Engine Turns Over: Troubleshooting a No Start Condition

So, your engine turns over, but will not start. It usually means your engine is having trouble with spark, fuel, compression or timing.

But, what do you do, if all those things check out good, and the engine still won’t start.

The source of the problem could be, a mechanical fault, or a faulty component in other systems.

Consequently, a no start condition, when the engine turns over, can be a number of issues. But, you need to start somewhere, so lets dive in.

Faults in other systems, not just ignition, fuel, compression and timing, can prevent your engine from starting. Because, a system component itself may be faulty, or there may be a problem with its wire connector or harness.

Then, You May Need To Expand Your Diagnostic Procedure, To Other Systems Listed Below:

Exhaust Gas Recirculation (EGR) Valve

• The (EGR) valve can fail and stick, either open or closed. When the valve sticks open, it may prevent your engine from starting. Other symptoms of a stuck-open (EGR) valve include, rough idle and stalling.

Cold Start Injector

• One of the first symptoms typically associated with a bad cold start injector is, a problem starting the vehicle. The cold start injector is there, to enrich the fuel mixture of the vehicle. Consequently, during low temperature conditions. However, the injector may have its own thermo switch. And, may be commanded by, the system control module. As a result, if either the switch or the computer circuit fails, you may have a engine no start condition.

Manifold Absolute Pressure Sensor (MAP)

• The Manifold Absolute Pressure (MAP) Sensor, compares the barometric (atmospheric) pressure, to the intake manifold vacuum. Consequently, when the sensor fails, it can prevent your engine from starting.

Mass Air Flow (MAF) Sensor

• The Mass Air Flow (MAF) Sensor tells the computer, the amount (the density) of the air entering the engine. A common (MAF) problem, is dirt or foreign matter blocking the sensing element. As a result, preventing the sensor from working. However, the sensor itself, may fail after miles of service.

Engine Coolant Temperature (ECT) Sensor

• The computer uses the Engine Coolant Temperature (ECT) Sensor to know, how much fuel the engine needs. And, when to enter, closed loop operation (that is, when the engine has reached operating temperature). Therefore, a bad (ECT) sensor, can upset ignition timing and the operation, of the transmission or cooling fan.

Evaporative Emissions Control System (EVAP) Canister Vent Valve

• The canister vent valve, is part of the Evaporative Emissions Control (EVAP) System. The (EVAP) system temporarily stores, harmful fuel vapors into a canister. As a result, preventing their release, into the atmosphere. The computer routes the fuel vapors out of the canister, through a vent valve and into the intake manifold. That’s why, a faulty valve, can prevent the engine from starting.

Throttle Position (TPS) Sensor

• The Throttle Position Sensor (TPS), monitors the position of the throttle valve. So, it sends a voltage signal to the computer. Then, the computer uses this information, to regulate the air-fuel mixture, according to engine needs. And, on some vehicle models, a worn out, failing or bad (TPS), will prevent your engine from starting.

Vacuum Leaks

• So, vacuum leaks are not uncommon. And, they are the source, of many engine performance problems. And, also include, a engine that will not start. In addition, depending on where the fault is located, vacuum leaks can be hard to find.

Furthermore, mayor vacuum leaks, that can make the engine hard to start, may also happen in the:

• Power booster vacuum hose.
• (EGR) valve.
• Main vacuum hose.
• Blown head.
• Intake manifold gasket leak.

Carburetor – If You Have One

• If you have an old vehicle model, with a carburetor, double check that the fuel level is properly adjusted. If the carburetor is flooded, you’ll probably perceive a strong fuel odor under the hood. A little trick you can use is, to fully depress the accelerator and try to start the engine. Then, if the engine doesn’t start, wait for a few minutes and try again.