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Help! Won't start or prime

Shellie Walker

New Member
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Crossville, TN
I have an 03 chevy 3500 with an lb7. First cold snap (and should not have been cold enough to cause diesel to gel - oops, forgot to plug it in). It started right up, but then stalled and won't restart. I'm in the process of changing the fuel filter (old one would not reprime and there is adequate fuel in it). No mods to my knowledge (I haven't done any). Has 250k on the engine. Hoping it's just a clogged filter or bad o-ring. If not, what should I be checking next? Bare in mind, this is my first diesel and yes, I'm a girl...gas engine, I'll work on anything but brakes or transmission...diesel is a whole new world.
If it won't prime don't bother even hitting the starter as it ain't going to start period. Common problems are a failed primer assembly, aka o-rings bad or dirt in primer, cracked fuel filter housing sucking air, Wix brand 'plastic body' fuel filter sucking air at WIF threads, or other air leaks. Aftermarket primer rebuild kits are available outside of GM if this is the only problem.
It has an ac delco filter. Have a new filter to install as soon as I can get the existing one off. It's never had an issue until now. And this was sudden. Driven the night before. Fired up and then stalled the next morning.
Welcome and glad you found the issue. Let us know when 100% resolved or if more problems continue.

For the future-As WarWagon mentioned, the primers fail. Usually it will crank and not start- pop he hood and pump he hecknout of the pluger. You’ll usually but not always notice it had a damp spot that dirt stuck to- but won’t usually see liquid diesel.

It can fail starting a week or so before leaving you stranded so most folks wait till the 2nd time of pump to start before buying the kit. Or just do it on a free weekend- not hard.

Don’t be thrown off by diesels. Every bit as easy to work on as gassers. The only dangerous thing a out yours is if it gets a fuel leak in the injector rail lines feeding to the injectors. The pressure is so high it could cut you like a knife. So if you ever suspect a high pressure leak don’t feel around for it.

Please dont be a “coal roller”. They are setting back so many advantages of diesels its sad. If your into it, fine but donit at the track- not on the street.
Of course it decided to pour when I got home with the new sensor...tomorrow is another day. Not a coal roller. This baby only smokes slightly if I really have to push it on a short ramp merging on the interstate. It is a beast of a truck...quad cab long bed 4x4 dually with a brush guard, b&w turnover and a magnum super hitch. I haven't found anything that truck can't pull. But as a farm girl through and through, it suits me.
I haven't found anything that truck can't pull.
You would be surprised. All trucks have a weight limit to what they can haul or pull. Quickest way to overload one is look at an RV... Just saying. Look up the specs of what it's configuration can haul or tow weight-wise and be mindful of it when hooking up...
New fuel filter and water in fuel sensor installed. Still won't prime. So I guess it's time to disassemble the primer assembly...could be an injector issue, could be the primer or could be an air leak somewhere...I'm at a loss
Yup. They wear out, so even if that isn’t it that’s just preventative maintenance.

If after that you dont get it, I would use a pressure regulator on an air line and charge the tank to 7 psi then listen for leak.

While Having pressurized it, try the primper pump to see if it is pushing fuel past there. Then at least you kjow what half of the rig you’re fighting.
Visual inspection of the fuel filter housing for cracks. (Cracks were common in the early years.) Did the O-Ring from the last filter come off completely?

Any damp spots looking at the entire fuel system?
Old o-ring for fuel filter came off intact. A little worn, but all in one piece. Haven't found any obvious leaks yet. I can hear air when I pump the primer with the bleeder screw open, but it's not pulling fuel into the filter
Odd thought, but, how much fuel is in the tank? GM fuel level sensors aren't all that reliable so a better question is how many miles since last fill up? Some add just $20 at a time so you have the best idea of how much fuel should be in there. Add 5 gal if in doubt what-so-ever. (I forget if these fail reading empty or full like the 6.5 rigs do. Also the gauge cluster can strip a gear and read wrong fuel level.)