No fuel pressure

[TSPowell]

I think my lift pump is dead... i was really wishing this wouldn't happen. I installed a fuel pressure gauge about 2 years ago (50,000 miles) which read about 8psi. After 1 year it was around 5 psi, and now it wont move off zero (88,000 miles). I was really hoping it was just a problem with the gauge isolator because ive had problems with it before (i wish there was something better). I just started my truck and removed the screw from the bottom of the isolator and got about two drops from it. How far can i drive with zero pressure going to the CP3, i need to make it home (150 miles, and have already gone about 350 on 0psi). Somewhere i read that the CP3 can actually pull its own vacuum. Im think i'll just put on a GDP unit if I need to replace the unit. Oh... i have my gauge installed on the CP3.

 

[JCasper]

Good luck, I hope you make it. Mine is down to about 6 psi, I wonder if it's on its way out.

 

[TSPowell]

just another note... ... . I thought I read somewhere that codes would be thrown if the pressure was too low in the CP3. My pressure is at 0 and no codes.

 

[RankRam]

Throw a new fuel filter in there before you try to finish your trip!



Good luck!!



On Edit: Maybe you shouldn't change the FF, you might not be able to prime the fuel system????

 

[rbattelle]

just another note... ... . I thought I read somewhere that codes would be thrown if the pressure was too low in the CP3. My pressure is at 0 and no codes.

Often it won't throw any codes when the lift pump dies. There's no specific code that is thrown when the supply pressure drops to 0.



Sometimes it will throw a rail pressure code if the fuel going to the CP-3 dries up, which causes the pump to run dry, which means the commanded rail pressure won't be achieved.



The way I see it, good or bad you've got no choice but to head for home the last 150 miles and pray the engine keeps running. It sucks.



Ryan

 

[LesStallings]

Back when I was operating nuclear power plants (Navy and civilian), I was taught to believe my indication. In other words, if the fuel pressure is dropping off, believe that your lift pump is dying.



I installed a fuel pressure gauge just so I can monitor the situation. The first time I see a problem I will change the fuel filter and be prepared to immediately purchase a fuel delivery solution if the filter is not the problem.



You bought a fuel pressure gauge - believe what it is telling you. Thats why you bought it!!!!

 

[SSalzer]

I thought that if your lift pump dies, your engine won't run? That was the whole idea behind re-locating it into the tank. So the big pump doesn't get starved of fuel and eat itself up.

 

[rbattelle]

I thought that if your lift pump dies, your engine won't run? That was the whole idea behind re-locating it into the tank. So the big pump doesn't get starved of fuel and eat itself up.

For the most part, this is true. However, there are circumstances where you can have 0 fuel pressure but a running engine (as we see in this thread).



It's possible that the pump is turning, very slowly. Not enough to generate any pressure, but just enough to allow the CP-3 to suck fuel through it.



You do have to be very careful in cases like this, because the CP-3 is fuel-cooled and fuel-lubricated. It is possible to burn it up.



Ryan

 

[TSPowell]

Well, I needed to go 150 miles and made it 130 miles... . it died. They only thing im worried about is the condition of CP3. I know I need a rail pressure gauge, but is there a way to know if its fried, other than not running. It will start right up but only run for a few seconds. During this time it still runs smooth so Im guessing its fine. ???

 

[Semicrazy]

I thought that if your lift pump dies, your engine won't run? That was the whole idea behind re-locating it into the tank. So the big pump doesn't get starved of fuel and eat itself up.

I am pretty sure the Duramax does not use a lift pump, but rather a larger CP3 to compinsate for not having a lift pump on their common rail set-up for more suction.



I think they also have a pump bulb on the fuel filter housing that you can pump by hand to prime the system after a filter change since they do not have a lift pump.

 

[rbattelle]

They only thing im worried about is the condition of CP3. I know I need a rail pressure gauge, but is there a way to know if its fried, other than not running. It will start right up but only run for a few seconds. During this time it still runs smooth so Im guessing its fine. ???

I wouldn't worry too much, I think you'll probably be okay.



Ryan

 

[raxley]

I thought the CP3 was designed to run w/o pressure (because of all the problems with pre-CR trucks) and the lift pump was the type that lets fuel though it even when it's dead?

I remember reading that it's not like the older trucks where it hurts the pump with no pressure.

If I read it it must be true, right?

 

[rbattelle]

I thought the CP3 was designed to run w/o pressure (because of all the problems with pre-CR trucks) and the lift pump was the type that lets fuel though it even when it's dead?

I remember reading that it's not like the older trucks where it hurts the pump with no pressure.

If I read it it must be true, right?

Nah, this stuff isn't true. The stock lift pump becomes a block when it turns off.



There is no pressure specification for the CP-3 - only a flow specification.



Ryan

 

[Parks]

rbattelle is correct about the lift pump. If it cuts off completely it does become a block. If you were to remove the block and prime the system, it will run fine.

I am sure you do not have any problems with your CP3. Just replace the pump and keep on going.



The Duramax engines do have a primer kind of like the 12 valves.

 

[TSPowell]

Im currently installing a walbro pump, i will post pics when im done. Also adding a dual remote mount filter setup with 2 mic filter.

 

[TSPowell]

The walbro is in and running like a champ @ 18psi. I think the truck idles a little smoother too!

 

[JDiepstra]

Man that is hilarious. Why did you even get a gauge?

 

[TSPowell]

Man that is hilarious. Why did you even get a gauge?

Im glad you think thats so funny.