2003 Duramax Diesel loosing prime and will not start until I lift the hood and pump the prime plunger on the fuel filter housing.

check your lift pump it sounds like an intermittent fault related to electrical harness and or a relay going bad also check for technical service bulletins at your local dealer they might have more specific information GOOD LUCK

After replacing the fuel filter did you prime the system? There should be a small circular pump on top of the filter assembly to prime it. I own a 2003 Duramax and it usually takes about 5 pumps / turn over / 5 more pumps / turn over / and 5 more and you should get it started. It will take longer if you didn't fill the fuel filter with diesel before installing it as well. Let me know. Thanks.

IS THE ENGINE TURNING OVER? IF IT IS YOU MAY HAVE TO BLEED AIR FROM THE FUEL SYSTEM, IF THERE IS A MANUAL PRIMING PUMP, USALY BUILT AS PART OF THE FILTER HOUSING OR REMOTELY MOUNTED ON THE FUEL SYSTEM PUMP THE PLUNGER THILL IT GETS HARD THERE SHOULD BE A BLEED SCREW MOUNTED OPEN IT AND STROKE PLUNGER UNTIL YOU SEE BUBBLE FREE FUEL COMING THROUGH CLOSE OFF THE BLEED SCREW AND PUMP PLUNGER TILL HARD AGAIN THEN TRY STARTING

Most likly the filter housing needs to be replaced and or the fule lines to and rom the housing. the housing has the plunger on top and the filter screwed under. The plunger goes bad on these and causes air to enter and then become air locked. this is also very comon on the IPR with the fuel filter housing mounted behind cab on frame rail driver side. road sault gets to these and degrades the unit untill it sucks air. On the c 4500 you need to get the oem fuel lines because of the tight space restrictions to route the lines. the OEM lines are molded to make the tight bends required.

Hope this helps... Good luck

you just srew old one off ,and fill new one with clean fuel if you have some ,and the prime it with plunger top of fuel filtre housing till it feels tight do not overtighten new filtre if car does not start prime again until it does

Hello and welcome. you will have to perform the bleed procedure using the fuel prime on the fuel filter housing. there is a pump on top of the fuel filter assembly, on the passenger side of engine.

Open the vent valve screw (1) by turning the screw counterclockwise several full turns.




Operate the priming pump (1) by repeatedly pumping until a small amount of fuel seeps from the vent valve. Allow the pump to fully return upward between pumps. When fuel is present, the filter is full of fuel and the system is primed.
Close the vent valve screw.

IF THIS IS AN 2007 YEAR THE FUEL PUMP SHOULD BE IN THE TANK. IF THIS IS A DEISEL THE PUMP COULD BE ON THE FRAME RAIL BUT ONLY HAS ONE PUMP THE PUMP RUNS BOTH TANKS.
CHECK FOR ANY CRACKS IN THE FUEL LINE ALSO. BUT IT SOUNDS LIKE THE FUEL DRAINS BACK INTO THE TANK WHEN IT SETS THIS IS A SIGN THAT THE FUEL PUMP IS NOT HOLDING IT'S PRIME AND THIS NEEDS TO BE REPLACED

fuel pump is obviouslynot working !
check it & its wiring!!!!!

Well, one problem is, if its an 8.1, its not a diesel. The 8.1, or Vortec 8100, is a gas engine. The DuraMax is a 6.6 engine. There is usually not a priming system on a gas engine, because the fuel pumps will usually get it through the smaller filters used quick enough you dont need them. However, if it is a DuraMax engine, then right on top of the fitting where you mount your diesel filter, there is a primer pump and an air bleed valve. What you do is, open up that air bleed valve ( its a little black plastic octagon shaped thing on the top of the filter mount) then you pump the primer (the silver button looking thing) until you get diesel squiting out the air vent without too many air bubbles or gurgles.

I see that you had the injectors replaced 20,000 miles ago. I would still check the oil to make sure it is not overfull. The new injectors could be bad. If the oil level is not overfull then get a paper towel and touch the dip stick tip on the paper towel while oil is on the dip stick. If it's only oil it will not spread. If it has diesel in the oil the oil with spread. If this test doesn't show the injectors to be bad then you have three other possibilities. The FICM (fuel injection control module), the fuel pressure regulator, or the injection pump. It's hard to pinpoint what the problem is without running more tests and the only way to run those tests is with the computer the dealership has. Just so you know your injectors are still under warranty until 100,000 miles. Most likely you will have to take it to the dealership to get you truck fixed. I hope this helps you some.