Cold start hesistation

[dwinters14]

Just bought a used 07 burb with 144k on the clock. 5.3L flex fuel. Truck started and drove perfectly fine but about 3 days ago ive noticed it struggling to turn over after resting for awhile. Once cranked over it starts fine and drives fine. Here are the things that have changed since i bought the truck:

Installed aftermarket sound system

E85 fuel.

Now when i go to start the truck my voltage is between 11.8-12 volts, and drops to about 10.1 when cranking. I primed the fuel pump after sitting for 12 hours and it still struggled to turn over.

Any ideas/things I can try to narrow down the issue?

 

[Doubeleive]

have the battery tested, anything under 10.5v on these trucks is not good and they tend to do goofy stuff then.

 

[dwinters14]

have the battery tested, anything under 10.5v on these trucks is not good and they tend to do goofy stuff then.

Coolio, I'll give that a go tomorrow, thanks.

 

[dwinters14]

Update: Got the battery and alternator tested at autozone and they read okay. Today I was driving and the engine died, steering went stiff and I heard a loud screeching noise for about 5 seconds. Pulled over to the side of the road, tried to start it and it'd die almost immediately, very rough idle. Now it won't turn over at all, just cranks. I swapped the alternator just because I had one and the same issue, just cranks and no fire.

No leaks, engine sounds like it's turning over, coolant level is full, engine oil is 2 ticks down from full. Could my fuel pump have given up? I don't have the means to test it, and will get it towed to a shop tomorrow to get some more information.