hey guys I am new to this but have been reading a lot of the conversations, I got a 08 lmm 120k miles and have issues with rail pressure with or with out efi tune from Duramax tuner. went back to stock fuel filter, got a bottle test done yesterday, no fuel. have read post about soft lines. When I did the bottle test I noticed the 3/8 line that is next to what looks like a 1/2 line is bent over pretty good, could see as to where that could cause issues. Is this the line that gm did a cut and replace with better fuel line? Is there a way to view balance rates through an autoal?
08 lmm limp mode issues
- Thread starter Johnrt
- Start date
Have you shimmed to relief valve or replaced it with a race plug? Might be causing your low rail problems
The 3/8 line is the return line, the 1/2 would be the supply line. They are on the driverside back where they come up if that's what you are referring to. Did you try to command fuel rail pressure to see if the relief valve is popping open? Give us more info on the truck. What all do you have done
No lift pump, started having issues towing so went back to stock tune and continued to have issues after awhile after. Was running wix filters as I was going through acdelco ones every 10k or less.
Truck is stock other than dsp5 tune. While the tune is loaded it will show low power mode, dump the fuel filter but does not go into limp mode. Stock tune will dump a brand new filter and go into limp mode. The rail pressure will drop with wot. But catches back up after shifts. Only 120k on truck, pulling less than 10k most of the towing life.
Sad part is it is doing this not even towing lately. On 3 rd filter in less than 10k miles. I have a data log of 3 12%grade wot pulls. Just not great with
Efi live to break it down effectively
Truck runs a little warm when towing, sounds to be the same as every other lmm of people I know That have one. I will have to crawl back under it and inspect lines.
What is the thoughts on brands of quality lift pumps?
What is the thoughts on brands of quality lift pumps?
As stated above, check the fuel lines on top of the drivers valve cover. A lift pump won't help it the supply line is collapsing shut. But I'd hook the hose from the lift pump right up to the metal hard line at the valve cover and remove the factory 1/2" supply.