Thanks for the clarifications. I came up with 3.42V @ 40 PSI.
The sensor is an AEM 5 bar pressure sensor.
PDF voltage chart
I bought the Arduino simulator program and it is very helpful. I found I don't need the analog reference at all.
Using the 3.42V as the desired input on input pin 3, this works out to 701 out of the 1023 steps (3.42V / 4.88 millivolts). I want to have the output pin (9 in this case) HIGH if the fuel pressure input value is <= 701. I also want to pulse the pump for 1/2 second when the board powers up.
I'm continuing to learn about coding. My coding is as follows and appears to work on the simulator, but I'm sure it needs refined:
int pwmPin = 9; // output pin supporting PWM
int inPin = 3; // voltage connected to analog pin 3, e.g. a potentiometer
int val = 0; // variable to store the read value
float volt = 0; // variable to hold the voltage read
// int fuelpress = analogRead(3) // Fuel pressure input on analog pin 3
void setup()
{
pinMode(pwmPin, OUTPUT); // sets the pin as output
}
void loop()
{
val = analogRead(inPin); // read the input pin
if (val <= 700)
analogWrite(pwmPin, 255);
else analogWrite(pwmPin, 0)
}