HELP !!! 2007 Classic 1500 wont start first try.

[jumpingJack]

6 month problem. 2 new delco fuel pumps... please help me fix it . It started one day when it had been sitting a few days in 30ish degrees. I went to start, han a bang like a hammer hitting block. Then rubbing noise after starting 3 hours later. Replaced engine, now wont start first time and fuel psi leaks down overnight 

[Magnus604]

On 6/15/2023 at 5:56 AM, jumpingJack said:

6 month problem. 2 new delco fuel pumps... please help me fix it . It started one day when it had been sitting a few days in 30ish degrees. I went to start, han a bang like a hammer hitting block. Then rubbing noise after starting 3 hours later. Replaced engine, now wont start first time and fuel psi leaks down overnight 

If you’re having leak down it’s probably your injector seals.

my 2000 Silverado had poor fuel pressure causing a hard start (turned over for several seconds before firing) and misfires in 1 and 7. I chased this for six months, replaced fuel pump twice, egr valve, the solenoid, the vapour canister, brought it to a shop (they replaced one injector, got rid of misfire for one month than came back). I ended up replacing all 8 injectors with remanufactured injectors, finally cleared it up. 
turned out I was having bad leaking seals in 2 injectors. 
 

these engine are very sensitive to low fuel pressure.