Tony Hesketh’s men fell to Division One leaders Hesketh Bank in a 4-3 humdinger, despite Matt Van Wyk’s hat-trick.
Bank will be joined in the last four by Burscough Richmond who saw off Hurst Green and Blackpool Wren Rovers who secured a 3-1 win at Pennington.
Walshaw Sports complete the semi-final line up after their penalty shoot-out win against Slyne last week.
Van Wyk put Fulwood ahead with a great finish before Kevin Edgar equalised straight from a corner.
Edgar struck again to put them ahead at the break, an advantage extended through Richard Burns in the second period.
Van Wyk got his second from the spot but a rocket header by Luke Smith made it 4-2.
Van Wyk completed his treble late on but it was not enough as Dan Birkby’s side enjoyed a notable scalp.
Burscough Richmond, who won the LFA Shield in 2016/17, saw off Hurst Green through two late goals from Ade Kirkbride and Raj Uppal.
Completing the trio was Blackpool Wren Rovers who triumphed 3-1 at Pennington thanks to goals from Jacob Aspinall, Luke McNaughton and Finn Marsh. Their hosts grabbed a consolation in second half injury time.
In the Westmorland Senior Cup quarter-finals, player manager Shaun Gardner led by example with both goals as Milnthorpe came behind to beat Windermere.
The hosts led early on but Gardner struck twice – once from the spot – to seal a 2-1 win.
Kendal United went down 1-0 to Penrith Reserves in another quarter-final tie.
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