Pickup wont stay running when it is started


#1

I have a 2001 gmc with the 5.3 engine. when I start the pickup it turns over and then dies. It seems like it is trying to run but it just has a rough idle. It will start after several trys, then it runs fine. What is the problem?


#2

Your fuel line is losing pressure when parked.

Try putting your key in the “on” position for a few seconds, perhaps a few times, before putting it in the “start” position. That’ll pressurize the system. If that solves the problem, you have your diagnosis. And your solution.


#3

why would my fuel line be losing pressure?


#4

There is a check valve in the system that prevents the fuel from running back into the gas tank when the car is off. Sometimes with age they don’t seal as efectively any more. That can allow the pressure to dissipate.

When you shut the vehicle off, the injectors all close (their normal deenergized position) and everything between that check valve and the injectors remains a sealed, closed system. Normally.


#5

While person A cranks the engine, person B observes the exhaust pipe for black smoke, or other visible emanations; and posts those observations here for analysis.


#6

ok, just did it. There is a very faint hardly any, white-gray. the temp outside is around 50F. So it could be just the vapor that exhaust gives off when it is cold.


#7

The idea was that, if the fuel injectors were leaking down after engine shut off, they would dump excess fuel into the intake manifold. Then, during start attempt, this overly rich mixture would only partially burn, giving a smoky exhaust. The exhaust didn’t smell like gasoline, did it?

Next, let’s see if the problem is lack of gasoline injected during start. Use Starting Spray in the large black plastic intake tube during start. A two second burst should do it. Results?