What should you do, when your engine cranks, but fails to start.
If your engine cranks normally, at least you know your battery is good and the starter motor works.
So, before your car would not start, did you notice anything out of the ordinary. Such as, low power or a check engine light? Most importantly, this could aid in the troubleshooting and diagnosis process.
However, the Engine Cranks – But, Fails To Start source, may also be a mechanical fault.
For example, a leaking valve, or faulty components in other systems.
Above all, to operate efficiently, an internal combustion gasoline engine needs:
- A good spark.
- The right amount of fuel.
- Good compression (a healthy mechanical condition).
Consequently, the lack of any of these three things, will prevent your engine from starting.
So, always start with a visual inspection of the engine. Is a wire loose? Did a vacuum line fall off ? Do not look for a complicated solution, to a simple problem. Consequently, it is common to have a problem in one area, that impacts three or four others.
So, because your engine cranks, you have eliminated the battery and starter. Next, let’s move on to spark, fuel and compression.
SPARK / FUEL / COMPRESSION
Consequently, if any of the three are missing your engine will not start.
Let’s Start With Spark
Conventional Ignition
(NOTE: If you have plug wires). To do a quick test for spark, remove one spark plug or use a spare spark plug. Attach the spark plug to the spark plug wire. Now, use a jumper cable and attach one end to the spark plug. And, the other to the negative post of the battery. Then, try turning over the starter and see if the spark plug is firing. Consequently, if the plug does not fire, there could be other problems.
Other possible causes of engine cranks, but no start include:
- Faulty Ignition Module
- PCM
- Distributor
- Ignition Switch
- Neutral Safety Switch
- Ignition Coil
- Anti Theft System
- Cam or Crank Position Sensor
Distributorless Or (COP) Ignition
However, you can’t check for spark the way described above on most newer cars. Because, they have what’s known generically as a, (DIS) or “distributorless ignition system“. Spark timing is controlled by the computer in this case. There will either be a coil pack or two (or more), depending on the number of cylinders.
If your car has either of these, you can check for spark, by following these steps:
- Remove a plug wire or coil from the spark plug.
- Connect a spark tester to the plug wire or coil.
- Clip the plug tester to a good ground.
- Have someone crank the engine over as you look for spark.
- Repeat for each cylinder.
- For any cylinder/plug wire/coil that does not generate a solid spark. Then, use a multimeter or test light to check for the presence of power. Consequently, the coil should have power, when cranking the engine.
- If no power is detected, locate the cam/crank sensor(s) and test them for power. And, for opening and closing as the engine cranks.
Moving On To Fuel
To do a quick test for no fuel, get a can of starting fluid or propane. Spray some into the air intake system, through a hole where there is a fitting. Or, hose opening to the throttle body/carb/etc. Try to start the engine. Consequently, if it starts and then turns off, you are not getting fuel, from your gas tank to the engine.
Other possible causes of engine cranks, but no start include:
- Bad Fuel Pump ( Tip: Turn of key and listen for buzzing Noise From Fuel Tank )
- Blown Fuse
- Fuel Pump Relay
- Low or No Fuel Pressure
- Fuel Injectors or Relay
- Bad PCM
Finally, Check For Compression
To do a quick test for no compression, do a compression test. So, you need to have at least, 125 lbs. of compression for your engine to run. If you have good compression in all but one cylinder, it will still run, but miss on one cylinder.
Other possible causes of engine cranks, but no start include:
- Broken or Slipped Timing Belt or Chain
- Burnt or Bent Valves
- Worn or Damaged Pistons or Rings
- Broken Camshaft or Crankshaft
Also, faults in other systems, not just ignition, fuel, or compression problems, can prevent your engine from starting. Consequently, a system component itself, may be faulty. Or, there may be a problem, with its wire connector or harness.
Any one or combination of the following issues, may be the source of the problem:
- Plugged Exhaust System
- Check Engine Trouble Codes
- Test Fuses
- Check the Security System
- Worn out tune-up parts
- Fuel injection problems
- Vacuum leaks
- Contaminated fuel
- Weak fuel pump or fuel pump relay
- Bad contacts in the ignition switch, key code problems
- Ignition coil or module
Intermittent Engine Cranks – No Start Problems
Sometimes a car may have an intermittent problem. When it starts most of the time, but once in a while the engine cranks, but fails to start.
What will help to find a problem of this type is:
- If you notice when.
- Under what conditions
- What helps to get it started
For example, if you notice that wiggling the ignition key, helps to get the car started. Then, it may tell you that the problem is likely, with the ignition switch, which is very common.
But, if the security light flashes on the instrument panel, each time the engine cranks, but doesn’t start. That could tell you to begin with, checking the security system.
Conclusion
So, as you can see starting issues, are not that easy to solve and can be time consuming. This guide not only tells you where to start, but helps you build your diagnostic strategy. And, reminds you of some simple, but easy-to-forget places to look into. Finally, most of the time, using just this blog post, you’ll be able to zero in on the problem.
Thank You !
