82 W150 no spark

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Glad things worked out for you.
Funny how those troubleshooting procedures that I posted led you right to the problem that your test results indicated.
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Max

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Yea, sure it was. Sounds to me like he swapped the part and got lucky but good for him either way.
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"Max Dodge" < snipped-for-privacy@verizon.net> wrote in message
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If you had as much of a clue about the proper troubleshooting steps as you say, you'd know thats exactly what he did.
Have a nice day.
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You're welcome. I'm glad you got it running.
As for the other, it seems, any more, that if I post anything, someone starts a "pissing match" over it.
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Budd Cochran

Romans 3:23, Romans 6:23,
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You have +12V on both sides of the coil because there is no ground available. The ignition works by switching the ground on and off on the coil primary and yours is in a switched off mode. I don't remember what type of transistor it is using so this may be normal when the engine is not cranking and if so would indicate either a bad pickup coil or reluctor (star shaped wheel in the distributor) otherwise it could be a bad connection between the coil negative and the ECU. It could also be that the pickup coil is loose and has moved to far away from the reluctor to send a strong enough trigger signal to the ECU.
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"CordobaMan" < snipped-for-privacy@surfy.net> wrote in message
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He'll have 12v on both sides because the switch isn't inside the coil. Since he has voltage on both sides of the coil, its an indication that the primary side is good, since it should have complete circuit through it. Resistance according to spec should be about 1.6 to 1.8 ohms for Prestolite and 1.4 to 1.55 for Essex on the primary side.
This would be found during testing by looking for battery voltage on the #2 cavity on the ECU connector. This comes from the ignition switch. Switching is inside the ECU.

All of which can be found with the tests I described. I'd bet on a rusted ground for the ECU, or a pickup coil failure, assuming all wires are still in good shape.
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OK. My spare ECU must be dead. No continuity between pin 5 and it's body. The "old" ECU does have continuity between pin 5 and its body, do I wire-brushed the mount, bolts, and firewall. Good continuity between pin 5 and ground now. Still no start/spark.
NOW...I noticed that there was some ooze on the firewall starting directly under the bottom of the ECU. Also a rusty spot on the ECU at the same spot.
I'm on my way to the parts store for a new ECU unless someone has another test to run first?
THANKS ALL!
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CordobaMan wrote:

No Go with the new ECU..and it's cold and snowing like mad. Obviously, thowing parts at it isn't the answer, so I'll have to find my gremlin in the wiring somewhere...
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According to the FSM, the only other thing that can be wrong is the coil. The FSM actually suggests swapping out the ECU and then the coil if the new ECU doesn't work. Beyond that, ring out the wiring and see if there are any shorts. Given that I'm looking at 1975 info, you should find a 1982 manual if at all possible.
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Did you try replacing the pickup coil in the distributor or at least check for continuity between the two pins coming from the distributor?
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Part of the test procedure that I listed for him does exactly that. It does not have perfect continuity, and I listed the resistance value as well.
You awake and ok?
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Just because you told him to do it doesn't mean that he did so I asked. Are you awake?
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Yup, I read his reply where he listed what he did in reply to my post.
Just checking.
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He checked the resistance but I don't see where he checked the gap.
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"Max Dodge" < snipped-for-privacy@verizon.net> wrote in message
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What in the hell are you talking about Max? The coil not being grounded is the ONLY reason that he is getting 12V on both sides. You really need to pick up a little electrical theory here dude.

If the internals of the coil are ok or completely shorted he will still get 12V on both sides if the negative terminal is not grounded so getting 12V on both sides of the coil only indicates that the coil is not open, not that it is good. It also indicates that the coil primary is not grounded at that point which may also be normal when the engine is not running. Your resistance measurement is the only way to tell if the primary side is good.

I think that I already said that but it is the ground that is switched, not the hot side.

I doubt that the ground on the ECU has anything to do with it as he has already replaced it and simply removing and retightening the ECU should have cleaned up that ground enough to work. It could be a pickup coil failure or a wiring problem but I doubt much else.
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And you need to look at hte wiring diagram. Coil on this set up is fed from the ignition switch, so its hot on both sides unless it has a break in the windings. It is switched at ground (you knew that!) and as such will be hot on both sides no matter what the switch position is.

Correct, but the voltage reading on both sides indicates that the circuit (not the coil) is functioning as it should.

Precisely why the coil will have 12v on both positive and negative terminals.

Personal experience tells me you could be wrong on the rust issue. Test results posted by the OP tell me you are wrong on the pickup coil.
That leaves coil and wiring issues, as I stated previously.
Interesting idea... test the coil while cranking, see if the ign switch feeds 12v during cranking as well as "run".
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I am aware of the wiring Max and if you understood it you would realise that it is impossible for 12V to be on both sides of the coil at all times. When the switch is "on" or conducting, the voltage on the negative side will be just about zero as the coil will drop the voltage and for that matter, even the positive side will not be at 12V due to a voltage drop from the ballast resistor.

How do you know? If the circuit is not conducting and never does, then something IS wrong and that 12V on both sides means little, only that it is not completely dead.

You need to do a little review of a simple circuit to see how wrong you are here. If one side is grounded, then there will be no measurable voltage on that side so during the non-conducting phase you would be correct but during the conducting phase (coil build up) the ground side has to be zero.

I could be but I doubt it. As for the pickup coil, since he replaced everything but the pickup and reluctor, it looks like the most likely cause. If it is a ground issue, just put a continuity tester on one of the bolts holding the ECU and the other side on the negative of the battery. If he has continuity, then he has a ground, simple as that.

You will never get 12V when cranking as the starter motor draws too much current. That is why the ballast resistor is bypassed during cranking to boost the voltage up as much as possible. What he really should do is put a dwell meter across the coil and crank it. If he gets a valid reading, then the primary side of the circuit is ok.
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I got about 6-1/2 volts at the prime coil + while cranking...measured before I replaced the coil (and not since). As far as it being the PU coil/reluctor, those are "after" the primary coil and I am not getting a spark out it when holding the coil wire near ground during crank.
Here's a scan from the FSM of the wiring diagram:
http://www.geocities.com/thecordobaman/82dodge.JPG
Note that I have the SINGLE pickup system in my distrib (the diagram in the book is for the dual style, however everything else is the same).
As soon as the wind/snow dies down I'm going to start the FSM troubleshoot proceure all over again, fresh.
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6.5v is too low. Look for a problem between the battery and the ignition switch, and then to the ballast resister, and then to the coil positive. This voltage would indicate that cavity two isn't getting battery voltage like it should to pass the test procedure.

Cavity two will be a problem. Trace back through:
coil negative coil positive ballast resistor connections
If all those fail to show 12v or the required voltage by your FSM (mine calls for 12v) suspect the ignition switch as the cause. Also, its possible the ammeter is doing weird things, as its in the circuit.
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Max

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That voltage seems a bit on the low side. Unplug the ballast resistor and try measuring voltage again while cranking. If you have no voltage then you have a problem with the ignition switch and if it is still at around 6 volts, I would reconnect the ballast resistor and attempt a jump start (even if it seems to be cranking ok). This could be nothing more than a bad battery.

They are NOT "after the primary circuit, in fact, they control it. They take the place of the points in a standard ignition system as far as triggering the spark. The difference is that they don't deal with the voltage and current from the coil that points do, that is handled by the ECU. Did you check the air gap between the reluctor and the pickup coil with a non-magnetic feeler gauge? You are not getting spark because either nothing is triggering the coil or the coil is bad. To test the coil, connect your jumper wire to the negative side of the coil and with the ignition on and holding the coil wire near ground, connect you jumper to ground and then remove it again. You should get a spark every time you remove it from ground.

I am very familiar with this ignition system after dealing with it for many years.

That just simplifies the system and removes more possible points of failure.

Here is something else to look at. Does the distributor rotate when you are cranking the engine? I would check this first if you have not already done so.
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