Greetings! First thing to do is check to see if the coil has power with the key in the on position. You can use a test light or a voltmeter.
Next step would be to see if its getting a ground signal trigger. This is done with a test light. But only you would hook it up backwards. Hook the alligator clip of the test light and hook it to battery positive, and take the tip of the test light and touch it the signal wire of the coil. (If you need a diagram let me know). The test light should blink when cranking over the engine if its getting a signal. Good luck!
I found a TSB for this problem.
87ford20NO START - EEC IV - "E" COILArticle No. 87-20-18FORD: 1983-86 LTD 1983-87 ESCORT, EXP, MUSTANG, THUNDERBIRD, CROWN VICTORIA 1984-87 TEMPO 1986-87 TAURUS
LINCOLN-MERCURY: 1983 LN7 1983-86 MARQUIS 1983-87 LYNX, COUGAR, GRAND MARQUIS, MARK VII, CONTINENTAL, LINCOLN TOWN CAR 1984-87 TOPAZ 1986-87 SABLE
LIGHT TRUCK: 1983-87 RANGER, E-SERIES, F-SERIES, BRONCO 1984-87 BRONCO II 1986-87 AEROSTAR This article is being republished in its entirety to expand the model year coverage.
ISSUE: The primary winding of the E-core ignition coil may be damaged if the wire harness containing the tachometer circuit has a short to ground. ACTION: Before replacing the E-core ignition coil, perform the following diagnostic procedure. 1. Turn ignition to "ON" position. 2. Measure and record battery voltage.
Measure and record voltage between negative terminal and coil and battery ground post as shown, Figure 50. 4. If the differencce in readings is greater than 1.0 volt, check tachometer circuit for a potential short to ground. 5. If a short is present, make necessary wire harness repair. 6. Replace ignition coil as required. OTHER APPLICABLE ARTICLES: Supersedes 84-14-18, 84-14-18-S, 85-16-13, 86-2-21 WARRANTY STATUS: "INFORMATION ONLY"
Here is another one for this problem.
Article No. 86-2-20
IGNITION SYSTEM - TFI - WEAK OR NO SPARK - DIAGNOSTIC TIP
FORD 1982-86 ESCORT, EXP; 1983-86 THUNDERBIRD, LTD, CROWN VICTORIA, MUSTANG; 1984-86 TEMPO; 1986 TAURUS
LINCOLN-MERCURY 1982-83 LN7; 1982-86 LYNX; 1983-86 COUGAR, MERCURY, GRAND MARQUIS, CONTINENTAL, MARK VII, LINCOLN; 1984-86 TOPAZ; 1986 SABLE
LIGHT TRUCK 1983-86 EAND F-SERIES, RANGER, BRONCO; 1984-86 BRONCO II; 1986 AEROSTAR
CALIBRATIONS: All with TFI Systems
If the TFI module fails and causes a short to ground, the primary winding of the ignition coil can be damaged. The TFI diagnostic procedure published in the Shop Manual will not identify this condition.
When servicing a weak or no spark condition, perform the following:
1. Check for spark using the procedures found in the Manual Information, Computerized Engine, Quick Test Section, Test 1. 2. If there is no spark, test the coil primary resistance using Rotunda digital volt-ohmmeter 007-00001, as shown. 3. If the coil primary resistance is O.K., continue with the diagnostic procedure in Test 1. 4. If the coil primary resistance is not O.K., replace the coil and recheck for weak or no spark. If the spark is now O.K., the problem is resolved. 5. If the spark is still NOT O.K., continue with normal diagnostic procedure in Test 1. OTHER APPLICABLE ARTICLES: None WARRANTY STATUS: "INFORMATION ONLY"
TEST EQUIPMENT: VOM, STRAIGHT PIN
1. Separate wiring harness connector from ignition module. Inspect for dirt, corrosion, and damage.
NOTE: PUSH connector tabs to separate. 2. Disconnect wire at S terminal of starter relay. 3. Attach negative (-) VOM, Rotunda Number 007-00001, lead to distributor base. 4. Measure battery voltage. 5. Following table below, measure connector terminal voltage by attaching VOM to small straight pin inserted into connector terminal and turning ignition switch to position shown.
CAUTION: Do not allow straight pin to contact electrical ground.
CONNECTOR IGNITION SWITCHTERMINAL WIRE/CIRCUIT TEST POSITION
#2 TO IGNITION RUN COIL (-) TERMINAL
#3 RUN CIRCUIT RUN AND START
#4 START CIRCUIT START
6. Turn ignition switch to Off position. 7. Remove straight pin. 8. Reconnect wire to S terminal of starter relay.
TEST RESULT TEST RESOLUTION
90 percent of ^ Test result OK. battery ^ Go to Part 2, Test 6. voltage minimum
Less than 90 ^ Inspect for faults in wiringpercent of harness and connectors.battery ^ Refer to vehicle wiringvoltage diagram for appropriate circuit. ^ Damaged or worn ignition switch, Refer to Shop Manual, Group 33.
Primary Circuit Continuity
1. Separate wiring harness connector from ignition module. Inspect for dirt, corrosion, and damage.NOTE: PUSH connector tabs to separate. 2. Attach negative (-) VOM, Rotunda Number 007-00001, lead to distributor base. 3. Measure battery voltage. 4. Attach VOM to small straight pin inserted into connector terminal No. 2.
CAUTION: Do not allow straight pin to contact electrical ground. 5. Turn ignition switch to Run position and measure terminal No. 2 voltage. 6. Turn ignition switch to Off position. 7. Remove straight pin.
90 percent of ^ Go to Part 2, Test 5. battery voltage minimum
Less than 90 ^ Go to Part 2, Test 9.percent of battery voltage
Ignition Coil Primary Resistance
TEST EQUIPMENT: VOM
1. Turn ignition switch to Off. 2. Disconnect ignition coil connector. Inspect for dirt, corrosion, and damage. 3. Measure resistance from positive (+) to negative (-) terminal of ignition coil, using Rotunda digital volt-ohmmeter 007-00001.
0.3 to 1.0 ^ Test result OK. ohm ^ Go to Test 4.
Less than ^ Replace ignition coil. 0.3 ohm or greater than 1.0 ohm
Let me know!
If we are checking it right, sounds like there is no ground signal trigger to the coil.
If the pick up was replaced, the only think left would be the module provided the wiring is ok.
Well if we had a lab scope, we could see the signal from the pick up sensor.
But I am willing to bet, you don't have a lab scope, I would just recommend to use a voltmeter.
If all checks out, We are going to need to check into the wiring that goes to the module
You are close. Disconnect the wires and measure AC voltage while cranking.
Or you can measure resistance without cranking it over.
Disconnect distributor electrical connector. Inspect connections for dirt or corrosion. Using a suitable ohmmeter, measure resistance across orange and purple wires in distributor connector. If readings obtained are within 400---1000 ohms, circuit is satisfactory. If readings are less than 400 or more than 1000 ohms, replace stator assembly.
I would just check the AC voltage from this sensor while cranking.
If that checks out good, then we will look closely at the module wiring. Inputs and outputs.
At least about 300 Milli Volts
The Ignition Module shuts off the primary circuit each time it receives a pulse from the magnetic pick-up Fig. 9 . A timing circuit in the ignition module turns the primary current back on after a short period of time. High voltage is created each time the magnetic field is built up and collapsed. The red ignition module wire provides operating voltage for the module's electronic components in the Run mode. The white module wire and start bypass provide increased voltage for the module and coil during Start mode.
Dura Spark II systems with UIM (Universal Ignition Module) Fig. 10 can respond to another control signal from either an Ignition Barometric Pressure Switch, Ignition Timing Vacuum Switch, or the Microprocessor Control Unit (MCU), depending on the engine calibration. Responding to this second signal, the UIM provides additional spark timing control for certain operating conditions by shutting off the ignition coil current flow at a different time than with just the distributor pick-up signal.
For proper ignition module identification refer to Fig. 1. The modules are not interchangeable, Dura Spark II has 6 wire connector while Dura Spark III has a 5 wire connector.
How many powers do we have going into the module when cranking?
You are correct!
Is this what we have on the vehicle?
Wow! I think you might have a bad ignition switch. As long as you have 12 volts going in while cranking, my guess is the switch is bad!
You can try applying full battery voltage to the white wire at the module while cranking only, and see if you get spark.
Alright... lets move on.
SO we dont have a trigger on the dark green wire coming out of the module while cranking... correct?
Have we tested for the pick up signal right at the module?
What kind of AC signal are we getting while cranking at the module?
I was just going off of the top of my head when I said that I think it should be at least 200 Milli volts when cranking. I think it should even be a bit more. But if it was replaced with a new one, then we should be good to go.
I think thats the only thing that it could be.
You said you have replaced the module with a known good one... correct?
If this does not work, I think you might have a bad new module. We have gone over everything!
The only thing left would be a wiring issue.
Also, try disconnecting the coil and see if you get a trigger on that wire while cranking. Just a thought.
I thought we decided to replace the module again.
The ohm reading you are getting is good. .612 is 600 ohms.
But measuring resistance on this sensor is kinda like placing a voltmeter on a battery and getting a good reading and saying the battery is good. It does not work this way. The sensor needs to be put under a load. To me, ohm tests are useless.
Lets go ahead and get a different module in there.
That reading is good!
Are we sure this reading is getting to the module? Are you taking the reading right at the module with everything hooked up?
Is this wire grounded?
According to the diagram, that one last wire from the distributor to the module needs to be grounded. I believe the module itself needs to needs to be grounded. Maybe this is it! The module cannot ground the coil because it does not have a ground itself!
And this did not work?
Boy... we covered just about everything. I am starting to think maybe we have the wrong module on the vehicle.
Something is just not adding up. Maybe a wiring issue?
I honestly have tried my best but do not know where to go from here. I think we are just overlooking something simple.
I am going to have to leave this question open for other experts. Good luck!
Yes... according to the diagram it goes to the tach.
Can you tell me how you are testing for this signal to the coil?
Yes! there should! This ignition system could be a completely different system that I am used to dealing with. Maybe there is such a minor trigger coming from the module to the coil that we cant even see. Maybe on this type of ignition system, a regular conventional test light will not work to check the signal to the coil.
I am sure a lab scope would work. But I am pretty sure you do not have one handy...correct? So with that said, I believe we covered everything else that we should have. The distributor signal powers and grounds going to the module... the only thing that is left would the the coil. Unless you got the power wires to the module mixed up? Maybe the one power wire goes were the other should go and vice versa.
Sure... there are lots of places. You will have to call around to places in your local area.
Being such an old vehicle, you might be better off looking in junk yards for the harness.
TO be honest with you, I am not too sure.
But I do know, that the tach gets the same singal that goes to the coil. The ground signal trigger while cranking.
Why? What do you have on these two wires?
If the timing was off, then we would have spark, but just at the wrong time.
But from what you have been telling me, there is spark because of a lack of signal from the module. Therefore we would not have any spark.
Thanks for the accept!
I do have a few pictures available. for the ignition timing.
If you think that the distributor might be in wrong, we will just have to time it just like ever other motor out there. Pull off the distributor cap and see where the rotor is positioned. Pull out the number one spark plug and put the piston at tdc. If the rotor is not close to pointing to cylinder one on the distributor cap, then the distributor will have to be pulled back out and reset correctly.