A long crank time when the engine is warm. Causes and fixes

Experiencing a long crank time when the engine is warm is a common phenomenon. The most likely diagnosis is poor fuel delivery to the engine.

To start the car, quite a large amount of fuel is needed to undergo vaporization and subsequent combustion in the engine to produce enough energy.

However, when there is poor fuel delivery to the engine, more time is taken to accumulate adequate fuel needed to start the car, leading to longer crank time. 

Reasons for a long crack time when the engine is warm

Poor fuel delivery

This can result from vapor lock. Vapor lock occurs when fuel vaporizes prematurely before reaching the combustion chamber. Fuel lines are usually located near the engine block.

When the engine gets hot, a portion of the fuel inside the fuel lines tends to get vaporized and mixed with the liquid fuel, interrupting the fuel flow into the engine.

Vapor lock not only causes increased crank time but can also lead to a lack of power and car stalling issues.

A clogged air filtration system can also cause low fuel pressure in the engine. The correct air-fuel ratio needs to be achieved to start your car properly.

Unlike a vapor lock which reduces the amount of fuel getting into the combustion chamber, a clogged air filter decreases the amount of air being transmitted into the combustion chamber.

Air filters prevent engine contamination by filtering the air pumped into the engine. Over time, air filters accumulate debris and become clogged, reducing their filtration effectiveness.

This reduces air intake into the engine, causing low fuel pressure. In addition to causing increased crank time, clogged air filters can lead to poor acceleration and reduced engine power.

A faulty engine coolant temperature sensor

Another probable cause of long crank time. When working efficiently, the coolant temperature sensor detects high engine temperatures and relays this information to the ECU (Engine Control Unit), which then regulates the amount of fuel transmitted to the combustion chamber.

A faulty temperature sensor fails to relay proper information to the ECU, thus can cause more fuel than is needed to be injected into a warm engine, disrupting the air-fuel ratio.

Too much fuel and insufficient air in the combustion chamber result in high fuel pressure. When the car has high fuel pressure, the crank time is increased.

Other consequences of high fuel pressure include a rough-running engine, poor gas mileage, and the presence of dark smoke originating from the car’s exhaust.

Worn-out battery cables

The increased crank time when the engine is warm can be due to worn-out battery cables. Battery cables are constantly subjected to temperature fluctuations making them brittle and worn.

Compared to new cables, worn cables have higher internal resistance, and the resistance of these cables increases with an increase in temperature.

This reduces the amount of current transmitted by the cables, thus affecting power delivery to the starter motor. Without enough power, the starter cannot immediately start the car, leading to increased crank time.

How can this issue be fixed?

To resolve low fuel pressure from vapor lock, you can insulate the fuel lines, thus preventing direct contact between the fuel lines and the engine, effectively reducing overheating.

This is a long-term solution to the problem. However, placing a bag of ice over the fuel lines for some minutes can provide immediate relief to the situation. 

Likewise, clogged air filters can be fixed by replacing the air filter during regular car maintenance. Since most people tend to forget this step, creating a maintenance checklist can help jog the memory. 

The battery cables should also be regularly checked and the worn-out cables replaced. You can consult the manufacturer or mechanic to determine when to replace your car’s battery cables

Additionally, by simply unplugging and plugging the faulty engine coolant temperature sensor, we can fix the sensor, therefore, resolve the issue of high fuel pressure.

However, if this does not work, you should seek a professional’s help to replace the sensor. 

Closing thoughts

The long crank time when the engine is warm can symbolize many potential car problems. These include worn battery cables, faulty engine coolant temperature sensors, low fuel pressure from vapor lock, and clogged air filters.

These problems can be addressed by conducting regular car maintenance, including replacing worn-out parts. In cases where you cannot diagnose the problem, you can consult your mechanic.

By resolving these issues at their onset, you can avoid more serious car troubles, such as car stalling issues and engine overheating and failure, which would cost more to fix.

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