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Hey guys and girls,

I am new to this site and this is my first question on here, and be prepared to hear the weirdest Duramax problem yet. I have a 2004.5 GMC Sierra 2500HD LLY. I have had it for 3 winters now and every year it does the same thing. Keep in mind that the truck runs perfect all of the months that are above 50 degrees. Here comes the issue, whenever it drops below 50, my truck wont start, until it warms up outside. if I plug it in, it will start. (that seems too warm to have to plug a truck in).


Once I prime the fuel filter a few times and get it going, I reach my second problem.


When I start driving, the truck will shut off if I hit a speed bump, pot hole, curb, crack in the road, etc. It will fire back up as long as I prime it. This morning I raised my hood to prime it, and then it started, then I shut my hood, and the truck shut off.

I then raised the hood and started it again, then I started smacking anything that the hood comes in contact with, and I tapped the fuse box and the RPM's dropped. I hit the fuse box hard and the truck shut off. This made me think that it is a wiring issue, but as stated before, the truck runs perfect when its above 50 degrees.


I'm not looking for a complete answer for all of this, but any guidance/help is much appreciated. Thank you.



Key Problems:
Truck wont start in 50 degree weather
Truck shuts off on bumps
tapping the fuse box makes it shut off
runs PERFECT when its above 50 degrees
 

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You have posted in PRE Duramax. you may want to re-post in LLY section. If you have to prime it to start you have a vacuum leak in the fuel system. Being cold it could be seals in the filter head. if you have never serviced the filter head. I would just replace the whole unit. Assembly w/filter is less than $120
 
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