Diagnosing starter problems begins with knowing the basics of how an engine actually starts.
So, before any engine will start, the first thing that has to happen is it must be cranked over.
But, if that does not happen, this is where diagnosing starter problems begins.
First of all, cranking the engine over, draws air and fuel into the cylinders and compresses the mixture. Cranking the engine, generates the ignition and crankshaft position sensor signals.
So, if a starter fails to crank the engine or turns too slowly, the engine will not start.
Diagnosing Starter Problems, What To Check
The first thing to inspect is the battery, to make sure it has enough voltage to operate the starter. A discharged battery may not be capable, of producing enough voltage or amps to start the engine.
Unfortunately, starting problems are not always simple to diagnose. Sometimes the starter is incorrectly blamed for a hard starting or no-start condition. As a result, some starters are replaced unnecessarily.
One way to avoid such predicaments is to bench test the starter first. After removing your old starter, you can take it to an auto parts store. Most stores can test the starter’s current draw and cranking speed.
Any number of things can prevent an engine from cranking or starting. An engine needs the right combination of air, fuel, compression and ignition to start. Consequently, if any of these things are lacking; the engine may crank normally but be hard to start or not start at all.
If Nothing Happens When The Ignition Switch Is Turned On:
- It may mean the starter has failed.
- There may be an open circuit in the ignition switch or starter circuit wiring.
- A failed neutral safety switch on the transmission linkage.
Vehicles with manual transmissions have a safety switch on the clutch pedal. Consequently, preventing the starter from cranking; unless the clutch pedal is depressed.
Other causes of no cranking may include:
- A bad solenoid.
- Loose or corroded battery cables.
- A low or dead battery.
Diagnosing Starter Problems, Testing The Starter
Using a jumper to bypass the solenoid is a trick that will show if the starter spins or not. If the starter works when bypassing the solenoid, the problem is in the solenoid or ignition circuit.
If an engine cranks at normal speed but refuses to start, it is probably not the starter. It is possible the starter is pulling too many amps from the battery. As a result, there is not enough voltage left to power the ignition system and fuel injectors.
Normal Starter Amperage Draw:
- A good starter will normally draw 125 to 150 amps when cranking a four cylinder engine.
- And, 150 to 175 amps when cranking a V6 engine.
- But, as much as 200 to 225 amps when cranking a large V8 engine.
The current draw depends on the type of starter and the application. So, look up the test specs for your vehicle to see if the starter is drawing too much current.
Bad Starter Solenoid
A bad solenoid can also be a source of starter problems. The solenoid acts like a relay to route power directly to the starter from the battery.
Corrosion, poor ground at the solenoid mount, or poor battery cable connections will prevent the solenoid from doing its job. Replacement is necessary if the solenoid is defective or stuck open or closed.
How The Starter Actually Works
The starter itself is a high torque direct current electric motor. Inside are a rotating armature, four brushes and a pair of field coils or permanent magnets (on new models). The starter uses the opposing magnetic forces of the armature and field coils; to convert electrical energy into mechanical energy.
So, what happens when the ignition switch is turned on:
- Voltage is routed through a solenoid or relay to the starter.
- As the starter begins to spin; the drive gear extends and engages the teeth on the flywheel ring gear.
- When the engine starts, the drive gear retracts and the starter stops spinning.
- An overrunning clutch in the starter drive; prevents the starter from being over-revved and being damaged.
Cranking an engine is hard work and pulls a lot of amps out of the battery. The cranking load is even greater during cold weather. Because, low temperatures thicken the viscosity of the oil in the crankcase and increase drag. At the same time, the battery has less amps available. Because, cold temperature slows down the chemical processes inside the battery that release stored electrical power.
Other Starter Issues
Continuous and prolonged cranking is very hard on a starter because it generates excessive heat. The starter needs to cool every 30 seconds or, the starter will be damaged by continuous cranking. Fuel injection has reduced the strain on starters because it takes fewer cranks for the engine to start. Consequently, starter sales for newer vehicles with fuel injection are much lower than those for older vehicles.
Starter Drive And Flywheel Problems ( ring gear )
Watch out for damaged teeth on the flywheel. If the starter can’t engage the flywheel, it can’t crank the engine.
If the starter cranks the engine normally, but you hear a grinding noise after the engine starts; the starter drive may be hanging up, preventing the starter drive gear from retracting away from the flywheel. This can damage both the starter drive gear, the starter and the teeth on the flywheel.
Starter Replacement Tips:
When you need a starter, the replacement should have the same or higher cranking capacity as the original.
One item you should also replace along with the starter is the solenoid (if not included with the replacement starter). Solenoids wear too, so replacing this component will help assure reliable starting.
If the cables are damaged or corroded, replace them. It is important to make sure the replacement cables are heavy enough to handle the amp load.
Also be sure to check the engine’s ground straps. These straps ground the engine to the chassis. Corroded or loose ground straps create a poor electrical connection and can cause slow cranking speeds. The smaller the diameter of the wire, the fewer the amps it can carry. New ground straps may also be needed if the original straps are missing or damaged.
Upgraded Battery Power For Cold Weather Starting
Lastly, a more powerful battery with a higher cold cranking amps (CCA) rating; may provide some added kick for reliable cold-weather starting.
The average battery only last about four years. So, if the original battery is more than four years old, replace it.
If the vehicle also has any weaknesses in the charging system, it needs to be fixed. A weak alternator may not be capable of keeping a battery fully charged; and without a full charge reliable starting may not be possible during cold weather.
Replacing the alternator and drive belt may also be recommended if this is the case.
Starter Shims On Older GM Applications
On certain older GM applications, the starter has to be shimmed. So, the starter drive and flywheel line up properly. Reusing the old shims is no guarantee the alignment will be correct. The installer should measure the drive gear to flywheel clearance to determine the correct shims to use.
Many starters also have a heat shield over the motor to protect it against heat from a nearby exhaust pipe. So, don’t forget to replace it. Failure to do so may cause the motor to fail prematurely, or lead to hot starting problems.
So, once you’ve identified which problem you’re dealing with, then you can start to remedy it. Finally, for all issues, the initial troubleshooting is the same, you always start with the battery.
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