LBZ Fuel Pressure Issues...

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LBZ DMAX

Member
Nov 7, 2006
397
0
16
Fontana, CA
Is anyone else experiencing this issue:

• Rail pressure will not go past 12.5K PSI when desired
is 26K PSI
• Will stay like this for a day or two
• Happens only when drag racing or driving around
under WOT conditions

Haven’t done the bottle test to completely rule out the possibility of a weak FPRV; I guess that would need to be the first step. What I find the most puzzling is it only comes up (most often) after drag racing. It is real aggravating when driving around with half power and to the best of my knowledge, lift pumps are doing their job.

Would a weak/heading south CP3 cause this kind of problem? I’m leaning towards changing out the regulator with a modified one and taking my chances of that being the culprit.

Any input would be greatly appreciated.

Thanks!
 
bullfrogjohnson

bullfrogjohnson

Big Girl!
Nov 20, 2006
4,167
1
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39
Locust, NC
i would do the bottle test first then check your pumps. I have heard of people complaining that the dual pumps will drain down. Your truck is too new for a bad CP3.
 
sweetdiesel

sweetdiesel

That's better
Aug 6, 2006
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Thailand
well bottle test would rule it out?
how about just bad fuel and filters?
hot fuel maybe???

if the CP3 is bad it would probably lope real bad to?Im thinking
 
L

LBZ DMAX

Member
Nov 7, 2006
397
0
16
Fontana, CA
sweetdiesel said:
well bottle test would rule it out?
how about just bad fuel and filters?
hot fuel maybe???

if the CP3 is bad it would probably lope real bad to?Im thinking
Click to expand...

Back in the 05 days, bottle test proved the shim popping brought down the actual psi to sub 10K psi.

Filter is fairly new. Last time this happened, I changed the filter and it immediately didn't go away, but eventually did.

Could be hot fuel, but wouldn't other dmaxes also do it?:confused:

No loping...no codes (other than p0087)...:confused:

Thanks!:)
 
sweetdiesel

sweetdiesel

That's better
Aug 6, 2006
10,390
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Thailand
Ralph

Im thinking that the hot fuel is not the problom,Just throwing ideas??
and I didnt know the Pop Valve would drain that much....WOW My 05 has been shimmed since day 1

I geuss i would still do a bottle test,Its a easy way to eliminate things
 
L

LBZ DMAX

Member
Nov 7, 2006
397
0
16
Fontana, CA
sweetdiesel said:
Ralph

Im thinking that the hot fuel is not the problom,Just throwing ideas??
and I didnt know the Pop Valve would drain that much....WOW My 05 has been shimmed since day 1

I geuss i would still do a bottle test,Its a easy way to eliminate things
Click to expand...

The good ole 'shimming' days...:rofl:

Pat disassembled the first FPRV in our area and we stuck it into my truck. It was nice not having to worry about 1093's when the 'duramax guru' thought it was related to tuning...:D

Bottle test is on the list...:(
 
L

LBZrcks

.........
Jun 2, 2007
5,297
12
38
38
SoCal
LBZ DMAX said:
Mah truck ain't mating with anyone/anything, thank you!:D

Picture of this device??!?!
Click to expand...

:eek::eek: jeez what's on your mind? D*N**E? :joker:lol. I don't have a pic, but it's a regular looking guage that measures fuel psi 0-30 psi, it has a sensor that screws into your bleeder screw on top of your filter
 
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