Weird Starting Issue After Truck Sits More Than A Few Hours

[TylerHagerdorn]

If you were running the heat on full blast along with seat heaters on while cranking the stereo then maybe yes but if all those are off then a 105a alternator is not going to be the cause of your problems. Circuit low could be wiring or component shorted pulling down the feed to the composition sensor or even a corroded connector in the composition wiring from the sensor or all the way back to its feed. These conditions both would cause low voltage to the composition sensor and the sensors output voltage being lower than what the PCM expects. Time to get the voltmeter out and factory troubleshooting chart with known voltages.

And as many have said....the grounds corroded. A very common problem on C and K chassis.

There's no corroded connector to the FCS or the purge valve. All the connectors I've checked are very clean no broken or split wires or anything.

 

[hagar]

If you have a scanner, turn on your key while the engine is cold and before you have tried to start it, and check what the coolant sensor and air intake sensor are reporting for temperatures. I have seen before a coolant temp sensor that was reporting max cold and causing a huge amount of fuel to be dumped during cold start cranking.
Like yours, the only solution was holding it at wot clear flood to get it going.

 

[rockola1971]

Id get a voltage feed reading at composition sensor and see what the voltage is and compare the reading to specs. Then compare sensor out reading to spec as well. These 2 readings will give clues. If the sensor feed is good to go then either your sensor is bad or the sensor is good and reading what is in the tank. Id have to see the factory manual to see if the output of the sensor goes up or down proportional to alcohol content and vice versa. Either way your code is saying that the value is lower than the what the PCM is expecting to see so there is a problem and your timing is adjusted in conjunction with the composition sensors readings.

 

[HACK BLOCK]

it's the fuel pump. the pump is supposed to have a type of 1 way check valve that holds volume and pressure in the fuel lines and when it sits for a while like over night all that gas drains back into the tank and when u go to crank it you have to wait till all that volume and pressure builds back up

 

[Scottydoggs]

it's the fuel pump. the pump is supposed to have a type of 1 way check valve that holds volume and pressure in the fuel lines and when it sits for a while like over night all that gas drains back into the tank and when u go to crank it you have to wait till all that volume and pressure builds back up

theres no one way nothing to keep pressure in the line.

 

[Fless]

We have no way of knowing if it's 1) pressure bleeding off; 2) too much pressure; or 3) pressure in spec, since the OP hasn't provided that. So we don't have enough info to come to any kind of conclusion about the pump or the FPR. As well, there is resistance -- pun intended -- to using a DVOM to test circuits. A clean connector doesn't mean that the voltages are correct. However, one can assume...

Side pic of said 105A alternator?

 

[Doubeleive]

well as dumb as it sounds a key-on fuel pressure test is the place to start. regardless if the pump was put in 5 minutes ago or 10 years ago
then once you have eliminated that simple thing, move on to other possible issues it's called K.I.S.S.

 

[HACK BLOCK]

theres no one way nothing to keep pressure in the line.

happened to me on another car. long crank after sitting over night and new fuel pump fixed it. that was the explanation I got.

 

[Scottydoggs]

happened to me on another car. long crank after sitting over night and new fuel pump fixed it. that was the explanation I got.

they lied to you. or they have no clue. no set up will hold fuel pressure in the rail fully over night. you turn the key, the pump turns on and the injectors "prime" aka sprays some gas in the cylinders. thats what the engine first fires up on. once it fires up the injectors start spraying normally.

dead fuel pump just fails to pump fuel.

 

[hagar]

they lied to you. or they have no clue. no set up will hold fuel pressure in the rail fully over night. you turn the key, the pump turns on and the injectors "prime" aka sprays some gas in the cylinders. thats what the engine first fires up on. once it fires up the injectors start spraying normally.

dead fuel pump just fails to pump fuel.

Lots of systems have anti drain back valves, they are often deleted in performance pump applications to help higher flow pumps flow better. I take them out of 03/04 cobra applications as well as f bodies and corvettes all the time. Not that they hold 60 psi over night, but they certainly help Maintain volume in the system.

Once the anti drain backs are removed in performance applications, I have to increase the fuel pump prime time on key on, In order to allow the pump to run longer before attempting to crank the vehicle. The factory prime time isn't enough to fill the volume. Change all the lines and rails on a bone stock truck, then turn the key to start as normal, and it won't fire up. It will need a couple key primes to fill the system.