bluejets:
The solenoid shown would have no problem switching at the intervals described.
I know it wont, since thats what the one in my truck and thousands (millions?) of other 6.9/7.3 trucks have been doing for 30 years. The stock controllers are junk and mine died many moons ago.
bluejets:
Looks like the op may want to switch some serious current though, solenoid like this probably capable of 200 amps DC or more.
Glowplugs. Pretty sure they pull close to 300 amps when heating up.
bluejets:
I doubt coil current would be 5 amps, more likely 500mA .
Thats what I was thinking.
raschemmel:
car starter solenoid tutorial
What am I supposed to be finding in here?
cat_herder:
That type starter solenoid has one side of the coil grounded internally (through the metal base) so you'll have to switch a positive voltage to control it - and it's gotta be ~12v DC.
This was mentioned in my first post.
cat_herder:
Even if the Arduino pin could supply enough current to trigger the relay it'd be far short of the needed voltage.
Which is why I was thinking a relay module like this to supply +12v to the solenoid:

cat_herder:
The way to do it with the fewest number of parts is to set your output pin to go low (ground) when active, and use that to control the gate on a beefy P-channel MOSFET. Ground the MOSFET's gate, and it connects the solenoid coil to B+.
Ill have to look up how mosfets work but that sounds like a decent idea.
cat_herder:
Some of those big starter relays already have flyback diodes inside to shunt the high voltage when the coil turns off. If there's no diode, it can damage the MOSFET (usually not immediately, it'll work for a while until it suddenly doesn't). Adding an external diode is a good idea, even if there's already one inside the solenoid. Two diodes in parallel will still work fine.
No idea if it does, but I could add one. I have a couple 3 amp diodes laying around.