Ignition problem- New parts, no spark- 454 HEI

HotRodPC · Jan 21, 2014

suburble said:
OK. Worth checking in any case. It's cranking over just fine on the starter, though. Problem is it has no spark and won't fire off.

I understand that. But, power to the dizzy in most cases, does actually go through the starter solenoid.

It's been said many times, although not true, that the S on the solenoid means Start, and the R means Run. In older vehicles, you actually got 12 volts while cranking and as soon as the motor started, the power to the coil was cut to 6v. This could be done through the Solenoid to a RESISTOR WIRE, or a Ballast Resistor. Just suggesting to check it so that you know the ignition system is getting it's power to and through the solenoid.

suburble · Jan 21, 2014

HotRodPC said:
I understand that. But, power to the dizzy in most cases, does actually go through the starter solenoid.

It's been said many times, although not true, that the S on the solenoid means Start, and the R means Run. In older vehicles, you actually got 12 volts while cranking and as soon as the motor started, the power to the coil was cut to 6v. This could be done through the Solenoid to a RESISTOR WIRE, or a Ballast Resistor. Just suggesting to check it so that you know the ignition system is getting it's power to and through the solenoid.

I'll definitely give it a look, then.

chengny · Jan 21, 2014

-Neutral safety switch is not the problem per functional testing; the starter turns the motor over just fine in P or N, but not in gear.

I just went back and read the "expert advice" I provided to help you with your no-spark issue - WTF was I thinking!

Needless to say; you can disregard everything I posted about the NSS having anything to do with the coil primary circuitry. The NSS/CSS are to the control circuit of the starter solenoid - they have nothing to do with the ignition system.

I apologize if I made you waste any time on a wild goose chase. I was trying to answer too many questions in a short period of time (and probably drank too many Natty Ice's in a short period of time as well).

Some info on the solenoid R & S terminals and how they relate to the ignition coil:

chengny · Jan 21, 2014

So... If I'm correct in assuming I should be seeing 12v at the plug in from the firewall to the distributor (which I am not seeing on my multimeter), then it should be either a bad ignition switch or a wiring issue (possibly the 2nd fusible link).

That would be correct. But then you also say/ask the following:

I'm assuming the 2-wire connector from the firewall is keyed 12v for the coil, and should show 12v across the 2 terminals when they key is at "start" or "run".

When I measured across those 2 terminals (with my wife inside the 'burb turning the key) I saw a small jump to about 1.5v when the key was first turned, then nothing.

Am I correct in thinking I should be seeing 12v?

That would be wrong. Checking for voltage across the terminals of the 2 wire plug would not show voltage even if it was available. The only wire you should be concerned with is the red wire (i.e. the one that clips onto the stab marked BATT.

If you look closley at the top of the square plug receptacle (it sticks out on the LH side of the coil cover) you should see 2 markings with a stab under the cap. One is labeled TACH (this is the impluse signal to any tachometer that may be installed), the other will be marked BATT (this is the power from the ignition switch to the coil).

The wire that connects to the stab under the BATT marking is where you will put the red probe of your meter.

The white wire has nothing to do with measuring coil supply voltage so disregard it.

What you need to do with the black test probe is touch it to a good, clean & and paint free area on the body or frame. Doing that will provide your meter with a proper ground.

With the black probe of the meter now connected to ground, the red probe in contact with the red wire in the harness plug and the meter set to VDC - turn the ignition key to the RUN position.

If everything is okay, you should get a reading of about 13.5 volts.

suburble · Jan 21, 2014

chengny said:
The wire that connects to the stab under the BATT marking is where you will put the red probe of your meter.

The white wire has nothing to do with measuring coil supply voltage so disregard it.

What you need to do with the black test probe is touch it to a good, clean & and paint free area on the body or frame. Doing that will provide your meter with a proper ground.

With the black probe of the meter now connected to ground, the red probe in contact with the red wire in the harness plug and the meter set to VDC - turn the ignition key to the RUN position.

If everything is okay, you should get a reading of about 13.5 volts.

Yes! Thank you, that's what I was (unclearly) trying to ask. I need to re-measure, since I checked across the 2 terminals, and not red wire to ground. It sounds like my testing yesterday was not conclusive.

Thanks.

suburble · Jan 21, 2014

OK, now we're getting somewhere. I retested with the meter between the red "batt" terminal at the distributor and a body ground and got 11.9v with the key at "run". Switched from body ground to negative battery terminal, same results- also 11.9v.

So... Is 11.9v enough to run the coil?

Thanks everyone for the help so far.

-Josh

chengny · Jan 22, 2014

Yes, you're fine. The GM specified minimum primary coil voltage - that which is required to produce a "robust" spark in the ignition secondary (i.e. enough voltage to produce a bright blue arc across the spark plug gaps) - is 10.5 volts.

NOTE: While 10.5 is stated as the minimum primary voltage in some places, the diagnostic chart below specifies 7 volts as the minimum. Go figure.

Regardless, you are well above the minimum (at least during non-crank conditions). However, things can change when the key is moved to START and the starter motor places a large load on the entire electrical sysytem. Checking coil primary voltage - while cranking the engine with the starter - is the next step. Notice that it is also the first step in the diagnostic chart below:

Do the voltage test again, but this time take it one step further. While you observe the voltage across the red wire/ground test points, have an assistant crank the starter. While the starter is cranking watch the VOM closely. If it is a digital type it make take a second or so to re-calculate and display the change in voltage (if any). If you happen to have an analog multimeter (with a needle type indication) use it - any change in voltage will cause the needle to deflect downwards immediately.

After that - if there is no issue with voltage supply to the coil primary you need to start looking inside the distributor

Here is a description of operation for the GM HEI system:

The HEI system utilizes an all electronic module, pickup coil and timer core in place of the conventional breaker points, condenser and distributor cam. In addition, a specially designed ignition coil, distributor cap, rotor and high tension leads are used to provide and distribute high intensity secondary system voltages to the spark plugs. Typical HEI system components are illustrated in Figs. 1 and 2.
The magnetic pickup consists of a rotating timer core attached to the distributor shaft, a stationary pole piece, permanent magnet and pickup coil. When the distributor shaft rotates, the teeth of the timer core line up and pass the teeth of the pole piece inducing voltage in the pickup coil which signals the electronic module to open the ignition coil primary circuit. Since this is a full 12 volt system that does not use a resistance wire, high current saturation occurs in the coil primary windings. Maximum inductance occurs at the moment the timer core teeth are lined up with the teeth on the pole piece. At the instant the timer core teeth start to pass the pole teeth, the module opens the primary circuit, and the current decay causes a high voltage to be induced in the ignition coil secondary winding. The high secondary voltage is directed through a specially designed cap, rotor and high voltage leads to fire the spark plugs.
HEI systems use conventional vacuum and centrifugal advance mechanisms. The vacuum diaphragm is connected by linkage to the pole piece. When the diaphragm moves against spring pressure it rotates the pole piece allowing the poles to advance relative to the timer core. The timer core is rotated about the shaft by conventional advance weights, thus providing centrifugal advance.
Some models are equipped with and Electronic Spark Control (ESC) system that controls spark timing in order to provide maximum engine performance while preventing detonation. The ESC system consists of an engine mounted knock sensor and an electronic controller, Fig. 3. ESC is a closed loop system that monitors engine detonation through a sensor and constantly adjusts ignition timing to provide the maximum usable spark advance while preventing prolonged detonation.
The ESC knock sensor monitors the presence and intensity of engine detonation by sensing the resultant vibrations. The sensor produces a voltage signal which is proportional to the intensity of the detonation and this voltage signal is transmitted to the controller. The ESC controller is a hard wired signal processor/amplifier that operates in the 6-16 volt range, and has no memory storage provisions. The controller monitors knock sensor voltage output, processes these signals and controls the amount of spark advance through a special circuit in the HEI ignition module.
In addition, models with automatic transmissions include an ESC vacuum switch. The vacuum switch provides a signal to the ESC controller during throttle tip-in which causes the module to momentarily retard spark timing to prevent detonation on acceleration.
Component views and diagnostic chart for your particular type of ignition system - "HEI without ESC/EST and with Integral Coil":

chengny · Jan 22, 2014

THE GM HEI SYSTEM

Any conversation about electronic ignition leads to the GM HEI, which is an abbreviation for high-energy ignition. Chrysler was the first company to offer electronic triggering to the masses; it was available on some models in 1972 and became standard across the board for the 1973 model year. Ford Motor Company made its Dura-Spark system standard in 1975, the same year that GM introduced HEI.
The attributes of electronic ignition, made possible by advances in transistor technology, finally answered the call to eliminate breaker points, and the undesirable features associated with them. The benefits of electronic ignition include:

· The elimination of wearable parts
· High voltage and current output
· Variable dwell instead of fixed dwell (coil saturation)
· The elimination of the resistor circuit
· Allowed for widened spark plug gaps to support leaner mixtures
· Minimized cross-firing (by increasing distributor cap post spacing)

With the arrival of the 1973-'74 energy crisis and the federal government's new fuel economy and emissions standards, the constant degradation of ignition output with breaker points needed to be eliminated. The problem was the constant wear they suffered. As the rubbing block wore, the ignition's output would diminish; additionally, a one-degree change in dwell would impact the ignition timing a like amount, which we'll explain in detail later in the article.

Another concern was the limited voltage input that a breaker ignition could take while still maintaining an acceptable lifespan. Due to the breaker's inability to withstand a constant 12 volts, a resistance circuit was required to reduce the primary voltage to approximately 7 volts. The power was supplied through the ignition switch, arranged so that the engine would crank on full battery voltage, but when the ignition key was released to the run position, the circuit would be redirected and the voltage dropped by a resistance wire or ballast resistor. Abiding by the laws of physics, this limited the spark output potential of the coil, along with the gap of the spark plug.

The HEI difference
When Delco set out to design HEI, it addressed all of the problems with points. By eliminating the mechanical breaker system and replacing it with a transistor that had no moving parts, HEI eliminated wear problems. The additional available energy allowed for a constant output with longer spark plug life and the wider gap that was needed to remain emissions compliant.

Additionally, HEI addressed limited output. It is possible to obtain higher secondary voltage by simply increasing the current in the primary circuit: Coil energy is equal to one-half of the coil inductance multiplied by the current squared. The higher current-carrying capabilities of a transistor over breaker points automatically increased the ignition output. In most breaker point systems, the primary current was limited to 3.5 to 4.0 amperes. Maximum point life was realized with only one ampere flowing across the contacts. As current increased, point life decreased steadily until just over four amperes was reached. Above this value, point life decreased dramatically.

Transistors don't have this limitation. A switching transistor can handle a full 12 volts with a current capacity of over five amperes. This allowed HEI to offer 40 percent more voltage output with 85 percent higher energy levels than the breaker point ignition it replaced.

For the ignition coil to produce maximum secondary voltage, the limit for primary current must be reached before the primary circuit is broken, allowing the field in the coil to collapse and discharge through the spark plug. In a points system, the length of time the primary current is turned on and charging the coil is referred to as "dwell" and is controlled by the cam in the distributor.

Dwell is defined as the degrees of distributor cam rotation the primary ignition circuit is turned on. Most V-8 engines using breaker points have a nominal dwell value of 30 degrees. The dwell angle remains constant regardless of engine rpm. As the speed of the engine increases, the length of physical time that the points are closed decreases. This reduces the available voltage and coil energy.

In a points ignition system, as the engine speed increases, the available energy to meet the demand of the spark plug decreases. HEI eliminated this problem by removing the resistance wire and applying full alternator output to the primary circuit.

Another unique feature of HEI is a dwell period that responds to changes in engine speed. Identified as an expanding dwell, the saturation time of the coil is controlled by engine rpm. At idle, an HEI system will experience a dwell time of 10 to 15 degrees and will increase to 30 to 35 degrees by 2,500 to 3,000 rpm. The ignition now has the output when the engine needs it--at high speeds and under load.

In a points system, it would take 10 milliseconds for the current to reach maximum with a coil that has 2.6 ohms of resistance. The primary windings of an HEI coil have only 0.5-ohm resistance, allowing maximum current to be reached in approximately 3.4 milliseconds. Because it takes less time to reach full coil potential, saturation can be obtained at much higher engine speeds.

A coil can be thought of as a checking account: the more you put in, the more you can withdraw. By increasing the primary voltage input, the secondary output is increased, but more important, the length of time that the spark can burn--and the amperage at which it burns--is also increased. Electricity is passive--it uses only what it needs to get the job done. As an example, an HEI system has the ability to produce 40,000 volts to the spark plug for short periods of time. This can be likened to a car that has a top speed of 150 mph. If the load on the engine only requires 6,000 volts to bridge the gap of the spark plug, that is all that is consumed. In the same manner, a 150-mph car can cruise at 65 mph, using only a small amount of its potential power.

This analogy can be modified to describe an ignition coil: It can produce low voltage for a long time period or high voltage for a short time. Instead of referencing mph, an ignition system is measured in milliseconds (ms) and degrees of crankshaft rotation (CA). As the electrical demand increases, the length of time the arc across the spark plug can be maintained decreases.

Attaching some numbers to this, an HEI system can arc a spark plug for 2ms and 20 degrees CA. A points ignition would, at best, only support approximately 1.1 to 1.5ms and 10 to 15 degrees CA. At higher engine speeds, the coil has less time to charge. There is even less energy available to keep the spark plug lit and turn the fuel into power.

Ford and Chrysler were not as ingenious with their electronic ignitions. While both were able to eliminate the issue of breaker-point wear, the Mopar unit, though transistorized, still used a ballast circuit, limiting spark output. Ford designed the Dura-Spark with full charging circuit voltage but maintained the fixed dwell period of points. As time went on, almost every automaker in the world copied the Delco HEI design; it is considered by many to be the father of all modern ignition systems.

chengny · Jan 22, 2014

Servicing the HEI

Due to its trouble-free nature, the HEI is an often-neglected component. Since it is electronic, many people seem to believe that if it is working, all must be well. That may be the case, but once a problem does occur, it is important to be able to diagnose it. By following the steps in this primer, you will be able to accurately diagnose and repair any GM HEI system. We traveled to Classic Restoration Enterprises in Pine Island, New York, where technician Richard Wiegand worked with us using a brand-new ACCEL HEI unit to illustrate the inner workings of the HEI and how to service it.
There are three main components in an HEI: the ignition module, the pick-up coil and the integral high-tension coil. The other components of the distributor, such as the mechanical and vacuum advance, gear drive and shaft, are all very similar in function to those found on a breaker-point system. Comparing the HEI components to those in a conventional distributor makes it easier to understand and repair.
The ignition module can be thought of as the contacts of the breaker points, while the pick-up coil and reluctor (the tooth wheel on the distributor shaft) serves the same function as the distributor cam and rubbing block. Thus, for the module to charge and then collapse the coil, it needs to receive a signal from the pick-up coil. The output of the pick-up coil is identified as a saw-tooth sine wave and can be confirmed with a voltmeter.
You cannot check the module itself internally, so the diagnostic steps required generally involve confirming operation of everything else: If the other parts test fine, replace the module. Often, the diagnostic steps are skipped and the person working on the car assumes the module has failed, using parts replacement as a diagnostic procedure. The diagnostic steps allow you to avoid this practice.
Check the dwell on an HEI module to confirm the circuit is evoking the longer (expanding) dwell time as the engine speed is increased. To do this, connect a tune-up tach and dwell meter to the "TACH" terminal on the distributor cap and then start the engine. At idle on a V-8, the dwell with a Delco module should be between 10 and 15 degrees. As the engine speed is raised, the dwell should increase to 30 to 35 degrees by 2,500 rpm. If it does, the module is working properly.
Note that some aftermarket ignition modules do not provide the proper expansion of dwell: They often have an excessive amount at idle and provide little increase at high speeds. This can cause a misfire at high rpm, because the coil saturation is not sufficient. Conversely, if the dwell sticks on the module, the engine can exhibit a very rough idle with a dead misfire, hesitation at light load, pinging and overall poor performance. If the dwell period is incorrect, the diagnosis is simple: Replace the module.
The only time a properly working HEI module will show a fixed dwell of around 30 degrees is if an aftermarket CD ignition box, like an MSD or similar unit, is attached. The current draw of the CD unit will drive the module to a dwell period that is similar to that at high engine speeds in a stock application.
Ignition system design is still evolving today with distributor-less and coil-on-plug systems. With every new theory, the same basic premise still applies: Widen the gap of the spark plug to increase the ionization window and keep the plug arced for as long in the crankshaft's rotation as possible. Though no production version of the original HEI system is in use today, it was clearly a design that revolutionized the industry and laid the groundwork for today's modern ignition systems.

NOTE CORRESPONDING IMAGES ARE BELOW THE TEXT

The original HEI design featured an integral ignition coil and a one-wire hook-up of 12 volts. The cap is marked to identify the tach and voltage supply.