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Discussion Starter · #1 ·
I know this issue has been addressed numerous times, but I need some more info.
My son in law has an 02 LB7 that will not start without a shot of ether, I know that's not good, but it's the only way. We have rebuilt the filter head and replaced the fuel line to the test port, but it's still getting air from somewhere. My Autoenginuity scantool gives me 2 codes po1094 fuel rail pressure low at idle and decel defuel, and po380 glow plug circuit A malfunction. When switching to the live data mode the injector balance is within limits, rail pressure when cranking is about 700psi and around 4400 at idle, as it comes off idle the rail pressure runs pretty even with the desired rail pressure. I maintain that we cannot even think about high pressure problems at idle until the system is airtight. Is this a valid assumption? Also, what is the minimum rail pressure required for fuel command from the electronics?Thanks in advance:help
 

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You need minimum 1450 PSI to fire the injectors, but closer to 2500 PSI for a decent idle.
 

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My first thought before reading it all was the air is getting in through the filter head seals/O-rings, but since you said you replaced it (I'm assuming a new unit with NEW seals and rings) that would not be the problem as it was with my truck. Second thought would be the cp3 might be getting weak..
 

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Discussion Starter · #4 ·
Supposedly had a new cp3 installed just before he bought it, what about frpr or frps, its still getting air from somewhere, the filter head was rebuilt, not replaced, but passed bench tests, my theory is that the air at cranking and idle speed is messing with the rail pressure. Rail pressure at idle is around 4400 psi, desired pressure is about 5200. Since air is more comressible than the fuel, I can't help but wonder if that is messing with the pressure. truck idles well once it's running and rail pressure is spot on above idle. Also, is there a minimum rpm spec while cranking to get injector command like the 7.3 Pstrokes.
 
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