How to diagnose a crank no start sponsored by Muller Auto LLC, mobile mechanic Fort Wayne.

Check your battery for a full charge and connect a charger if possible

Remember the basics. You need fuel, spark, and compression. It’s usually one of those issues. Occasionally it can be a bad mass airflow sensor or unmetered air. If you have a scantool monitor data while cranking or blowing on the mass airflow sensor. look up specs for your car. Also take a peek at the throttle body and make sure it moves. Electronic throttle bodies will act differently than cable driven. If its electronic do not be surprised if it doesnt really open when cranking. Occasionally it will be timing or a sensor that indicated timing. If you have no rpms stop here and diagnose that. A scan tool with live data can help a lot and make these steps faster. These will be basic tests to help determine what part of the starting system has failed.

This is a video of a fuel pressure issue and you can hear what good compression sounds like. to be considered cranking it ought to sound like this.

Fuel is the most common culprit in my experience. There are many ways to test this. the best way is by hooking up a pressure gauge to the rail. This isn’t always possible and sometimes a quick test is easier. Try spraying starter fluid or combustable fluid into the intake where the engine air filter is. Aim deep inside the tube going towards the engine. This won’t always work on newer cars but if the car momentarily starts, fuel is a likely culprit. Confirm with another test to be sure. Another good test is disconnecting the fuel line anywhere with easy quick connect fittings. If you have to un bolt stuff its probably not a good or safe spot. Be ready for some fuel to come out. A hot engine or open flame is dangerous. The best test is to measure the specific PSI but if no fuel comes out that indicated the fuel pump isn’t working for some reason or the line is restricted.

Another fuel check should be injectors. listen to them to make sure they’re firing. A stethoscope or screwdriver can be used for this. Put the screwdriver on the injector and to your ear. Note the sound. Check all injectors for the same sound. If you don’t hear it clicking or a few aren’t clicking the same investigate it, but this is a less likely culprit. Don’t jump down this rabbit hole unless you’re sure you should be in it.

Spark should be checked next. a multimeter can be helpful to test wiring to the coils. Usually theres a 12v power and the control side is the ground. To test the full circuit operation remove one spark plug and coil, whichever is easiest. A Spark tester is the correct answer but the garage test is as follows. Install the plug into the coil and ground the plug. This can be done by running a wire from the plug to ground, touching the plug to the ground on the battery, or touching some ground on or near where the coil goes. The latter is usually the easiest. You are looking for a consistent and strong spark. white or blue in color. Side note, this is a good time to get a look at your plugs. May be time to swap them. If you can get one plug to consistently and strongly spark, try one or two more. Rule out an issue with this system and move to compression.

Compression is the most in depth cause and if this is the issue it likely needs to go to a mechanic. First verify the battery is charged and strong. If you have a battery charger, make sure it’s on. Results will be manipulated by a low or failing battery. Crank and listen to the cadence. Consistent rhythm and noise level is what you want. A dead cylinder or bad timing chain can usually be heard by this alone. Verify with a compression tester. Look up a few types of compression tests and how to interpret the readings. There are too many to go over in a simple paragraph. General rule of thumb you’re looking for all cylinders to be within 10 percent of each other. For example, cylinder 1 at 150 means you have a 15 psi variance you can play with. Make sure you disable fuel supply or injectors so you don’t wash the cylinders and cause issue. Also pull all the plugs first and then take readings. pulling one plug at a time can skew readings.