lb7 power problem ?????????

[perseverellc]

now first off in new to the duramax engine , and this forum..........
i bought an 02 duramax for cheap that was rust free high miles 300k
one owner..... needed injectors .. the owner owed money to the guy i got it from so i dont have a complete history but looked taken care of... im not new to diesels.. i replaced the injectors without a hitch ... and lots of frustration ......... since i put in a ppe accelerator standard 90 hp tune... once i put in the pyro and boost gauge .... its been a long time since ive been in a duramax .. i didn't realize
i was lacking low end power for a while...... if i mashed it from a stop it wouldn't even atempt to break loose the stock 245-16 tires ... now at 2000 to 2500 it really wakes up and takes off.... but not much boost till 2000 1.5 to 3 lbs at 70 mph flat to slight grade ..... no smoke only a little once it lights up wot ..on the 90 tune ... as far as i know the cp3 could have never been changed ... its throwing no codes ... i've changed the oil and all filters this weekend and cleaned the mas....... i'm getting confusing readings off the ppe for fuel press .. it says 5500 at idle but drops when i mash it it comes up a little goes way down than back up may be im reading it wrong or its reading wrong {missing a row of #s}
but im sort of lost ....:banghead:

 

[Neal Driedger]

Sounds to me like your cp3 is shot! But it wouldn't hurt finding somebody that can get u a accurate reading on your fuel pressure

 

[Dirtymaxx03]

Try the 120 tune

 

[jgt1982]

Cp3 my truck is doing the samething with low rail pressure check on here but find someone to check out for you to be safe
Posted via Mobile Device

 

[perseverellc]

ill try it but i was scared with a trans with 300k on it..... ill either get a gauge or have someone check it...... good to know i was on the right trank thanks

 

[Mike_S]

You wont find a gauge to read rail pressure...you can tap in and see vacuum before the cp3. Do you have a lift pump installed? Will it reach 160 MPA when commanded? Coukd be either the pump or possibly the regulator. No reason to change the pump if its the regulator or relief valve.

 

[perseverellc]

??????? i see gauges for sale .... i need a lift pump for a 50 of 90 hp tune ..if that would solve the problem i think the cp3 is already weak ......

 

[Neal Driedger]

Is it a red ccsb by any chance?

 

[Mike_S]

??????? i see gauges for sale .... i need a lift pump for a 50 of 90 hp tune ..if that would solve the problem i think the cp3 is already weak ......

No test guages. You can get a guage, sure, but you will be splicing into the factory harness so that it can read off of the factory rail pressure sensor. These guages are more for permanent cab mounting.

You need to get some more clear information before anyone can really tell you where to start looking.

As far as the lift pump is concerned, it is more for taking some load off the CP3 so this problem doesnt arise as quickly/often.

Find someone with EFI Live or a tech 2 so you can do some objective tests to rule out the little things before you drop the coin on an expensive and dificult to change part.

 

[perseverellc]

ok i see id be reading a pre existing signal that could be wrong... plus i just need a more solid info to go on......
i understand the lift pump will help my cp3 last longer if i need a new cp3 i would
get one with the mods ive done and plan to do it only makes sense..
this truck was stock blue gmc l/b s/c a long distance work truck from nj to the oil spill in the gulf.... thanks again guys for the info...

 

[Maricopaagent]

check fuel rail pressure. then check maf.