Hard starts/glow plugs
 

Recently purchased a 2001 f350 7.3 with 350000 miles and is a California vehicle. Since cold nghts have started here in southern california, maybe 40 degrees, and yes i know this is not cold by normal standards, starting up is become stressed/ hard. During summer time temps there were no problems or "hard" starts. Recently my morning starts are "hard," even to the point not starting this morning. I have replaced the glow plug relay and still get no voltage to the second large post when turning the key and charging the glow plugs. Is there a way to test if the GPR control is bad or perhaps if the glow plugs are bad? I am a mechanic by trial and error, so any and all information is welcome. In fact more information and detail is very welcome. Thanks in advance for the help
:tu:

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quick update: I found a thread on diesel bombers on how to use a voltmeter to test glow plugs. All four glow plugs read 0.9 ohms, so according the the thread they are good.
Also forgot to add in the original thread i have 2 new batteries and a new alternator installed. Any help would be great. Thanks

Update 2: i have bench tested the GPR and it is good, i can hear it click on when activated. But when it is installed in the vehicle, it will not activate. I checked all connections on GPR and they seem fine. Anybody got a suggestion on where to look next. Thanks

two things... first off, there are 8 glow plugs, not just four.
secondly, your glow plug control module is probably shot
this is different from the glow plug relay

So i just installed a new GPR controller I purchased from Rockauto. Now when I turn the key, all I get is a audible "click." Where do i go from here. Thanks