Posted October 15, 2022. Glow plugs are to assist starting when very cold. They are used when they are not essential, it helps start quicker and smoother on warm up and better for emission output whilst warming up. Most cars in our climate can still be used with no glowplugs ( but rougher starting and more emissions) . Disconnect the power to the glow plug relay and try another fuse. If the fuse holds, then you'll know it's somewhere between the relay and the glowplugs. You probably have a bad spot in the wiring that is grounding out. Reply Like. # 3. 11-09-2003, 11:56 PM. F250 won't start. 1987 - 1996 F150 & Larger F-Series Trucks - Glow Plug Relay - When I got this truck a week ago, (93 F250 7.3 Turbo, 188k miles) the glow plug relay clicked a couple times a second when Wait to Start was on. It had, what I believe, were stock GP's, so I replaced them with Motorcraft. Tractor Electric System Fix! 4 Reasons It Won't Start Glow Plug Relay And Control Module ReplacementDISCOUNT CODES!! Grower Solution Discount: Pre-Power Stroke Diesel (7.3L IDI & 6.9L) - 1994 F350 7.3 glow plugs - 1994 F350 7.3, the issue is the glow plug relay, have replaced once and daughter's mechanic says its bad again. Mechanic says that instead of replaceing the relay again, he can bypass the relay and wire the glow plugs to a button she would have to 3C92.