Doesn't start first attempt

[tbland]

1999 GMC Sierra 1500 2-wheel drive 5.3 245,000 miles. Replaced valley cover gasket due to leakage. Replaced Cam sensor because I couldn't get o ring separately. Replaced Oil Pressure sending unit because it looked wet. Now when starting, half of the time it cranks and doesn't start. Starts immediately on the second attempt. Always started first attempt before the gasket repair. Always. Suppose it could be the Cam Sensor? Thanks for any input.

[richard wysong]

check fuel pressure, mite just be the pump not powering up, relay? op switch?

[buddyo]

This happened to me about a year ago. Had a transmission shop change rear main seal and evidently when they reinstalled the transmission they pinched the cam sensor wiring (easy to do if your not careful). They changed out the pigtail and cam sensor to no avail. Took it to a reputable auto shop, they couldn’t find the problem. Went to this forum for advice and one of the guys said to ditch that cheap crap they bought and get new sensor from the dealer. I did and never had a problem starting on first attempt again.