LMM: Low pressure limp (with specifics)

[Dustins_dmax]

2008 lmm about to roll over 270k
5” exhaust
Fass lift pump
Cat 2 micron filter in stock location
Edge race evolution (lvl 2 always)
Replaced the fuel lines at the filter housing

I have pulled all winter, heavy and light weight with no issues. About the heaviest thing I pull is a 33’ 5thwheel - no issues

Today it was 85+ out of nowhere. I pulled my 25hp tractor (mid size) on a (16’) car hauler. It limped on me up a slight grade with the low rail pressure code. It did this last summer a few times, especially with the camper.. but nothing when it’s cooler.. never when unloaded hot or cold. Truck runs fantastic, balance rates are great (I know it doesn’t mean much in this case)

I think I’m going to replace the braided fuel lines under the truck as people say they will collapse however I thought this was no issue with a lift pump? Do I possible have bad injectors? Or cp3? Please let me know your thoughts.

Thanks


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[2004LB7]

I would address all of the rubber lines first and see if the issue persists. If it does the I would run a return rate test on the CP3 first then the injectors

It may be a good idea to verify that you actually do have positive pressure at the input to the CP3 and there is no restrictions or failed LP

 

[Dustins_dmax]

2008 lmm about to roll over 270k
5” exhaust
Fass lift pump
Cat 2 micron filter in stock location
Edge race evolution (lvl 2 always)
Replaced the fuel lines at the filter housing

I have pulled all winter, heavy and light weight with no issues. About the heaviest thing I pull is a 33’ 5thwheel - no issues

Today it was 85+ out of nowhere. I pulled my 25hp tractor (mid size) on a (16’) car hauler. It limped on me up a slight grade with the low rail pressure code. It did this last summer a few times, especially with the camper.. but nothing when it’s cooler.. never when unloaded hot or cold. Truck runs fantastic, balance rates are great (I know it doesn’t mean much in this case)

I think I’m going to replace the braided fuel lines under the truck as people say they will collapse however I thought this was no issue with a lift pump? Do I possible have bad injectors? Or cp3? Please let me know your thoughts.

Thanks


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Thanks, I will look into this. I failed to mention the truck also has ppe race valve in it as well, previous owner must have installed it. I wonder if a better or additional fuel cooler would help since this is only an issue in warmer conditions? I think my CTS can show me fuel temp. I will have to see as I can watch for the “magic” number that sets it off


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[ikeG]

I think you're delaying the inevitable/throwing money away with the fuel cooler idea. I'm sure it's either the injectors or cp3 returning too much, especially at 270k. I personally have not had to replace a lmm cp3 for these reasons, it's always been the injectors for me. Easy enough to test the two and narrow it down.

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[clrussell]

I think you're delaying the inevitable/throwing money away with the fuel cooler idea. I'm sure it's either the injectors or cp3 returning too much, especially at 270k. I personally have not had to replace a lmm cp3 for these reasons, it's always been the injectors for me. Easy enough to test the two and narrow it down.

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This x1000

 

[Mike L.]

Isn't the Cat filter kind-of restricting?

 

[Dustins_dmax]

Isn't the Cat filter kind-of restricting?

Can someone weigh in on this?


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[Chevy1925]

without a lift pump, yes it can pose an issue. ought to be one of the first things i would change though with this issue.

since you have a lift pump, i wouldnt see it an issue unless the filter is plugging up.

 

[Dustins_dmax]

I need to take another look at my cooler as well. I have not sprayed it out in a while. Not sure it would make much difference anyhow..


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[Chevy1925]

I need to take another look at my cooler as well. I have not sprayed it out in a while. Not sure it would make much difference anyhow..


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it wont but you can try it. stock cooler is crap and makes hardly any difference

 

[Burn Down]

Keep it simple... I’d ck the fuel line at the drivers rear of the engine. When the engine torques over under heavy load it can kink the line and restrict fuel causing P0098. If the engine mounts are bad or worn it can make it worse. Feel the underside of the bigger line next to the quick coupler for a kink.

 

[Dustins_dmax]

Keep it simple... I’d ck the fuel line at the drivers rear of the engine. When the engine torques over under heavy load it can kink the line and restrict fuel causing P0098. If the engine mounts are bad or worn it can make it worse. Feel the underside of the bigger line next to the quick coupler for a kink.

I will do this for sure. Thanks

I failed to mention something else that I feel I have read somewhere else also. If I hold the truck in 5th or manually downshift (pulling a hill for ex) the truck will not set the code. And do just fine under the hottest temps and heaviest loads.


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[WVRigrat05]

Sounds like injectors are returning too much, when mine went out I installed a race plug and cranked up my lift pump it wouldn't limp towing but would only hold 18k rail pressure, if yours is still limping with a race plug I would look at rubber lines at firewall, change fuel filter and then monitor rail pressure towing and do a return test on injectors if still an issue. Wouldn't hurt to check cp3 return either.