Not Getting 12 Volts at Coil

-
1

1974DartSport

Senior Member
Joined
Dec 5, 2007
Messages
131
Reaction score
1
Location
Mandeville, Louisiana
I have spent countless hours testing resistance in my 74 Dart's wiring harness. Most of the wires have no problem, yet I did find one break in the neutral safety harness that comes from the starter relay to the wire harness that leads down to the neutral safety switch which I repaired. I have multimetered and test lighted the wires and have drawn my own diagrams to get a better understanding of the battery flow and where the wires go. I cannot get 12 volts at the + coil.

Facts - Engine from a 1973 slant 6 w/ with a Holley 1920 carb that I just rebuilt with a Walker rebuild kit in my 1974 Dart.

Last driven in 1990 - stored in covered barn - complete body restoration and paint job in black. Very minor rust at rear quarters. Wiring harness still has original factory tape and looks extremely good. New alternator, new fuel pump, new gas tank, new radiator, new ballast resistor, new voltage regulator, new starter relay, new five pin electronic control unit, new coil, new battery and battery cables. Engine cylinder head rebuilt by local Mopar guru. The car is at TDC compression stroke and valve lash cold has been done.

The distributor is factory original and the spark plug/coil wires are from 1989 (less than 2000 miles on them). The starter is the original and has been tested good.

The car cranks with no problem. It just won't fire and run. I have 6 volts at the + coil in the run and about 8.5 at the + coil in start position. It cranked and ran a few seconds two weeks ago before I found a break in the wire that comes up from the neutral safety switch on the transmission into the wire harness that runs along the firewall. That break has been repaired and that section of wire/connectors has been reinstalled.

I did try to remove the starter switch in the steering column, but gave up when I couldn't press out the pin that holds the steering column locking mechanism in order to get to the starter switch behind it. (Chrysler says you need a special too to press that pin out and DO NOT HAMMER IT OUT). I gave up and put the steering column back together.

Who can help me find a problem in my coil power circuit? I am ready to scream. I am not a mechanic.
 
the ballast resistor plays a part in this. it steps down the voltage to the ignition system. if it was me i would take a long wire and hot wire the coil to the battery so you have a full 12 volts. and see if it starts . it shouldnt hurt anything if its only for a short time. if it runs then you can eliminate the dist, coil, wires plugs etc. if it still doesnt run then you must have trouble in your distrib. or the brain box (module) .
 
If you've been cranking a lot, check the connector at the steering column. I've found resistance in that circuit before because of overheating the wiring. You can also find a lower resistance ballast to get higher voltage to the coil... But you need to have battery voltage going in to it.
 
moper said:
If you've been cranking a lot, check the connector at the steering column. I've found resistance in that circuit before because of overheating the wiring. You can also find a lower resistance ballast to get higher voltage to the coil... But you need to have battery voltage going in to it.
Click to expand...

I wouldn't say I have been cranking a lot. The connector at the steering column you mention - is that the one underdash wrapped around the steering wheel or the wiring inside the steering column?

I have run a jumper from the + battery post to the + coil. The cranking sounds much stronger with this jumper, however it still won't fire up. Any suggestions?

I have not changed the distributor (the cap is new) or the spark plug/coil wires.
 
There are two under there. One is the turn signal switch. One is the ignition switch. You want the ignition switch.
 
Check your relucter airgap? .008, Clean the coil bracket mounting points? Good ground on ecu? When you find your gremlin, smack em once for me:-D Also is rotor turning?
 
My quarter is bet on the ECU being the culprit.
That pin in the column is tapered and drives out only one way. Normally goes out toward the drivers window ( can you hear the glass breaking ? LOL ) taking for granted the wheels are centered. They ignition switch is a whole lot of trouble to change on a gambling guess though. Some of those new aftermarket switches have wires in the wrong positions at their lower harness connecter too ( thanks china ).
 
moper said:
There are two under there. One is the turn signal switch. One is the ignition switch. You want the ignition switch.
Click to expand...

I understand the difference in the turn signal switch and the ignition switch because I took apart the steering column a few days ago. Since I could not press out the pin holding the steering wheel locking mechanism, I could not get to the ignition switch. I feel my problem is either the ignition switch (don't know how to get to it to replace it) or my distributor. You say I want the ignition switch. How? What do I need to do with it and how do I get to it?

I have checked the gap in my distributor. It was .008. Yes the rotor is turning. I have spark at the plugs, just not enough.

I need to eliminate the ignition switch or the distributor as my problem. How do I run wires from a remote starter to completely remove the ignition switch from the equation? If someone has done this before, please explain how to run wires from the starter, ballast, and battery to the remote starter. (I do not have a remoter starter, but I will buy one if you think this test is necessary to rule out the ignition switch as my problem.)

If I do start it with a remote starter, how do you kill it after it runs?
 
RedFish said:
My quarter is bet on the ECU being the culprit.
That pin in the column is tapered and drives out only one way. Normally goes out toward the drivers window ( can you hear the glass breaking ? LOL ) taking for granted the wheels are centered. They ignition switch is a whole lot of trouble to change on a gambling guess though. Some of those new aftermarket switches have wires in the wrong positions at their lower harness connecter too ( thanks china ).
Click to expand...

You may be right, however the ECU is new and I have run a ground wire from the bolt to the inner fender. Is there a way to verify I have a good ground?
 
1974DartSport said:
You may be right, however the ECU is new and I have run a ground wire from the bolt to the inner fender. Is there a way to verify I have a good ground?
Click to expand...

With an ohm meter , one probe on neg. battery post, other probe on ECU case, distributer housing, etc. Looking for a close to zero ohm resistance between componenys and battery ground.
Question.. are the factory connecters at ballast resister clean and tight.
I've seen those broken and allowing the female space connecters push out. I've seen those females worn, streched open, corroded.
So many little things easily overlooked.
To find out the parts store sold you a bad ECU can burn your bisquits but to find out the problem was fuel quality all along will too. So lets rule that out. Get a can of starting fluid, aresol ether. Block the choke butterfly open , give it a shot and try to start it. Hotter fuel will fire with a weak spark.
Kinda wish I was there to help. I wouldn't be able to sleep until I made the darn thing run. LOL
 
I took the ohm meter as you instructed and put one probe on the battery negative post and the other probe on the ECU bolt where I ran a ground wire tot the fender. The 1 on the meter went to zero. When I tried the other bolt on the ECU the 1 did not move. Is it properly grounded?

I did the same thing to the voltage regulator, however when I touched either bolts holding the voltage regulator to the inner fender the 1 went to zero. Why did the voltage regulator show ground on both bolts versus the ECU?

Some time ago, I took a dremel to all four female connectors on the ballast resistor and cleaned them to a nice shine. All four fit very tight on the four ballast resistor prongs.

I will buy a can of aerosol ether tomorrow. I'll let you know. You are right. Not being able to start this is making me crazy.
 
Probe component cases instead of there mounting bolts. Paint can insulate and interupt ground.
 
Most ignition cylinders can be taken out but the key must be in the switch and turned to the run position. The locking pin can then be depressed and you can remove the key cylinder.
 
you have already ruled out the ignition switch and components with the hot wire from the battery to the + side of the coil. all that's left is gas quantity or quality and correct firing order. my best guess is the latter.
 
I have talked to Randy on the phone many times regarding his problem with not being able to start this ol' girl. I can't tell you guys how determined he is to defeat this on his own. He is VERY meticulous about everything he does, and he goes to the nth degree in trying to explain/understand everything he does. Randy is the type of guy you want to pull for and do whatever you can to help him - he does his homework before asking questions as a last resort. Let's all try to get his slant going.

I walked Randy through the process of getting down to his ignition switch, but as he said, he was defeated by the pin that holds the locking hub. He wanted to confirm the switch is still good. Short of a complete steering column tear-down, I suggested that he simply by-pass the switch and "hot wire" the car under the hood to see if it will start with a remote starter switch. At least that would eliminate the ignition switch from the formula.

Question already asked...
How do you by-pass the ignition? I have a remote switch (new in package) that I never used. It is simply a push button with two terminals on the back. Do you run a hot wire off the "battery" post of the starter relay to one of the button's terminals and a second wire from the other terminal over to the post on the relay where the "starter" wire is connected? In effect, the switch performs the ol' "cross the screwdriver over the two posts" trick.

Obviously, that would completely by-pass the column ignition switch. But, wouldn't you also have to energize the ignition system with a hot lead to the ballast resistor? Can someone please explain? I am about out of ideas, myself.

Jerry
 
1974DartSport said:
You may be right, however the ECU is new and I have run a ground wire from the bolt to the inner fender. Is there a way to verify I have a good ground?
Click to expand...
You can always run a ground wire back to your battery.
 
I could not get my car to start a few weeks ago and checked everything electric and it turned out the gas just wasn't any good. We put a little fresh in the carb and it fired right up.

After you hot wired your coil did you pull a plug and check it for spark? Have you checked the firing order?
 
I have verified that all sparkplug wires are connected to the proper tower on the distributor. Starting with rotor positioned under #1 tower of cap and rotating distributor clockwise 1-5-3-6-2-4. This is the correct firing order for a slant six. Before hotwiring it I pulled #1 sparkplug wire, put a test light in the number one wire connection, and tried cranking it. The test light lit up.
 
The remote switch you have is simply a mechaics helper that gets tagged onto a starter relay or sylinod switch to engage the starter and rotate the engine. For the engine to start and run the ignition switch must be in the run position.
You could purchase a new ignition switch and connect it at the factory harness connecter instead of fully installing it. Turn it by hand. The switch would be grounded when installed but isn't depending on a ground to make circuits in its various positions.
Another simple test would be hook up a good battery charger and set it on 50 amp boost. That would make the entire system hotter.
 
RedFish said:
For the engine to start and run the ignition switch must be in the run position.
Click to expand...

Let's stay with that logic for a second and follow it through. Switches, by definition, are used to complete or break a circuit. So, if the ignition switch is bad and won't complete the "run" circuit, is there something you can do under the hood to complete the circuit? I keep thinking someone told me one day that a wire to the ballast resistor accomplishes this.

I know that an engine will crank in the "start" position, but will die in the "run" position, if the ballast resistor is bad - so it must be necessary in the ignition circuit. If you wanted to use a remote starter (and the column ignition switch was entirely missing), could you still somehow start the car?

I didn't mean to highjack your thread, Randy, but it was a good place to ask this pertinent question.
 
I know lots of different ways to hotwire various vehicles. Most I can start withour raising the hood. I wont sit here and type out instructions for stealing cars. sorry
 
Jerry just Pm'd me with the best explanation and testing procedures for this exact problem he found on a 73 Dart 340. He said he found it on another site and would have to kill me if he disclosed where it came from. I am very hopeful and heading home to do all the tests in Jerry's PM. I'll let you know.

I also bought a can of aerosol starter today at lunch.
 
Instructions given to me are in lower case letters. MY ANSWERS ARE ALL UPPER CASE.
1. With the wiring to the + coil terminal disconnected, the wire should register 12 volts when ignition is on and also when cranking. Test for this with a test light and voltmeter. (When using a test light, the light may be dim when ignition is on but bright when cranking. This is normal because voltage is cut in half by the ballast resistor when ignition is in RUN, but not when cranking. Either way, you should see 12v whenever the coil wire is not connected to anything but a meter.)

10.7 VOLTS WITH IGNITION IN RUN. 9.6 VOLTS WITH IGNITION IN START.

2. Test for good coil signal by connecting a test light between the battery positive terminal and the coil negative terminal, and then cranking the engine. A bright flashing light means the signal from the ECU is GOOD. No flash means the ECU may not be grounded properly or it is not getting switching signal from the distributor.

MY TEST LIGHT CLAMPED ON THE (-) COIL TERMINAL AND THE TEST LIGHT PROBE ON THE + BATTERY TERMINAL. LIGHT WAS STEADY ON. WHEN CRANKING, IT DID NOT FLASH.

3. All these problems can be caused by bad connections between components you have replaced or bad grounds. If your engine starts fine when supplying 12v directly to the coil positive terminal from the positive terminal (hotwiring), then you must check for bad wiring between the battery and coil via the ballast resistor wiring, ignition switch and starter wiring.

I HAVE TRIED A JUMPER WIRE FROM THE + BATTERY POST TO THE + COIL POST MANY TIMES. THE STARTER WORKS FINE, BUT THE ENGINE DID NOT RUN ON ANY OF THESE ATTEMPTS. THE BALLAST RESISTOR IS NEW.

4. Using test light connected to body ground, probe coil POSITIVE WIRE with coil disconnected from it. – Bright in Crank, dim in RUN.

WITH MY TEST LIGHT CLIPPED TO THE BODY GROUND, PROBE TAPED TO THE + COIL WIRE, NO CHANGE IN BRIGHTNESS FROM RUN TO START.

5. Now, hook the coil back up. At the wiring harness connector that plugs into the ECU (ECU unplugged):

Terminal 1 – Bright in RUN, dim in START.

NO LIGHT IN RUN. LIGHT IN START.

Terminal 2 – Dim in START, even dimmer in RUN. – No light at all means open coil circuit.

NO LIGHT EITHER WAY. I HAVE NO IDEA WHAT OPEN COIL MEANS OR HOW TO CORRECT THIS.

Terminal 3 – Dim in RUN, even dimmer in CRANK.

NO LIGHT IN RUN. LIGHT IN START.

6. If these tests are good, the ballast resistor wiring and the ignition switch are OK.

I DON’T KNOW WHAT MY RESULTS TELL ME. MY BALLAST RESISTOR IS NEW. I KNOW THAT THE TESTING ON TERMINALS 1, 2, AND 3 WERE NOT WHAT THEY SHOULD HAVE BEEN. WHAT DO I DO NEXT?

7. Terminals 4 and 5 – probe with ohmmeter for resistance through pickup coil and back. Should be between 150-900 ohms.

MULTIMETER SET AT 2000 OHMS – 449 READING.

8. If all this checks okay, inspect for correct pickup gap inside the distributor using a plastic or brass feeler gauge. Spec gap is .008 and no more than .010 with vacuum applied to advance canister.

I DID THIS SOME TIME BACK. IT WAS .008.

9. Check the resistance between pin 5 on the ECU and body ground. It has to be less than .5 ohms. If it’s more, clean and remount the ECU. If still shows resistance then ECU is bad.

I PUT THE NEGATIVE PROBE OF THE OHMMETER ON THE BODY GROUND AND SET THE OHMMETER TO 20 OHMS, 200 OHMS, AND 2000 OHMS AND TOUCHED THE POSITIVE PROBE TO THE #5 PIN IN THE WIRING HARNESS. THE 1 DID NOT MOVE. I THINK I DID THIS TEST WRONG, SO I TOUCHED THE POSITIVE PROBE TO THE #5 PIN ON THE ECU UNIT:
20 OHMS - 1 MOVED TO 2.20. 200 OHMS - 1 MOVED TO 23.9. 2000 OHMS – 1 BOUNCED AROUND 560-580.

10. Lastly, check resistance between pin 5 on the ECU and the battery negative terminal. If resistance is found, then repair the battery ground.

I PUT THE NEGATIVE PROBE OF THE OHMMETER ON THE BATTERY NEGATIVE TERMINAL AND SET THE OHMMETER TO 20 OHMS, 200 OHMS, AND 2000 OHMS AND TOUCHED THE POSITIVE PROBE TO THE #5 PIN IN THE WIRING HARNESS. THE 1 DID NOT MOVE. I THINK I DID THIS TEST WRONG, SO I TOUCHED THE POSITIVE PROBE TO THE #5 PIN ON THE ECU UNIT:
20 OHMS - 1 MOVED TO 2.25. 200 OHMS - 1 MOVED TO 24.5. 2000 OHMS – 1 BOUNCED AROUND 569-590.

DO I HAVE RESISTANCE? IF SO HOW DO I REPAIR IT. MY CAR AND ENGINE COMPARTMENT HAVE BEEN PROFESSIONALLY PAINTED. DO I NEED TO SCUFF UP CERTAIN AREAS SUCH AS THE BATTERY GROUND OR THE ECU MOUNTING AREA? WHAT NEXT?
 
You must log in or register to reply here.
-

Back
Top