Jeff's DIY

Advice on doing your own diagnosis and repair

Advice from the book Can I Do It Myself?

Engine Starting

Why doesn't my car start? (gasoline engines)

Tips on how to troubleshoot a car "no start" condition

Here are the basics on getting a car to start:
1. Turn over (crank)
2. Fuel
3. Spark (Fire)
4. Ignition and valve timing

Let's go thru each one. You can obviously scroll if you have already ruled some of these out.

1. Click here to go to the "No Crank" section.

2. Fuel. Assuming the engine cranks, next check for fuel. A good first check if fuel delivery problems are suspected is to spray some starting fluid into the intake system while someone cranks the engine. If the engine starts or tries to start with starting fluid, it is not getting fuel. In most modern cars, the fuel pump is inside the gas tank and is also usually sold with the fuel gage sending unit--an expensive and laborious R&R job. If the pump is working, you should hear it at least momentarily when the key is turned to the "on" position. If the pump is not working, the cause could be a fuse, a relay, an accident "kill" switch that needs resetting, or the pump itself. You'll want to rule out all of the inexpensive possibilities first. Use your owner's manual (you can often find these online if you don't have the original) to locate the applicable fuse, relay, and/or cutoff switch. To check the relay and ignition switch, follow my relay check procedures. You can also check for voltage at the pump connector with a test light.

Assuming your pump works, fuel still needs to get to the engine. A clogged filter will certainly limit fuel flow, but will rarely prevent a car from starting. That said, filter replacement is an inexpensive bit of maintenance. The most likely cause of fuel not getting to the engine when the pump is working is the fuel injection system (not an issue for carbureted engines). Injection systems are beyond the scope of this tip, but there are a couple things you can check. Many anti-theft systems cut off the injectors when activated. If you have such a system, make sure your anti-theft system has not been activated. Also, the injectors require a certain level of fuel pressure. Though your pump may be working, it may not be producing pressure. If possible, check or have your fuel pressure checked at the fuel rail. Some designs include a Schrader valve on the fuel rail for pressure tests. You can carefully push in the valve stem for a crude pressure test. The injectors are usually controlled directly by the engine or powertrain control module/computer. The signals sent to the injectors can be checked using a special tester or oscilloscope. If you have a voltmeter, set it to volts AC and measure the voltage at one of the injector connectors while someone cranks the engine. (You can remove the connector from the injector for this test--just remember to put it back.) It should register a few AC volts. A simple but crude method of checking injector operation when you don't have a meter is to put a long screwdriver on the injector body and hold the handle to your ear while someone cranks the engine. If the injectors are working, you should hear the solenoid click once every two engine revolutions.

Finally, if you are getting fuel to the engine, make sure it isn't very old or contaminated fuel.

3. Fire. Assuming you have crank and fuel, check for fire. An easy way to check for spark is to pull an ignition wire from the coil or distributor and hold it with an insulator (oven mitt or pliers with plastic grips) close to the terminal you removed it from while someone cranks the engine. You may have to push the wire into the boot to expose the terminal or use a Phillips screwdriver to reach into the terminal to get the spark out of the boot. Place the shaft of the screwdriver within 1/4" of a ground point. Here is a pic showing how to do that:

spark from plug wire


If sparks jump across when cranking the engine, you have fire. If you have fire at the coil/distributor, you must still verify that the ignition wires are properly connected to the correct spark plugs. This is especially important in cases where the plugs or wires were replaced just prior to the "no start" condition. Look up the firing order specifications for your engine and verify that the wires are connected in order. See my tip on firing order. If your coils are atop the spark plugs, make sure the wires to the coils have not been swapped.

If you do not have fire, use a (12 volt) tester to check the coil terminal for ignition power. The coil voltage varies from car to car, but should be between 9-15 volts. If there is no voltage to the coil with the key on, check the ignition fuse and relay. Not all vehicles have an ignition relay; but if your car does, see my relay tips to interrogate the relay socket. In these designs, the command signal from the ignition switch may be negative or positive. If you aren't sure, see if you can get the wiring diagram for the circuit. If the command signal is not getting to the socket, your ignition switch or ignition wire from the switch are bad. If the command signal is getting to the socket but the relay is not clicking, replace the relay.

Assuming now you have power to the coil but no fire, either the coil is bad or the ignition module is not sending the timing signal to the coil. If you have more than one coil, check them all. This is a good way to isolate and identify individual coils for replacement. Ignition modules are beyond the scope of this tip, but I can provide a few ideas on where to start. It is a good idea to extract any and all fault codes indicated by the "check engine" light when you are not getting a spark from a powered coil. Please see my tip on fault codes.

Use the fault codes to further troubleshoot the ignition system. It is advisable to get the wiring diagrams for your ignition system to troubleshoot. If you have a fault code relating to the crankshaft sensor, this fault may prevent the computer from timing the spark. Check the wiring and connector to the sensor and make sure the sensor is tightly installed.

Most modern cars have an engine or powertrain control computer/module to send signals to the ignition coils and fuel injectors. If your car's design allows easy access to individual ignition coil terminals and you have an oscilloscope or other meter that can sense a waveform, use it to check the signal to the negative coil terminal(s). If the signals are not rectangular and periodic, suspect your ECM/PCM is bad or is getting bad data from the crankshaft position sensor. A regular voltmeter in AC volts mode can also be used to verify a signal is getting to the coil. The meter should register a few volts at the coil terminals while someone is cranking the engine. Knock sensors may, in some cases, also affect the computer output, though these are generally used only to modify the ignition timing while the engine is running with a knock.

If your car is a bit older, it may just have a distributor with a pickup coil and ignition modulator to generate the signals to the coil. In these systems, the modulator charges the coil and then cuts the charge signal when it receives a blip from the pickup coil in the distributor, thereby releasing the spark. The spark then travels from the coil to the distributor and is routed to the appropriate spark plug via the rotor. The signal to the coil should still be rectangular, and if not, suspect the modulator is bad.

4. Timing. The spark plugs must fire when the cylinder is on the compression stroke or the cylinder will not fire. In many cars, the timing is controlled by the computer (in such cases, a possible cause for bad ignition timing is failure of the engine control module/computer or the knock or crankshaft position sensor). In others, there is a tab with numbers next to the crankshaft pulley and a mark on the pulley or vice-versa. If the timing is somewhere between -8 and +2, the engine should fire. Where it is adjustable, there is a specified value and method for setting the timing for optimal operation. A timing light can be used to check the timing while cranking the engine. Use chalk to mark both the moving and non-moving marks that you need to line up. Ignition timing is usually not a reason for a "no start" condition, unless someone has changed the setting or removed the distributor before the condition arose.

The valves must also be properly timed for the engine to fire up. A typical failure in valve timing is for the belt or chain to slip a tooth or 2 on the crankshaft gear. In some cases, the belt may lose all of its teeth in a short region of the belt and just stop turning the camshaft completely. If the chain/belt slips a tooth or two, the car may start but will have much reduced power and may backfire or shoot fuel/air mixture back up the air horn. This behavior is a strong indication of slipped valve timing.

Slipped valve timing can also be damaging to the engine if your particular engine design is what we call an interference design. In such engines, it is possible for the valves to hit the pistons when the valve timing is off. For this reason, if you suspect a valve timing issue and you don't know if the engine is an interference design or not, do not attempt to start the engine. Instead, remove the timing cover and check the gears for proper timing. Consult a manual or contact me for a picture of the timing marks. In some overhead cam engines, it may be possible to remove just the upper timing covers to check valve timing. If your valve timing has slipped, replace the belt or the chain/gear set. Also check the tensioner to ensure the new belt or chain does not slip. Make certain the timing is correct before closing up the engine.


Engine Doesn't Crank (Turn Over)

Troubleshooting tips for a car/truck that does not crank:

Some people confuse the terms "crank" and "turn over" as being different, but we use them interchangeably. If your engine turns fast enough to start the car but the car doesn't start, please refer back to my tip on "no start." To turn over, the car needs battery power or a jump from a good battery or high-power charger. Do not assume you have a bad battery just because it will not crank the engine. Troubleshooting steps depend on the exact symptom you are experiencing. If the starter solenoid is clicking, your start circuit is likely to be good and the troubleshooting will be more limited. We will first consider this easier case and then the case of no sound at all.
PLEASE READ THIS: When jumping a car, always keep the other car running and make sure you have a rock solid connection to the correct terminals. A buzzing or click-click-click... is almost always caused by a low battery or bad jumper connection.

Solenoid clicks but starter does not crank: run these tests:
1. Try to jump start at battery terminals. If this doesn't work, go to the next step.
2. Unhook the jumpers and jump the solenoid as follows. With the car in park or neutral and the parking brake on, short the hot terminal (one with the big red wire attached) of the starter solenoid to the smaller (ignition switch) terminal. Be careful not to let your screwdriver touch anything else, especially do not touch the big ground terminal closest to the starter motor. Here is a picture to guide you:

Jumping the starter


3. Only if tests 1 and 2 above fail to crank the engine, smack the starter motor (not the solenoid) with a hammer, then try to start.

Solution options for solenoid clicks case: Based on results of above tests, here are solution options:

If it will not jump start but will crank when the solenoid is jumped, the problem is with the start circuit not getting sufficient current to the solenoid. This usually only happens when there is a separate starter relay (in the engine compartment relay box) that is worn out. Replace the starter relay.

Solenoid Does Not Click-no sound: If there is no sound when you try to start the car, run the following tests:
1. Try to jump start the car. If the car jump starts, your problem is power. Make sure the battery terminals are clean and tight, and if this isn't the problem check the battery and alternator. Try charging the battery. If the battery will not charge, replace the battery. If the battery will charge, go to the dead battery troubleshooting tip in the electrical section.

No Jump: If the car will not jump-start, first also verify that the red cable from the battery to the starter is strong. If this cable is solid and connected firmly, either your starter/solenoid is bad or your start circuitry is bad. There are various starter/solenoid designs, but in most modern cases the solenoid is mounted to the starter and serves only to make a high amperage connection from the battery to the starter. (Some designs, notably older Fords, have the solenoid separate from the starter while some older GM designs used the soldnoid to also engage the starter gear with the flexplate/flywheel). When the battery is low, you can usually hear the solenoid click but the starter will not get enough power to crank the engine.

Going forward from here, I'm assuming your battery is well charged or you are jumping from a well charged battery. Most starting circuits include the elements shown below, but many have additional elements. The figure is intended as an aid to explaining basic starting circuits. For stubborn issues, you should really get the diagram for your particular car.

Typical starting circuit.
typical start circuit schematic


Not all systems have the extra starter relay or body control module components. There may be an additional "start" fuse or relay in the engine compartment relay box. The fuse may be before or after the ignition switch in the circuit. In the above diagram, the ignition switch and fuse are before the top of the diagram. Check any fuse marked "start" first. If there is a relay, you can use my relay tips to interrogate the relay socket. In these designs, the command signal from the ignition switch may be negative or positive. If you aren't sure, see if you can get the wiring diagram for the circuit. If the command signal is not getting to the socket, your ignition switch or start wire from the switch are bad, or your safety interlock is not closing. In the above case, the ground side of the relay is also dependent on a signal from the body control module, which checks for a "go" indication from the anti-theft system. If the command signal is getting to the socket, but the relay is not clicking, replace the relay.

If you don't have a start relay and you do not hear anything when you turn the key to start, the problem is usually with your safety interlock switch, immobilizer/security system, wiring, ignition switch, or solenoid. Let's first check the full circuit to eliminate the solenoid.

If you don't have a voltmeter, you can check the complete circuit with a simple test light. Connect the clip of the tester to a good ground point, such as the big solenoid terminal with a black wire, and hold the tip to the smaller solenoid terminal. The test light should illuminate when the key is turned to "start." While you're there (assuming your solenoid is mounted on your starter), you can also verify that the big red wire to the starter is hot by touching your tester to that terminal. If you are getting 12 volts to the small solenoid terminal but the solenoid is not clicking, replace the solenoid.

An even simpler (though not quite as safe) reverse test to check the starter/solenoid is given under test 2 of the solenoid clicks case near the top of this tip. Run the solenoid jump test, and if the motor does not crank, the starter/solenoid is not working. If you hear only a solid click, the solenoid is probably working. If the starter sometimes works and sometimes doesn't work, you may have a dead spot on the starter commutator. In such a case, smack the starter square on the side with a hammer. If it then works, replace the starter. If the starter turns too slow or overheats, it probably has an internal short or open windings. If you aren't sure whether the starter or solenoid is bad, take the whole starter assembly to the parts store for testing, or just replace the whole assembly.

If the motor cranks the engine during this test (start circuit is bad), your ignition switch, starter fuse, or relay is bad, the start wire or safety interlock is open, or your immobilizer/security system is activated. We have already discussed the start relay, in case you have one. I cannot cover security systems here due to the large number of them and difficulty in resolving these issues. If your security light is flashing, seek help in deactivating your particular security system.

Safety interlock: Most cars built in or after the 80s have an interlock switch to ensure the transmission is not engaged during start. In automatics, the interlock is on the shifter or the transmission, at the cable attach point. Try moving the shifter while holding down the brake pedal and holding the key in the start position. Most interlocks will also allow you to start in Neutral. In many modern designs, the safety switch may be called the transmission range sensor and may serve many additional purposes, such as turning on back-up lights, illuminating the current gear display, and providing gear info to the pcm/ecm for use in operating the drivetrain.

On manual transmissions, the interlock is usually mounted on the clutch pedal. In these cases, it is a simple matter to pull the connector off the switch and connect a wire across the 2 terminals inside the connector. Push in the clutch and try to start the car. If your interlock is not allowing the car to start, adjust or replace the interlock, as necessary.

Lastly, if everything else works, you are down to the ignition switch. If you are good at electrical work, you can open the ignition switch for repair or at least jump the hot lead to the start lead to verify the wiring is good. If the starter will jump at the switch terminals, you know you have a bad switch. If it will not jump, check the wire from the start terminal to the engine compartment for an open.


Where Is My Starter and How Do I Replace It?

1. First, please be sure your starter is bad. If you have tried to jump start the car/truck with a good battery and the engine will not crank, it's a pretty good bet that either the starter or solenoid is bad. It is often difficult to tell which one is bad, so the stores usually sell them together, especially since most cars now have them bolted together anyway. If the engine cranks at or close to the normal speed, your starter and solenoid are fine. Go to my "no-start" troubleshooting tip.

2. Gather your tools. Mainly a 3/8" drive socket set appropriate to the make and year of the car (metric for anything after the 80s). You will also need a 1/4" set or nut driver set to remove the nuts from the solenoid terminals. If you have the new starter on hand, take it with you under the car. If not, that's OK, because you're going to have to take the old starter to the parts store anyway to get a refund on the core.

3. Disconnect the negative battery terminal. I know, we always say that and you may think it's a waste of time; but in this case it's really important. You are about to disconnect a really big hot wire that can melt metal if you touch your wrench to anything on the engine.

4. Set the brake and jack up the car, if necessary, to get to where the starter is located. Always put a jack stand or big wood block at a solid place under the car in case your jack slips. If you let the car down on a good jack stand, you'll be safer yet. If you have ramps, those are fine too, but be sure to set the brake.

5. Locate the starter. So, if you haven't worked on a car before you can still do this, but it may be a bit challenging. The starter is going to be somewhere next to the engine with its end sticking into the transmission. It is usually near the bottom on either side of the engine. Some cars have the starter on the upper side of the engine. It will likely have the solenoid attached and 3 or more wires going to it. It looks like this, except you cannot see the open part as that will be sticking into the tranny, and the body may be gold or silver in color:

typical starter with solenoid


If you cannot find the starter, it is probably hidden behind something. In such cases, it is best to get specific instructions for your vehicle by either buying or borrowing (library?) a repair manual for your vehicle. In many cases, you may even find a procedure online. has a free registration repair site with a large catalog of cars.

6. Unscrew the nuts on the back of the solenoid. Remove the wires and tag each one with a way to remember where it went. Keep the nuts in case the new one doesn't come with nuts. If you didn't remove the negative battery terminal like I told you to, you'd better be careful with that big red wire!

7. Loosen the bolts holding the starter to the transmission. Also remove any other brace that may be holding the starter. As you loosen up the bolts, the starter will start to tilt under its weight, and you might get some fluids dripping out of the tranny (if there are any leaks back there). Once all the bolts are loose, you should be able to hold the starter with one hand and remove the bolts with your other hand. Once they are all out, the starter should slip straight back out of the tranny. If your car is older, there may be some shims between the starter and the tranny. Keep them, as you will probably need to put them back in to get the new starter to engage without binding.

8. Take a break and get cleaned up, then reverse procedure (we love saying that--saves us a lot of typing) to put in the new starter.

9. Start the car with your new starter.

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