Well...... something is wrong.

Fuel trims are back up and now I have the fun of a starting issue. I crank the engine and It tries for however long I have the key turned but will not start up unless I turn the key to off and crank it a second time.

This happens even when I have pressure in the fuel rail prior to attempting to start.

 

https://charm.li/Chevy%20Truck/1999/...s%20Not%20Run/

 

Check and make sure the EVAP system is operating properly.

 

Checked the EGR valve this morning and all looks well. I put the old spark plugs back in and the hard start is gone. Fuel trims are still high. I'm gonna check the O2 sensors and Cat today. I know the downstreams are reading high right now.

 

EVAP is your fuel tank vent lines, not exhaust gas re-circulation (EGR)

 

A new MAF sensor brought the fuel trims down to +5% - +12% depending on load. Looks like the old MAF (That I cleaned with no improvement) was reporting fairly accurately at idle and underreporting under load.

Now that that is better, I can see that the fuel trims ar not balanced between bank 1 and bank 2. I believe the o2 sensors are going out, I can see that bank 1 voltage never reaches the .875v now. I'll replace those soon.

As an aside, the fuel pump check valve went out so I'm adding an in line check valve right by the tank.