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Discussion Starter #1
Hello everyone, I am having a problem that a lot of others seem to have too. I hear this is common with bad injectors but i have no other symptoms other than the hard warm starts. No smoke at idle, no loss of power, no fuel in the oil as far as I can tell. Also I'm pretty sure its not the FPR because it idles smooth and quiet as can be. Not sure if the FPRV is leaking off though. The truck runs and drives amazing all the time. Starts up fine when cold but after it warms up and you kill it, it will sometimes extended crank then start and other times it wont start at all. It has had the factory filter head bypassed due to the FASS system so I'm not sure where to go. I have not gotten a chance to check balances rates yet. I hope it doesn't need injectors again so soon. I figured its time to go to the professionals! Based off my sig what do you all think? Maybe the CP3 is getting weak? Thank you all in advance!
 

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Welcome to the Forum!

Another injector problem with LB7s is failure of the ball seat inside that becomes eroded and does not allow the return circuit ball to seal properly. When that happens, the main fuel pump (CP3) is unable to establish minimum rail pressure to wake up the Fuel Injection Control Module (FICM) and begin lighting up injectors. Diesel viscosity obviously changes with temp, and when it is cold, the thicker diesel can be properly controlled by the return circuit, but when the engine warms, the thinner diesel goes past the check ball and seat, minimum rail pressure is hard to establish and long crank times result.

Ironic that 8 tiny balls, not seating properly can bring down a 7,000# behemoth.

Use advanced search and look up return rate tests (maybe put in my user name as I’ve written about this before) and you will find an easy way to check total return (fairly easy) or return at each bank (a bit more fussy).

Unfortunately, if it is the return circuit, no fix except injector R&R :(. (And yipe, only 35k on Bosch injectors).

May also be a temp sensitive fuel supply issue. Does the primer help on hot starts?

Keep in touch.
 

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Discussion Starter #3
Welcome to the Forum!

Another injector problem with LB7s is failure of the ball seat inside that becomes eroded and does not allow the return circuit ball to seal properly. When that happens, the main fuel pump (CP3) is unable to establish minimum rail pressure to wake up the Fuel Injection Control Module (FICM) and begins lighting up injectors. Diesel viscosity obviously changes with temp, and when it is cold, the thicker diesel can be properly controlled by the return circuit, but when the engine warms, the thinner diesel goes past the check ball and seat, minimum rail pressure is hard to establish and long crank times result.

Ironic that 8 tiny balls, not seating properly can bring down a 7,000# behemoth.

Use advanced search and look up return rate tests (maybe put in my user name as I’ve written about this before) and you will find an easy way to check total return (fairly easy) or return at each bank (a bit more fussy).

Unfortunately, if it is the return circuit, no fix except injector R&R :(. (And yipe, only 35k on Bosch injectors).

May also be a temp sensitive fuel supply issue. Does the primer help on hot starts?

Keep in touch.
Ah I gotcha and I totally understand that. Yes that is ironic. Okay I will definitely do that. Alright I gotcha and yes I know it would be shocking to me too. I have not tried the primer yet, i will do that and report back to you. I sure will thank you!
 

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Unfortunately, sounds like time for some new sticks. I love my LB7 but next time I need injectors I'm going SAC style from Lincoln Diesel.
 

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Discussion Starter #6
What kind of miles are on the truck or injectors? Sounds like injector or cp3 pump that has high return rates.

Can you check your actual vs desired fuel rail pressure while cranking?
The truck has almost 177K but the injectors were just done 35k ago with brand new 20% overs from Bosch. I thought it might be the cp3 too. I have not yet but I can check that and I will asap. What do I need to disable so that it wont try and start?
 

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If its not losing prime I wouldnt suspect a leak in the system. Check the fuel line if theyre the original ones they could be kinked or collapsed @ almost 20 years old and cause issues when hot as the rubber hoses expands. Specifically the ones by the hydroboost and the one return line exiting the cooler that goes into the tank does a upward 180 degree turn.
Also not 100 percent certain but this could be the reason the replacement injectors dont last long as the raising pressure in return line causes the injectors to fire under more pressure.w hich would make sense that some people have luck going with sac 30+ injectors they are rated for more pressure. Plus the fuel lines themselves are dirty inside not just rusted but they get overlooked when replacing injectors. Doesnt hurt to give it a look.
 
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