Crank no start

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ike61

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Here we go again. 68 plymouth slant 6. Electronic ignition. Cranks but wont start. It will fire every once in a while. Pulled plug out. Has weak spark. Here are some numbers i have:
Battery 12.6 volts
-coil key on 1.3 volts
+coil key on 6.5 volts
Tested original brn/blue wire that went to ballast 8.6 volts crank/6.7 key on
Tested original blue wire that went to ballast 6.2 crank/11.0 key on
Here is a pic. Do i have it wired right? Original single blue wire has power with the key on.

7397CFFA-A8E8-4F7A-AA8E-25BCF745FADE.jpeg
 
It looks to me like you have it right. The end with the jumpers goes to "ignition run". One of the two at the opposite end goes to the coil and the brown bypass wire. But I cannot tell on that end which terminal you have hooked to what. it matters. The "U" in the near end of the ballast in the photo is an index, as the two resistors are different values

This simplified diagram does not show the brown bypass wire, but it must go to the coil+ side of the ballast, and the index marks of the ballast must be as pictured. What they are calling "existing wire" at far top right goes to key on/ ign1 "ignition run"

Ignition_System_5pin.jpg


Anyhow the coil+ cranking voltage should be close to same as battery when cranking. So if battery is say, 11V when cranking, the coil should be close to that, and in no case below 10-10.5V

If you have it wired right, you have voltage drop in the harness somewhere or in the ignition switch or it's connector.

The quite low coil NEG reading is good because it shows the box is conducting through the coil and that the box is therefore trying to operate and that the box is grounded.

One test you can make is to disconnect the dist. connector. Take the ECU end of that connector and tap the bare protruding terminal to ground with the key on. Each time you should get one "snap" spark. That will prove the coil/ box is working. Always cast a suspicious eye to the dist connector for dirt/ corrosion/ looseness, and have a look at the pickup/ reluctor for wobble, shaft wear, damage, rust. etc. Scare yourself up a .008" (inches not metric) feeler and check the reluctor to pickup gap You set it just like breaker points by adjusting the pickup with a set screw
 
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I should have disclosed, when cranking 8.6 volts at the positive side of the coil
 
Try & isolate the problem. Connect a jumper from the coil [+] terminal direct to the bat [+] terminal & see if it starts.

If it does, then it seems you have a low voltage problem. Could be high resistance in ign swtch, wiring, plugs/sockets etc.
 
67Dart273 is the man in this department. Couple of things. If you unplug your box does it have 4 pins or 5 pins. My green wire was hooked up but when I checked my box it was a 4 pin unit . This means you no longer need your green wire and can go to a single ballast resistor. That's just fyi not your problem On my ignition I have 2 brown wires 1 to coil and 1 (brown key cranking) I don't see if yours is wired like that.

Electronic ignition dual ballast.jpg
 
Adding to what the others have said, how well is the case of the Ignition Module grounded? It has to be grounded or no worky.
 
Take a jumper cable and grab the ECU case on some clean metal and the new battery post, see if that changes anything. Thats your grounded case test. reduced voltage to coil is not mandatory, jump that too with the other side of your jumper cables to battery positive unless someone here can tell us it could damage something...? Mopar electronic ignition....let's count the threads on this board relating to this topic! Mallory box with stock E-distributor......damn that ballast resistor!
 
67Dart273 said:
One test you can make is to disconnect the dist. connector. Take the ECU end of that connector and tap the bare protruding terminal to ground with the key on. Each time you should get one "snap" spark. That will prove the coil/ box is working. Always cast a suspicious eye to the dist connector for dirt/ corrosion/ looseness, and have a look at the pickup/ reluctor for wobble, shaft wear, damage, rust. etc. Scare yourself up a .008" (inches not metric) feeler and check the reluctor to pickup gap You set it just like breaker points by adjusting the pickup with a set screw
Click to expand...
I tried this and there isn’t spark. I can ‘hear’ spark if that makes sense
 
If you can hear spark, you might have a faulty coil that has internal tracking, or carbon tracking inside/outside on the dist cap or rotor. Could also be a bad coil-to-dist high tension lead.
 
ike61 said:
I tried this and there isn’t spark. I can ‘hear’ spark if that makes sense
Click to expand...
What exactly are you using for a test gap? For example if you are using the original coil high tension wire, it might just be that it's as simple as a bad coil wire!!



Also if you have not done so, I would "dewire" the system from the car until you get it fixed. That is, direct hotwire the system until you discover "is it" the ignition system, or "is it" the car wiring harness, etc?

Don't leave it powered for long while testing. You want to bypass the ballast that is connect all 3 circuits together and jumper power into it. As before, measure coil NEG and if it's a volt or two that tells you the ECU is conducting through the coil, which is good. Try again with the "tap" test, and finally if that part is good, "work" the dist. connector in/ out several times to feel for tightness and to scrub the terminals. Then spin the dist or crank it and see if you have spark at the coil
 
Bewy said:
Try & isolate the problem. Connect a jumper from the coil [+] terminal direct to the bat [+] terminal & see if it starts.

If it does, then it seems you have a low voltage problem. Could be high resistance in ign swtch, wiring, plugs/sockets etc.
Click to expand...

ok tried to hot wire. Ran a wire from battery positive to coil positive. No start. Checked voltage at the end of the wire i ran to the coil 12.1 volts. Hooked it coil 11.2 volts. Hooked to +coil and Cranked with key 8 volts. How in the hell does that happen?
 
When i unplug the main coil wire from the distributor, hold it near a ground, and crank with key i get spark, but appears to me to be weak
 
Well that is why I'm trying to get you to completely isolate the thing from the harness and then jumper power to it separately. You may have a problem EG in the brown bypass circuit. This is a separate contact in the ign switch, and only has one job.....to feed "hot" battery power to the ign during start. It works the same way as the "start" contacts in the switch but it's a separate set of contacts to prevent feedback into the starter relay. The functional path is .........power to ignition switch..........brown IGN2 "in start"......out the switch.......through the switch harness connector........out the bulkhead connector..........and to the coil + side of the ballast. So there's several places for drop............First is the battery up? What is battery read during cranking? The drop can be BEFORE the ign switch IE the ammeter circuit supplying the ign switch, and it can be ANY of the terminals I mentioned.......along with the switch contacts themselves AS WELL AS "additive" IE a little in each one.
 
Able to tinker a little today. Here is what i did:
Battery 12.5 volts
Battery 10.55 volts cranking
Ignition switch ‘battery’ wire 12.5 volts
Ignition switch ‘battery’ wire 11.6 volts key on
Ignition switch ‘battery’ wire 9.7 volts crank
Ignition switch ‘ignition 1’ wire 11.5 volts key on
Ignition switch ‘ignition 1’ wire 6.6 volts crank
Ignition switch ‘ignition 2’ wire 6.4 volts key on
Ignition switch ‘ignition 2’ wire 9.2 volts crank
This was all done at the ignition switch
 
You have a LOT of drop. Follow the path. Battery........connections........cables.........starter relay stud........fuse link............bulkhead connector..........ignition switch connector.........through the switch.........out on various switch outputs.........through the switch connector..........back through the bulkhead connector.

Each point separated by dots is a source of drop. There can be one, 2, or all, each one adding a tenth here, a few tenths there. It adds up

The battery cranking, 10.55.......is that right at the battery posts? If so the battery is marginal or low on charge. Either that or the starter is dragging or engine bearings/ something else dragging, or its "really cold" LOL
 
67Dart273 said:
You have a LOT of drop. Follow the path. Battery........connections........cables.........starter relay stud........fuse link............bulkhead connector..........ignition switch connector.........through the switch.........out on various switch outputs.........through the switch connector..........back through the bulkhead connector.

Each point separated by dots is a source of drop. There can be one, 2, or all, each one adding a tenth here, a few tenths there. It adds up

The battery cranking, 10.55.......is that right at the battery posts? If so the battery is marginal or low on charge. Either that or the starter is dragging or engine bearings/ something else dragging, or its "really cold" LOL
Click to expand...
Lol. Battery fully charged. Yes that was at the posts
 
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