Not getting spark-towed it home

-
standup303

standup303

Well-Known Member
Joined
Jul 22, 2022
Messages
528
Reaction score
354
Location
Colorado
Hey all, first time ever I had to get the car towed home last night. Just got a new carb, torque converter and from 3.23 to 3.91 in the rear. This was the second drive since the new parts. Car was stumbling from 3,200-4,000 but overall running good. Pulled in a parking lot and it just shut off. Has refused to start since.

I can physically see fuel squirting into the venturis while applying throttle. Just got 1/2 tank fresh gas. I popped the coil wire off the distributor and held it close to a bolt on the motor while having someone turn the ignition over. Got 1 pretty weak spark on multiple cranks. So not getting spark I would say.

I had a spare ballast resistor so swapped that. I’m getting 11.9v on the input side of the ballast and 6.5 on the output side, key on, not cranking the ignition though. When it’s cranked I’m only getting 8.5 at the secondary side and at the coil.

I had an older coil I knew was working before, I hooked it up and still didn’t do anything. No spark on the coil wire holding it to a bolt. It started to fire once or twice for a split second but didn’t go.

Not sure where to go from this point. ECU?

I was reading the brown wire on the secondary side of the ballast is supposed to be a “start” circuit and put a full 12v to the coil, and only had 8.5v. But have also read the coil only needs Between 6-12v for start?

Any help would be greatly appreciated.
 
if this is a stock system i would start at the bulkhead connector . wiggle it around a bit and check for spark or unplug and clean and look for burnt spots .
 
I bypassed the ballast resistor and it cranked, ran extremely rough for 5 seconds now have to wait for the battery to charge again. I’m thinking the start circuit is broken somewhere.

I checked the bulkhead and looked like one of the female ports is broken but the pins are still making contact. Going to investigate further.
 
Coil gets "full 12V" during cranking HOWEVER that DEPENDS on voltage drop in the harness AND how far down the battery is dragged for cranking. Your reading might be "good" depending such things

Key on/ engine stopped, coil voltage is normally way down through the ballast, it varies. Maybe 5-8, so that is good.

One test is to turn key on, hold coil wire near metal, and pull apart the dist. pickup connector. Take the end going to the ECU and tap the bare terminal to ground. Each tap should produce one spark.

It is difficult to evaluate spark "quality" through factory RF suppressed plug/ coil wires.
 
Thanks 67dart I’ll give it a shot tomorrow. Now only getting 6v cranking at the coil with ballast resistor bypassed even trying to jump the battery with my truck. I’m going to let it charge and try again tomorrow
 

Measure your battery voltage right at the posts while cranking for an indicator of battery condition and state of charge. You need a minimum of 10--10.5

The drop could be anywhere in the harness path and an additive combination. IE poor connections in the bulkhead connector, the ignition switch connector, or the switch contacts themselves. The ammeter circuit is a big part of that as well, as (if not modified) the big read leading from the fuse link is what feeds power through the bulkhead connector, through the ammeter, and to the ignition switch.

Your full "path" then is battery--cable--to starter relay "big stud", to fuse link, through the bulkhead (big red) to ammeter and through, out on black, to the welded splice, to the ignition switch connector, through the switch, out on the "run" line IGN1 (with key in run) usually b lue, out through the bulkhead, and to the ballast.

In cranking, the output of the key becomes out of the switch on IGN2 (usually brown) back out the bulkhead, and to the coil side of the ballast
 
67Dart273 said:
Coil gets "full 12V" during cranking HOWEVER that DEPENDS on voltage drop in the harness AND how far down the battery is dragged for cranking. Your reading might be "good" depending such things

Key on/ engine stopped, coil voltage is normally way down through the ballast, it varies. Maybe 5-8, so that is good.

One test is to turn key on, hold coil wire near metal, and pull apart the dist. pickup connector. Take the end going to the ECU and tap the bare terminal to ground. Each tap should produce one spark.

It is difficult to evaluate spark "quality" through factory RF suppressed plug/ coil wires.
Click to expand...
I did this test and got zero spark. I went through the ignition wiring and have 11.2v at the input side of the ballast with key in Run position. I do get lower voltage to the coil + under crank, about 9v. I disconnected the coil+terminal, connected 12v straight from battery, pulled distributor coil wire from the distributor and held it close to a bolt while the wife cranked the car, zero spark.

What would be next? ECU? One thing I did do I’m kicking myself for. I moved the ECU from the fender to the firewall. May have cooked it? It’s been there about 400 miles.
 
My pickup going to the distributor has 396 ohms and there is 12v to the ECU.
 
.5v ac cranking with dist unpluged was what i remember .....its been 30 years though .....faster it cranks higher a/c voltage ...should have that on the "box"
 
standup303 said:
I did this test and got zero spark. I went through the ignition wiring and have 11.2v at the input side of the ballast with key in Run position. I do get lower voltage to the coil + under crank, about 9v. I disconnected the coil+terminal, connected 12v straight from battery, pulled distributor coil wire from the distributor and held it close to a bolt while the wife cranked the car, zero spark.

What would be next? ECU? One thing I did do I’m kicking myself for. I moved the ECU from the fender to the firewall. May have cooked it? It’s been there about 400 miles.
Click to expand...
May be the ECU but do further tests. The ECU/ coil draw current anytime the key is on. So with the key "in run" the coil + should be anywhere from say, 6-10v, it varies. This would show that the coil is drawing current through the ECU. If not, check the coil for continuity and check and be CERTAIN that the ECU is grounded.

You already show you are getting power to the ballast.

If the last test is good, the coil has continuity, I would try an ECU
 
Reread post #6.

standup303 said:
I did this test and got zero spark. I went through the ignition wiring and have 11.2v at the input side of the ballast with key in Run position. I do get lower voltage to the coil + under crank, about 9v. I disconnected the coil+terminal, connected 12v straight from battery, pulled distributor coil wire from the distributor and held it close to a bolt while the wife cranked the car, zero spark.
Click to expand...
67Dart273 said:
Measure your battery voltage right at the posts while cranking for an indicator of battery condition and state of charge. You need a minimum of 10--10.5
Click to expand...
If it dropped below 10 V during start then the battery is too weak.
67Dart273 said:
In cranking, the output of the key becomes out of the switch on IGN2 (usually brown) back out the bulkhead, and to the coil side of the ballast
Click to expand...
Notice he did not say to test by removing the feed from the coil.
How did you expect the ECU to get power?


standup303 said:
What would be next? ECU? One thing I did do I’m kicking myself for. I moved the ECU from the fender to the firewall. May have cooked it? It’s been there about 400 miles.
Click to expand...
Maybe the wiring and yes in general the car companies come up with a cool protected location for stuff like ECUs.
 
standup303 said:
I was reading the brown wire on the secondary side of the ballast is supposed to be a “start” circuit and put a full 12v to the coil, and only had 8.5v. But have also read the coil only needs Between 6-12v for start?
Click to expand...
With points thats fine.
Add in the ECU and it needs to get power to pickup the signal and electronicly open and close the coil's connection to ground.
Whether the car has a 5 pin or a 4 pin ECU, the power for the ECU during start comes from the Ignition 2 (start) wire and must go through the 1/2 ohm ballast resistor. It doesn't draw much power but does seem to need a minimum voltage to operate.
 
1744430448675.png


key in start
Electric current flows from the battery to the key switch, then through the switch to two circuits.
Ignition 2 is the start circuit, usually a 16 ga brown wire. It powers the coil and ECU during start.
Starter circuit goes to the relay and is completed through the safety switch.

This assumes the car doesn't have the 74 into early 75 model year seat belt interlock...

During start the voltage at the battery positive and the coil should be very close.
Even across the 1/2 ohm resistor I would expect fairly small voltage loss since the current is small.
 
If you spliced any wires to move the ignition module, I would also make sure no splices have come undone. Often the last change should be the first suspect.
 
One thing I noticed is I have 13.1v at battery and 13.1v coming on the blue wire to input side of ballast resistor, just the wire. When I put a very solid crimp on voltage drops to 9.8 on the crimp. I’ll probably get some better crimps, brass.

Hooked my truck battery up and still no spark on the distributor coil wire held close to a bolt under crank.

ECU has power under run and crank, pickup wires have 396 ohm. ECU is grounded checked continuity from block to ECU mount. At this point I’m ordering a new ECU from summit and will try that.

Considering it was running good and just died after having zero issues along with mounting the ECU in a dumb place, I’m willing to throw $45 at a new ECU and see what happens.

If that doesn’t work ill
Probably rewire the entire ignition circuit with new wire and quality crimps, move the ECU, coil, ballast resistor to a safer place.

Thanks for all the help to this point.
 
standup303 said:
One thing I noticed is I have 13.1v at battery and 13.1v coming on the blue wire to input side of ballast resistor, just the wire. When I put a very solid crimp on voltage drops to 9.8 on the crimp. I’ll probably get some better crimps, brass.
Click to expand...
Run this by me again!!!??? Crimp is "where?"

Now are you measuring this 13x with the wire DISconnected? You have to be specific. You cannot take two measurements with connections changed and not notate them, as the CURRENT FLOW in the circuit changes things.
 
And want to check voltage with the circuit loaded ....one strand of wire unloaded will still read 12v
 
67Dart273 said:
Run this by me again!!!??? Crimp is "where?"

Now are you measuring this 13x with the wire DISconnected? You have to be specific. You cannot take two measurements with connections changed and not notate them, as the CURRENT FLOW in the circuit changes things.
Click to expand...
nutz said:
And want to check voltage with the circuit loaded ....one strand of wire unloaded will still read 12v
Click to expand...
Oops didn’t notice these reply’s. I had 13v on the blue white to the input side of the ballast. Crimped it and then had 9v, almost like a crappy quality crimp.

Got a new ECU, still won’t turn over. I CAN now pull the coil wire off the distributor, hold it close to a bolt and tap the disconnected pickup and get a spark. Couldn’t do that before.

But with the pickup plugged back in I cannot get spark from the coil wire held close to a ground under crank.

I am also not getting any spark from a spark plug held against ground and plugged into a plug wire.

Tomorrow I’m going to put a full 12v to the positive side of the coil, crank and see if I get spark. Getting pretty close to just requiring the damn circuit and buying new coil.
 
if you a/c on your volt meter hook up to pick-up (unpluged) 1/2 volt cranking a/c voltage if no voltage pick-up or air gap or tone ring lost ground
 
nutz said:
if you a/c on your volt meter hook up to pick-up (unpluged) 1/2 volt cranking a/c voltage if no voltage pick-up or air gap or tone ring lost ground
Click to expand...
My god man. Please learn. It's not a "tone ring" and THERE IS NO ground.

You MUST use actual sentences.

IF THE TAP TEST gives you spark, then likely, the wiring the ECU, and the coil are OK. But you MAY still have a problem in the ballast bypass test.

Let's back up.

Turn key to "run." Don't leave the key on longer that necessary to run the test. The system, and the coil, draws current, and this heats up the coil, and the ballast, and the ECU, and is not good for particularly the coil.

NOW, put your meter on the "key" side of the ballast. If not known, this should be the wires at one end of the ballast that are jumpered together with a short wire. From there to ground, you should have very close to "same as battery."

Next, move the "hot" meter probe to coil +. Now the voltage should be much LOWER and this is variable, somewhere around 6-10V. If so, this shows that the ECU and coil are properly drawing current.

Do the tap test if you like at this point. You should "rig" a test wire from the coil tower to a test gap and use a METAL core wire, even if a low voltage wire, rig it so the wire does not touch, and to a test gap. The "taps" should give you a nice hot snappy spark, once each time you "tap."

Now test the bypass. Here is how this works. When the key is in "run" ;and power to the coil goes through the ballast, THAT RUN POWER is KILLED when you twist the key to "start." This is in part to shut off the alternator field, VR and any other power during cranking.


HOW THEN does the ignition system get power when the key is in START? The answer is the brown/ IGN2/ bypass circuit. This is a separate contact in the ignition switch that acts just like "START." When you twist the key to START, the brown IGN2 comes alive, and sends full battery power to the coil + side of the ballast.

TEST THIS by rigging your meter to the coil + and ground, and twist the key to start, let it crank for a few moments while you get a stable reading on the meter. THE READING should be at LEAST 10-10.5V OR HIGHER. If not you need to trouble shoot that circuit. It is simple. ONE wire, from the coil + side of the ballast, usually brown, through the bulkhead connector, and to the ignition switch connector.

IF YOU DO NOT get that power or not at least the 10.5 reading, the thing will not fire

IF THAT IS OK

Now Pull apart the dist. connector and inspect with a light for corrosion, and work it in/ out several times to feel for tight and to "scrub" oxidation off the contacts. If that does not give you spark, get a BRASS feeler gauge and CHECK the gap for the reluctor in the dist. Also check for undue wear/ play in the dist shaft, for rust/ debri between the reluctor tips and the pickup, and check the pickup resistance. The actual resistance is not that critical, but if it is open or all else fails, replace the pickup. If the reluctor is chewed up or damaged from striking the pickup, replace the reluctor.

THE AC TEST. Put your meter on low volts AC, not DC. "rig" the meter into the distributor pickup connector and crank the engine. You should get about 1V AC being generated by the pickup unit. If all this tests OK, then we have missed something.
 
Just for kicks, have you wiggled and or unplugged and plugged the firewall connectors? They are usually suspect in something like this.
 
RustyRatRod said:
Just for kicks, have you wiggled and or unplugged and plugged the firewall connectors? They are usually suspect in something like this.
Click to expand...
In fact ANY connector. Connector to the distributor is a big trouble area, the ECU connector can be, But moreover this MAY be a "great" example of "you need to learn to troubleshoot." It just might be that you could throw a lot of parts at this and not fix it, as it may be something............like a bad connection. If you cannot get anywhere with this, it would be a good idea to scare up someone locally who knows automotive electrical. Not necessarily Mopars, but who knows how to test and diagnose.
 
Thanks for all of the input. I do not have 10.5 to the coil when cranking. Going to dig in more this weekend and will report back.
 
You must log in or register to reply here.
-

Similar threads

T
No spark
Replies
11
Views
539
67Dart273
67Dart273
S
1974 Plymouth Duster no power through bulkhead.
Replies
23
Views
567
superchargedblackbird@gma
S
WAYNE0
IT WILL NOT START
Replies
7
Views
638
WAYNE0
WAYNE0
cudabob
What coil and wires to use.
Replies
9
Views
294
Dart Frog
Dart Frog
aa-1159
68 Cuda no start
Replies
19
Views
861
aa-1159
aa-1159
Back
Top Bottom