Mallory unilite...need help!

[Glenn72]

Good news is my 72 car runs, bad news is that it misses on all cylinders. I have cleaned and checked and double checked all grounds. During the rebuild I replaced the starter, alternator, coil, distibutor, spark plugs and wires. I have rebuilt webers which are sync'd and operating fine. The call starts right up and is very driveable but it misses. I wired it up per Century Performance "new" hook-up diagram. They said that I must have NO less than 8 volts at the negative side of the coil during idle and I have 5 volts. They said this is the problem. I have had a second set of eyes look at it to make sure I didn't hook it up wrong but we think its right. I also checked the module and it tests OK as well as inspecting the distributor cap. Here is how I hooked it up.

Green....coil (-)

BW coil (+)

Red along with BW (12V with ignition on) on one side of ballast

GW on other side of ballast

Can someone with same installation check their wiring and possibly measure their coil negative to ground? Any suggestions greatly appreciated.

Glenn

[jmortensen]

I'm no wiring expert, but unless the Unilite has points, and I don't think it does, why would you need the ballast resistor at all? When installing the 280ZX distributor your choices are to jump the ballast resistor or to remove it entirely and connect the wires that attach to either side together directly. I'd try running a jumper cable across the resistor and then check your voltage.

[=Enigma=]

As I understood it, the job of the ballast resistor is to reduce(roughly half) the the voltage leading to the points to prevent them from geting fryed. 12volts / 2 = 6 volts. Minus a little voltage loss somewhere in the wires leading to the ballast resistor would put you in that 5 volt range you're seeing. If you're not using a points based dizzy, I'd simply bypass or remove the ballast resistor.

Otherwise, check the voltage at both sides of the resistor with the key in the ON position. This should tell you how much voltage is making it to the resistor and how much is being let through. If it's less than your required 8 volts, and I would think it would be, you'll need to bypass the resistor.

[Glenn72]

OK lets say this isn't the problem, can anyone tell me what else it could possibly be? As mention I know my grounds are good. I have noticed that my voltage gauge sometimes jumps a bit, is that normal in a Z? I have just installed a new voltage regulator and it made no difference.

[Carl Beck]

Glenn:

See the instructions on the Z Car Home Page.

<a href=http://zhome.com/ZCMnL/tech/MalloryDist.htm TARGET=NEW>http://zhome.com/ZCMnL/tech/MalloryDist.htm</a>

On my 72 I needed to add a second balest resister to get the tach to work correctly...

FWIW,

Carl B.

Carl Beck

Clearwater, FL USA

http://ZHome.com

[Glenn72]

Carl, I originally had it hooked up like on Zhome but in an effort to get the voltage up I removed the extra resistor. I then had a problem getting the tach to work but figured it out and it works fine. Maybe I'm chasing my tail assuming the less than 8V on coil negative is the cause of the miss. Thats why I was hoping someone with the same set-up could measure with voltmeter and see what they have. Century Performance tells assures me this is the problem but I'm not so sure.

[TBK1]

I have the mallory Unilite that came with the new engine I got and had to wire it up to my 77. Mine only has 3 wires. According to the diagram and intructions I found on the e-net it says You MUST use a bal resister or you will burn out the Ignition module in the Dizzy. Brown goes to engine ground. Green goes to negiative side of Coil. Red goes to Balist Resistor and the other side of Resistor goes to coil Posistive. dont remeber but Think I had about 6 volts and no prob, I can Check it later and Post it needed.

[Glenn72]

TBK1 that would be great if you could check it out. Maybe this isn't my problem but that pretty much then means I'm stumped.

[TBK1]

Ok Glenn here is what I have. This is a 2600 (260 motor) with trip webers installed in an original 77 fuel inj car. switched to mechanical fuel pump.( only gets 3lbs fuel press dont know if thats right). mallory unilite dizzy. and Msd blaster 2 coil with it's supplied resistor. tapped off the positive side of the original ballist resistor to one side of the MSD resistor, other side of resistor to the red going to the dizzy. Green to the neg side of coil. brown to ground.

used this sites info and wiring diagram, http://go.mrgasket.com/Brands.aspx?BrandID=6&brandselection=10

but now after re-reading and testing these voltages not SURE that I am RIGHT. But mine does run fine, alittle rough at idle but I think i still have minor carb issues and possible timing issue, currently playing with setting.

all these voltages are in ref to GRD.

power sourse from orignial ballist resistor + side = 11.5 VDC

power at one side of new ballsit resistor = 11.5 VDC

power out of new ballsit resistor = 11.5 VDC (now Im really confused)

power at - side of coil = 3.8 VDC (HUMMMMM)

power at coil + =6.7 VDC

Think Ill email Mr. Gasket and ask tech advice. See what they come up with!

[TBK1]

Ok! changed my wiring to this

hot wire from old ballsist res to new resistor AND the red to dizzy.

disconnect old res wires to coil

green to coil -

other side of new resistor to coil +

brw to GRD

all voltage reading changed to this (in respect to GRD)

to one side of new resistor (+ feed) 12.2 VDC (witch also feeds the red dizzy wire)

out or other side of new resistor to coil + reads 8 to 8.5 VDC (varrying)

Coil - side 4.3 to 5.3 VDC (varrying)

appears to have fixed my stubble upon acceleration will no more later after testing.

Almost forgot, had to rehook my (old Blue wire) to - side of new coil to get TACH to work

[Glenn72]

TBK1 thanks for all your help, hopefully this did you some good as well. So it sounds like my 5 V on the coil neg. is OK after all. My problem has to me in the distributor then, I mean what else could cause missing on all cylinders? I borrowed a coil from a friend and I will try it just to rule one more thing out.

I have spent hours reading books on these webers and have mine tuned in fairly well. I do still have a stumble under WOT. I tried changing the exhaust pump to 0 and it seemed to help a bit. Focus then shifted to solve this problem. Hey does your amp gauge ever jump a round? Mine does a bit and I don't know if its a Z thing or is signaling an electrical issue.

[Carl Beck]

Just a comment..

If I'm following this correctly - TBK1 has a 77 280Z with the L26. Glenn72 has a 72 240-Z with an L28.

The tach's in the 70-73 240-Z's function via an inductive loop, but the tach's in the 280Z's use a negative coil trigger. So the tach hook-up's will be different between the two...

I think that the 240-Z's were equipped with an Amp Meter - and the 280Z's used a Volt Meter.

Glenn72 what coil are you using?

What advance position, do you have your distributor set too? That is to say what is the timing curve your trying to use?...

regards,

Carl B.