LMM: Low Rail Pressure

[03Tommy]

Current mods in sig. Race valve not installed yet.

Truck has 180k on it, but runs great. With the PPE on level 4 or higher, rp will not go above 17k actual. It threw a 0087 one time when pulling my camper but no codes since. No lift pump yet as my LLY never had rp issues on level 4 and it also had 180k on it when I got rid of it. On level 5 and 6 this truck barely smokes. Just a light haze at wot. Putting the race valve in today, think it will do the trick or do I have bigger problems?

I never had issues like this on my LB7 or LLY, that is why I have not gotten a lift pump yet. I have searched for hours on end and cannot figure out what the issue could be other than the FPRV or CP3. Balance rates look good.

 

[03Tommy]

Race Valve installed. What a PITA! No change.

So, think I just need a lift pump? Truck runs strong and rail pressure catches up, but still little smoke.

 

[S Phinney]

You might should check for fuel restrictions then look into other fueling issues.

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[redws6rocket]

Probably have an injector or 2 returning to much fuel, we have been seeing a lot of these issues at the dealership

 

[03Tommy]

Update

Raptor 150 installed, Rail pressure now drops to only about 20k instead of 17k. I did turn the pressure on the pump up to just over 20psi. Still no smoke to speak of. Checked all fuel lines front to back and even replaced one. I had some issues out of my Hot+2 today while changing tunes. I put the truck back to stock and it still acted like it was on level 4 except it threw dpf codes. Put the tune back in then back to stock and it seemed stock. I am going to call Dan tomorrow but have an h&s mini maxx standing by to try to rule out the tuning in case I cant get ahold of him.

I still think the truck runs excellent and fuel mileage is good. Problem is that in the back of my head I know something is wrong and it is driving me nuts. Again, all injector balance rates are good.

Any other ideas?

 

[LWATSON]

CP3 getting weak?

 

[03Tommy]

CP3 is the only other thing it could be I guess. What are the signs of one letting go? After I talk to PPE, if we dont figure it out, I guess I am going to take it to somebody to help diagnose.

 

[Ne-max]

How much pressure is it asking for?

 

[03Tommy]

26.5k

 

[Rhall]

I will never own a Lmm again. I have been fighting this with my dually for a year. Put a fass on, shimmed the valve, changed injectors, only thing left is the cp3. We did find the fuel lines were kinked where they came over the motor. I guess that's common too. Still didn't fix it. I never had this many problems with my lb7 haul rigs with way more miles and injectors were a lot cheaper. It does tow better, but my next haul rig will be a real truck. A peterbilt.

 

[DuramaxPowered]

Have you bottle tested to make sure that the race valve is tight enough?....I have a buddy that put one in and swore it was TIGHT, but was leaking slightly.

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[03Tommy]

I will never own a Lmm again. I have been fighting this with my dually for a year. Put a fass on, shimmed the valve, changed injectors, only thing left is the cp3. We did find the fuel lines were kinked where they came over the motor. I guess that's common too. Still didn't fix it. I never had this many problems with my lb7 haul rigs with way more miles and injectors were a lot cheaper. It does tow better, but my next haul rig will be a real truck. A peterbilt.

I have owned this thing for 30 days, today. It may be going up for sale. After the problems I had with my LLY and now this, if I cant find a decent LBZ or LB7 I will be back in a cummins. Hell, if I didnt have a camper to pull, I would just go back to a gasser at this point.

I love everything about this truck, except the fuel problem. I am going to do a bottle test today and then try some different tuning(truck threw some codes it shouldnt have on the way to work today.) If neither of these work, its going on craigs list. I guess a good selling point is that it doest smoke :roflmao: