No spark / running out of ideas

I pulled off the old heads and put on some gt40 heads from 5.0 as well as an edelbrock performer intake.  I did new plugs and wires at the same time.  After I put everything back together I don't have a spark...   Initially it looked like the distributor cap was bad.  The spring loaded connection between the cap and the rotor was tired and didn't seem to be making a connection.  I replaced the cap/coil and got a new battery with more cranking amps ( i think 900) at the same time.  Still no spark.  I tested the timing light on a car at this point as well and it does work....   I then replaced the distributor with a davis unified ignition.  The cables from the battery to the solenoid were pretty corroded so I replaced those.  There was some dip in the voltage to the coil with cranking so I got a second battery and connected the hot wire to coil to it to make sure I was getting 12v to the coil.  Still nothing.  The DUI people said that the distributor would need to be spinning ~ 300 rpm to make a spark.  The starter was not doing that so I replaced it (solenoid to) and while the cranking speed is much better Im still not getting any spark.  I cleaned the ground site on the block really well.  I not sure if maybe raising the compression is making it harder on the starter and I dont have enough cranking speed.  I may add another battery I have in the garage to the mix.  I did the test that DUI prescribed on the coil/distributor and it seems to check out.  I emailed them as well.  I'm stumped.

Okay, ignore (almost) everything I said below the dotted line since I thought you had conventional coil and points.  After writing that up, I when back and saw that you replaced the distributor with a David Unified Ignition (distributor).  I thought you had gotten a new coil, not an electronic distributor, so had to look it up.

That said, I honestly don't buy the '300 RPM or it won't spark line).  A standard coil and points will spark (if appropriate voltage) whether it is 5,000 RPM or 1 RPM.  The problem with this all-in-one unit is it is hard to determine where the problem lies, as well as trigger a spark.

You said you have +12v voltage to the unit.  I'm assuming it has the snot grounded out of it so you don't need a separate ground (negative) connection.  However, in this picture https://www.jegs.com/i/DUI/314/M35820BK/10002/-1

 I see red and black wires, so it could be possible that it needs a separate ground along with 12v power.  Make sure you have a good ground; maybe the electronic module is internally isolated and it needs its own ground separate from the distributor body, and it needs to be a good ground.

What's the test that DUI had you do?  I'm curious.  That info will help us understand what is going on, and how that test confirms operation.

There should be a way to confirm that it will generate a spark.  

And even if you installed the distributor incorrectly (not at TDC), the most that would do is to cause a spark at the incorrect time in one of the strokes.  But there should still be a spark.  So that isn't it.

At this point, I suspect a wiring issue (ground), or an issue with the unit.  The problem is you don't have a separate coil so you can test that high tension line or the coil itself.  If it is powered correctly, then either it is not sensing the rotating shaft (pick up), or it is flat out DOA.

Interesting, my '97 with PCM GT40 MPI and electronic ignition still uses a conventional distributor cap and rotor; the 'coil' is part of the ignition module, which is near the throttle body, but it has a high tension line that goes to the center of the distributor just like a convention points distributor (except instead of points it has a pick up that sends the signal to fire a spark to the module).

Let us know.

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IF YOU HAVE STANDARD COIL AND POINTS:

I'd do the following:

1.  Check the points gap?  Are you sure they are opening and closing by the distributor shaft lobes as it turns?  I've had them work lose before on a car and stop opening.

2.  With the ignition on (12v to the coil), you should be able to manually open and close the points with a screwdriver.  The points will probably spark slightly, and if you run the coil high tension output to near a ground, you should get a good strong spark.

3. If you still are not getting a spark and you still have 12v to the coil, jump the negative side of the coil directly to ground).  You should be able to short that negative wire fro the coil directly to ground (which imitates points closing, thereby powering/charging up the coil).  When you un-short it from ground (which is the same as the points opening), you should get a spark out of the high tension line.  If you don't, then your coil is suspect (note:  Don't leave the coil connected to ground for long periods; it may overheat).

4. If you get spark when shorting and un-shorting the coil negative side to ground but don't when you move the points, then you have a wiring problem between the coil and the points.

5.  If you see a lot of points sparking when opening/closing them by hand and you are getting a weak or no spark from the high tension wire, it could be the condenser is bad.  That rarely happened back in the day where all cars had points, condenser, and coil (at least in my case), but you will not get a good spark if the condenser is bad (or it could even be shorting out).  So if you did all of the above with no spark, I'd probably change it.

Let us know what you find out.

Get the VOM back out and check the resistance between a good ground on the block to the DUI. This should tell you if the DUI has a good ground?

Jim, I take it there is only one wire connection to the DUI, the +12v supply line, and not a separate ground connection (ground is through the distributor).

Let us know when you get a chance on the tests DUI had you do to confirm operation.

Also, the coil and magnetic pick up tests only test static resistance.  They don't have you do a manual energize test on the coil, nor do they have you do anything to confirm that the magnetic pick up actually sends the signal.

I know this is a lame question, but is the pick up wheel/spokes there and lined up to where the pick up sensor is?

I'm gonna dis my own suggestion & say it ain't worth the time, as long as you are sure rotor is turning when engine cranks.  If you are getting 12V to input of dizzy & have a good ground, then it is either trigger module or coil.

I assume you have good connection to spark plug wires.  Have you tried to pull plugs & watch for spark from them? 

You replaced starter - are you sure it is turning the right direction?

I worked in a heavy equipment assy factory & we had brand new electronics modules, that had passed testing at supplier, fail every day.  Amazing, isn't it.