Join Date: Dec 2008
Location: Spokane WA. area
Thanked 990 Times in 755 Posts
Being the truck is only hard to start after sitting overnight and not the rest of the day, makes me think something is bleeding down or weak batteries. Use that ScanGauge to check some things.
Look at ICP and IPR and battery voltage when hard cold start occurs.
1. Make sure the truck is running a factory oil filter with a factory black plastic oil cap. Aftermarket tall style oil caps with the wrong matching oil filter can cause oil starvation by allowing the drain valve in the bottom of the filter housing to remain open.
2. Battery voltage should start out at 12.5v or higher and drop to mid to high 11v range when glow plug cycle is on and maintain above 10.5v while cranking to start. Once running, the glow plugs will remain on for another minute or so with battery-charging voltage reading around 11.4-11.8v until glow plugs time out, then charging should jump to 13.9-14.3v
3. Make sure the fuel injector spool valves are buzzing during the glow plug cycle before cranking the starter.
4. IPR% should never be higher than around 55% while cranking to start, most will reach 35% while cranking and be running already with ICP jumping up to 1300psi or more as it fires up.
5. If you have real high IPR%, say 75-85%IPR and ICP barely reaches 500psi, then you have a high pressure oil issue.
6. Fuel pressure...can't read it with any scan device as there is no sender for a signal, need to tap into the secondary fuel filter bowl test port with a gauge or install a sending unit and gauge. Highly recommend just installing the blue spring fuel pressure regulator upgrade kit to bump up the fuel pressures another 10-15psi. Also fuel filters should be checked or replaced.
7. Don't overlook the glow plugs, even if the glow light seems normal in function.
8. Most diesel cold start issues can be attributed to either...weak batteries...low compression...bad glow plugs or controller...weak FICM...bad starter motor...clogged air filter...clogged fuel filter...bad injectors...loose or high resistance electrical connection or battery cables.
9. Need some data before anything can be determined. Thinner grade motor oils like a 5w40 or 10w30 can help with cold start function.
10. Sounds like you probably already know most everything I mentioned already, but it dosen't hurt to check the basics.
Good luck on this and keep us posted, one can never know enough about these complex motors.
Jan 03' built 6.0/F250cc4wd trqsft/SCT-tuned by KEM-Performance/Garrett Powermax vg-turbo/blue spring mod/gauges=egt+boost+fuel+SG2/exhaust/airaid intake/DR 4.5 lift/dual bilsteins/315's/greasable ball joints/powerstop/smittybuilt/kc lights/high idle mod/roll-n-lock/Mobil Delvac1 ESP 5W40 with (Archoil AR9100 in the oil) and (AR6200 in the fuel)