intermittant miss

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Brickren
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intermittant miss

Post by Brickren »

Hello. My '75 has a miss that comes and goes. I can go for a drive and all is fine. Shut off, go in store, restart and iI have a miss. Shut off for a few seconds. Restart, all is fine. Go a few miles, miss comes back.. Now I went 4 wheeling this weekend. The whole way here, miss came and went. Wanted to turn and go home, but went anyway. While there, she ran fine. And all way home, ran fine, although I now have another problem. Maybe related. Barely charging. 24.3 volts running. Put headlights on, batteries die after about 45 miles. It isn't constant enough to say its this or that. I adj valves, and cleaned/gaped plugs. Dielectric greased wires. OEM wires with P'tronic ign.
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1975 710M
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undysworld
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Re: intermittant miss

Post by undysworld »

To Commander of Pinz Sub,

It looks like you've been under the sea for a while, as evidenced by the water in your fish bowl, er... headlight. :oops: (New gaskets in the lights might prevent this.) Based on the fish bowl, I'd be suspecting watery electronics too.

I'll assume you've already looked for water in the distributor. I'd suggest at least cleaning and dielectric greasing the molex connector for the alternator, if you haven't done so already. And since we're talking water, I'd add a bit of Heat (red) to the fuel to ensure that the fuel isn't causing you problems.
63rover
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Re: intermittant miss

Post by 63rover »

Pa is cold in the winter too. Was the fuel tank full? You may have some water in the fuel from condensation. A pint of methyl hydrate (from the paint dept at Walmart) may do the trick. (It the same thing that is packaged as gas line antifreeze.) Cheap, simple and quick. I had a car acting up once so badly I wanted to go home, if I could make it. A quick stop at the pharmacy (they sell it too) and it was like I had a new engine.

Good luck
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Brickren
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Re: intermittant miss

Post by Brickren »

Thank you for the tip. I was having the trouble before I went four wheeling this weekend. But I will try because of the cold weather. That's a good thing about the fuel additive. It was actually running better after I came home from four wheeling. I will check the connectors also double check the distributor. I was thinking maybe a spark plug wire was going bad, but I don't believe it would be intermittent like this.
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Re: intermittant miss

Post by undysworld »

If the spark plug wire had any breaks in the insulation, it would likely exhibiit more problems in wet or humid weather, as the spark jumps to ground instead of going through the plug. To test, wait until dark, then run the truck and mist the wires with water. You should see the electricity if / where it's leaking.
Stekay
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Re: intermittant miss

Post by Stekay »

Alternator belt slipping
'76 710K
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Jimm391730
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Re: intermittant miss

Post by Jimm391730 »

Barely charging. 24.3 volts running.
Alternator belt slipping
Or mud/dirt in the alternator, keeping the brushes from making proper connections to the slip rings. Or corroded molex connections. Or failed voltage regulator.

If you were in deep muddy water, rinse out the alternator well with clean watter and follow with WD40, see if charging comes back. Check Molex connections in three places: Wire to connectors (on both sides of the Molex) and between the Molex connectors themselves. Lastly, replace the voltage regulator (it is cheap enough at about $30-40 that it is easy to just replace if in doubt).
Jim M.
712W and 710M
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Brickren
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Re: intermittant miss

Post by Brickren »

okay, here is what I got. With the engine running and warmed up, the batteries are 24. 27 volts. the alternator, the big bolt is 35.5 volts. the secondary bolt is 29.6 volts. the connector plug in the back of the alternator, the top one is 7.5 volts and the bottom one is. 01 volts. The outer casing of the alternator on the top, the outside case reads 34 volts.the actual body of the alternator reads 0 volts. the molex connector on the inside of the tin, the red wire is 30 volts, on the outsides 24.2 volts. The black and yellow wire on the inside is 5 volts and the outside 7.5 volts. the jumper wire on the end is 24 volts. The bottom of the molex connector 29 6 in and out and the middle bottom of both sides read 0.
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Haf-e
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Re: intermittant miss

Post by Haf-e »

Wow - I can't follow that and I work on electrical systems all the time. Are all of the reading you made done with the negative of the volt meter connected to the chassis "ground"?

On the molex connectors - are they still plugged in when you made the readings? You can usually probe them through the end of the connector where the insulated wire exits if your probes are long and narrow enough.

Based on your numbers there is something definitely wrong! but what it is I can't say from the numbers provided...
Haf-e

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undysworld
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Re: intermittant miss

Post by undysworld »

Assuming I'm understanding what you just wrote (and I'm not sure of that), I'm still leaning towards a corrosion issue at the Molex. As Haf-e asked, were all the readings taken with the negative of the meter grounded well to chassis (or to the proper negative in the battery box)? If not, it would help to have those readings.

The fact that you read different voltages at different sides of the connector leads me to suspect resistance there. Clean it out, apply dielectric grease, and see what happens. Then, if you still have problems, take new readings with the meter properly grounded.

You may also be having more than just one problem, especially if there was water in things.
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Brickren
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Re: intermittant miss

Post by Brickren »

I grounded the digital meter to the coil mounting stud. I was getting readings swaying between half a Volt up and down constantly. . but I still don't understand the voltage drop from the main stud on back of the alternator which is the red wire to the other end of the red wire where it leads into the back of the molex connector. that was like a volt drop. Is that a resistor wire? Also touching the back of the alternator and getting a 33 volt reading, I didn't understand why the casting would be hot.( voltage).
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Re: intermittant miss

Post by undysworld »

You're saying some things I don't understand, and you're not saying some things I'd expect to hear.

I don't understand what this means:
I did program through the connector
I still haven't heard that you cleaned that Molex. This is a common failure point in the wiring harness. Water can cause corrosion, and your initial post suggests water. The connector pins get corrosion between each other and between themselves and the wires sometimes too. Check for resistance between the connector end and the wire, but mainly clean between the connector pins where they plug together (within the Molex).

This is THE connection between the alternator and the rest of the wiring harness. Flaky connections here can give you a variety of problems, since there are several connectors there. Electricity often has to go somewhere, and if it cannot go where it was engineered to go, it seeks other routes. My strong suspicion is that this is what you are detecting.

Jimmi (who has already given his input) is the guy here best equipped (knowledge-wise) to answer your problem, IMHO. He too has pointed to the Molex. If you have not yet followed his instructions, you ought to. He referred to WD-40, and I'll remind you that the "WD" in WD-40 stands for "water displacement". We both think water is the culprit and has caused your failures.

Until you clean the Molex, I do not think any readings will be significant to diagnosing your problem. I'm out'a suggestions otherwise.
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Brickren
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Re: intermittant miss

Post by Brickren »

Hello. I was using my phones speech to text and it didn't come out correctly. Sorry. I've not had a chance to work on her, yet. I Power washed truck inside and out last night. Wide fan spray as to not put any excessive pressure on anything delicate. I'm going to oil, grease, lubricate anything and everything today. Payed close attn to alternator and topside of engine to make sure fins were clean. I'm going to take connector apart and service terminals inside of plug. WD-40 and dielectric grease will be my best friends, today.
On the alternator, The "B" Terminal read 35.5 volts. At the other end of the wire, Probing the back of the molex connector on engine side, I read 30 volts. Probing the outside of tin, red wire only reads 24.2 volts. So I have a connection problem. Ok. But why the voltage drop from alternator to inside molex terminal? Is that a resistor wire? And back of Alt is reading 34 volts.
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Re: intermittant miss

Post by undysworld »

Aha. Not to come off as a total luddite fossil, but that's one reason why the only thing I do with my phone is talk into it. Too easy to be misunderstood otherwise.

From the schematic, it does not appear that there is a resistor inline: viewtopic.php?f=14&t=8985

I'll try one more time. Until after you have cleaned and checked the impedance at the Molex connector, I do not believe that any readings you take at the alternator will help us to point you to the problem.

It may be that the Molex connections are your only problem. Or, you could have multiple problems. But since that Molex is in the midst of everything, you really need to :!: start there :!: .

If we are all correct, water is the root of your troubles. So, quit throwing more water at the truck with your power washer. Unless it's a lot different than mine, it's friggin' impossible to prevent mist from going where you do not want it to go, especially if you're using it inside the truck.
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Jimm391730
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Re: intermittant miss

Post by Jimm391730 »

Your last photo is very telling - any good connection will have essentially identical voltages on both ends; a very poor connection or no connection is the only reason for different voltages (24 and 30V).

If I assume you measured the 30+ volts at the alternator bolt then there the most likely culprit is still the Molex, but we did have a member a few years ago who found that the wire itself (from the alternator to the inside of the Molex) was open. Some auto wiring includes "fusible links" which is a wire that is intended to become open, like a fuse, inside the insulation as a safety feature. I do not have any idea if Steyr used any fusible links but in that instance they were getting ~70V at the alternator bolt and ~24V on the outside of the Molex. The point is when you see differing voltages at ends of what is supposed to be a current carrying path (wire, connector, mating connector, etc.) there is something wrong -- and don't just "assume" that the wire is good, it might not be good.
Jim M.
712W and 710M
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