air in fuel system without leak?

[MathewHennessy]

Hi,
More fun with starting the car: This 25F degree AM I had the usual starting behavior (glow, crank for 10s, stop, glow, starts immediately), let it warm up for 3-4m while the defrosters were defrosting, drive off, then park it about 5m later for some coffee. When I get in to start it, I crank it for like 20s and it's very fast (since the motor's warm) but it won't start. I do this 2x more, then on the 4th try it starts right up.

I don't think it's in the glow plug system (having tested the plug wire resistance, leads and relay voltage). I presume the injection pump is priming itself all the time? I recently had leaky o-rings replaced, which cured a leak which was causing me to have to assist the priming of the IP by loosening the injector lines when parked uphill. But now there's no discernible leaks under the car when parking uphill or downhill. Could there be an air leakage into the fuel system before it hits the lines or any device that would leak out fuel?

I've also recently had the timing chain replaced, as well as the fuel filters. After all this work, when removing the fuel cap, I noticed I wasn't getting a *gasp* from the filler neck anymore, and that when the tank got very low the fuel gauge needle would bounce before the low fuel light turned on, and that hadn't happened before.