Cranking Time Before Starting
Super Member
Joined: Nov 2011
Posts: 1,139
From: Pennsylvania
The first thing I would do is listen for the fuel pump prime by turning your ignition to run and "aiming" your ears toward the rear of the truck. It should prime for ~2 seconds. Note there is also a buzz that comes from the IAC valve under the hood. So insure you're hearing the pump.
In the event you are not getting power to the relay from the primary signal, your oil pressure sensor will send the power to the fuel pump once oil pressure reaches 4 psi. Which is why it will start after a long crank. It's not actually for that purpose, it's actually a GM safety device in event of an accident. But regardless, it will still provide power to the pump.
If you do hear fuel pump prime, I would cycle the key from off to run a few times with ~10 seconds in between each cycle and then try to start the truck. If it seems to fire up correctly, I would head in direction of Fuel Pressure Leakdown test (link below my signature)
When you go to start watch your tach very closely. If it's a long crank, you should see your tach needle flutter just a tiny bit. If it stays rock steady bottomed out, I might look at the Crank Position Sensor as the problem and run tests on that....
EDIT:...at the same time I would be considering Fuel Pump Relay. Especially if tach needle does flutter a tiny bit.
EDIT2: Need to correct myself (already deleted above) oil pressure switch gets power from the same fuse as pump, so pump wouldn't run at all if fuse was blown. Don't know what I was thinking.
In the event you are not getting power to the relay from the primary signal, your oil pressure sensor will send the power to the fuel pump once oil pressure reaches 4 psi. Which is why it will start after a long crank. It's not actually for that purpose, it's actually a GM safety device in event of an accident. But regardless, it will still provide power to the pump.
If you do hear fuel pump prime, I would cycle the key from off to run a few times with ~10 seconds in between each cycle and then try to start the truck. If it seems to fire up correctly, I would head in direction of Fuel Pressure Leakdown test (link below my signature)
When you go to start watch your tach very closely. If it's a long crank, you should see your tach needle flutter just a tiny bit. If it stays rock steady bottomed out, I might look at the Crank Position Sensor as the problem and run tests on that....
EDIT:...at the same time I would be considering Fuel Pump Relay. Especially if tach needle does flutter a tiny bit.
EDIT2: Need to correct myself (already deleted above) oil pressure switch gets power from the same fuse as pump, so pump wouldn't run at all if fuse was blown. Don't know what I was thinking.
Last edited by rockp2; Dec 29, 2022 at 04:08 PM.
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