fuel coming from lift pump reurn

[Kyle Reasbeck]

I have an 07 5.9. Truck was smoking a bit at start up, had the injectors rebuilt, installed them, and instantly had tons of fuel in the crankcase (1.5-2 gal in 80 miles). Did an injector flow return test, got 20ml/30 sec @ idle and 60 ml/30 sec at 18ksi (my scanner didnt have the flow pressure test). Pulled injectors again, #2 came out super easy and #4 had a crack and no ball above the mounting plate of the injector. Shop retested, noticed a slow leak of fuel out of #4, and provided another rebuilt injector. All others retested fine.

Now for the question....when i ran the injector return test i had fuel coming out of the return line from the tank when it was running. I did read that the lift pump has a crossover check valve in the tank. Is this normal for fuel to be coming out of the tank return and if the injector returns come through the back of the head and join the CP3 return, does the injector return have to fill and meet a certain pressure to overcome the backfeed from the lift pump? Just worried that the injector return could be meeting resistance trying to get back to the tank, filling and then bypassing the injector body o-ring and filling the crankcase?

Any help would be greatly appreciated!

 

[jhenderson]

The problem is you have paid no attention to all recommendations against reman injectors. Now you are paying the price.

 

[Kyle Reasbeck]

i understand that, hence getting them from a bosch certified shop. But i dont understand what that has to do with

a) fuel from the return port of the lift pump due to the crossover check valves
b) design return pressure from the return galley

 

[cerberusiam]

Both the CP-3 and injectors return fuel to the tank in the same circuit. Even if you block off the injector return the CP-3 is still returning fuel to the tank.

Should not in any way be hooked into the LP circuits. All the return fuel from the LP should be internal and directly back into the basket.

The check valve in the back of the head maintians about 15 psi of pressure in the head and if it plugs it will push fuel back into the engine and\or blow the solenoids off the injectors.

From the souds of it yo just got some really bad remans and lack of QC on the rebuild process.

 

[Kyle Reasbeck]

Thank you cerberusiam! I agree that is sounds like the injectors aren't up to par and i haven't been real happy about it but given they were a bosch certified shop and a local case dealer uses them with very good results swayed me to use them as opposed to going with a random rebuild off of someone per the many discussions on the various boards. I'm probably over thinking things as i did not have a fuel in oil problem previous to sending them out but was curious as to make sure that it's not possible (or likely) that the lift pump return at the lift pump itself was creating a backpressure that the cp3/rail/injector return couldnt overcome and that the return galley was then unable to drain. I did get another check valve in case and will probably check it prior to running the truck even though i agree that its likely the injectors i had gotten.

 

[sag2]

I posted photos of the proper procedure to check return flow but I could not find them in a search. I don't think I started the thread, just responded to one. You need a 9012 special tool in place of the banjo bolt at the rear of the filter housing and cap off the return from the tank. Without the tool you will not get correct results.