Recently purchased a 2008 ZD28. Unit is in great shape with under 550 hours on it. I have recently serviced it (fuel filters and fresh fluids) got it all ready to go for the season. When I went to cut the grass for the first time today I made about three passes and noticed a trail of fuel on the ground. Shut the mower down and noticed that the small round cap below the injection pump had come out and fuel was leaking from said area. A bearing was visible in the approx 2" hole the cap was covering. Can anyone tell we what the cap is covering and if I can reinstall? What would cause it to pop out and can I put it back/should i use some RTV if I do pop it back in? Thanks for your help!