hard start when engine is warm

Reply Subscribe

Thread Tools

Search this Thread

Apr 10, 2011 | 08:07 PM

perryau1996

Thread Starter

Mountain Pass

Joined: Dec 2007

Posts: 124

Likes: 0

hard start when engine is warm

I have a 1996 f150 with a 351. I've been having a hard start when warm problem since i bought this truck month ago. I've replaced fuel filter, plugs, dist. button and cap and plug wires. No change. I've hooked up a fuel pressure gauge and have some issues....I think. My chilton manual doesn' give me the answers I need. When i turn key to the on position, the fuel pump makes prime noise. Fuel pressure gauge goes to 20. When i turn engine over the guage drops to 5 or 10. It will start but it bucks and jumps, and shakes. If i play with the throttle it will smooth out and pressure goes to 35 and runs and idles great. When i turn the truck off the pressure goes to 40 and stays there and holds pressure for about ten minutes then will bleed down to zero after about an hour.

Truck always fires up first time when engine is allowed to cool completely off. This truck runs great and gets decent mileage once it gets going. I have some lean bank 1 and 2 codes. Egr is working properly. Is my fuel pump weak, or do I need a new fuel pressure regulator or both? I have one tank on my truck.