Hi all, I posted earlier on the forum regarding my bike hard starting since changing the in tank fuel lines, I have double checked the fitting direction of the feed and return and there is a good flow of fuel while priming and intermittent while cranking, you can hear a flow of fuel back to the tank, I have fitted new plugs and it appears to be creating a good spark, but still it seems hard to start when left over night, when i first refitted the hoses I got the flow and return backwards fuel discharged from the clipped hose at the fuel tank on the none return valve, but once I swapped them everything seemed ok but then shortly after created the starting problem, my question is do you think I have a damaged regulator which is not pressurizing the fuel rail enough at start up the feed rubber pipe does harden when pump is running but I wouldn't say over hard also I haven't ridden the bike so its only run on not much more than 1500rpm in my yard, once we have the bike running it seems to start well after but not when left for hours, any help would be much appreciated re Alistair

Perhaps one or both of the injectors is leaking fuel into the engine overnight. The additional fuel in the cylinders would make it too rich for an quick start until it the engine had been cranked over a few times to clear it. When the fuel lines were incorrectly fitted the system pressure possibly leaked back to the tank so the injectors wouldn't leak with no pressure.

Another possibility is that the cold start problem isn't related to the fuel pump/regulator. At switch-on the pump runs for a few seconds bringing the system up to pressure. So it should be at the regulated pressure immediately. If the regulator is faulty such that the pressure is lower than it should be then I'd expect the overall running to be affected. The amount of fuel injected is a function of the duration for which the injector is open and the system pressure. So if the pressure is low it will run lean across the range.
At a cold start the mixture is enriched by the ECU increasing the injection duration and this is determined by the voltage it receives from the coolant temperature sensor. The coolant temperature sensors on Ducatis are well known for giving problems and a faulty sensor could be reason for the cold start issues. They are the same as those fitted to the Fiat 1.2 Punto engines and can be got from motor factors and eBay for about £10 or so.

Thanks for your reply I think you might be onto something with the injectors leaking over night as when I change the plugs it started first time, but only straight after changing them then problem was back next day, I will have a mess with things and let you know how it goes, once again cheers for your help re Alistair