Hopefully someone has had the same issue.. last week I parked in the driveway, watched some TV came back outside and fixed my exhaust leak on the drivers side. I went to start it up and it wouldn't. It cranks fine, battery has good voltage but it wasn't getting spark while cranking. I put the test light between the coil and distributor and it only sparks when I turn the key from run to start and then once more when I turn they key back from start to off. I immediately thought burnt pickup in the dizzy. REplaced the dizzy and same thing. I checked power to coil and its good. however i removed both positives from the coil and checked the negative side(the one with the green wire that comes from the ignition module) and it had 9 volts.. surely this isnt normal and means i have a burnt ignition module right?

 

sorry didnt really give much info.. its a 1979 f100 with a 302 and duraspark distributor and an msd blaster 2 coil. stock ignition module. I actually got my MSD in the mail right before it started giving me trouble.

Thanks to everyone who reads this

 

Let's find out. Reconnect the coil, and connect a 12-volt test light from the TACH TEST (negative) terminal of the coil to clean, unpainted metal on the engine (ground). Crank the engine over from the cab, and the light should BLINK. If the light BLINKs, then you know that the pickup module is sending a trigger signal to the ignition module, the module is firing the coil, and it has power. If the light does not blink, does not come on, or just stays on, then the module is not firing the coil. Since you've replaced the pickup module, then either the ignition module is not receiving power, or it's bad.

I can't say for sure that you shouldn't see voltage on the TACH TEST signal at the coil with the coil power removed. It's not intuitive to me at first why it would happen, but it's possible that there is capacitance inside the module that may retain some stray voltage. A multimeter is high-impedance, so it will stay at the voltage you're reading for some time if the capacitance is otherwise open-circuit. I'm not saying it's normal, I'm just saying it's not useful information at this point. But your question was if the ignition module is bad, and I can only tell you if it's bad by whether or not it's doing its job, which is why I've outlined the test light procedure above.

If the primary winding resistance of an aftermarket coil is much lower than the stock coil, it can stress the power transistor in the ignition module due to the added current draw. I read on MSD's website that the primary winding resistance of the Blaster 2 coil is 0.7 ohms which is less than the stock coil. This will increase the power dissipated in the module. The module is not designed to properly dissipate heat in the first place, and if it's already old to begin with, the added power dissipation could be enough to put it over the edge.

As a side note, it's really not cost effective to install a "performance" coil on an otherwise stock ignition system. For a given plug gap, it takes a specific voltage to jump the gap. Any more and the plugs burn up prematurely, any less and the spark simply won't jump. The stock Duraspark system with the stock coil does the job exactly as needed.

 

Thanks for the reply, I'll test that tomorrow when i have a helper. also is the ignition module required to have a ground through the mount? Mine is sorta loosely mounted on the fenderwell..

 

Nope, no ground at the module itself. The ignition module grounds in the distributor. The BLACK wire going from the ignition module to the three-prong connector at the distributor is responsible for grounding the ignition module.

 

I checked my ground wire coming out of the ignition module and it reads the same positive 9 volts that im getting sent to the negative side of the coil..

 

I'm assuming you're doing this test with the other connector hooked up (RED and WHITE wires)? What is the position of the key when you're doing this? Where are you putting the red and black leads of your multimeter when performing this test?

 

Correct the the 2 pin plug coming out of the ignition module is plugged in. The key is in the run position and I am using a digital multimeter with the positive lead touching the black ground wire coming from the ignition module( not connected to the dizzy during this test.) and the black lead from the multimeter touching the grounded frame of the truck. Multimeter shows a positive 9 volts.

 

Thanks for that information. If you know for sure that the battery is a full 12 volts, and you're seeing a reading less than the battery voltage at any connection to the module with the 4-prong pigtail disconnected, then the only way that's possible is if there is an internal short to the casing of the module itself. In other words, if you've disconnected the module's ground, but the voltage is dropping internally somehow, then there must be a ground coming from somewhere else.

If you insulate the module from the fender so that the case is not touching any sheetmetal, does the voltage you're measuring on the BLACK wire (disconnected from the distributor, just as you measured before) go up?

 

I wired up the MSD in place of the stock ignition module today and i am getting spark now, means my module was burnt or the wiring went bad somewhere.. On;y problem is I have a rebuilt duraspark dizzy and i dont know which wire is positive and negative. I have the red and black one from the dizzy going to the purple msd wire and the purple and black from the dizzy going to the green msd wire. it sparks but the truck wouldnt start.. not sure if I dropped the dizzy in a tooth off or not. Battery is dead.. guess i'll try again tomorrow. Thanks guys

 

What MSD box is this? I'm not sure what's compatible with what. The wire colors coming from the Duraspark distributor should be ORANGE, PURPLE, and BLACK. ORANGE and PURPLE are the Hall Effect trigger signals, and BLACK is ground.

 

The wires coming from the distributor are not orange, purple or black. Its also from NAPA if that explains the odd colors.. Red/Black , Purple/Black , and the other is ground. Its a Digital 6al, I think its the same wiring as the Normal 6al. The only difference I know of is the revlimiter adjustment.

 

Here is a link to the MSD instructions for this unit:

http://www.msdignition.com/uploadedF...5_frm29772.pdf

The top of page 15 shows how to wire in the original Duraspark pickup into the MSD box. I'm guessing that RED with BLACK stripe on the Napa distributor is supposed to be the same as the original ORANGE wire. If that's the case, then looking at this diagram, it sounds like you've got it wired correctly in your previous post, but it mentions some other connections too that you should check.

Since it sounds like you've got spark, you'll want to move on to check for fuel, and that the distributor is statically timed correctly (and not off a tooth or 180 degrees out).

 

Thanks for the help everybody! I took the battery over to O'reillys and got it charged up. Went back to the house and tried to start it up once more before messing with pulling the dizzy and nothing but a sputter, went 180 out nothing.. went back to where it was and clockwise nothing.. two counter clockwise and it was perfect, cranked right up. Notes on the msd runs alot smoother and my exhaust doesnt smell like gas! actually it doesn't really smell like anything too much. now i need a cheap tach since i have a wire for it! Also in case anyone is searching for similar issue.. Napa Ford Distributor magnetic pickup wires colors red and black with black and purple. I'm a master at dropping that dizzy down into place now haha

 

I have no spark on my 1975 6Cyl, which is in a 66 F100. The EI, coil and distributor were all installed new a few months ago and it ran OK. The only thing that's happened that I know of is that a couple of the wires, where I had spliced them to the ignition wires coming out of the firewall, likely touched together where they were exposed (I know, they should have been covered, but I just got it running and in out of the weather). Now, when I put the test light on the BATT side of the coil and turn the key to ON, the ligght comes on. But when I attach it to the TACH side and cranck the engine it doesn't blink, as I understand it's supposed to. Am I right to assume this is likely a problem with the EI module, and this might have happened if an when those wires touched?