What causes an ignition system to intermittently cut out?

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magnumdust

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So i'm at a complete loss as to what my ignition system is doing.

The car is rewired via a ron francis kit and the only alteration from their instructions is that instead of the "column/ignition" post, i'm using one of the switched accessory prongs. Because the kit is intended for chevy/ididit type steering columns and can't fit 3 prongs on that post. I wouldn't think this should be an issue, but tomorrow's last straw before i concede to sending to a shop is to splice the column wires and put the ignition prong there.

While running if you try to use a timing light, you'll see that there is an intermittent miss. Instead of the constant strobe, it will be flashing and then a half second-1 second of nothing, then it will flash like normal and repeat the cycle.

1st ignition setup:
4-pin hei with a pro-comp e-coil mounted to a piece of aluminum for a heat sink(thickest sheet i could find at ace hardware). Wiring was from the acc. post to a 4 pin relay, same relay also turns on my efi system.

It runs and sounds okay cold, then goes to hell as soon as the car warms up a little(say 2-3min in the driveway). I tried a few modifications, redid the hei mount, but the problem persisted.

Then i got frustrated and figured something wasnt working for me w/ the hei. So i purchased the second ignition system. A nice pertronix II billet distributor.

The car ran *slightly* better, but the problem persisted yet again. I tried buying another coil to make sure it wasnt the pro-comp coil. Still the problem persisted. I eliminated the relay from the wiring and still the problem persists. :banghead:
 
the miss shows up on the timing light?...

ever try another timing light?....

can you feel the miss driving down the road?
 
70aarcuda said:
the miss shows up on the timing light?...

ever try another timing light?....

can you feel the miss driving down the road?
Click to expand...

badly, and it gets progressively worse as you drive. The car was "fine" for about 4 miles then it felt like the whole car feels like its only running on a few cylinders.
 
You cannot go by a timing light. Many of them will not trigger on every single fire

Since you seem to have a few parts, I would "rig" each ignition system using NO parts from the other system, and try each system separately.

Eliminate all harness in car wiring, and "hot wire" it from a good solid point such as the starter relay.

Do this with both systems.

Double check all high tension components, cap, rotor, coil wire and plug wires.

And speaking of the coil, suspect it as well. It used to be common, "back in the day" for a coil going bad to fail "partially" when warm / hot.

I'm not normally one to "throw parts" at a problem, but this might be the time.
 
67Dart273 said:
You cannot go by a timing light. Many of them will not trigger on every single fire

Since you seem to have a few parts, I would "rig" each ignition system using NO parts from the other system, and try each system separately.

Eliminate all harness in car wiring, and "hot wire" it from a good solid point such as the starter relay.

Do this with both systems.

Double check all high tension components, cap, rotor, coil wire and plug wires.

And speaking of the coil, suspect it as well. It used to be common, "back in the day" for a coil going bad to fail "partially" when warm / hot.

I'm not normally one to "throw parts" at a problem, but this might be the time.
Click to expand...


I did mention that i double checked the coil using a standard parts store 12v coil.
 
^^^ This. Did you upgrade the stock alternator before/during the f.I. swap?
 
Abodybomber said:
^^^ This. Did you upgrade the stock alternator before/during the f.I. swap?
Click to expand...

Will find out the volts @ the coil tomorrow. However, if it were less than 12v, the efi system would bug out too.(it doesn't seem to be)

It's a stock alternator, but its one of the gargantuan 90amp alternators. And my volt gauge shows its not having trouble keeping up.
 
That part (the alt setup) should be good. I just didn't know,what you had.
 
This sounds,like a primary voltage(before the coil...),problem.
 
Abodybomber said:
This sounds,like a primary voltage(before the coil...),problem.
Click to expand...

That's what I "think" as well, which is why I suggest wiring up as "hot wired"--to eliminate all factory wiring and therefore "split" the problem...........

is it

A: in the ignition system proper or

B; a primary power supply problem
 
I wired both the ignition and efi separately today. I'm showing 11.8v at the coil.

Still the problem persisted. I'm gonna check to see if the efi lost its tune and maybe once it warms up the oem tune isnt enough for the engine.(longshot though i think)
 
You are NOT running a coil resistor, right?

Under what conditions is this measured? Engine off? What is battery voltage?
 
67Dart273 said:
You are NOT running a coil resistor, right?

Under what conditions is this measured? Engine off? What is battery voltage?
Click to expand...

Engine off, key on

My dash volt gauge shows the batter at 12 volts key on. 14 while the engine is running.

edit: no, no coil resistor. The car has 100% new wiring and i didn't bother hooking up the factory style ignition.
 
KitCarlson said:
Have you checked the engine to firewall ground connections?
Click to expand...

Well a lack of grounding is what may be the issue, but on top of that i found another issue.

On the advice of my friend i ran a test wire ground from the neg. side of my coil to the block, the car went from starting and running like crap to not starting at all.

So then i rechecked the timing and found that i made a tragic error. The distributor alignment on my parts store distributor was off and at TDC the rotor didn't point to number one.(So we just numbered around that issue). The pertronix distributor isnt a pos, and it does point in the right direction at tdc.

Today i was gonna put it all back together with the correct timing. And what do you know, the first storm of fall is here. :banghead:

My current hypothesis is this: The coil didn't have good grounding and was giving an intermittent spark that allowed the car to run even with the timing being off.

Maybe tomorrow the rain will let up.
 
NO

First, there is no "ground" on an ignition coil except on MSD or other capacitive discharge systems.


By grounding the neg side of the coil, you eliminated the switching action that takes place, here's how these work (except for MSD, which works like a photoflash)

Power comes from the key, possibly through a ballast if used, and to the positive side of the coil

If you are using "a conventional style" ignition which is NOT MSD or "capacitive discharge,"

so points, Mopar ECU, pertronix, or GM HEI module, they work by a trigger in the distributor which controls "the box" which then................

SWITCHES the NEG side of the coil to ground at the time of the ignition trigger (reluctor wheel)

It is IMPORTANT to have the battery, the engine and the body grounded together, and IMPORTANT to have the regulator and ignition module grounded to the body, or in the case of HEI, "in the distributor" grounded to the engine

When you said? above? that your coil voltage was 11. something, this is LOW!!! Either you have a lot of voltage drop, or the battery is low or bad. That is why I suggested wiring this up with NO harness being used from the car, rather, "hot wire" a system until you discover the problem.

A fully charged battery should be 12.6V. This means that if the battery is "up" and you "hot wire" the system, even if the key is on and supplying other loads, the thing should be over 12V for a bit

So far as the distributor "pointing wrong............."

If you have some serious mechanical /internal issue with the distributor, it could be that the rotor is not "in time" with the trigger. In a stock Mopar dist. this can happen if the reluctor wheel is installed for a big block instead of a small block. There's a left and right arrow on the top of the reluctor wheel. You must be using the "key" slot coinciding with the CW arrow for a SM

Otherwise, as one on here famously said, "the rotor can point to china." What this means is, in the case of most any US V8, you can close your eyes and "toss" the distributor into the engine. On a Ford/ GM, with gear drive, this can be ANYWHERE. On a mopar, it will be one of two directions.

Then, you simply bring up no1 ready to fire and stuff the no1 wire in wherever the rotor points, set the timing the last few degrees and it will RUN

In other words if the timing HAD been correct, and nothing mechanical slipped anywhere, there is no reason to screw with the distributor or timing.

But you should be able to CHECK the timing, even "on the starter"
 
Have you checked the engine to firewall ground, HEI ground?

Snap us a picture of the ignition wiring for the HEI, distributor, and coil. I seem to remember from a way back post that the wiring was a mess. Now that it has been rewired a look may help.
 
Keep thinking about it like this.
Four things are needed to run, compression, fuel, timing and spark.

Compression, lets assume for now that it is not intermittantly changing. (unless the valves are adjustable and are too tight)

Timing, could be a factor but again not likely to change intermittantly. (EFI though, who knows)

Fuel, who knows but it's verifyable.

Spark, also who knows but verifyable.

The 4 pin HEI modules require a full 12 volts to function correctly.
I think Del had a good suggestion that should be verified for sure. (Power both the EFI and the HEI units separatly with a direct to battery connection), and that coupled with your EFI software chk.
This would answer a lot of questions I think.
 
To add to TB, what is the running battery voltage? Many EFI systems get fussy on low voltage
 
So let me try to update this as best i can.

1. For everyone who seems to have missed it, there is no HEI on the car now. I swapped to a pertronix distributor.

2. Timing was an issue because after the fire i had to pull the distributor to replace the guts. But i thought i had that all sorted well before now as the car did fire and *seem* to run okay before i finished the rest of the wiring.

3. When i swapped to the pertronix distributor, the rotor was clocked differently than the mopar distributor and that had the car out of time.

4. checked software on the efi, no issues there.

So here's where i'm at today...really really F'ing hating this car. 4yrs and i've driven it maybe 1500 miles(a very high guestimate). At this point, i'm just want to make it run so i can get rid of it ASAP.

So i started off yesterday verifying timing and was sure i had it correct, rotor points to number 1 w/ number 1 @ TDC. I routed the plug wires and proceeded to start it. I had a succession of little backfires, so i retarded the timing a bit, got a few coughs, I had to rotate the distributor to the point where the wires would need to be re-routed for it to even run. And when it did, of course it ran like crap.

The battery was low, and prior to the above, i went and had it charged. So at rest it read 12.5v(voltmeter), when running it the gauge in my car(hooked to the starter solenoid) reads 14v.
 
May have figured it out. We'll see what happens next week. I think the 02 sensor is bad. Everything else is new and getting the right voltage, but the 02 sensor came with my used efi kit and I was sold to me as "everything works". But a bad 02 sensor could account for the erratic missing that the car does now.
 
I've got a new Holley HP system, "just the computer" and harness upgrade for my old Holley Commander 950. Partly my own fault, I damaged the O2 sensor. The car didn't run bad with the O2 UNPLUGGED but with the bad one plugged in it would barely run. It was not driveable by any means. So you might try just simply unhooking the sensor
 
I would try that, but my new wideband 02 sensor is suppose to arrive on the same day i have time to work on it. So i'll probably just put the new one in and see what happens.
 
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