2003 Long Crank when warm

[Robbydiesel91]

Hello everyone, looking for a little help here. I’m new to duramaxs, but not diesels.

Background: Last month I bought a 1 owner 2003 GMC 2500HD with 186,xxx miles. The guy kept every receipt and had the injectors replaced last year. It’s an extremely clean and well taken care of truck, which is why I bought it. Only mods are a cat-back MBRP exhaust and AirDog Fuel Propreator.

I replaced the fuel filter and water separator on the AirDog about 2 weeks ago just so I knew it was done. All was smooth. Didn’t do the one under the engine yet because I just haven’t had the time yet.

Truck drives phenomenal but the last couple of days it has had a long crank when warm before firing up. Most of the google searches I’ve done, just go to “Injectors are bad!!!” They were replaced last year, so while possible, I doubt it.

Where should I start? Thanks in advance!

 

[TheBac]

Depends. Since you have all the receipts, where'd he buy the injectors from?

 

[Robbydiesel91]

GM dealership done on 4/22/22

 

[TheBac]

Going to have to put a scan tool on it and monitor desired and actual rail pressure on warm start. Might be a weak CP3.

(I dont want to know what he paid a dealer for that injector job. Yikes.)

 

[Robbydiesel91]

He paid about $6300, lol. I did go out and prime the button. It reduced the start time substantially. Maybe just replace the filter and go from there?

 

[2004LB7]

I'd put a clear test hose on it after the filter to watch for air in the lines. If it looks good then you need to do a return rate test to see how much fuel is leaking past the injectors, CP3 and relief

 

[Robbydiesel91]

Going to have to put a scan tool on it and monitor desired and actual rail pressure on warm start. Might be a weak CP3.

(I dont want to know what he paid a dealer for that injector job. Yikes.)

What scan tool would you recommend?

 

[NC-smokinlmm]

Check your battery cables, especially the grounds.

 

[Robbydiesel91]

I ordered an Edge Insight CTS3 last night that should be here Friday. My plan is to swap the fuel filter that day as well and check for leaks and loose clamps on the fuel lines.

This morning went I went to start it: Cranked for about 2-3 second (which I'd considered about normal) before starting. Ran for about 5 seconds and died. I got out, primed it using the button and it started after 2-3 seconds of cranking. Went to fill up because I was getting low and it cranked for 3-4 seconds before starting.

I'll check battery cables tonight, I wondered if that had anything to do with it.

 

[2004LB7]

Sounds like an air leak on the fuel lines or filter. May also be time to rebuild the filter housing if it's leaking

 

[Robbydiesel91]

Sounds like an air leak on the fuel lines or filter. May also be time to rebuild the filter housing if it's leaking

I will check that as well. Any recommendations on a good rebuild kit?

 

[TheBac]

Sounds like an air leak on the fuel lines or filter. May also be time to rebuild the filter housing if it's leaking

Now that he posted that info, Id have to agree with you. Filter head rebuild kits can be found just about anywhere.

 

[NC-smokinlmm]

Yes, if it shut off it’s fuel related.

 

[Robbydiesel91]

Changed fuel filter, oil, air filter and transmission filter today. Truck runs and starts so much better.