LB7: low rail pressure no start

D

dher

New member
Sep 13, 2015
8
0
0
hi I have a 03 lb7 that will only start with a shot of starting fluid (I know its bad for it so I im only using to diagnose) I had 5900 psi on the rail pressure so I replaced the cp3 got it back together and it fired right up.. went back out latter and it wouldn't start again. hooked the scanner back up and still have low rail pressure!!
im thinkin bad injectors. any suggestions?
 
D

dher

New member
Sep 13, 2015
8
0
0
andy-stevenson said:
You've checked the fuel filter housing?
Click to expand...

ya filter housing is good with no air leaks but I just went out and pumped the shit out of it and it seems to not be getting pressurized. not getting hard at all

ok so after some screwing with it it does actually get hard as a rock as soon as I turn the key on.. i did just install a airdog 150 lift pump so maybe that changes the prime somehow
 
Last edited:
RHallenbeck

RHallenbeck

New member
Aug 21, 2014
50
0
0
Beaumont, Texas
Good batteries to insure good RPM from starter? Had a friend with one that spun and spun before it would start.. Noticed it would reboot his TechII while cranking. Went to checking and found passenger side +lead was loose nad not contributing. Tightened it and TechII stayed on and it cranked after about a 2 second spin...
 
D

dher

New member
Sep 13, 2015
8
0
0
batteries are both new and it cranks fast fuel filter housing is good with no air leaks and holds excellent pressure on the prime when key is turned on (still only will start with a shot of ether)
 
catman3126

catman3126

Ehhh?.... You don't say?
Jul 24, 2012
2,636
0
36
NE Oregon
SO what is your rail pressure when cranking? If your only seeing a 1000 psi and its not losing prime its a good chance your injectors are bypassing enough that the pump can't achieve enough rail pressure at cranking speed.
 
Awenta

Awenta

Active member
Sep 28, 2014
4,090
2
38
CT
The prime gets hard when you turn the key because of the lift pump. So a leak should be easy enough to spot.

^^ I agree. Time to do a return rate test

Sent from my SM-N910V using Tapatalk
 
D

dher

New member
Sep 13, 2015
8
0
0
k thanx guys i'll get it to a shop so they can check the return rate on the injectors. would it not start from 1 injector going bad or would multiple go bad at the same time??? also, I've been running a tri bullydog on the truck for 3 yrs now and have read that programmers can be hard on injectors, anyone know if there's truth to that?
 
D

dher

New member
Sep 13, 2015
8
0
0
well i decided to take my truck in to diesel day dreams in denver. i will post back and let everyone know exactly what the problem was, so you know what to fix if your having similar issues!!!
 
D

dher

New member
Sep 13, 2015
8
0
0
dher said:
well i decided to take my truck in to diesel day dreams in denver. i will post back and let everyone know exactly what the problem was, so you know what to fix if your having similar issues!!!
Click to expand...

so the problem was 2 bad injectors after all. they replaced all of them and my truck runs awesome again!!
 
You must log in or register to reply here.
Top Bottom