- January 26, 2004
- Reaction score
- City, State
- Mechanicsville, Virginia
- Year, Model & Trim Level
- 2004 Acura TL
The Thing Just Won't Start
In this write-up you will find out how to diagnose a No Start/Slow Start condition. With a lower mileage car, most of the time it is just your battery that is either dead or you don't have enough amps to do anything. For you all with an older vehicle with a good amount of mileage, your problems can be the following: Battery, Starter, Solenoid, and/or Wires (connections). To first get anywhere, you need to understand the basics of a starting circuit.
Finding Your Way
"Click-Click-Click" - Refer to the Voltage Drop Testing section (usually a bad/dead battery)
Slow Crank/No crank - Refer to Amperage Testing section and diagram at the bottom
Most modern cranking circuits include a Starter Motor (an electric motor that can develop nearly 8 horsepower for a very short time when first cranking a cold engine), a Battery (must be at least 75% charged to make the cranking circuit work properly), a Starter Solenoid or Relay (turns the starter on and off), Starter Drive (inside the motor, made up of a shaft and pinon gear on the end which engages into the engine flywheel and rotates the engine), and Ignition Switch (controls the starter motor operations)
Everyone Loves Pictures:
Starter Drive (w/ Pinion Gear):
Most vehicles are equipped with a neutral safety switch which allows the vehicle to be only started in park or neutral on an automatic transmission. The clutch pedal takes place of this switch in a manual transmission. Starters work on magnetism, by field coils and magnets, which build up current that turns and causes it to spend the motor over.
Voltage drop is the drop in voltage that occurs when current is flowing through a resistance. If voltage drop is too high, which can be caused by dirty battery terminals, might inhibit the ability of the starter and not allow it to operate.
Connect the positive voltmeter test lead to the most-positive end of the cable being tested. The most-positive end of a cable is the end closest to the positive terminal of the battery.
Connect the negative lead to the other end of the cable being tested. With no current flowing through the cable, the voltmeter should read zero because both ends of the cable have the same voltage.
Crank the engine. The voltmeter should read less than .2 volts
Evaluate the results. If the voltmeter reads zero, the cable being tested has no resistance and is good. If the voltmeter reads higher than specified, then the cable should be replaced. But, before replacing, check connects of the cable to make sure they are clean and tight.
TIP: If a cable is hot to the touch, there is electrical resistance in the cable. Touch the battery cables and while cranking feel for heat. If any cable is hot to the touch, it should be replaced or cleaned.
Also, you can test right across the battery. You should have around 12.6 volts for a fully charged battery and when the starter is energized, it should cause the voltage to drop down to about 9-10 volts.
Voltage Drop Testing Diagram:
Starter Amperage Test
To test for amperage draw, an AVR is the easiest tool to use. To test correctly, you must have a 75% or more charged battery to get an accurate reading. Connect the positive and negative leads of the AVR to the battery in the correct position, and then put your amp probe/clamp on the negative battery cable. Begin to crank the engine and read how many amps are being drawn from the battery. Here is a general maximum amperage draw chart for testing a starter on a vehicle:
Four Cylinder: 150-185 amps
Six Cylinder: 160 to 200 amps
Eight Cylinder: 185 to 250 amps
What will an amp reading tell you? It should tell you if the starter is good or not. If it is drawing too much current/amps, then it is severly worn and needs to be replaced. Excessive current draw indicates one or more of the following:
1. Binding of starter armature as a result of worn bushing
2. Oil too thick (viscosity too high) for weather conditions
3. Shorted or grounded starter windings (inside starter) or cables
4. Tight or seized engine
5. Shorted started motor (usually caused by fault with the field coils or armature - which is inside the starter)
You can also use a multimeter with an amp clamp to read the amperage draw of a starter.
Typical AVR Machine:
(Photo Link Is Dead - Edited by Admin)
Ohm Out A Solenoid:
To testing the solenoid with an ohmmeter, connect your leads to the starter terminal (usually smaller in size) on the starter and ground your ground lead to the starters casing. should be .4 to .6 ohms (winding check). Then check from the starter terminal to the motor terminal and it should be .2 to .4 ohms (winding check).
Here is a helpful chart:
Don't Hit It: In the past, it was common to see people using a hammer to beat on the side of a starter to "free-it-up", and it would sometimes work. However, most of todays starters use permanent magnet fields, which can be broken if hit hard enough.
Watch The Dome Lights: Whenver diagnosing any starter-related problem, open the door of the vehicle and observe the brightness of the dome or interior light(s). The brightness of any electrical lamp is proportional to the voltage. Normal operation of the starter results in a slight dimming of the dome light. If the light remains bright, the problem is usually an open circuit in the control circuit. If the light goes out or almost goes out, the problem is usually a shorted or grounded armatuer of field coils inside the starter or possibly a bad battery.
One Of My Stories: My parents called me up one day and my dad says "hey listen!" and puts the phone near the cranking engine and all you hear is "click-clack-click-click" and all this harsh noise. At first I was running through all of my thoughts of what exactly it could be since we replaced the battery about a year ago. Well, then I thought about the mileage on the vehicle (around 68K) and then a few other things. When I got there it became more obvious; you open the door and the light are hardly dim and would die out as soon as you tried to start it. Which indicated to me a battery or starter problem. I didn't have a voltmeter with me, so we took the battery out and went down the street to autozone and got it tested. When a load was put on it, it went down to like .56 of a volt. Obviously that isn't enough to start a vehicle. Most starters run on 2-3 volts. We got a new battery for free (under warranty) and was on our way. Put the new battery in and it fired right up.
Good luck. Hopefully other people will put in their information and their expierences.