Arduino Uno and 5V Pump without Relay

[hodenklaus420]

You mean this?

I just unplugged it for a better view

I think the polarity is correct.
If I plug it the other way round nothing will happen.

[theeccentricgenius]

Thank you for clarification.
Is the diode around the right way?

[JCA34F]

This is impossible, I'm out. good luck.

[hodenklaus420]

Lol it now works, I had to let the pump flutter 15 seconds and at the end the pump ran.
Before I only tried for a few seconds because I didn't want to damage it

[TomGeorge]

Sounds like it needed to prime itself.

Tom..

[hodenklaus420]

Thank you all for your patience!

So the pump is now running again with the MOSFET.
This is my circuit:

This is my program:

int pumpPin = 9;

void setup() {
  pinMode(pumpPin,OUTPUT);
  Serial.begin(9600);
  Serial.println("Motor");
}

void loop() {
  digitalWrite(pumpPin, HIGH);
  delay(5000);
  digitalWrite(pumpPin, LOW);
  delay(5000);
}

The red LED on the MOSFET alternates between ON and OFF.

When the LED is ON, the pump is on 100%
When the LED is OFF, the pump is on 50%

How to turn the pump off?

I also tried to connect the TRIG/PWM directly to arduino 5V instead of the digital pin 9, but that will give 100% permanently.