Is that relay the "short one" next to the fuel bowl?:tu:

passenger side of motor, 2nd relay, the one more towards the turbo.

Thanks for the reply. I will check on pricing and get that one changed out!

Does anyone know what the compression should read on these? Our 02 f250 is doing the same thing and has since I put a used engine in it. I have replaced the glow plugs and harness with new vc gaskets, tested the relay and checked the power drain to the glow plugs to make sure they were heating. It will not start cold but will when pluged in. I tested the compression but haven't been able to find out what it is supposed to be. The old engine with 1 bad cylinder and a bad hpop started better than the used engine and I used the injectors from the engine I pulled out so my guess is compression with ours.

Anything below 300 is low... 425 is new or very new...

2002 7.3 hard to start when not plugged into block heater
 

Hey there. I also have the 2002 F350 SD CC X Bed 4x4. Mine has ~185K on it right now. Mine also just noticeably started being hard to start when it's 40 deg or below without being plugged into the heater. I researched and read a lot of material and things seem to indicate the Glow Plug relay. So I called the dealership where I live, told them the situation and dropped it off for diagnosis. They said in my case it was not the relay but it was both glow plug relay harness faulting; therefore not sending enough voltage to 5 of the 8 plugs. They changed all 8 plugs and both harnesses and I left out of there $600 lighter in my pocket, but the issue is now resolved in my case.

Ouch! $600.00. At least I know what my services are worth!!LOL. I have changed out both relays(there are 2 ya know), all 8 glow plugs, with new harnesses, and I had a mechanic shop change out 2 of the injectors that did not "buzz" test properly. With now 332,332.0 miles on my truck I am still using 6 original injectors(I know, should've changed them out long ago!). It is starting to get cool(Florida=hot!)and it is time to use the block heater again! Works like a champ always! Love my 7.3!!