Silverado 4.8 Delayed start when warm
03-30-2019, 09:34 PM
#12
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I am monitoring it with a bluetooth OBDII app called Torque pro. I will admit it may not be the best thing in the world but it has always done what ive needed it to do.
I drove the truck and parked it for about an hour and went out to start it. IAT was 77 degrees at start up. I drove for about 10 minutes and the IAT stabilized at about 57 degrees.
Engine is completely stock 4.8L, rebuild/built transmission.
Something I just discovered is that I have a mal functioning fuel tank pressure sensor. It is stuck at 4.2 volts (I've run multiple tests on the sensor and circuit) and so it is telling the computer it is always under vacuum. I have no idea if this is related or not but is a part that has been order.
Thanks everyone for all the help!
I drove the truck and parked it for about an hour and went out to start it. IAT was 77 degrees at start up. I drove for about 10 minutes and the IAT stabilized at about 57 degrees.
Engine is completely stock 4.8L, rebuild/built transmission.
Something I just discovered is that I have a mal functioning fuel tank pressure sensor. It is stuck at 4.2 volts (I've run multiple tests on the sensor and circuit) and so it is telling the computer it is always under vacuum. I have no idea if this is related or not but is a part that has been order.
Thanks everyone for all the help!
04-17-2021, 02:16 PM
#13
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Hello everyone,
I have a 2002 Sierra 1500 4.8L.
The truck has a hard time starting only when the engine has warmed up. First thing in the morning it starts up fine. Also once its warmed up if i turn it off and immediately re start it, its fine. Only when the engine is warm and I run into say the store for a few minutes and come back out it will crank for about 4 or 5 seconds.
Im assuming that the truck is starting fine in open loop and the problem is in closed loop? When its warm and I immediately re start it, the truck remembers the fuel trim and can start with the appropriate fuel but after sitting for a few minutes something resets and it tries to start in closed loop but with out remembering any of the fuel trims. ( I could be totally wrong on this)
Other than that it seems to run pretty good. Just cant seem to figure out the hard start when warm. Any thoughts? Thanks!!
Fuel pressure is 55 PSI regardless of engine temp (morning or after driving, sitting)
Fuel pressure regulator has been replaced
I have a 2002 Sierra 1500 4.8L.
The truck has a hard time starting only when the engine has warmed up. First thing in the morning it starts up fine. Also once its warmed up if i turn it off and immediately re start it, its fine. Only when the engine is warm and I run into say the store for a few minutes and come back out it will crank for about 4 or 5 seconds.
Im assuming that the truck is starting fine in open loop and the problem is in closed loop? When its warm and I immediately re start it, the truck remembers the fuel trim and can start with the appropriate fuel but after sitting for a few minutes something resets and it tries to start in closed loop but with out remembering any of the fuel trims. ( I could be totally wrong on this)
Other than that it seems to run pretty good. Just cant seem to figure out the hard start when warm. Any thoughts? Thanks!!
Fuel pressure is 55 PSI regardless of engine temp (morning or after driving, sitting)
Fuel pressure regulator has been replaced
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