OK, yes I searched, I have a typical small block Chevy with a Mallory unilight. I tried to start it tonight and I am getting really weak spark. How can I check the coil and the resistor? Am I missing somthing else? I thank you in advance.
Do you have the correct coil??? Mallory recomends that you use a coil custom made for the unilite system. Oh by the whey they also make the coil that they say is suited for their distributor>>>>.
I don't know if it's just a snowjob or not, but they also recommend a particular ballast resistor, their model #700.
I had 3 unilights fail on me before I got smart and used a different system. The biggest cause of problems is not having a ground to the distributor. I had a seperate ground wire from the body of the dist. to the engine block. Helped some but they still let me down over time. Try a set of points in the dist to check whether it's the coil or the unit. Try a different coil or try the suspect coil in a known good running car. Just my experience with unilites. jerry
I've got two years on one with zero trouble. I do have a matched coil and resistor. The Mallory website has a great deal of tech help, give it a shot.
I must have gotten lucky too..I've had one in my 57 for over 10 years without a problem..without thier coil or ballast.. HOWEVER, i know of many that have gone bad, especially the early one's with the infra-red sensor pickup.. Now, this may sound like a lame, simple thought, but what condition are the cap and rotor? I've seen poor cap's create weak spark many time's at my daily job as a wrench....had it happened to my 235 in my 53 chevy too not that long ago. Just a quick thought.
In reference to the Unilite itself- as mentioned, grounding is a major issue...also check the pickup for dust...they also fail rather quickly if the coil is left energized (i.e. key left in "on" position) but engine is not running...also susceptible to voltage spikes. Beyond that, resistors can be checked with an ohm meter if you know the value...usually when they fail, though, it's fairly plain to see. The easiest way to check a coil, if you don't know the specs & can't put a meter on it, is to use a known good one. Even a std. Chevy "can" coil will work well enough to subs***ute for a bit, although as noted Mallory prefers you to use theirs. I'm guessing by your post that the system was running fine for some time before this...(not just installed, in other words). Are the cap, rotor, wires, etc. OK?
Running a Unilite on my 350 powered 56 Chevy for going on 4 years and its never missed a beat. They are great for firewall clearance issues.
You do not need a special coil or resistor for a Unilite..... Been running one for 3 years with a resistor I found in my parts bin, along with some old coil from who knows where..... Most issues are ground related....
The cap and rotor are really important-check them first. Since you have some spark, it doesn't sound like you've popped the unit by crossing a wire. They will blow like a fuse if that happens. Ground and ballast are important, including ground from the block to the ch***is. They work fine for long periods of time if they are set up right at the beginning, but they don't seem to be very tollerant of messing around.
I had some isssues my self and this is what I did. I got the power filter, and the specfic coil for the distributor, then I made sure I didnt have a factory installed resitor wire in the harness, and it ran fine. If your going to have a unilite you need to get the whole package, also make sure you have a good ground connection. When I called summit they had the part numbers I needed. Thats where I would start. I think if they put out some info how to install it correctly, or made a package list of parts so it all works together they would lose less customers.
Try jumping out the resistor. If the engine runs OK, it's probably the ignition module. The Unilite only needs 9 volts to run ,hence the resistor but when the light in the module gets dim,it needs the whole 12 volts to complete the circuit.
I've had one on my 389 Pontiac for 15 years without any problems. I'm running it with a MSD 6A box and a MSD Blaster 2 coil. As mentioned above I made sure that the factory resistor wire was disconected. One problem I have seen happen with them is that from the factory the wiring under the rotor was routed to close to the shaft and it rubbed into the wires causing the problem you're talking about. The spot it wore through the wire was'nt hardly enough to notice, but certainly enough to cause a problem.
In my opinon they ****... I've had two go south on me, and I know of few others that just stopped working. As mentioned i'm sure they're some that run 10+ years but i just don't think they're very reliable. If you can't affored a MSD, i'd suggest just going with petronix.
Wow, you guys are great. I will check the ground and sawp a coil. But I have a gut feeling its the ground. It ran great for the summer. No problem. Yeah I do like the size. I needed it when I had my 2X4s on there. Another VICTIM of expansive gas.
If you are getting any spark, the Unilite is working, look at the coil and connections. FWIW, Ihave one on a BB Chevy that has been going strong for 19 years, and one on a 351 that has been in use for 10 years.
Don't know about y'all but I'm tired of hearing all the BS about Unilites being junk. I'm sure just as many problems occur with HEI's, Pertronics or any other distributor. My Unilite has kept my SBC running like a top, never had a problem.
If you don't want to hear it go to the next topic... Pertonics do have problems from time to time (but usally it's installer related) HEI are really dummy proof i've hardly ever had problems, my biggest issue with Unilite is that they just give up for no real reason. I know of 2 that the lenses have cracked on. That's something due to normal usage.
Big secret on the unilite- periodically clean the "eye" with denatured alcolol-I.e. a Hooters wing sauce removal pad. and if You still hate it, They have a magnetic breakerless system, too-just like M.S.D. as far as Ignition boxes are concerned, My hyfire IV kicked the **** out of my 6al. Waaay better spark. They weirdest thing I have seen with a Mallory unit was this- one of the little studs that hold the Mechanical advance mecanism fatigued and broke, then lodged between one of the bolts that holds the cap clips down and the main body, causing the whole distributor to spin. (This was on a 44 mopar , so it wasn't that weird, all things considered...I mean it IS a dodge, after all....) and to answer The question- it isn't the light- more likely to be the coil or ballast resistor. while You're there, check the ground wire (brown one, I think) and clean it's connection point, too. because unitlite's don't ground through the distributor. also, check the little carbon rod inside of the cap. they get broken off really easy if You ham hand the cap on.
I've had five Unilites in five different cars over the past 20 years, and none of them ever had any problems. I think you just need a good ground to the engine block. I use them with stock coils, Accel coils, no-name chrome coils and different ballast resistors with no problem. They sell a new version of the module now that's a lot cheaper now ($35 instead of $80). It's a bolt in replacement. But I've never needed to replace the module in any of the cars I've had except for replacing the module in a used Mallory Unilite I bought on Ebay last year. I think people that have problems must hook them up with weak ground connections, or try to ground them back at the firewall instead of to the engine block like you're supposed to. I ground them with a stainless bolt and a serrated stainless washer to a good clean place like a tapped hole in an aluminum intake manifold. They sell a "power conditioner" little box, but I've never used one. I still think it's just when people have a bad ground that causes the problems.
I ran a Unilite conversion in the OEM distributor in my 428SCJ for 13 years with a MSD Blaster coil and a Mallory adjustable rev controller. The new owner still has everything in the car is still running fine. Are you sure you have the coil hooked up correctly? If its backward it'll still fire the plugs but the spark will be weak. FYI - negative side goes to the distributor. -Bigchief.
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