It sounds like you’re experiencing a frustrating starting issue, especially after your injectors were cleaned. Let’s break down the potential causes, particularly given the important detail: “my car has no ECU,” or rather, you likely have an aftermarket Engine Control Unit (ECU). This changes the diagnostic approach significantly compared to a car with a factory ECU.
Firstly, regarding the injector cleaning service – a reputable service should indeed identify any injectors that are still leaking after cleaning and recommend replacement. A leaky injector could contribute to fuel pressure loss, which you mentioned as a potential issue after parking your car.
Fuel pressure loss after the car sits can manifest as a momentary starting problem. You might experience a longer crank time on the first attempt. Usually, on the second try, the fuel pump has fully primed the system, and the engine starts. However, it might run roughly for a few seconds until the fuel mixture stabilizes. Common culprits for this pressure loss include:
- Drooling Injectors: As mentioned, injectors that don’t seal properly can leak fuel into the cylinders after the engine is off, reducing system pressure.
- Leaky Check Valve in the Fuel Pump: The check valve is designed to maintain pressure in the fuel line when the pump is off. If it’s leaking, pressure can bleed back into the tank.
- Leaky Fuel Pressure Regulator: A faulty regulator might not hold pressure correctly after shutdown.
- Fuel Piping Leaks: While less common, physical leaks in the fuel lines would usually be accompanied by a noticeable fuel smell.
Alt text: A mechanic uses a fuel pressure gauge connected to a car’s fuel system to diagnose a fuel pressure issue, a common step in troubleshooting car starting problems.
The most reliable way to diagnose fuel pressure loss is using a fuel pressure gauge connected at the fuel filter discharge port. Turn the car’s power on (without starting the engine) to let the fuel pump prime and build pressure to the factory specification. Then, turn the car off and observe the gauge. The pressure should remain just below the specified level. A rapid pressure drop after pump shut-off indicates a leak somewhere in the system. If injectors and the fuel pump are known to be good, the regulator could be suspect.
However, fuel pressure loss when parked might not be the root of your starting problem, especially if persistent cranking doesn’t solve it. The symptoms you describe might point towards a “hot start” fuel mixture issue instead.
You mentioned a “Spoon ECU.” This is where things become more complex compared to diagnosing a car with a standard, factory ECU. Spoon ECUs are aftermarket performance ECUs, and their behavior, especially during startup, can differ significantly from OEM systems.
If this hot start issue is a recent development, checking the operating fuel pressures during a hot start is a good initial step. Also, investigating the engine coolant temperature sensor readings is crucial. With an OEM ECU, you could typically use a service check connector to display error codes, which could indicate temperature sensor problems.
Alt text: Close-up of an OBD2 diagnostic connector in a car, the standard port used to read error codes and diagnose issues, though compatibility with aftermarket ECUs like Spoon ECU may vary.
With a factory ECU, a common troubleshooting step for a potential fuel mixture issue is to try starting in “flood clear mode.” This is usually activated by pressing the throttle pedal all the way to the floor while cranking the engine. If the engine starts in flood clear mode (typically within 3-7 seconds), it suggests an over-fueling problem during startup. However, the effectiveness of flood clear mode, and even its existence, depends entirely on your Spoon ECU.
Since you have an aftermarket Spoon ECU, the diagnostic approach needs to shift. We need to consider a few possibilities:
- Spoon ECU Based on OEM: Is your Spoon ECU a modified OEM ECU (“chipped”)? If so, it might retain some OEM functionalities, including flood clear mode and similar startup parameters. Trying the flood clear method (throttle fully depressed while cranking) is worth a shot. If it’s chipped, it’s less likely the base startup configuration is drastically altered unless Spoon intentionally modified those parameters, or there was an error in their modification.
- Completely User-Configurable Spoon ECU: If the Spoon ECU is a fully programmable standalone system, it may or may not have a flood clear mode, and its startup parameters are entirely determined by its configuration. If you have the configuration software for your Spoon ECU, you should examine the hot start parameters. See if a flood clear function is enabled and, more importantly, check the fuel and ignition settings for hot starts. If the hot start problem has been present since you got the car, a configuration issue within the Spoon ECU is highly probable.
Therefore, to effectively diagnose your starting problem, especially with the Spoon ECU, the next steps are:
- Confirm Resting Fuel Pressure: Perform the fuel pressure test described earlier to definitively rule out fuel pressure loss as a contributing factor.
- Gather Spoon ECU Details: Provide more information about your Spoon ECU. Is it chipped OEM or a standalone system? Do you have access to its configuration software? Knowing more about the ECU’s type and your ability to access its settings is crucial for further diagnosis.
Understanding the specifics of your aftermarket ECU is key to moving forward and resolving your car’s starting issues.
