I have a 2000 model 502 EFI that is hard to start cold after it has sat all week and over night. Once it starts i dont have a problem with it the rest of the day. I'm just looking for some suggestions on what it might be that i need to look into. Thanks

I found a focused effort to only use no-alcohol fuel and use of a fuel treatment improved starting and initial start smoke markedly on my carb 454.

I started with Lucas fuel treatment and had good results but switched to Conklin fuel mate plus due to it having both fuel stabilization and cleaning properties. (and a buddy was pushing the Conklin as a dealer)

one of a couple of things. the system probably has an internal leak somewhere ... an injector or something that allows the fuel pressure to bleed to zero and "dry out " the rail or rails. its pretty common. beyond fixing it is to turn the ign on and the pump will run for a few seconds. when it stops turn the ign off and on again and let the pump run again and do this a couple or three times. this will go some distance in rebuilding the pressure in the rails and make it easier to start. beyond that, make sure the water temp switch ( not the gage... the temp switch for the injection ) is good and the connections are good.

taking the injectors out and cycling them with cleaner backwards often fixes the leaking issues.

I would check the temp sensor Probably not telling the ecm that the engine is cold and not richening the fuel mixture on startup.

fuel system cleaner. could be a leak, but probably a sensor.

I'd put a fuel psi gauge on it, and see how long the fuel psi holds with engine off. Like steve says, sounds like the psi is leaking off, thru a injector, o ring, or even a valve in the fuel pump.

Having the same problem but with carb motors. Maybe fuel evaporating from bowls over extended period of shut down. Any thoughts??? Fixes??

I had the same problem, I found if I rubbed my hands together really fast then place them on a big set of boobs she fired right up. OOPS wrong thread....

Ok i've only had a chance to try turning the key on 4 or 5 times letting the pump run each time. Unfortunately this didn't help any. Still took along time to start.

Ignition control module going bad? I would have to crank and crank my engine to get it to fire unitl I just replaced it. There was also a lack of upper rpms and hesitation in the throttle.