fact that it starts up again after cooling down indicates that it is something designed to handle a lot of power (otherwise it would create a permanent short) so look for something with a big heat sink on it. As an fyi, many typical electronic devices like radio's or iPod's that failed like this would pull so much current that they would literally smoke and the damage would be permanent so the culprit is likely a device that can typically handle high currents but is starting to fail.

HTH
 

· Mark 3.1 (Sold)
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If the voltage to the battery is actually reaching 20 volts, the battery would be drawing a considerable amount of current. So the culprit is most likely the regulator. The voltage regulator should never allow the voltage to rise above about 14.5 volts max.
 

· Speed-crazed and Confused
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2,349 Posts
Bob,
Over the years, I have had a lot of issues with Autoxone stuff. Even though it has a lifetime warranty, they seem to fail quicker. After 3 alternators from AZ, I bought one from NAPA and never had another issue.

I have also had this issue with brake pads and really short lifespan. Despite the lifetime warranty. The ink on the reciept fades with exposure to oxygen/moisture. I learned that after 2 refusals because they couldnt read the reciept anymore.

Might try a voltage reg from NAPA or even Ford.

What TJMotter says abov makes a lot more sense anyway.,

my $0.02 anyway :)
 

· Premium Member
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Mine endedup being the main power wire going to the ECU (electromotive)..they said it had an goofy break in it that would show good one moment and then bad the next...I had been messing with this for at least 4 months until it died for good...had to finally get a tow truck...only to have it fire right up when I got back from work...then die 10 minutes later...that was enough for me...sent it in ....rock solid since!
 

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Discussion Starter · #10 ·
Hmmm. Interesting. The only things on the car that pulls a lot of power is the ignition and fuel pump. The fuel pump has a dedicated high amp circuit, circuit breaker, and relay. The ignition coils are run directly from the ECU. Both are mounted in places that get a lot of cooling air flow.

There's nothing on the car that has a big heat sink.

Do I really know the circuit breaker is tripping? Maybe. Below is a screen shot of the data log. The data log automatically stops when the ECU shuts down. The lap top displays "Off Line". The green line in the bottom graph is the volts.



I'm begining to wonder if it's something inside the ECU. I'm going to try and rig my LM-1 to monitor Volts, and see what happens. Then I can look at the circuit breaker panel directly, without passing through the ECU. This is such an intermittent problem that's it's really tough to track it down.
 

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exactly what my issue was( so intermittent ) ...my vote is either power supply to the ECU and/or the ECU itself.
 
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