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Gm distributorless ignition system

Distributorless ignition systems DIS have been around for almost a decade now, and have eliminated much of the maintenance that used to be associated with the ignition system.

Distributorless Ignition Systems (DIS)

No distributor means there is no distributor cap or rotor to replace, and no troublesome vacuum or mechanical advance mechanisms to cause timing problems. Consequently, DIS ignition systems are pretty reliable. Even so, that does not mean they are trouble-free. Failures can and do occur for a variety of reasons. So knowing how to identify and diagnose common DIS problems can save you a lot of guesswork the next time you encounter an engine that cranks but refuses to start, or one that runs but is missing or misfiring on one or more cylinders.

If an engine cranks but will not start, is it fuel, ignition or compression? Ignition is usually the easiest of the three to check because on most engines, all you have to do is pull off a plug wire and check for spark when the engine is cranked.

On coil-over-plug DIS systems, there are no plug wires so you have to remove a coil and use a plug wire or adapter to check for a spark. If there is no spark in one cylinder, try another. Many engines that are equipped with electronic fuel injection also use the crankshaft position sensor signal to trigger the fuel injectors. So, if there is no spark and no injector activity, the problem is likely in the crank position sensor. No spark in only one cylinder or two cylinders that share a coil would tell you a coil has probably failed.

The coils in DIS ignition systems function the same as those in ordinary ignition systems, so testing is essentially the same. But the driveability symptoms caused by a weak coil or dead coil will be limited to one or two cylinders rather than all the cylinders. Many DIS systems use the "waste spark" setup where one coil fires a pair of spark plugs that are opposite one another in the firing order. Others, including the newer coil-over-plug systems, have a separate coil for each spark plug.

Individual DIS coils are tested in essentially the same way as epoxy-filled square-type ignition coils. First, isolate the coil pack by disconnecting all the leads. Set the ohmmeter in the low range, and recalibrate if necessary. Connect the ohmmeter leads across the ignition coil primary terminals, and compare the primary resistance reading to specifications typically less than 2 ohms.

Then connect the ohmmeter leads across the coil secondary terminals and compare the secondary resistance reading to specifications typically 6, ohms. If readings are outside the specified range, the coil is defective and needs to be replaced. If measuring the secondary resistance of a DIS coil is difficult because of the coils location, try removing the wires from the spark plugs and measure secondary resistance through the plug wires rather than at the secondary terminals on the coils.

Just remember to add in a maximum of 8, ohms of resistance per foot for the plug wires. Here is a little trick that will literally show you if a DIS module and its crankshaft sensor circuit are working: connect a halogen headlamp to the spade terminals that mate the DIS module to the coils.

A headlamp is recommended here because it puts more of a load on the module than a test lamp. If the headlamp flashes when the engine is cranked, the DIS module and crankshaft position sensor circuit are functioning. Therefore, the problem is in the coils. If the headlamp does not flash, or there is no voltage to the module or coil pack when the engine is cranked, the problem is most likely in the crankshaft sensor circuit.

On most vehicles, a bad crank position sensor will usually set a fault code, so use a scan tool to check for a code.

Or, check the crank sensor itself. Magnetic crank sensors can be tested by unplugging the electrical connector and checking resistance between the appropriate terminals. If resistance is not within specs, the sensor is bad and needs to be replaced. Magnetic crank position sensors produce an alternating current when the engine is cranked so a voltage output check is another test that can be performed.A distributorless ignition system replaces traditional distributor ignition systems.

The higher voltage and hotter spark help ignite leaner fuel mixtures used in lower emissions engines. DIS ignition systems use one ignition coil for every two cylinders.

The ignition coil may be designed as a separate unit, called a coil pack or may be built as several ignition coils integrated into a single unit. When configured with individual coils, a repair can be as simple as replacing just the bad coil pack.

However, when configured as a single ignition unit, the failure of one coil in the pack requires the replacement of the entire unit. The ignition module receives camshaft rotation data from the camshaft position sensor. Just like in a distributor system, the camshaft position data is used to calculate when to disconnect power to the ignition coil. When the ignition coil is powered it creates a strong magnetic field. When the power is shut off, the magnetic field collapses, creating a high voltage that flows to the spark plug and jumps the gap to create ignition.

In a traditional distributor ignition system, a single ignition coil generates the magnetic field and spark. The length of the coil on time is referred to as dwell.

Since the coil must serve all cylinders, the dwell time is short especially at higher RPMs. Since a DIS system uses multiple ignition coils, each coil can remain powered for longer periods. The longer dwell time creates a more powerful magnetic field, which in turn, provides a higher voltage and hotter spark. Once the power is shut off to a DIS coil, the field collapses and the spark jumps from the spark plug center electrode to the side electrode in the firing cylinder, causing the fuel mixture to ignite.

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[HINDI] Distributorless Ignition System : Circuit - Animaiton - Advantages

Prominent words coil pack dis ignition distributor ignition distributor system distributorless ignition distributorless ignition system dwell time higher voltage and hotter higher voltage and hotter spark hotter spark ignition coil ignition system ignition systems magnetic field spark plug system traditional distributor traditional distributor ignition voltage and hotter voltage and hotter spark.There are currently two types of ignition systems in use in cars and trucks.

The first is the electronic ignition system and the second is the distributorless ignition system DIS. You can easily tell which you have when you pop the hood by looking at the spark plugs. Prior to electronic ignition, which became ubiquitous in the late 70s and early 80s, there was also the points-type ignition system.

This type of ignition system can be identified by the presence of a small aluminum can mounted either on the side of the distributor or very close to it on the engine. Quite often, except with newer electronic ignition systems, both points-type and electronic systems will also have what is called a ballast resistor mounted to the bulkhead behind and above the engine.

On most ignition systems, the charge that creates the spark is created and contained by an inductive ignition coil. However, some performance ignition systems use a capacitor to store this charge. Whether an ignition system uses a capacitor or an inductor, the circuit creating the charge is broken, causing an electrical field on the ignition primary side to collapse, sending the charge to the proper plug on the secondary side.

Points-type and most electronic ignition systems use a cap and rotor to pass the secondary, high current-voltage spark to the plugs. DIS systems use a series of sensors and switches to open and close the primary ignition circuit and fire the secondary side. The points-type ignition system uses a set of contacts, known as points, and a capacitor to filter AC noiseknown as a condenser, to break the electrical circuit, creating the spark.

The points are attached to a plate in the distributor. As the distributor shaft rotates, a cam riding on a bumper on the points rides up and breaks the points contact. For this reason these are also known as breaker-type ignitions. These ignition systems are capable of passing large amounts of current and electricity, which makes them great for high performance automotive ignition systems.

I had an old Mopar a Charger that I first used on an Accel dual-point the distributor held two sets of points instead of one distributor in it.

gm distributorless ignition system

No spark at the plug? Pull the cap and make sure the points are opening and closing properly and are properly gapped. The problem is keeping even single-point distributors properly adjusted. Performance engines vibrate, causing the adjuster to move over time. Also, even when you use the recommended lube on the cam and rider pad, both wear over time, especially the pad, as do the springs and plates inside the distributor, making them even harder to keep properly adjusted for maximum performance.

It can be done in a couple of hours in your garage with minimal tools.

gm distributorless ignition system

Electronic ignition systems use a magnetic field to open and close the ignition primary circuit. Instead of an ignition breaker, a special type of transistor which is called the pickup that works with a magnetism is used. Instead of a cam spinning on the distributor shaft, a component known as a reluctor rotates with the shaft. This reluctor has several small magnets on it which pass the pickup as the shaft rotates.

The primary circuit is opened when the reluctor magnet passes the pickup, sending a signal to the electronic ignition control module. The control module reads engine speed and throttle position to determine the timing and temperature for the spark. The ignition control module then opens and closes the primary circuit on the ignition coil, sending the spark to the distributor cap, through the ignition rotor, back through the cap, and finally to the plug.

This is what I did with my Charger. Out with the old distributor, in with the new, mount the new racing coil I bought, and hook up a few wires and connectors. The hardest part was finding a spot for the control module and the over-sized racing coil that I liked. Take a look at the MSD performance electronic ignition system in the image above. More things can go wrong with an electronic ignition system, too. The plate that the pickup is mounted to can wear and move, causing the reluctor and pickup to move out of adjustment and stop working.

The reluctor itself can wear and chip in extreme cases.Sure, they eliminated the whirling mechanical device that spins a rotor that aims high voltage to the plugs. But then the OEs had to purchase eight expensive ignition coils—one for each cylinder. When buying millions of these units every year, the piece price is ridiculously low, but it's still an investment.

Let's take a quick look at why they went this route. Distributor technology goes back to a man named Charles Kettering not long after the first internal combustion engine made noise. Today, with a simple crank and cam sensor, the computer knows exactly where the engine is in the firing order and can very accurately trigger when the spark should occur. With this increased accuracy, the next biggest limitation was coil energy at high engine speeds.

At 6, rpm, the engine is firing all eight cylinders 3, times per minute or 50 times per second. This leaves 0. As a result, spark energy is drastically reduced at higher engine speeds.

Of course, this was acknowledged back in the '70s when capacitive discharge ignition systems first became popular with drag racers. See our sidebar on inductive versus CD ignitions and the relative advantages of each. Small Block Chevy Engine So what does this have to do with building a stronger street engine? Imagine if you could convert an original small block Chevy engine over to DIS. What advantages would there be for the average enthusiast?

Sure, you'd have a much more accurate spark that's not affected by backlash in the cam drive system and all kinds of issues with distributors. You'd also have a much hotter spark at higher engine speeds because now you have a single coil for each cylinder, so it has plenty of time to recharge and fire a much stronger spark to the cylinder. In actuality, your engine misfires hundreds of times in just one pass down the dragstrip and thousands of times just driving down to the auto parts store for an oil filter.

You may not feel it as a dropped cylinder, because a misfire is actually defined as incomplete combustion, meaning a spark initiates combustion, but the cylinder never achieves complete combustion. The result is reduced power from the combustion event. But what if you could produce a stronger spark delivered at precisely the right moment throughout the engine's entire operation range? Would it be possible to make more power?

DIS ignition is partially responsible for the LS, new Chrysler Hemi, and Ford mod motors making more power per cubic inch and being more fuel efficient than their year-old cousins. So why not use LS engine technology to give a leg up to older engines to make more power?

His company makes a conversion system that uses either the 24x or later 58x crankshaft trigger wheels to indicate crankshaft position within the engine. In either case, a spinning shutter wheel on the crankshaft is read by the crankshaft position sensor to indicate engine rotating position. Because each piston arrives at TDC twice within the four-stroke cycle, the computer needs to know which of these two events represents the power stroke.

That's the job of the camshaft sensor.In this case you can often use the tach output of the CD control box. Distributor a. Basically this would be a distributor based ignition system, with an internal crank trigger mechanism based on:. The sensor will generally have two wires, and will magnetically read the teeth as they pass by. There will be a magnet on one side of the wheel and a sensor on the other, and the windows and non-windowed areas of the wheel will interrupt and pass-thru the magnetic field which is read by the sensor.

For an Optical Sensor triggerthere is an LED not visible light usually and a sensor on opposite sides of a flat disc with small slits it in. With this type of distributor you have a cam with a number of flat areas and lobes. The switching arm follows the cam and opens and closes the points. This would probably be more commonly called the trigger wheel, or Crank Angle Sensor Wheel. CAS Wheel for short. That animation best represents a VR Sensor setup, with a 4-toothed wheel.

Notice that the teeth are evenly spaced 90 degrees apart. The distributor spins at cam speed, which is half of crank speed.

Which means that for every complete engine cycle two complete rotations of the crank, or degrees the cam and any wheel spinning at cam speed spins one complete rotation, degrees. So each time a tooth passes the sensor every 90 degrees of trigger wheel rotation the crank has rotated degrees.

This works perfect for a 4 cylinder car, with one tooth passing the sensor each time a piston reaches TDC Top Dead Centeror a set number of degrees before or after TDC which the computer accounts for when firing the coil, which is then directed to the correct plug by the distributor.

These all are so there is no concern. All three of the above distributors will trigger the MegaSqyurt just fine! Note: This is based on the wheel spinning at CAM speed, as the distributor generally does. If the wheel is spinning at CRANK speed, such as when the wheel is mounted to the crank pulley directly, the story is different.

gm distributorless ignition system

Often these trigger wheels will work just fine as well. Remember you are looking for consistent trigger points positions evenly spaced apart.Precise ignition timing is essential for high-performance engine tuning and ensuring your small-block or big-block is delivering every horsepower within its capability. Since the era of poodle skirts, flattops, and Ed Sullivan, that's been handled by a camshaft-driven distributor.

Will the MegaSquirt work with my stock ignition system?

A gear at the rear of the camshaft meshes with another on the distributor shaft, spinning it and a rotor beneath the cap at half the speed of the crankshaft's rotation triggering—or distributing—electrical energy from the ignition coil to each spark plug per the engine's firing order.

As mechanical systems go, it's a feather in the cap of man's engineering prowess, particularly when you consider the speed engines are capable of achieving. There are cons to this type of ignition system, too. Regardless of whether you've ditched original-style points for an electronic conversion or changed to an HEI-type distributor, timing accuracy typically erodes over time due to wear in the associated components.

The cam and distributor shaft gears wear after constant contact, for example, while a stretched timing chain at the front of the engine can affect the camshaft's rotational relationship to the crankshaft, throwing off the timing.

And at high rpm in a performance engine, the camshaft can deflect inside the cylinder block and "spark scatter" inside the distributor cap can affect the timing and spark distribution, too, affecting timing in both cases. Of course, you can always adjust your engine's timing periodically, but that doesn't always address high-rpm timing issues and doesn't help at all with spark scatter. A more contemporary method of ensuring spark-timing accuracy across the rpm band is basing it on the crankshaft's rotation rather than the camshaft.

Such "crank-trigger" systems have been used by car manufacturers for nearly 30 years—and while converting a classic small- or big-block to such a system isn't a new idea, it's one that is growing in popularity because of the timing precision it offers for high-performance engines. And let's be clear here: A crank trigger system offers the greatest benefit for higher-horsepower engines designed for high-rpm performance.

We're talking mostly about engines used primarily on the strip or circle track, but you'll still see the benefits of more precise timing and less need for periodic adjustments when used on a street engine. Another benefit of a crank-triggered ignition is the opportunity to move to a distributorless system such as the OE-style coil-per-cylinder design used for years now on production vehicles.

In fact, if you're running EFI, the controller will handle the job of the distributor, sending the spark energy to the appropriate plug, thereby eliminating the need for the distributor altogether and allowing for a more contemporary appearance of your classic small- or big-block. The systems are relatively simple in design and similar to how OEM ignition systems are triggered. Basically, a trigger wheel with spokes, studs, magnets, or holes is mounted to the harmonic balancer and spins with the rotation of the crankshaft.

As it does, the spokes, magnets, or holes pass a pickup sensor that sends a signal to the ignition box or EFI control unit indicating the rotational angle of the crankshaft. That crank-angle signal triggers the precisely timed spark for the appropriate cylinder.

Typical crank trigger conversion kit shown—this one is from FAST. Pretty simple stuff. Unlike other systems that use magnets imbedded in the wheel, FAST's system features tabs on the outside of the wheel that are read by the inductive sensor. It's a design similar to OEM systems. MSD's "flying magnet" crank trigger design is the opposite of FAST's, with magnets in the wheel rather than the pickup.

They pass a non-magnetic pickup to trigger the ignition signal, which the company claims offers greater accuracy because there is less chance for false triggers. The pickup sensor is shown here in line with one of the embedded magnets in MSD's system. The sensor "reads" the magnet as it passes by, triggering the ignition signal. Each system has an air gap specification between the sensor and wheel that must be set during installation to ensure the trigger signal is picked up accurately.

Distributorless Ignition System (DIS) – Replaces The Distributor

What about an LS-style 58x ignition system?The evolution of ignition systems has provided a number of benefits. Even so, that does not mean they are trouble free. Failures can and do occur for a variety of reasons. So, Knowing how to identify and diagnose common DIS problems can save you a lot of guesswork. This will help the next time your engine cranks but refuses to start; or one that runs but is missing.

If an engine cranks but will not start; is it fuel, ignition or compression? Ignition is usually the easiest of the three to check. On most engines all you have to do is pull off a plug wire; and check for spark when the engine is cranked.

If there is no spark in one cylinder, try another. Many engines with electronic fuel injection also use the crankshaft position sensor signal to trigger the injectors. So, if there is no spark and no injector activity; the problem is likely in the crank position sensor. No spark in one or two cylinders that share a coil; would tell you a coil has probably failed. The coils in a DIS system functions the same as those in ordinary ignition systems.

So, testing is essentially the same. But, the driveability symptoms caused by a weak or dead coil will be limited; to one or two cylinders; rather than all the cylinders.

A Low MAP sensor output voltage; or a coolant sensor that always reads cold; will allow more spark advance than normal. This, in turn, may cause detonation spark knock problems when the engine is under load. A High MAP output voltage or a misadjusted throttle position sensor can have the opposite effect.

This would cause the spark control system to retard timing more than normal. Retarded timing will reduce performance and fuel economy. Do not forget, that ordinary secondary ignition problems can also cause misfires the same as a conventional ignition system. A bad spark plug wire or a fouled spark plug will act just like a weak or bad DIS coil. A fuel pump relay functions primarily to maintain a consistent voltage supply to the fuel pump.

The ignition or powertrain control module PCM usually controls […]. If you are able to read a spark plug it can be a valuable tuning aid. The […]. Most of the images displayed are of unknown origin. We do not intend to infringe any legitimate intellectual right, artistic rights or copyright.

Hence, The Distributorless Ignition System.


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