Tip & How-To about Mercedes-Benz E-Class

Engine electricals

3) Spark: From battery to spark plug

The battery is the source of stored electrical power in the vehicle. A voltmeter between the terminals of a healthy battery should read 12.5 volts. A reading of 12.2 volts indicates a flat battery and a reading of 10.4 volts indicates a dead cell (each cell beingabout 2 volts). A battery should be capable of sustaining high current, as needed by the starter motor when turning the engine over. When the car is running the voltage measured across the terminals shouldbe between 14.2 and 14.5 volts. The value is the voltage being supplied to the battery by the output charge from the alternator. THis charging voltage should not alter much when additional load is applied to the battery (head lights on etc).
When the ignition key is turned to the second position,often referred to as 'key on engine off', all car functions are powered up including lights and fuel pump. When the key is turned to position 3 many ancillary functions are temporarily interrupted to allow the battery to meet the extra needs of the starter motor. Electrical charge from the starter switch passes through a master fuse and starter relay before energizing the starter solenoid. The starter solenoid moves the pinion gear on the starter motor to engage with peripheral teeth of the flywheel. Simultaneously, heavy copper contacts are bridged by this same movement causing the starter motor coils to become energized thereby turning the engine over.
During the ignition process electrical charge passes through the primary windings of the ignition coil(s). The engine control unit (ECU), taking signalsfrom the engine crank position sensor, collapses the field of the coil(s) appropriate to the cylinder requiring ignition. As the field collapses the secondary coil windings discharge very high voltage through the high tension lead to the spark plug. The charge is so high that at the spark plug gap the charge jumps across with a spark. The compressed fuel air mixture in the cylinder is ignited by this spark.
Checking the spark process starts with the plugs. The condition of the removed plugs reveals a lot about the nature of the ignition within the cylinders. Dark sooty deposits indicate overly rich fuel air mix and glazed plugs indicate overly hot lean mixtures. Removing the plugs (with the fuel pump relay unplugged) and holding the screw threads to the cylinder head whilst turning the engine over will reveal the quality of spark. The spark holders and leads should be examined for discharge through the insulation to the cylinder head. Removing the leads from the coil should reveal sparks emanating from the exposed connectors. Failure to see sparks at this point indicatesa failed coil (especially if neighboring coils show good spark) or a failed crank sensor if all coils show no spark.
NEXT 1.1 MAF Mass Air Flow sensor

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I have a 2006 Kia Sorento. It was working fine this morning but when I went to start it this evening, the key would not engage the starter, then all the lights stayed on and I had to disconnect the ba

    • 1 Turn the key on until the lights on the dash come on. If the dash lights fail to come on, the battery or battery connections are suspect, and you have eliminated an engine performance problem. If the lights come on, try to start the engine. If the engine does not turn over (it just makes a clicking sound), the battery is suspect. If the lights are on, and the engine turns over, but does not start, the issue is with performance. Go to Step 2 if the engine does not turn over. Go to Step 6 if the engine cranks but does not start.
    • 2 Inspect the battery terminal for corrosion and security. Clean the terminals if necessary by wetting them with water and pouring baking soda on the terminals. The baking soda neutralizes the acid and cleans the terminals. Wait for the terminals to stop foaming and clean with water. Take off the negative terminal and clean it with a wire brush. Leaving the negative terminal off, remove the positive and clean it with a wire brush. Reinstall the terminals with the positive first. Check to see if that solved the problem. If not take the voltmeter and check the voltage across the terminals, red lead of voltmeter on positive terminal and black on negative. There should be showing 12.3 or better volts. If the voltage is low it is under charged or incapable of holding a charge. Take the caps off the battery and check the cells one at a time with the hydrometer. The hydrometer reading should be the same on all cells if all cells are good. A fully charged battery will show 1,260 specific gravity on the hydrometer. Check the water level in the battery and fill as necessary with distilled water.
    • 3 Replace the caps on the battery and hook the load tester to the battery. Watch the voltage as you press the load button for five seconds. Note how much the voltage dropped while the load was being applied. Look on the battery label on top and look for the CCA, or cold cranking amps. Compare this with the diagrams on the load tester for that size battery. For example, a 550 cold cranking amp battery should not drop below 10.5 volts when a load is applied. This would indicate a bad cell in the battery and require replacement of battery.
    • 4 Check the black negative cable where it attaches to the engine and make sure it is tight. Check the positive cable and be sure it is tight on the starter.
    • 5 Disconnect the small wire from the starter solenoid. Clip the red lead on the voltmeter to the small wire and clip the black lead on the voltmeter to the battery. Have a friend turn the key to the start position. There should be power to the wire every time the ignition is turned to start. If there is power then the starter is the problem and needs to be replaced. If there is no power, check the fuse in the relay box on the driver's side fenderwell. If it is good then pull the starter relay out and check for power at one terminal. Put the red positive lead of the voltmeter in the relay terminal and touch the negative to the negative battery post to check for power. If there is power then have the assistant turn the key to the start position and check to see if another terminal has power. There should be two terminals with power when the ignition is in start. If there is power at a second terminal turn the key off. Take a jumper wire and jump the terminal with the power on constantly with one of the terminals that had no power. Try the next terminal if no response at the starter. When jumped, if the starter engages, the relay is at fault and needs to be replaced. If there was no power to the relay when the key was in the start position, then the ignition switch is at fault.
    • 6 Insert an extra spark plug into the end of one of the spark plug wires. Do not take a spark plug out of the engine for this test. If it is a coil over system, remove the 10 millimeter bolts from the coil and pull it out of the head and insert the plug and lay it on the valve cover or in a spot where the plug is grounded by touching metal. Do not touch this during this test or you will get shocked. Have the helper turn the engine over. Look at the plug for a spark every few revolutions. If there is no spark, there is an issue with the engine management system. Take the car to a shop with the right test equipment. If you see spark, the problem is in the fuel system.
    • 7 Look at the top of the engine and locate the fuel rail on the injectors. There should be a Schrader valve on the rail. Make sure to extinguish any cigarettes or heat source like an electric light bulb during this step. Take a small screwdriver or a nail and push in on the Schrader valve. Have the helper turn the key on and look for fuel pressure at the valve. If there was no Schrader on the rail, just loosen the fuel line for the same results. If there is no fuel expelled, check the fuel pump fuse and relay located in the relay box. If these are not faulty, the fuel pump has failed and is need of replacement.

Mar 07, 2013 | Cars & Trucks

1 Answer

I have 2000 Kia spectra. It shut off while ideling. I have changed the fuel pump and checked fuses/relays. We used a insulated wire and ran it from the battery to the fuel pump relay fuse socket in the fuse box and we could hear the pump running. The relays are not getting power from the fuse box.....HELP! Do I need a new EGI?

You need to troubleshoot the relay and terminals. First try a different relay. Another relay in your car may be same part number relay as you pump relay, so check for that. Swap in a known good relay and try it.
If no help, look at relay. Is it 4 terminal or 5 terminal? If 4 terminal, easier to check. One terminal will be your power source, and hot at all times, so check for that-use your jumper wire (if no testlight or voltmeter), stick end in terminal and just touch metal, looking for spark indicating power. If no terminal has power, maybe only hot with key on, so turn key on and check for power. If no power, the feed from battery to fuse block is lost. If you have one power source, another terminal will be to the pump, the one you turned pump on with. Terminals 3 and 4 will be the signaling source to turn relay on through coil side of relay, and a terminal to ground, also on the coil side of relay. If you have constant power on one terminal, check for the signaling power. When the car is cranking over, the signal terminal should be hot-the signal will be coming from engine computer. So when cranking, relay socket should have two hot terminals. If you don't have two, you're right, relay is not getting correct power to the fuse block. BTW, don't use jumper wire to check for signaling source, use a testlight. Don't want to cause spark from computer wire.
What is EGI? Not familiar with that.

Jan 07, 2013 | 2000 Kia Spectra

1 Answer

how to replace freeze plug on 1998 dodge ram pickup

Use your crescent wrench to disconnect the positive and negative battery cables. Be careful not to touch both battery posts together with your wrench, as this will damage the battery and possibly harm you.

Use your spark plug socket to gently grab the insulated end of the spark plug wire; pull it away from the tip of the plug. The spark plug socket looks like a regular set of pliers, except that the jaws have rubber inserts to grip the insulation without damaging it. The plug wire itself looks like a 15-gauge wire with a rubber boot on each end: One end is connected to the spark plug present in each of the eight cylinders, while the other end is connected to a coil pack terminal, usually located on the right rear side of the engine compartment. The coil pack is a square, black, solid-state component that has eight terminals for each of the eight plug wires.

Use your spark plug socket to gently pull the coil pack end of the plug wire away from the terminal. Repeat the last two steps until all eight wires are removed.

Consult the service manual for your vehicle's year model and determine the exact firing order. You will need to connect each new wire to the numbered coil pack terminal and the corresponding engine cylinder. Failure to replace the wires in the right order will result in failure of engine operation.

Use your crescent wrench to reconnect the battery cables (black wire to black terminal, red wires to red terminal).

Start the vehicle and make sure it is running smoothly. If you hear misfiring in the engine, use the spark plug wrench to make sure all the connections are properly seated. If the condition continues, you will need to further diagnose the electrical system.

Jul 15, 2012 | 1998 Dodge Ram

2 Answers

I have a 1993 Geo Prizm LSI, that cranks, but will not start, and has no spark. The problem began as a cold engine hard starting problem, but after I replaced the distributor with a rebuild, it stopped starting at all. The rotor, the cap, the plugs, and plug wires are new as well. The battery is new. I replaced the ECM with a used unit, and still no luck. Any Ideas gents?

Are you sure you got the dustributor in the right tooth? Check timing using procedure at link below. Or, maybe you got a bad rebuilt. Here are some tests to check it out:
See Figures 6 and 7
  1. Check for spark at each spark plug with a spark tester. Check at least 2 plug wires.
  2. If spark is only detected at some plugs, check for a faulty distributor cap or rotor. Also check the spark plugs and plug wires. Replace, if necessary.
  3. Measure the resistance of the distributor connector C1 when cold, between terminals 3 and 6, using a digital voltmeter. If the camshaft position (CMP) sensor resistance is not between 185-275 ohms, replace the distributor housing.
  4. Measure the resistance of the distributor connector C1 when cold, between terminals 2 and 5, using a digital voltmeter. If the camshaft position (CMP) sensor resistance is not between 370-550 ohms, replace the distributor housing.
  5. Measure the resistance of the distributor connector C1 when hot, between terminals 3 and 6, using a digital voltmeter. If the camshaft position (CMP) sensor resistance is not between 240-325 ohms, replace the distributor housing.
  6. Measure the resistance of the distributor connector C1 when hot, between terminals 2 and 5, using a digital voltmeter. If the camshaft position (CMP) sensor resistance is not between 475-650 ohms, replace the distributor housing.
  7. Measure the air gap between the signal rotor and the camshaft position (CMP) sensor. If the air gap is not 0.008-0.016 inch (0.2-0.4 mm), replace the distributor housing.

Fig 6
Fig 7
Repair Guides Ignition Timing Checking And Adjustment AutoZone com

Sep 07, 2017 | 1995 Geo Prizm

1 Answer

Where is the negative side for my ignition coil?

In all the automotive vehicle the positive terminals are connected to the body/frame. the wiring which runs around for all the electrical part is always negative terminal.

Smilarly the ignition coil lead is one terminal & the body of the spark plug is other terminal.

That is the reason you see the spark jumps from the center to the lug in spark plug.

Jun 05, 2010 | 1997 Hyundai Accent

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