Intermittent Slight hard start

[maxwedgehead]

Truck is in sig, injectors dont even have 10k on them. Sometimes on these cooler mornings, and I've noticed it seems when the truck has 1/4 tank or this. Stock lift pump I jump in to crank it and 2 turns it usually starts but it has a stumble but cant take off and 2 more turns it fire right up. Today it done it again and it idles fine. I free revved it and it stumbled and then cleaned right up like theres air in the lines. Whats the deal? I dont want to pull the injectors and send them back to exergy for no reason.

 

[TxDiesel007]

I would start with checking the crossover tubes.. as the simplest solution

there are way to many variables to why these things don't start right away, (please see my other threads and posts for more suggestions) it can be anything from a loose ground wire, bad battery, alternator going weak, dtc codes causing a fit, crossover tubes, or finally an injector returning too much fuel causing your harder start issue...

but with yours stumbling.. id start with the tubes... did you replace them when you did the injectors? hairline cracks wont be seen and will cause them to suck in a bit of air...

 

[Amish Elegance]

^ This. Bad connector tubes will also increase your return flow. If you just do a return flow test, this can present erroneously as an injector fault.

Also, for the long crank, check your relief valve on the rail; make sure that's not leaking.

Since your on the stock lift pump, answer me this: If you key on and bump the starter(to start the lift pump cycling), wait for 10 seconds while keeping the key on, then try to start; does it still stumble?

 

[SixOhh]

^ This. Bad connector tubes will also increase your return flow. If you just do a return flow test, this can present erroneously as an injector fault.

Also, for the long crank, check your relief valve on the rail; make sure that's not leaking.

Since your on the stock lift pump, answer me this: If you key on and bump the starter(to start the lift pump cycling), wait for 10 seconds while keeping the key on, then try to start; does it still stumble?

you beat me to it.... thats an excellent question to ask.... LP on the way out, if not, cross tubes.