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  #1  
Old June 14th, 2012, 02:24 PM
slowpoke496
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Bryan
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losing spark??

My 94 D-90 3.9L was losing power and dying while driving. No codes are displayed. Now the truck will run for 5 minutes then die.
If I pull the lead from the center of the distributor and check for spark there is none during cranking. While turning the key to the off position there is one spark? Not sure if that is normal. If I pull the lead from the coil to the dizzy and wait a few minutes the truck will begin to spark again. I can get the truck to run again. I have been able to repeat this process a few times and get the truck to run as normal.
Since I felt it was time to replace some old components I have replaced the following:
1) Fuel Pump
2) bosch metal relays (fuel pump relay)
3) Idler control valve
4) VSS
5) Spark plugs new wires only 1.5 years old
6) Been running a Mallory unilite dizzy for a few years
7) Replaced coil with new Mallory coil (no ballast as it is not necessary)
8) New fuel temp sensor
9) New coolant sensor
10) Swapped in spare ECU
11) New PCV hoses
12) Running ford injectors approx. 5 years old
13) Flexilite dual fans – running for 5+ years
14) Replaced electrical portion of ignition switch 2 years ago.
15) Replaced O2 sensors approx. 2 years ago.
16) Alternator new 3years
17)brand new optimum battery
Have rovergauge running and logged the failure one time I can share the log but what I notice is voltage fluctuation at stall and then while inspecting (checked coil wires and such) under the hood until I restarted it. It jumped from 13.7 to 15.3v then dropped to 12-10v when I restarted truck leveled right off at 13.7 ran fine the next 10 miles to work.
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  #2  
Old June 14th, 2012, 10:55 PM
slowpoke496
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just read my post and realized it should read.
Help my truck IS losing the spark.
i have done all of the above and still the problem occurs.
it may be time to send it in to the shop
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  #3  
Old June 19th, 2012, 09:48 PM
slowpoke496
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Cautiously Optimistic

Cautiously Optimistic
I retested the Mallory Ignition Module and it passed the tests 8 times in succession. On the 9th try it did not drop voltage properly as stated in test procedure below:

“With the DMM still connected to the negative side of the coil you are going to watch the meter while blocking the optics on the module with your credit card. Placing the credit card or other device between the towers on the module blocks the optics. When the optics are blocked the readings on your meter MUST drop below 2-volts. It may be just for an instant, or it may hold below two volts until you unblock the module. Either is OK. But if the voltage does not drop below 2-volts the module has been damaged and must be replaced.”

The unit dropped to 2.9 something.

I ordered a replacement module. Installed it and have driven approx. 20 miles without incident. I am not yet considering this solved but I wanted to post my findings to anyone with an electronic distributor setup.

Note I did ask the shop that did my rear crossmember replacement to disconnect the distributor before welding. Cannot confirm they did or did not.
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  #4  
Old June 19th, 2012, 10:22 PM
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Yah they all have electronic dizzers. The trusty Lucas dizzle has an external amplifier module while the Unilite one is inside. Both thingys do the same job. If everything else checks out good its usually the module that bit the dust
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  #5  
Old March 19th, 2013, 03:33 PM
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Pete Gerbine, III
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Quote:
Originally Posted by slowpoke496 View Post
My 94 D-90 3.9L was losing power and dying while driving. No codes are displayed. Now the truck will run for 5 minutes then die.
If I pull the lead from the center of the distributor and check for spark there is none during cranking. While turning the key to the off position there is one spark? Not sure if that is normal. If I pull the lead from the coil to the dizzy and wait a few minutes the truck will begin to spark again. I can get the truck to run again. I have been able to repeat this process a few times and get the truck to run as normal..
Were you able to determine what the problem was? My '93 110 is doing the same exact thing. When the spark does come back and I'm able to get it to start and run for a few minutes, the idle is rough and there is a high pitched squeal when I rev the engine...like a belt squealing. New belts installed a couple of months ago. After a few minutes of runnning, the coil quits putting out. I've replaced the connectors to the coil since they were in bad shape, hoping just a connection issue...again, had great spark....started up...ran a few minutes and died again, with no spark. I am also running a Mallory Unilite.

Does anyone have a pic of the ignition module?...read a little on that as well, while searching.

Thanks,
Pete
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  #6  
Old March 19th, 2013, 03:54 PM
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I had this trial and tribulation with a RRC. As long as the truck was moving @ highway speed and the ignition module was cool the truck ran great. Stop for a light or get caught in traffic-it died. Once cooled down it would start right up but if left sitting @ idle would soon get warm and die again. Great fun to diagnose.
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Old March 19th, 2013, 09:03 PM
slowpoke496
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Pete
It turned out to be the unilite ignition module. The my unit was most likely damaged during the welding of my crossmember. Mallory site has the test procedure on their site. Note it took multiple tests to actually have it fail... i have replaced it with no reoccurring issues. Not home right now but if you can not locate the test procedure i will check to see if i saved a digital copy.
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  #8  
Old March 19th, 2013, 09:21 PM
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Thanks, Bryan...I'll see what info I can get from Mallory and go from there.
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  #9  
Old March 19th, 2013, 11:07 PM
slowpoke496
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found the procedure

Step by Step Module Testing - Unilite® and E-Spark®

Tools Needed: Volt Meter or DMM (Digital Multimeter), and a Credit Card (or piece of thin cardboard)

VERY IMPORTANT! If you are using a CD (capacitive discharge) or other type of amplifier box (Crane, Mallory Hyfire®, MSD, Jacobs, Accel 300+, etc.) on your vehicle you must first remove (unwire) it from the system or you will not get a valid test result! You can bypass some of these with a supplied connector that came with the unit, but otherwise you MUST unwire it from the distributor and coil! After removing the amplifier you will need a ballast resistor installed in the system to prevent killing a good module (if you attempt to start the engine). Once unwired from the system, follow your distributor instructions for proper installation using ONLY the distributor, coil, and resistor.

The CD or inductive amplifier box is an intermediary between the distributor and coil. The amplifier box picks up a triggering signal from the distributor and then tells the coil what to do. When a amplifier is in use on the vehicle it manages nearly all aspects of ignition coil function. Because the amplifier also provides a low-power supply (signal) to the distributor, and the distributor replies with a low-power (un-amplified) triggering signal, by providing this energy supply the box interferes with proper testing procedure of the Mallory ignition module.

Remove the distributor cap and rotor. The Mallory distributor rotors are usually pretty tight on the rotor shaft, but it is only a press fit. You will be able to get the rotor off by firmly pulling straight up, though in all honesty it may hurt your fingers a bit the first couple times you attempt it until you get the grip correct. Try NOT to use a screwdriver or other device to pry on it. This would be a last resort, and will likely damage the rotor.
Turn the ignition key ON and use your DMM (Digital Multi-Meter) to measure supply voltage. First check voltage at the POSITIVE side of the coil by connecting the black lead of your meter to a good ground (engine block), and the red cable to the coil. The meter should read close to battery voltage. Now check voltage at the NEGATIVE side of the coil by moving the red lead from your meter to the negative side of the coil. Your meter should also read close to battery voltage. If everything is good here, continue.

NOTE: If you do not see a voltage reading that is close to battery voltage on both sides of the coil you have one of two problems:
Make sure there is not a power supply problem. Take a jumper wire from the positive post on your battery to the positive side of the coil. Re-do the test. Do you now have battery voltage on BOTH sides of the coil? If so, find out why battery power is not properly reaching the coil. Remove this power jumper wire.
If the reading on ONLY the NEGATIVE side of the coil is low, the module is artificially energizing the coil when it is not supposed to be. You will need to replace the module. The only time the module should be allowing the coil to charge is when the photo-optic is blocked. The rotor has been removed and there should be nothing blocking the L.E.D. optic; therefore, the module has been damaged and must be replaced.

With the DMM/Voltmeter still connected to the negative side of the coil (black DMM wire to ground, red DMM wire to the negative side of the coil) you are going to watch the meter while blocking the L.E.D. optics on the module with your credit card. Placing the credit card or other device between the towers on the module will block the L.E.D. optic. When the optics are blocked the readings on your DMM/voltmeter MUST drop below 2.0 volts. It may be just for an instant, or it may hold below two volts until you unblock the module. Either is OK. But if the voltage does not drop below 2.0v the module has been damaged and must be replaced. Again, voltage MUST drop below 2.0 volts when the optic is blocked!
Now, unblock the module after performing step #3 above and the voltage reading on your meter MUST return to battery voltage. If the voltage does not instantly jump back up, it stays at its "optic blocked" reading, or does not fully recover, the module must be replaced.



EXPLANATIONS:

Based upon the test procedure above we can come to a few conclusions:

If the battery voltage is not initially present you have either an electrical problem prior to the coil (ignition switch, low battery, corroded cable, etc.), or the module is charging the coil when it is not supposed to. The module has been exposed to voltage spikes or installation errors.
If the voltage does not drop when the optic is blocked, the module is "open" and this was likely caused by a power surge, excessively high resistance in the plugs or plug leads, or improper grounds. Replace the module!
When the voltage always stays below 3.0 volts it means that the module has been spiked by high voltage or amperage, lack of a ballast resistor (if not using an amplifier box), or the wiring was incorrect. Replace the module!
If the voltage only drops to 3-4 volts you will get a noticeably weak spark. This is also caused by poor grounds, or a power spike. Replace the module!



POSSIBLE CAUSES:

A faulty charging system (stuck or shorted regulator/alternator), or high amp single wire alternators with a cheap diode.
Ineffective or inadequate vehicle grounds. The module brown wire must be connected to the engine block. The vehicle grounds should consist of: Battery to Engine; Battery to Body; Engine to Frame; Engine to Body; Body to Frame
Trying to start the engine using a battery booster-charger. Most of these units have very dirty electrical signals which cause power surges or spikes. The proper procedure is to disconnect the battery, charge it, and then reconnecting the battery.
Using non-suppression plug wire leads. You must use suppression core type plug wires, no solid core wires (stainless steel or copper). Spiral core is best, but carbon or any suppression core plug wire will also work.
High amp stereo equipment that is not properly grounded or the vehicle grounds have not been updated to handle the added capacity. The surges created by high power media systems can play havoc with a vehicle's electrical system. Proper sized cabling, using relays, and adequate battery supply is imperative!
Direct shorts in the vehicle's electrical system.
Welding on the vehicle or working on the vehicle's electrical system while the distributor harness is connected.
Faulty starting system (excess starter drag, not enough voltage/amperage getting to the starter, worn brushes/armature).
(Not that many people are using these anymore!) CB radio spiking on mic click into electrical system (typically only on power modified CB radios).



One more time on the testing procedure - SHORT VERSION:

Remove Cap & Rotor
Turn Ignition Key ON
Is there Battery Voltage (+/- 14v) on the POSITIVE side of the coil? YES = GOOD!
Is there Battery Voltage (+/- 14v) on the NEGATIVE side of the coil? YES = GOOD! NO or Much Less Than Positive Side of Coil = BAD!
Voltage Drop Test - Voltmeter still on Negative side of coil. Voltage Drops BELOW 2.0v = GOOD! NO Drop = BAD!
Voltage RECOVERS to BATTERY VOLTAGE after unblocking the optic? YES = GOOD NO = BAD



As soon as you get to a BAD in the procedure above, there is no need to test any more ... replace the module.

Here is a copy of Mallory's description of this testing procedure (I feel mine is more clear, but if you want it in their words, here ya go): UniliteTest.pdf

A Few Tips and Lesser Known Facts?

The Mallory Unilite® and E-Spark® modules require a drop in voltage for the trigger side (green wire) of the module, even though the power supply side (red wire) can handle 14.0+ volts. Even though the ballast resistor is wired inline on the positive side of the coil it is actually dropping the voltage to the negative side of the coil (trigger side). This means that you MUST have ONE of these installed:

The correct ballast resistor. The Mallory part #700 is the best, but another ballast of compatible specs is also acceptable. (usually around 0.85 Ohms) <or>
OEM resistance wire in the factory wiring harness <or>
Internally resisted ignition coil (cannot be used with external ignition amplifier units). <or>
An ignition amplifier like the Mallory Hyfire, Crane, Accel, MSD, or other comparable units.


On applications that are not using an ignition amplifier you can verify that your system has the correct resistance by connecting a volt meter to the negative side of the coil with the engine running at idle. The measured voltage should be roughly 8-9 volts.

If you are using an ignition amplifier you do not need a ballast resistor, but you should keep one handy. If you ever need to bypass or remove the amplifier you will need a ballast to prevent damage to the module.

Anytime you do anything type of electrical work on your vehicle, no matter what, you should unplug the 3-wire connector at your distributor. This will guarantee that you do not spike the module while working on your vehicle. Remember, it is not the module killing itself that causes failures. It is some other component or human error that kills it.

NEVER try to boost start your vehicle using a battery starter/charger. The dirty power supply and excess amperage can and will damage your ignition module. Disconnect your distributor harness, or disconnect and fully charge your battery, then reconnect everything and start the vehicle. If you own a newer computer-controlled vehicle, this is the same procedure recommended by the vehicle manufacturers to prevent damage to vehicle computer and diagnostic systems.

------ Follow up post added March 19th, 2013 11:14 PM ------

earlier you requested a picture of the ignition module. i should note that when i changed out the module that came with the original mallory distributor i went with an E-Spark it looked the same the part number was 6100M
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Old March 19th, 2013, 11:36 PM
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Thanks for the detailed testing procedure! I will try to get into the distributor in the morning to test the module. I was able to check voltage on my coil and it seemed a little low on the (+) side of the coil...9.35v, and a lot low on the (-) side of the coil...2.05v, with my battery voltage at 12.54v.

Hopefully I will get somewhere with it tomorrow... thanks, again!
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  #11  
Old March 20th, 2013, 12:00 AM
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When I had my trucking cutting out randomly, I replaced a litany of things. It turned out to be the ignition switch. Worth checking.
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Old March 20th, 2013, 12:22 PM
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Oh man...this is fun!!...and by "fun", I mean this is absolutely driving me crazy!

Voltage at battery = 12.5v
Voltage at pos. side of coil = 9.3v
Voltage at neg. side of coil = 2.0v

Jumped wire from battery pos. to coil pos. = 11.7v
With jumper on pos. side of coil, neg. side of coil still = 2.0v

Did "credit card" test...
Without jumper, neg. on coil = 1.9v
With jumper on pos. side of coil, neg. side of coil = 2.1v

NOW THE "FUN" PART:
Removed the credit card and jumper...
11.4v on both sides of the coil!!....momentarily...then back to 9.3v (+) and 2.0v (-).

Mallory Tech. stated:
"I would say there is a good chance the coil has failed. The ignition module would either work or not work, it would not cause an intermittent issue like you are experiencing."

And still not sure what is causing the horrific squealing when it does start up...before it loses spark and dies again....FUN!!
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Old March 20th, 2013, 12:33 PM
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I have been trouble shooting my own issues--I am running the Mallory Unilite distributor with the Promaster 30451 coil (doesn't use ballast resistor). I had this coil from over a year or two ago but never installed it-- the weather was nice and I wanted to play with the truck so I decided to install it and now I stumble at low RPM under load. Should have left my old coil in. I went to check my Unilite module and did the credit card test. 11.9 at both sides of coil with sensor open, then dropped to almost 0V with the credit card in the slot. Ran the test 3 times just to make sure, on the third time, voltage dropped to only 10V where it now resides. I am 99% sure my issue wasn't the module although now it is part of my problem. Sensitive things--friggin blew my own module. This sucks. Just so you know, and back on point, with the credit card in, my voltage was way under 2V, almost to 0. FYI.
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  #14  
Old March 20th, 2013, 12:45 PM
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Any suggestions on the best way to test the ignition switch?
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Old March 27th, 2013, 09:54 AM
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When I tested mine, I used a test light at the coil. When the car would not start, I saw no voltage at the coil, which points directly to the ignition switch.
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Old March 27th, 2013, 12:08 PM
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My new coil is supposed to arrive today...hopefully I'll have something figured out soon!

Can you tell me the best way to get to the ignition switch?
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Old March 28th, 2013, 12:14 PM
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We're up and running!

I changed the coil, as instructed by the Mallory tech. He thought since it was an intermittent issue that it must me the coil and not the ignition module. He said the module would either work or not work. I ended up putting the Mallory 30451 in there...the epoxy filled rather than oil filled unit.

While changing it out, there were some pretty poor connections to the coil so I redid some connections and it fired right up!.....BUT WAIT!....I let it run for a few minutes...then it just died again.....NO FIRE!!

So...I went ahead and swapped out the ignition module, and now everything seems to be working as it should. Starts seem to be stronger, as well.

I think it was a combination of some bad connections....maybe a bad old Bosch coil....and ultimately, the ignition module...but everything feels good and strong now. Hopefully that has eliminated that issue, altogther.

Thanks for the help, D-90!...ready to tackle the next gremlin, when it shows its head...
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