2001 7.3 hard start when cold

[pugsleyadams]

I have a 2001 F-550 4wd automatic with a 7.3. I bought this truck during the summer and it always started up in the morning. When it started to get colder in the winter around 30 degrees the truck was hard to start. If it sat just overnight it would start but stumble like it ran out of gas and then smooth out in about 3 minutes. If the truck sits over a weekend it very hard to start. After around 15 tries it starts and stumbles. If i plug the block heater in it starts fine even after sitting a weekend. I changed the GPR and the intake relay. My mechanic says my HPOP is leaking down. Does any of this make sense? Any help would be appreciated.

[Rich D]

Doesn't sound right to me. HPOP doesn't care what temp it is outside other than the oil type your using. You would need a diagnosotic tool hooked up to the truck to see the HPOP psi on crank/start/running. Have you verified the glow plugs are actually working? You can check your battery voltage when you start the truck and monitor it for a few minutes you'll see the voltage draw down when there on and jump back up into the 13vdc range after they kick off.

[klhansen]

The HPOP system actually compensates for cold weather by increasing the HP oil pressure.

Your glow plugs may be bad. Just because you replaced the GPR doesn't mean the glow plugs are working.

Check the Hard/No Start link in my signature for how to check the glow plugs.

[roland13]

My F650 doesn't like to start when it is below freezing either. Although my truck is from California and I moved it up here to the great white north, Maybe its just been mad at me for the last 2 winters? My old 99 F350 was the same, Didn't like starting below zero. I just plug in the block heater, problem solved. Although even with the block heater plugged in, they still are a hard start at -25 celcius.

[INFRNL]

You may want to test your injectors too. I had 1 bad injector and it really screwed things up in cold morning starts.
I would say to start with glow plugs and check uvch's
You can also run 5w40 oilwhich helps a lot in cold weather starting.