I have a 1996 f150 with a 5.8 in it. I just bought it 2 weeks and it ran great when I test drove it. Now it's hard to start when the engine gets warm. Sometimes it will start right up and vibrates like crazy then will smooth out and run great. I checked codes and it turned up a po385 which mean crankshaft pos sensor. Could this be my hard start when hot problem. I've changed the fuel filter (gas that came out looked like oil), cleaned the iac, and the egr. Battery and starter are fine. Thanks for any ideas.

 

That would be a good place to start. Do you have a manual? I'd test the circuit before throwing a part at it.

 

It could be many things but check the Fuel Pressure Regulator for a leaking diaphragm. Pull the vacuum hose off and check for the smell of gas. Check the wiring harness that leads to to the CPS and make sure all the grounds are good.
regards
rikard

 

Will do, thanks

 

I went ahead and changed the crankshaft sensor since it was cheap and easy to do. I pulled the vacuum line off of fuel pressure regulator and didn't see or smell gas but I did hear a small hiss. It's still doing the same thing. When i park it and let it sit15-30 minutes it will start but buck and jump then stall...then not start at all...wait an hour, starts first time.

 

I have also noticed another thing it does when i have the hard start or no start when hot. I will turn the key to the on position over and over to cycle the fuel pump to make sure the system is getting primed. It sounds fine but it won't start. BUt then on the tenth or eleventh cycle the pump will come on but will make a louder hum in the last part of it. It will make a low hum then a louder hum and it will fire right up Bad fuel pump? I plan on checking fuel pressure as soon as I can find an adapter so the gauge will fit my shrader valve.