New fuel pump, hard start.

[Mcneils10]

Hello everyone.
New here. I recently bought a 09 yukon denali with a blown up 6.2, I rebuilt it and but it back in. Now I'm a month down the road and I had to replace the pump due to rust at the assembly. After I replaced it I still had about 3-5 gallons of fuel in the tank, I tried to start and it started but took a few seconds probably around 5-10 seconds of cranking before it fired. I filled it to a half tank no issues but still take a few seconds of cranking to start or I have to try to start it a few times before it will fire. Any one know what could be going on? I'm checking the pressure in the morning.

 

[Fless]

Definitely check the fuel pressure to verify it's in spec.

When it's warmed up and running do a quick cam-crank correlation (CASE) procedure with a capable scanner, especially if either sensor was changed. Might not be your issue but with changes to the engine it might be the cause.

 

[Mcneils10]

I'll talk to my brother who tunes cars about the correlation sensor. Thank you for the advice.

 

[j91z28d1]

was it an oem pump?

I put a napa pump in my 96 and it was hard starting after that. I believe it wasn't holding fuel pressure correctly when it was off. if I clicked the key forward and paused for a second for it to build pressure. it would fire off cleanly every time like normal, if I didn't it would crank a few seconds longer and stumble a bit after the flare and then clean up.

I've just seen that newer gm now with the push button start will activate the fuel pump for a few seconds when you open the door to prime the system before cranking. I found that interesting.

 

[petethepug]

Welcome from SoCal. Nice pull on the L9H in the Denali. Pull the charcoal emission canister and verify it’s not spilling carbon pellets into the field system.

Only use OEM f/p or Bosch, preferably with the lifetime warranty. Best prices on rockauto and parts geek. Generic f/p can have you chasing ghosts, intermittent ones at that.

Check your crank position sensor. I learned the hard way they fail and cause hard starts without sending a code.

 

[rdezs]

As do aftermarket camshaft position sensors.....