Troubleshooting Ignition Misfires

Diagnosing and correcting a misfire that develops on the track can be far more frustrating than trying to frame out why a car will not start. There are, however, some similarities in the middle of trying to determine the cause of a miss and why a car will not start.

Troubleshooting Ignition Misfires

Troubleshooting misfires can be nerve wracking. Is it certainly ignition linked or is it a fuel question causing the misfire?It may be caused by a mechanical question within the motor or even a cooling principles problem. Other than mentioning the need to check for a blown or leaking head gasket and a bad or low-pressure radiator cap, we will not dwell on the motor internals. However, cooling principles problems are responsible for over 20 percent of "ignition problems."

Fuel principles problems are more often than not attributed to ignition problems. Before delving too deeply into the ignition, rule out any basic fuel principles maladies: A fuel pressure gauge will identify a weak fuel pump, clogged fuel filter, or collapsed fuel line. A warped carburetor base, worn throttle shaft, or other vacuum leaks will show up as a lean condition. A clogged main jet may pass a optical inspection if it is blocked by a piece of sand or clear plastic. If in doubt, use a piece of thin wire to make sure that the jet is not clogged. A blown power valve should be clear from an overly rich exhaust.

Car+Alternator+Repair

In the early days of the automobile, good wire insulation was poor at best. Some early engines even used bare metal for spark plug "wire." In those early times, simplicity was the norm and wires were routed as neatly as hasten tracks. Today, wiring has become more complex. Insulation potential has improved many times over, allowing wires to be bundled and be more tightly routed. Unfortunately, high voltage and high impulse carrying wires are bundled with signal wires that carry pulses that are affected by high voltage much the same as a covenant car is buffeted by a tractor-trailer on the highway. Valuable signals are corrupted or lost. This can effect in a misfire.

A short checklist will help in determining the source of the problem:

· Using solid-core spark plug wires, including the coil wire, can induce an unwanted signal into the ignition amplifier, causing the amplifier to trigger at the wrong time.

· Poor connections on whether end of coil and / or spark plug wires may cause a misfire.

· Bad crimps or connectors not seating on the plug or in the coil can both cause problems.

· Sometimes, a minute moisture inside the plug wire boot turns to steam and blows the wire off. A thin film of oil will sacrifice corona and will help the moisture to escape.

· Spark plug wires must be separated. If possible, do not run them parallel to each other.

· In rare instances, having the coil mounted too close to the amplifier can cause problems.

· Do not run the coil secondary wire straight through the firewall with the jobber leads or the alternator lead as this can cause erratic performance due to "noise bleed over."

· A weak ignition can cause a misfire, reduced power, or poor performance. This may be the effect of a low battery or a malfunctioning alternator.

· Poor power connections, or wires and connectors that are too small can sacrifice ignition output.

· A master switch not rated for the application can restrict current flow enough to cause poor operation.

· Weak or damaged ignition components may work satisfactorily with a well-charged battery and cool conditions, but when the battery loses its outside charge or the box heats up, misfiring will occur. Low voltage and higher temperatures both need the ignition to work harder.

· Parts store switches might work well for a 10-amp blower or a 100-watt light but the ignition switch on current racecars may need less than 100 milliamps. This small number of current may not burn straight through a thin film of moisture or over an oxidized set of contacts. potential switches are a best and more trustworthy choice. A Mil-Spec number on a switch gives you, or the supplier, a reference where you can check and assess the qualities and capabilities of a given switch. Make sure that the switch you have chosen or are using will work well in your application. A parts store switch may work most of the time, but do you use supermarket motor oil in your race engine?

Misfire or Stumble

A voltmeter in the dash of the car helps you or the driver diagnose a problem. It can alert the driver to a malfunction before it develops into a misfire. If the alternator quits, permissible power administration may allow you to finish the race with all electrical power arrival from the battery. To perform this, all non-essential electrical consumption needs to be curtailed as soon as potential after the alternator quits. If the tach starts jumping, or the car starts missing, it probably too late to start a meaningful conservation of power. How the motor acts, combined with when and where on the track the motor skips, misses, or flattens out are all factors that may be used to diagnose problems.

Some factors to reconsider when determining the cause of a load or Rpm induced misfire:

What is the battery voltage when the question occurs? Twelve volts or less? Or in the middle of 13.5 to 14.5 volts? A12-v misfire normally indicates a lack of reserve power. To remedy this type of problem, you can sacrifice the spark plug gap, slow down the timing, and setup an alternator or 16-volt battery.

A misfire at 14.5-volt is a minute bit more complex. Does the tach fluctuate or get erratic? Does the question occur early in the race or practice, or is it all the time after the mean in the race?

Always have a box and coil known to be good, along with an emergency or test harness and a direct coil-to-distributor wire available. If, after changing these components, the question does not go away, look for a bad ground or a battery problem. Which way do the plates in the battery face? They should be aligned from left to right to forestall shorting in the turns due to centrifugal force. Where on the track does the question occur? Diving into a turn? Off the turn or midway down the straight?

If a question develops over time (10 or more laps), replacing components may "fix" the question until all things heats up or the battery loses its outside charge. Tachometer performance may indicate the source of an ignition problem. An erratic tachometer reading or a zero reading may indicate a loose relationship or low battery voltage.

Troubleshooting Ignition Misfires

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