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View Full Version : mallory unilite-no signal, was previously working, works in diff car



ALLstrokedOUT
08-04-2012, 05:30 PM
Hey guys, ive been having this issue and cant figure out what to look at for the issue...everything is wired the same as before when my car was working. 12v to a switched 12v, ground to a good ground, but I dont get a signal. I plug it into our 68 roadrunner which has the same ignition setup as my demon and it works. its like trying to diagnose a light switch, its so simple, but it doesnt work, its defying any logic.

I tested it how unilite suggests w/ a credit card to cover the optical eyes and it suggests in the troubleshooting that the boards fried, but its not because it works on the roadrunner just fine...ANY ideas dumb, obvious, whatever??? i dont know whats wrong with it or whats changed since it was working..

EDIT: Im now thinking that perhaps its a bad ground, its connected, but maybe some of the wire strands pulled out of the crimp? I thought it tested good on the multimeter, but thats the only thing i can think of.

NOT A TA
08-04-2012, 07:04 PM
Did you check your ground with a meter?

Do you have 12V at the negative coil post?

Are you getting no voltage drop or only a small drop if you do the optic block?

Do you have a capacitive discharge box? Hyfire, MSD etc? If so you need to bypass it before testing the distributor with the credit card trick.

You didn't mention if you removed all the wiring and put it back the same or if the wiring was left untouched since the engine last ran. If it was removed and reinstalled check for bad connections particularly if there was painting involved where the ground connection is.

ALLstrokedOUT
08-04-2012, 07:26 PM
I checked the ground with an ohm meter and it reads good

I have the wire harness setup now so its just the signal wire going to the multimeter, switched 12v to the red, and ground wire to the brown. I am getting no voltage drop, no voltage at all through the signal wire (i shouldnt need it connected to the coil to see voltage here should i??)

I have a capacitive discharge box(hyfire 6AL), but its hooked up to my Megasquirt system im trying to get running (but thats another story).

The wiring was swapped over from my duster to the demon, ive checked everything, but it cant hurt to double check it all or make a new 12v and ground wire directly to the battery as a test...

MrQuick
08-04-2012, 09:09 PM
Distributer shaft is spinning right?

ALLstrokedOUT
08-04-2012, 09:36 PM
yes it is, but to be sure it wasnt the rotor/shutter i also tested it with the ignition on, and a credit card to cover the optical sensor with no luck.

eric78
08-05-2012, 07:04 AM
I would try running a new ground. The wire could be hanging on by a couple little strands and it would still show good with an ohm meter. The ohm meter only flows a very small amount of current compared to what the wire will see hooked up in the system.

ALLstrokedOUT
08-05-2012, 10:28 AM
Problem solved, thanks guys for the help. The ground ended up being ok. Two issues were that 1) you need the signal wire to be connected to the coil for the tests, if its not it will not show any voltage. For my fuel injection system i need a "pullup" circuit of 12V and a resistor (the way i see it is mimicing a coils voltage). It turns out the resistor somehow broke before i ever cranked the engine over, and while i was testing it i thought the signal wire would have voltage through it without being connected to the coil...thanks again everyone, ive gotten the engine to run as much as 20 seconds long on the new MS fuel injection setup, i just need to learn how to tune it-and fast!

LS6 Tommy
10-30-2012, 04:48 PM
I'm glad you got it solved, but I'd switch to something else anyway. I don't want to be insulting, but the Unilite is one of the most unreliable, failure prone ignition systems ever foisted off on the general public...

Tommy

ALLstrokedOUT
11-03-2012, 06:22 PM
I dont take it as an insult, its good advice...We have 2 spares at our shop (my dads roadrunner HAD the same ignition system). With that being said ive heard a LOT of bad things about MSD and other name brands as well

My dad just had a month long ignition ordeal with his hyfire and unilite...replaced everything in the ignition system twice, checked 6 month old wiring countless times, and still couldnt get it to run reliably-he ended up going back to points for now. Both out our cars are driven regularly and had no issues to note beforehand, his issues came up out of the blue without warning. I had a unilite cause misfires straight out of the box..im hoping to go to a crank sensor with my efi after i bench test it enough over the next 6 months or so...