2020 Freightliner Cascadia DD15 – Hard Starting Issue (New Starter and Batteries Checked)

Check grounds . Hopefully you’re not losing antifreeze into pistons when shut off..

 

It's a fuel issue, you're losing prime on the fuel system. Check your Davco drain

 

"Startup behavior is similar to when a truck has weak batteries in cold weather " This would not be caused by a fuel issue.

 

He says it cranks but struggles to fire, it's got new starter and batteries, so what could it be?

My guess is fuel, or compression.

After he checks those he should check the spark plugs and distributor cap timing..... (sarcasm)

 

Two seconds? The old starter was doing this also? It sounds like the temp sensor on the starter is failing, but since it's new that might mean a short in the wiring to that sensor.

You really need the DDDL software to diagnose something like this.

 

Does the engine fire? If not, it's a diesel, you've got a fuel or compression issue, not a battery or start issue.

It;s a diesel, not a gas motor. If it has fuel and compression it will start in the third stroke, because it's a diesel.

That's why they run away at times, because once they start, that's all they need, fuel and compression.

 

You have fuel or compression problem, not a wiring or battery or starter problem

If you can't figure it out I'm always looking for a scrap DT12 tranny. PM me

 

I'm betting you actually have a PDM/PCM issue. I ran across a similar problem years ago, but it was probably a 17'ish model truck.

You could try jumping across the starter solenoid or the relay on top, I'm betting it still won't start.

There's a hell of a lot of difference between "similar to a cold/winter start problem" and "cranks for two seconds". Nobody can diagnose without proper info, and the OP ain't helping.