I have a 2001 4x4 Chevy 2500 HD Duramax 239000 miles

Rebuilt the injectors at 170,000

Throwing the P0093 code

I will drive 70/80 MPH for an hour plus then the truck puts me into limp mode. I pull over shut down for 10/20 seconds, restart the truck it will still say “service engine” soon but will run fine.

If I pull my trailer the truck does the same thing, but it will start a lot sooner to go into limp mode. Pull over shut down and restart, truck will drive fine for 30 or 40 miles then do it again.

 

things to check:

1st, Fuel filter. when is the last time you replaced it?

2nd, fuel supply leak. often at the filter housing. you can replace the line on the output side of the filter with a clear one and look for bubbles. there are rebuild kits that replace all of the wear items on the housing that can be bought quite cheep

3rd, Fuel pressure regulator valve. this is located on the CP3 fuel pump. these will ever so often go bad and miss-regulate the fuel pressure

4th, CP3. it is possible that the CP3 fuel pump is weak and cannot keep up with the fuel demand. you would need a tech 2 or other tool that can monitor fuel pressure to check this. same for # 3

5th, excessive fuel return on one or more injectors. no easy way to check this without tearing in to the valve covers to see which one(s) it is. you can check one bank of injectors at a time to help narrow it down. google "injector bottle test" to see what is involved

also, excessively hot fuel can cause this too. if your fuel cooler by the fuel tank is clogged try cleaning it and see if it persists.

good luck

 

Most commonly this is a bad Cp3. 2004LB7 is correct to check the list above first, but if you have any logging tools or preferably something like a Tech 2 or V2 then you would have bi-directional control. What will want to do is command full rail pressure then log it and see if the pump can keep up.

 

Thanks 2004lb7

I'm glad you responded to my post, it is good to have someone knowlegable and on the same page with this engine.

Everything you have brought up about the symptoms this code that my truck is showing is exactly what I have been trying to fix, but finding the right fix is the hard part.

I always change my fuel filter every other oil change, 10K miles. I had my mechanic put a race plug in to replace the fuel overflow plug witch didn't do anything anyway. That help but did not solve the problem.

On my way home this week I pulled my trailer and as expected the truck went into limp mode, but this time it did not take me down to 25 MPH but to 40 min MPH. I stayed with that speed for 10 miles then the truck came out of limp mode

I think the lift pump is week and in those 10 miles at 40 MPH it caught up and went back to normal driving mode.

So here is my plan what do you think? I'm going to start with a cat filter upgrade.
Clean the fuel cooler," this is one thing my mechanic and I did not think about, thank you"
I am then going to drive the truck and see if these two steps fixes the problem, I'm thinking not but its worth a try.

Then if that fail its time to change the lift pump, I would just change the fuel pressure regulator but, if I'm digging that deep into my engine I'm changing the pump, for the money its worth not having to do this twice and with 239,000 miles the pump probably should be changed anyway.

at this time I'm having my mechanic do a fuel flow pressure test, that will tell me if my injectors need some help.

What do you think, is there anything you would add to the list.

Thanks

Bruce

 

the 2 micron CAT filter is good but doesn't have any provisions for water removal. water is a major problem in these engines. if you have water in the fuel issues or freezing weather in your area i would stick with the recommended coalescing filter like Racor or from the dealers.

there is no true lift pump like most think of on these trucks. the "lift pump is a gear pump mounted on the back side of the CP3 (high pressure fuel pump) that is installed in the valley of the engine. this pump has to suck fuel from the fuel tank all the way to the engine. it sound like you already know this but may be using the wrong words.

as a band-aid some actually add a lift pump such as air dog or fass. this helps the CP3 get the fuel it needs to build the pressure. it also has the benefit of keeping air out of the lines and makes priming the filter a lot easier. something to consider.

 

Bruce,
Sounds like a good plan. I would hold off on changing the lift pump (airdog/fass/fuel lab). If you have a lift pump, you could just put an external gauge inline with it and test it prior to changing it out. At least a gauge would be cheaper than a whole new pump.

 

Speaking of wrong words...... you say some add a lift pump like a air dog/fass as a "band aid". In what way would using a fass or air dog be a band aid on a d max? I'm getting ready to instal the fass off my old dodge on my chevy and am curious as to why you say band aid?

 

it is a band-aid for a weak CP3. for a stock or mildly modded truck where the CP3 should be able to keep up but cant, a lift pump can sometimes help keep the fuel pressure up to the desired amount. it is a band-aid because it is often cheaper to add a lift pump then replace a week CP3

 

Just odd that the cummins uses pretty much the same pump but has a lift pump from the factory and that there is no help on the d max. Just seems like any kind of pump would make a brand new cp3 last longer and work less from the beginning. I wouldnt say band aid is remotely the word to use, more like doing something that the engineers should have done in the first place.

 

except for the fact that the two pumps are not exactly the same. the duramax version of the CP3 has a little more capacity then the cummins version. this may have been a deciding factor in determining if a lift pump was needed in the duramax