No spark at plug, no brain in skull

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MoparManimal

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I'm having trouble tracking down an ignition problem on a 67 Coronet with an Orange box. Car ran great a couple weeks ago (minus the weak bottom end). I swapped the engine out and now I have no spark and I'm baffled. Everything is wired the same as it was. Dual pin ballast resister. Using my timing light I get flash on the wire going into the distributor but I get nothing coming back out towards the plugs. I feel like I've double and triple checked that the wiring is correct to the ECU and coil (using diagrams from other threads found on this site, actually). Black from the ECU on the - side of the coil. Dark blue and the brown ign2 "start" on one side of the ballast going to the + at the coil. Blue striped from the ECU mated to the 12v ign1 "run" on the other side of the ballast. All as it was before. I've got 5-6v on the coil + with key on and 9-10v when cranking (seems lowish?). Along with checking the wiring basics I've swapped everything (for giggles), 3 different ballast resisters, 2 ECUs, 2 coils, 2 distributors, caps, rotors... and back again. It's driving me nuts. I also added another ground strap to the block at the ECU and tried bypassing the ballast resistor completely. Still no spark.

It seems to me if I have spark going into the top of the distributor and I get nothing on any plug wires then it's either 1) weak spark but enough to trip the timing light close to the source (coil) but not very far from it (even right at the cap), or 2) the spark is happening at the wrong time and not making the jump from the rotor to the leads in the cap (which doesn't seem possible given distributor adjustment). Right? Am I missing something?

I think I'm in the forest/trees mode and I have to be overlooking something simple. A fresh perspective would be helpful. Any thoughts?

THanks,
Chris
 
Is the case to the Orange box grounded? I run a ground wire to them to be sure. Scrape the paint off the box where the screw goes.

I can't impress enough to have good clean grounds.
 
I would...........

First make sure you have a "hot" spark. Bear in mind the 12V circuit is different between "using the key" to crank and "jumpering the relay" to crank.

Best way, then is to "rig" a test gap...........even a plug....from the coil tower to ground. Crank and see if you have a good hot snappy spark

If you have someone to twist the key, even better is to take a screwdriver, and ground it with an alligator clip lead. Hold the driver up right at the top of the coil tower and have the other crank the engine. A good snappy hot spark should occur at least 3/8 more like 1/2" long

If that is OK, I'd check cap for dirt, moisture, damage, and rotor. Then check timing.
 
I'd look at rotor phasing, incompatible rotor to cap, bad cap to rotor center terminal contact.
I've seen, on a few occasions, a bent center contact on the rotor, just missing contact with cap contactor. I've also seen missing cap center contactors. I've also seen caps and rotors mismatched.
 
If its a LA, Intermediate shaft left on the workbench, thus distributer not turning. That's a DOH! / brain fart scenario. Stranger things have happened.
 

1) If You have a steady pulsing flash from the coil wire, the dizzy's turning
2) What is the battery V when cranking, are You using a jump-box or booster?
3) Take a spare spark-plug and cut the ground electrode off square just before it bends into the 90, any good spark will jump that readily & test at the coil wire.
4) Are You certain the intermediate shaft is oriented correctly, is the rotor pointed at 1 or 6 w/the eng at TDC?
5) What engine is this? Is it possible You mix & matched different damper/timing covers?
 
Let's see... starting from the top... Dist was not off 180 and the box was grounded. Battery V dropped to 10 or 11 during cranking depending how much charge was in it at the time. Didn't change much with a booster on it. Manual spark tests with a screw driver or modified plug yielded nothing. I couldn't see or hear an arc. Timing cover is correct (plus I verified TDC using piston stop), intermediate shaft is good, everything pointed to initial timing being okay. I ended up getting an in-line spark tester and it turns out I was getting spark albiet weak. Enough to light the LED in-line tester, but not enough to trip the inductive sensor on the timing gun.

I did change out the cap and rotor to a known matched pair (good idea on that BTW) and I crimped new ends on the factory harness for ign1 and ign2 at the ballast resister. I also redid the grounds for the millionth time, pulled the spark plugs and wire brushed them. Voltage is still not quite where I'd like (still not tripping the timing light) but it did fire. It fired!

Now it seems I have a low fuel pressure problem. It runs on starting fluid but that's it. If I'm honest I think the problem was the rotor. It did look a little bit bent on the center tab so I probably messed it up one of the times I pulled the cap on and off when I was setting initial timing. I didn't have much time to play with the car this weekend but even just getting it to vroom for a few seconds on starting fluid was a victory.

So... thanks all for the advice and I may be back for more :)

Cheers,
Chris
 
MoparManimal said:
Let's see... starting from the top... Dist was not off 180 and the box was grounded. Battery V dropped to 10 or 11 during cranking depending how much charge was in it at the time. Didn't change much with a booster on it. Manual spark tests with a screw driver or modified plug yielded nothing. I couldn't see or hear an arc. Timing cover is correct (plus I verified TDC using piston stop), intermediate shaft is good, everything pointed to initial timing being okay. I ended up getting an in-line spark tester and it turns out I was getting spark albiet weak. Enough to light the LED in-line tester, but not enough to trip the inductive sensor on the timing gun.

I did change out the cap and rotor to a known matched pair (good idea on that BTW) and I crimped new ends on the factory harness for ign1 and ign2 at the ballast resister. I also redid the grounds for the millionth time, pulled the spark plugs and wire brushed them. Voltage is still not quite where I'd like (still not tripping the timing light) but it did fire. It fired!

Now it seems I have a low fuel pressure problem. It runs on starting fluid but that's it. If I'm honest I think the problem was the rotor. It did look a little bit bent on the center tab so I probably messed it up one of the times I pulled the cap on and off when I was setting initial timing. I didn't have much time to play with the car this weekend but even just getting it to vroom for a few seconds on starting fluid was a victory.

So... thanks all for the advice and I may be back for more :)

Cheers,
Chris
Click to expand...
thanks for the follow up.
 
You should be checking spark at the coil tower. If you have weak spark there, there is no sense (for the moment) worrying about anything else.

10V at the coil? Cranking? That is probably minimal but workable.

When you check spark I NEVER (if possible) use the stock resistor coil wire. I ALWAYS try and use "wire" either a wire core coil, or a grounded probe held at the tower.

You may have a weak coil. If you have a tach connected, temporarily unhook it. There should be a maximum of two wires hooked to coil+.......the wire from the ECU, and a tach.

The coil + should only have one terminal and possibly a radio supression cap. You might try jumpering 12V right to the coil during cranking to see if that improves the spark. Do NOT leave that jumper connected for long, no longer than necessary to test
 
rustycowll69 said:
a weak coil is a possibilty. Look for leaks and check for resistance.
Have you checked the gap between reluctor and pick-up?
Click to expand...

Another thing you can do if you suspect pickup trouble is to disconnect the distributor connector, and "take up" the engine side of the connector. With the key "on" tap the bare pin of the engine harness side on ground. Each time, this should produce one "snap" spark
 
67Dart273 said:
You should be checking spark at the coil tower. If you have weak spark there, there is no sense (for the moment) worrying about anything else.

10V at the coil? Cranking? That is probably minimal but workable.

When you check spark I NEVER (if possible) use the stock resistor coil wire. I ALWAYS try and use "wire" either a wire core coil, or a grounded probe held at the tower.

You may have a weak coil. If you have a tach connected, temporarily unhook it. There should be a maximum of two wires hooked to coil+.......the wire from the ECU, and a tach.

The coil + should only have one terminal and possibly a radio supression cap. You might try jumpering 12V right to the coil during cranking to see if that improves the spark. Do NOT leave that jumper connected for long, no longer than necessary to test
Click to expand...

I did actually do that - jumper from the battery to the coil +. Didn't seem to make any difference. Could be a weak coil. I put another coil on it early in testing but not since I've done all the latest stuff.
 
Great ideas guys - thanks. I'm really glad btw that I found this community - the Mopar focused forums I used to use seem to be all tumbleweeds these days.
 
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