This is intermittant.

My batteries arent the best, but it also happens with a charger on and/or boosting it. I havent been driving it much cause I dont want to get stranded when it doesnt start!
I can go out to the truck and crank it slow with a boost cause the batteries are weak. When I give it a few minutes to charge and go to start it again, it wont crank, wont click or anything. I know I have good power because the clock keeps the time, interior lights are bright, heater works good.
Is there a relay that might be getting stuck?

Once I start driving it regular, the batteries hold up. I dont want to start throwing parts at it unless I know what Im looking for.

Thanks

 

I'm no expert that is for sure, but I'm pretty sure you cannot go by clock, lights, or heater. And you're up there in the frozen land of Canada.... Sounds like battery to me, but I'm sure someone more in the know will be along shortly!

 

By now your batteries are at a point were they won't effectively hold a proper charge with enough power to start the truck.
Running the clock and some accessories will only draw a relatively small amount of current compared to the requirements of the trucks Starter.

By not driving the vehicle and/or very limited use, or idiling is not sufficient enough to keep the batteries up to par. Also the possible inconsistant over or under charging.

Once a battery is fully or partialy discharged a few times it's life fades quickly and starting becomes difficult, especially with your PSD.

The fact that you live in the cold makes a huge difference as well. Batteries hate the cold.

I would suggest if you don't use the vehicle much but need it for security i would purchase new batteries to start with (no pun intended). I would suggest a name brand that you can purchase locally that offers free replacements. Some of these like the MAX+ (avail. at Walmart) have a 3 yr. replacement warranty.

Make sure you clean all your terminals on the cable ends. This can even make a big difference on the system you currently have.

I would then suggest purchasing a charger with low/conditioned charging rates. here is a site you can get some ideas on. 12v Smart Battery Chargers | 12 Volt Gel Cell & Solar Batteries | BatteryStuff.com

 

batteries...batteries...batteries

 

I too believe your probably going to need batteries but the problem you describe of charging it and then it not cranking or clicking tells me you probably have a bad connection somewhere. I would start with cleaning all the battery terminals and then I would clean the contacts on the solenoid. I am not familiar with the diesels but there has to be a solenoid somewhere to transfer all the cranking amps required for the diesel.

 

The others are correct in saying batteries. A 7.3 takes a lot of power to turn over. When you first turn the key the WTS light comes on, after it goes out the GP can still run for up to 2 minutes. The WTS light is tied into the PCM. The GP's can draw close to 200A DC upon initial start up. They then level off a bit. I amprobed mine at one point and was suprised at the readings.

When you start the truck your IDM needs to see a minimum of 10.5 volts to fire the injectors. This is one reason why good batteries are important.

If you are running dino oil and it is cold this adds to the "drag" on the starter. More resistance = starter drawing more voltage from the batteries. I changed to Syn and have not regretted it at all.

Change out both batteries and make sure ll the connections are clean and not corroded. Check the grounds on the block, and the jumper to the chassis as well. Take a look at the wiring on the starter make sure that it is not corroded and is clean and tight.

We have seen where people have run their batteries down to low and it has taken the alt out with it.