Four basic every engine need to start: good compression, sufficient cranking speed, fuel and adequate ignition voltage. Now, you know if an engine fails to start, assuming one of requires essential ingredients is missing. The difficult part is to judge which one that missing.
You need to analyze more to find the source the problem. Probably you are dealing with a battery or starter problem when the engine won’t crank. Assuming starter is the source of the issue, check if it slows cranking or has unusual noises. Continue your analyze and ask yourself the engine won’t start or crank for the first time or before it already have the same problem?. Also, check if recently the battery cables and the battery be replaced?. Could be it part that becomes defective. Perhaps battery running down? There a maybe charging problem with the battery. Any electrical issues happened before? The answer to all analyze question will give you some shed of light and found the source of the problem.
Engine cranks but it would not start, could be there lacks the compression, ignition or fuel. The engine was running smoothly but is sudden death. Faulty of ignition module, failed fuel pump, or timing belt of the overhead cam that broken may causing this problem happen. Progressively harder to start happening to the engine, check the repair and maintenance history of the engine.
Engine Start Diagnosis Problem: Battery
You try out to start the engine, and nothing happens. If so, you need to check the battery state of charge. Starters need at least 10 volts from the battery to give it a start. The battery low is not always sourced a problem. While trying to start the engine, there a prolonged cranking that causing the battery run down. Or, the charging issue causing the low battery state of charge. If so, recharge the battery and test it out.
Assuming the battery is low due to the charging system issue, you need to try starting the engine using another battery or charger. Or if considering the charging problem causing the battery run down or the battery dies it will cause the engine crank but roars to life. While you test the battery and the result it’s OK and battery accept a charge, probably checking out the charging system output will help determine the problem you have.
On idle with lights and accessories off, usually the charging system should produce around 14 volts a charging voltage, and before tapper off, will rise quickly above the base battery voltage around 2 volts on the first engine started, and at specified voltage will level out. Depend on the temperature, the electrical system load, and state of charge battery; the charging voltage will be different. When the temperature is high, the charging system will low. However, at 80 degrees F the average charging range is about 13.9 volts to 14.4 volts for a typical alternator, it will increase at subzero temperatures around 14.9 volts to 15.8 volts.
Engine Start Diagnosis Problem: Bad Alternator Or Regulator
It could be a regulator or the alternator problem because the charging system cannot supply all required voltage. To know the alternator is working correctly, bypass the regulator by full fielding the alternator. Or you can do the bench test to the alternator on parts store that has the tools to test it out. When you bypass the regulator, and the charging voltage goes up, it tells the regulator is the problem. However if no voltage output change, the problem is the alternator.
Some cases of dropped unit output are causing the failure of several or one diodes in the alternator rectifier unit. There not enough current to fully charge the battery even the alternator still producing a current. On the oscilloscope will be read as missing humps (one or more) in the alternator waveform when this type of failure happens. The type problem like this, most charging system tools/analyzers can detect it.
Engine Cranking Problem
If the battery is charging in full and your engine cranks slowly or it won’t crank at all, you should check the starter circuit and pay attention to it. The easy way to identify an engine crank problem is to start the engine and switch the headlights on and watch what happens. If the headlight DO NOT light up, possibly the amps flow strangled by a poor battery cable connection. If so, try to check and clean up the ground straps of engine-to-chassis and all battery cable connections.
It’s a good way to find excessive resistance by measuring the voltage drop across connections. At any point, the voltmeter check result on the cable connections should not more than 0.1 volts drop, and for entire starter circuit no more than 0.4 volts. If you find the voltage drop is high, it tells an excessive resistance, and need for tightening or cleaning.
Undersized battery cables make the engine cranking is slow. Never buy a cables replacement with cheap ones; usually, cheap cables only has a thick insulation but has a small gauge wire. The physical cables size look same, however cheap cables have a small wire inside that cannot handle the amps.
Engine Cranking Problem: Solenoid Or Starter Relay Fault
When you try to start the engine and there no cranking, but the headlights shine brightly, it tells the starter does not have voltage to start the engine. It can cause faulty of solenoid or starter relay, misadjusted neutral/park safety switch, or ignition switch was going to bad. Fusible links and fuses should be checked for overload reason because it could be these protective devices blown when jump starting or cranking continuously.
When to start the engine and nothing happen, but the solenoid or the starter is clicking, possibly the starter is not spin because of not enough amps. Or could be you have a bad starter. Another possibility that causing the problem including ground or solenoid connection, battery cable that may be poor, or the solenoid itself has high resistance. Checking solenoid voltage can reveal the ignition switch circuit is receiving a voltage from the battery or not. If relay or solenoid get voltage from the battery but is not passing or closing enough the amps to the starter to spin it, the problem could be the solenoid contacts is corroded, worn or pitted or you have bad solenoid ground. Try to bypass the solenoid, if the starter is cranking, then you need to replace the solenoid with the new one.
Engine Cranking Problem: Weak Starter
The engine won’t start if you don’t get cranking speed around 200 rpm to 300 rpm, most engines need that speed to start the car, a weak starter can causing the engine won’t crank and there no compression because the engine is not fast enough to build it. In some case, even the starter is weak, engine fast enough to crank but not to start, this happens because ignition system and the injectors do not have enough power because the starter drains all power from the battery.
When to attempt to start the engine, and there no crank or just a little but the light is dim, could be the starter locked up, high internal resistance occurs on it, brushes that worn, armature or winding is opens or shorts. Doing current draw test on the starter, and it will tell starter pulling too many amps or not.
The starter is good if during the test you get a normal draw number between 60 amps to 150 amps without a load on it, and while the engine is cranking it should read up to 200 amps or more. The starter rating determines the no-load amps, while compression and displacement the engine determine the cranking amps. To know exact amp values, please refer to the OEM specs. It will vary, for example, the starter on Toyota with six cylinders engine commonly draw up to 175 amps, and Toyota with four cylinders engine draw around 130 amps to 150 amps. And no load draw for the starter on GM with “high torque” can be up to 250 amps.
The indication of field coils or grounded armature, shorted armature marked by low cranking speed or free turning speed and unusually high current draw. Also when the starter itself get an excessive friction (binding, dirty and worn bushings and bearings, curved armature shaft or between field coils and the armature contact occurred). Permanent magnet starters have magnets that can drag against the armature because the magnets separate from the housing or sometimes break.
Engine Cranking Problem: Checking Others Possibility
If starter draws a high current and is not turn at all has a ground in field coils or the terminals, or armature that frozen. The engine won’t crank even the start is OK, it caused the engine is hydrolocked or seized. Before blaming the starter, by the hand try turning the engine. The engine probably locked up if there won’t budge.
The starter draws zero amps and not spin at all may have a defective solenoid, defective brushes, open armature coils or open field circuit. Low current draw combined with free turning speed that low tells a high internal resistance (armature windings, open field coils, bad brushes or bad connections).
If the flywheels fail engaged by the starter but the starter motor is spin, could be there a starter drive that defective, flywheel’s teeth that broken or a weak solenoid. A starter drive that slips after engage briefly can cause it on the verge of failure. Pull off the starter and check the drive. It does not turn freely in the other direction but only turn in one direction. If the drive will not turn freely at all or turn freely in both directions, then you have a bad drive.
Car Cranks But Won’t Start
Car won’t start, but the engine is crank? Time to check fuel, ignition and the compression. Checking the ignition is easy, use the spark tester or positioning the wire plug in near a good ground. If you don’t see a spark, possibly the ignition module, CKP (crankshaft position sensor) or distributor pickup has failed.
There a tool can speed the diagnosis called as Ignition System Simulator, with timing input signal simulation the tool can tell the coil and the ignition module able to producing the spark or not. If spark generated on the signal simulation, a possible problem is a bad sensor of the crankshaft position or distributor pickup. If there no spark, you can suspect the coil and module are bad. To get rid of the coil as the culprit, please measure the primary and secondary ignition coils.
Commonly pickup and module problem are often caused by corroded, loose or broken wiring connectors or wiring terminals. Ignition modules on old GM HEI are notorious for this. You need to check the ground and the VRef (voltage reference) sensor if working on distributor-less ignition system (DIS) with Hall effect CKP (crankshaft position sensor). Five volts needed for the sensor or it will off permanent and will set a fault code because it does not generate any crank signal. Use engine block as ground and measure the voltage reference (VRef) between the ground and power supply wire sensor. Do not use circuit wire as sensor ground. If you don’t get 5 volts on the test result, you need to inspect wiring harness sensor for corroded or loose connectors. Also, the same result will apply (bad effect) on sensor operation and give bad voltage reference (VRef) supply if you have poor ground connections. Try checking the ground connections by measuring between the engine block and ground wire sensor for the voltage drop. You have bad ground connections if the test read 0.1 or more voltage drop. In this case, wiring harness and sensor mounting need to be check.
If power and ground exist on Hall effect crank sensor, then you need to check the output. The sensor must be “on,” and voltage reference (VRef) output should read 5 volts with sensor windows without nothing on it. Measure the sensor DC voltage output between ground (use the engine block) and signal output wire sensor. The output of sensor must drop to zero each time the gear tooth, magnetic button, notch or shutter blade goes through the sensor.
The plug wires, rotor, distributor cap and coil tower needs a visual inspection to identify the problem (check any defects) that prevent the spark is not going through to intended destination, if there trigger signal for the coil produced by the ignition system (primary side) but no voltage on the plugs.
Car Won’t Start Even Engine Cranks and Has Spark
Another problem car won’t start caused by fuel pump problem. It can be identified by engine cranks and has good spark, but the car won’t start. You can begin to check the fuel before suspect the fuel pump is bad.
The throttle of the pump is linkage and check the fuel squirting that comes into the carburetor throat if you are working on an engine with the carburetor. If there no fuel, any of the following could be the cause: a plugged fuel filter or fuel line, the mechanical fuel pump is bad, needle valve stuck in the carburetor.
On the engine with EFI (electronic fuel injection), check the fuel rail pressure by connect the pressure gauge into the fuel rail, and see if there any pressure in the line. When the key is on, and you don’t see any pressure, check pump relay, failed fuel pump, wiring and fuse problem. For Fords vehicles, you need to check the inertia safety switch fuel systems. It’s usually located under rear kick panel or hidden inside the trunk. When an accident happens, this switch will shut off the fuel pump for safety reason. You need to reset the switch if it has been tripped so it will bring flow the fuel to engine back. Pickup sock or fuel line obstructions inside the tank could be the cause of the lack of fuel. Many people skip checking the empty fuel tank, and you know many cars does not start due to there no gas in the tank.
On electronic fuel injection engines (EFI-equipped), is not always the engine get fuel injection by fuel pressure in the line. Listen for buzzing or clicking to identify if injectors are working. If you don’t hear a noise, check for ground and voltage at injectors. ECM will nor driving the injectors when it defective, or the relay of Electronic Fuel Injection power supply may call ECM quits. Injectors pulse generated by EFI-systems that rely on input from the camshaft position sensor. The system will not be functioning when losing the signal.
Even engine received the fuel; the engine will not starting if there a massive vacuum leak occur. The mixture will not ignite when a large vacuum leak happens because it will lean out the fuel/air ratio. Another possible cause could be a problem such as PCV house that disconnected, hose for power brake booster from the vacuum is loose, EGR (Exhaust Gas Recirculation) that stuck and wide open, or including similar leak also can cause the problem occurs. While cranking, you need to listen to unusual sucking noises and check all connections on the vacuum.
Engine Won’t Start Even Has Fuel and Spark
The engine should start if cranks normally, has spark and fuel, and no vacuum leaks that severely. Compression is possible another problem you may have. Especially if the engine has made a long trip and has a lot of miles, rubber timing belt on overhead cam engine, timing belt that broken. If the belt has never changed, but preventative maintenance recommendation from most OEMs is every 60,000 miles you need to replace OHC timing belt. In the end, they will break up, and in its tracks, the engine will stop dead. Some domestic and import engine that lack sufficient clearance of valve-to-piston could cause extensive damage (cracked pistons, valve-train components, and bent valves).
Severe overheating can cause overhead cams break and bind if the head wraps, or not enough lubrication for the cam bearings. During subzero cold start, a cam seizure may happen if oil is to slow getting the cam and it is too thick in the crankcase. Advised to use 5W-20 or 5W-30 for winter driving. Low oil level and overdue oil that does not change on some long period can cause the failure on high rpm cam.
Along with high mileage on pushrod engine, slipped or broken may happen to the timing chain. You can do a diagnosis another type of problem like this by doing checking on compression or removing the valve cover and pay attention to valve movement while the engine is cranking.
On the four-cylinder engine, a blown gasket will prevent engine start if there two cylinders are dead. It’s not will happen on six or eight cylinders engines, the engine will keep running even the gasket is blown. The gasket may hydro-lock the engine and create a cooling leak into the cylinder.