Arduino loop does not stop - only with smaller counters. Arduino Nano Every - c++

Question

I cannot explain to myself why this code works properly in some cases and in some not. Here is the situation:
I am trying to switch a relay with the Arduino Nano. Therefore I took the "Blink" example as a guide. It should switch on for like 5 minutes and switch off for like 25 minutes. Here is the code:
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);
pinMode(2, OUTPUT); // sets PIN 2 as switcher for the relay
}
// the loop function runs over and over again forever
void loop() {
int count = 0;
int run_pump = 300; // 5 Min run
int stop_pump = 1500; // 25 Min stop
digitalWrite(LED_BUILTIN, LOW); // turn the LED off (HIGH is the voltage level)
digitalWrite(2, HIGH); // turn the pump on
while(count < run_pump) {
count++;
delay(1000); // wait for a second
}
count = 0;
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on by making the voltage LOW
digitalWrite(2, LOW); // turn the pump off
while(count < stop_pump) {
count++;
delay(1000); // wait for a second
}
}
if I run this code on the Arduino it will just switch on the relay forever. BUT: If I set run_pump and stop_pump for like 10 sec. it will work properly! Is there an explanation why this does not work with the bigger counters? It's so confusing....
so this code here works absolutely fine, but why does the code above not?
// the setup function runs once when you press reset or power the board
void setup() {
// initialize digital pin LED_BUILTIN as an output.
pinMode(LED_BUILTIN, OUTPUT);
pinMode(2, OUTPUT); // sets PIN 2 as switcher for the relay
}
// the loop function runs over and over again forever
void loop() {
int count = 0;
int run_pump = 5; // 5 sec run
int stop_pump = 10; // 10 sec stop
digitalWrite(LED_BUILTIN, LOW); // turn the LED off (HIGH is the voltage level)
digitalWrite(2, HIGH); // turn the pump on
while(count < run_pump) {
count++;
delay(1000); // wait for a second
}
count = 0;
digitalWrite(LED_BUILTIN, HIGH); // turn the LED on by making the voltage LOW
digitalWrite(2, LOW); // turn the pump off
while(count < stop_pump) {
count++;
delay(1000); // wait for a second
}
}
Hope someone has a clue.... Thanks!
Tom

Answer 1

OK guys, I solved it. The problem was a cheap relay that was trying to communicate with the Arduino... Replacing it with a better one solved the whole problem. Thanks for the idea with the LED, this brought some stones to roll... :)