| fordmerc | -- 09-21-2011 @ 10:40 AM |
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After driving my '39 6-8 miles, engine shut off. Initially turned over vigorously and coughed, but didn't start. I cranked a few more times but battery died rapidly(few=3-4 for 5-6 sec). This has happened before with a different battery. I did not test for spark since I was on the street but near to home so I towed it home. Battery SpGr 1.015! Put in a new battery and it started right away. Last time I blamed coil, and present coil is different.The starter solenoid is also not the one in place when this happened before. Any ideas on what could cause such a sudden and total battery discharge?
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| supereal | -- 09-21-2011 @ 1:14 PM |
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Are you sure the battery discharged, or did one of the cables open up? Sudden full discharge of a battery is rare, unless there is physical damage to the battery itself. Your specific gravity test should clear the battery issue. Unless there is a very loose connection between the battery terminals and the cables, or the cables to the solenoid, I'd look for internal corrosion where the battery cables meet the clamp-on terminals. Acid creeps into that area and insulates the contact. Sometimes the heavy draw at cranking will cause enough heat at that point to reduce the output. That may be the reason installing a new battery seemed to cure the problem. The terminals were exercised enough to reestablish the contact. Occasionally, enough acid enters the cable at the terminal to corrode the cable, itself. There may be signs of heating, but not always. The best way to isolate these problems is to place the leads of a voltmeter across each connection, such as the actual battery post and the terminal. Any reading is an indication of loss. At 6 volts, it only takes one high resistance to cause the system to go dead. Unless your cables are of good quality copper, and properly sized, they should be replaced. Many cables sold today have undersized conductors hidden by thick insulation. Some are even aluminum, which oxidizes and forms an insulator. Good cables are expensive, but absolutely essential for reliable operation.
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| ford38v8 | -- 09-21-2011 @ 1:14 PM |
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fordmerc, I'm such a wizbang expert on electricity, I can afford to offer my golden rule tried and true advice: Don't touch electricity or it will snap at you like a vicious dog or an old wife. That said, I remember when I was a kid, a sick battery would take a charge and last a few more days, but now, they give no warning at all before they go belly up. My vast electrical knowledge now tells me to dump some money into a new battery, and I'm an electrical genius. Alan
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| fordmerc | -- 09-21-2011 @ 3:06 PM |
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Cables are "new", no visible corrosion; I cannot attest to their proper size. This has happened with a 3 year old battery (this time)and with a brand new one.(In fact I blamed the new one as bad, but later it took a charge well and I think it is OK; the newer one started the car this time). When the car "shut off", I was able to crank it with "full power"(?), but it didn't start and then further cranking just quickly ground to a halt.
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| 37RAGTOPMAN | -- 09-21-2011 @ 4:45 PM |
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fordmerc did you check the battery for a draw when attaching the battery cables.? check this out and get back to us with your finding thanks 37RAGTOPMAN
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| 51f1 | -- 09-21-2011 @ 4:48 PM |
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Check all of the cables and all of the connections between the battery and ground and the battery and the starter. Check the solenoid. There is probably a bad connection somewhere. If you have access to a battery load tester, check the battery. Richard
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| TomO | -- 09-21-2011 @ 6:19 PM |
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I agree with Supereal that sudden discharge of a battery without smoke is very unlikely. If the Neg battery cable or post touches the battery hold down, you would drain the battery, but there would be sparks and smoke. You should be able to see signs of this happening. The gas gauge reacts the quickest of all gauges. Do you notice a sudden change in the reading when this happens? If it goes towards empty or fluctuates, you may have an intermittent short circuit in the wire that feeds the dash. Your lights would also be affected, but you would only notice this at night. Just as a SWAG, I would examine the wires on the drivers side of the solenoid for signs that they may be making contact with the firewall. I would also look very closely where the harness goes through the firewall under the loom cover. I would also drive without the loom cover until I found the problem. As you have been fighting this problem for a while, it would be better to keep this thread going until it is fixed. It would also help if you listed all of the actions you have taken since this problem started. Did this start right after you finished the restoration, or did it start after you did some repair? Tom
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| supereal | -- 09-21-2011 @ 8:19 PM |
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The clue is that your cables are "new". That doesn't assure that they are not the cause of your problem. Defective parts are everywhere. Reread my original post. I've seen this problem many times, even with one of our shop trucks that left me stranded last year. The battery cable that was molded to one terminal on the battery made almost no connection when it was moved. It, too, was "new". This message was edited by supereal on 9-21-11 @ 8:21 PM
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| fordmerc | -- 09-22-2011 @ 11:56 AM |
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Thank You all for help. I will take advantage of TomO’s offer so here’s a rough chronology: I think this problem has been present ever since reassembly of the car. It is intermittent and not really reproducible, although it happens in about the same situation each time: drive 5-10 miles and the car stops. Therefore I'm afraid of it and am reluctant to venture farther. Things that have been done: (“new” means whatever is on offer at the vendors) 1. New wiring harness throughout 2. New ground and neg-to-solenoid cable. 3. 2 voltage regulators ( 1 new, 1 old) 5. 4. 2 different coils (one old, one new) 6. 3 different starter solenoids (1 old and 1 new ,1 used repro) 7. 3 different batteries (1 new, 1-3 yrs old, 1-4yrs old) Testing: 1. No current from neg terminal to solenoid with ign off 2. No cables touching firewall or battery hold-down 3. Starter button removed from circuit 4. No obvious corrosion or discoloration at any visible terminal 5. No warm or hot wires 6. Under loom cover looked fine 7. *On one occasion only (in past), spark when ground disconnected – I cannot reproduce this. Today: 1. No electric shorts identified. Newly charged battery=7.6V 2. Recheck after connecting battery same 3. Car started readily, runs fine. Drove around the block twice in space of 25 minutes, engine ran 25 min(mostly at idle) 4. At 24 minutes : a. *Batt gauge midposition, rather than “N” where it had rested b. Temp almost beyond “H” c. *Gas gauge closer to empty than half where it had been earlier (but mine moves around a lot) 5. At 26 min engine shut off; restarted quickly 2 min later 6. Testing: a. Batt voltage 7.4 V b. 7.4 V at batt terminal on solenoid c. 0 V at starter terminal on solenoid d. *No resistance between batt and starter terminals on solenoid !!!*** (there was no continuity when tested earlier) e. To the best of my ability to tell, no hot wires f. No current flow detected from batt at neg terminal 1 hour after shutting off engine: a. no change in testing b. Batt acid : approx SpGr 1.220! That’s too many words but I think I have covered most questions raised. The only suggestion not addressed is the cable but it seems that if it were too small it would be hot and if it were corroded I’d see it.
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| supereal | -- 09-22-2011 @ 2:59 PM |
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You have pretty well covered it. The corrosion or poor connection between the cable and the terminal is seldom visible. If the problem reappears, I'd change cables, just to be sure. I always run a second cable from the point where the ground strap connects to the the body and/or the engine to one of the starter mounting bolts. A common 12 volt cable with eyelet ends works fine. If you don't have a ground strap to one of the head nuts, be sure to add one. Remember, the starter draws a lot of current, usually measured in 100's of amps when under load. A good battery, such as the Optima, provides as much as 850 cold cranking amps, and is ideal for old 6 volt vehicles. If batteries in your car have a short (no pun) life, it is time to run a check of the charging system. I've spent over a half a century chasing electrical problems, and learned not to take anything for granted.
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| Dolman | -- 09-22-2011 @ 5:43 PM |
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fordmerc, I am suspecting the resistor in series with the coil. It's a wire wound resistor that could be opening when it gets warm and closes when it cools. I know that sounds counter intuitive but I had that experience in a different application. A new resistor would be worth a try. If that doesn't solve the problem, I'll do some more thinking.
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| ford38v8 | -- 09-22-2011 @ 6:04 PM |
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Fordmerc, Don't be so certain that you'd see corrosion on a cable. I have a a braided battery ground cable I took off my car one night after it failed. Not a spot of corrosion and hadn't been previously as i kept it clean. Test this cable and you get no continuity. It's a wall hanger now. Alan
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| TomO | -- 09-23-2011 @ 1:34 PM |
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After reviewing everything, I would do a load test on the battery to ensure that the battery is in good condition. Your first post in this string sounds like the battery did not have enough life to crank the engine for very long. This could be due to a weak battery or a partially discharged battery. The sudden stopping of the engine could be due to a defective ignition switch or a loose wire in the primary circuit of the coil. This would include a defective ignition resister. You can check this theory by connecting an analog volt meter to the coil connection and driving around until it fails. Unless your digital meter can handle the voltage spike common in these old cars, do not use it while the engine is running. In item 5, did you shut off the engine or did it stop on its own? Did the temp gauge move from normal to hot in just a few seconds or did it creep up slowly? The best way to test a battery cable is to measure the voltage drop across the cable when there is a high current draw such as the starter. Connect the COM lead of your meter to the NEG terminal of the battery and the POS lead of your meter to the solenoid terminal that the starter cable is connected to. Crank the engine with the ignition off and read the meter. It should read less than 0.5 volts. Tom
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| fordmerc | -- 09-24-2011 @ 2:24 PM |
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In response to TomO: I have not done a load test, but I'm thinking the batterey discharge occurred after the car stopped and I tried to start it within 60 sec - then it became weaker and weaker. The coil voltage and resistance readings have remained unchanged during this period of looking hard. In item 5, I had shut off the engine. Also, the temp rose slowly as I expected for a car at fast idle and no movement. Voltage drop is from 7.4V to 6.8V under the conditions you asked about.While this exceeds the 0.5 V standard,I don't that explains the findings at the solenoid(below) In the past days I have not had the car shut off by itself, but I have run it until temp gauge at H. At that time, there is continuity through the solenoid from BATT to Starter terminals (but no voltage at the starter terminal). After a while, that continuity disappears, only to reappear after I run the car again. Today, there was spark when I pulled ground at the time the solenoid terminals were continuous and no spark after they were discontinuous.I realize that usually means current flow so I'm trying to guess where that might be. Although the resistor is pretty warm, multimeter readings are unaffected by removing it from the circuit.
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| supereal | -- 09-24-2011 @ 6:20 PM |
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The ignition resistor would not drain the battery unless the ignition was left on for a long time. The only conductors heavy enough to quickly drain a good battery are the heavy cables. An easy way to track down a parasitic battery drain is to disconnect the battery cable and connect a light bulb between the battery post and the cable. If the bulb glows, a drain is present. Then disconnect parts of the system until the light goes out. A constant drain will sap enough from a weak battery to prevent starting. We have seen this with a stop light switch, an intermittent regulator cutout, and other places. A new wiring harness cam often have unexpected problems.
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| Dolman | -- 09-24-2011 @ 6:21 PM |
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fordmerc, Something is opening under heat that increases with time and cools within 2 minutes and recovers continuity. I rule out battery cables or their terminals because you were able to start the car regardless of their condition. (No offense Dr. Super) If they got hot enough after 25 minutes of running, their mass is too great to cool rapidly - say 2 minutes. I'm not clear what you were measuring when you removed the resistor. If it was on the bench to check its continuity, it would probably cool enough in the time to remove it to restore itself. I guess I'm obsessed with the resistor because in my previous life, intermittent failures because of overheated components were a real pain in troubleshooting (I started to use a different expression.) and I have to admit that sometimes they were my faulty designs. The EEs reading this are nodding their heads. Anyway it looks like it's the only thing you haven't replaced.
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| supereal | -- 09-24-2011 @ 8:30 PM |
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My understanding is that the engine wouldn't crank until it sat for a time. While a resistor failure isn't unusual, and often is due to poor connection at one end or the other, slow or no cranking isn't affected by the ignition resistor, nor would it run the battery down suddenly. A hot cable or connection will raise temperature at the site of the problem, and as the heat rises, so does resistance. If the resistor is suspected, just bypass it. I carry a clip lead in my road kit for just such occasions. A bad starter motor is also a suspect. If the bushings are worn, the armature will drag on the field poles when it gets hot, and will usually crank when it cools a bit. It is beginning to appear there is more than one problem. That still won't explain why the engine quit suddenly.
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| Dolman | -- 09-25-2011 @ 7:46 AM |
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Dr. Super, aside from fordmerc's problem, what is the effect on the longevity of the primary of the coil which is designed to see a nominal 3 volts and with the resistor bypassed, the coil then sees a nominal 6 volts? Keeping in mind that I have had only 1 cup of heart starter and I require 2 cups to fuel my brain, the resistor acts as a current limiter and with the engine running would drop 3 volts. The current through the primary would be 2 amps and dissipate 18 watts, ignoring the resistance of the coil, with the resistor jumped, the coil then drops 6 volts for a current of 6 amps and dissipates 36 watts. Considering Kirchoff's law, what is the current demand of the starter? I am clueless as to that value. If this discussion is inappropriate for this forum, if you have time, please PM me at amc@alaska.com
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| TomO | -- 09-25-2011 @ 11:29 AM |
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Fordmerc, You did not connect your meter leads correctly for the voltage drop test. One end should be connected to the stud with the cable going to the starter and the other end should be connected to the NEG battery post. With the starter engaged, the reading should be under 1 volt. You say that there is continuity between the battery terminal and the starter terminal on the solenoid, but no voltage present on the starter terminal. How are you measuring this? You should not be using an ohm meter on a circuit that has voltage applied to it, it will give you false readings. Because you have gas present after the engine stops, we are all assuming that the reason the engine stopped is electrical. The engine will keep running as long as the coil has enough voltage to provide a spark or the coil opens. You need to start like this is a new problem and try to isolate the sources of the problem. When the car dies, is the battery always dead? Have you checked for voltage at the coil when it dies and will not start? Have you tried vibrating the ignition switch, the resister board and the coil by tapping them with the insulated end of the screwdriver while the engine is running? Tom
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| supereal | -- 09-25-2011 @ 11:59 AM |
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When dealing with a coil, you have to know the impedance of the unit, as it involves both resistance (the copper loss) and the reactance of the windings. that means that without special equipment, the only test you can perform with a multimeter is resistance. The primary winding at 68 degrees F is .47 to .51 ohms, the secondary is 5800 ohms. Coils designed for 3.5 volts input will have lives shortened by higher inputs as the insulation and winding are heated. That is why the ignition resistor is used to provide a sort of voltage regulation. Anyone wishing to run coils at higher voltages, such as 12 volts, can have them specially wound for that purpose. As for the power demand of the starter, at maximum torque, 14 foot pounds, the current draw is 500 amperes. That is why the cables and connections must be correct. We check starter current with a clamp on meter, the only tool that can safely handle that level.
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| Dolman | -- 09-25-2011 @ 1:06 PM |
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Thanks for the reminder of the cranking amps (It's touted in every battery ad.) and the presence of reactance. Should of had the second cup of heart starter (pun intended). I'll accept the retroactive F now.
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| fordmerc | -- 09-25-2011 @ 6:44 PM |
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I'm convinced the problem is electrical. I have not been able to cause the engine to stop as it did on the road. Battery discharge seems to occur after the car has been sitting most of the times it happened; I think it rapidly occurred only twice. Continuity across the solenoid measured with an ohmeter is same with and without power to batt side. Yes, I've tried the bigger hammer approach. Plan will be to start to try and find a short somewhere; I.e.,start over. biggest challenge is that the problem resolves spontaneously at an unpredictable rate.
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| TomO | -- 09-26-2011 @ 11:20 AM |
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Fordmerc, You seem to be concerned about the continuity that you read across the solenoid. I went out to my car and checked out the continuity across the solenoid. I disconnected the ground cable from the battery and the ohm meter read 0 ohms. I suspected a ground loop, so I checked a spare starter. The meter reads continuity when it is connected from the starter lug to the case and a brush is on a commutator segment. I believe that this is what you are seeing. If a short is causing your car to stop, you should be able to smell smoke. Because you did not mention the smell, I am inclined to believe that you have an intermittent open circuit. The usual causes are loose connection at the ignition switch, resistor block and at the coil, a bad ignition switch or a bad resistor. The ignition switch is a brush that rides on a piece of Bakelite and makes contact with brass posts that the wires are connected to. After many years of wear, the Bakelite wears down and keeps the brush from making contact with the brass post. Tom
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| unclemark | -- 09-29-2011 @ 8:36 PM |
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I had a model T that did the exact same thing, it turned out to be the cut out on the generator, later in a different vehicle I had a similar problem resulting from a faulty regulator. Hope this helps a bit.
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| 37RAGTOPMAN | -- 09-30-2011 @ 6:52 AM |
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ford merc try a different starter solinoid, and see if it makes a difference, in might not be completely shutting off,and might be feeding a certain amount of elect to the starter, not enough to make it turn over,but enough to drain the battery, I had this problem with a MODEL A one time, feel the starter to see if it is warm or hot, also feel the generator if it is warm, does anything have a smell to it ? my 3 cents, 37RAGTOPMAN
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| fordmerc | -- 10-01-2011 @ 1:42 PM |
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A follow up note to all who have helped: TomO has solved my concern about the solenoid having continuity when battery is connected, but not when battery disconnected. The ignition switch was examined and tested on and off the car; it seems OK. There’s never been smoke. 3 solenoids do the same thing so that seems out, especially in view of TomO’s evidence. I’ve reached the conclusion that the engine shutoff and the sparking are 2 different problems: The engine shutoff may have been no gas in the tank!!! My plan is to isolate what seems to be a somewhat heat sensitive open circuit will be to isolate the various places that have been suggested as problem areas: brake switch and clock and anything else I can take out of the circuit; I can replace the current resistor with another. I feel I have eliminated the regulator cut out only because the problem has occurred with old and new voltage regulators . I have checked voltage at the coil and it is 3.4 V even when the short is present. I’ll let you all know when I have solved the problem, but it will take time because while it happens intermittently, I cannot reliably reproduce the problem. Thanks again for guidance.
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| supereal | -- 10-02-2011 @ 5:23 AM |
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Before you start swapping parts, put the leads of a voltmeter across each segment of the system with the power on. Any reading indicates loss in that part. Once you start to change parts, it is almost certain that you will have changed the problem, thinking it is fixed, only to have it happen again, probably at an inopportune time and place. As Henry put it, "diagnose, don't guess". This message was edited by supereal on 10-2-11 @ 5:24 AM
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