I have a question about the 3rd line coming off the filler neck. It looks like a 3/8 vacuum line. The truck is running rough when starting out and giving injector circuit code and random misfire and seems to run better the warm it is outside. I found that 3/8 line hanging down and before I get to into it I was wondering if anyone knows what its for and where it goes. It comes off the filler neck and is about 4 feet long. Thanks

 

would have to see pics to be sure....the line should be for vapour recovery when refueling. as fuel passes the other end of the line it creates a vacuum at the top of the filler neck...pulling vapour into the tank vs release to atmosphere. you want it connected to for evap leak testing purposes. not related to the injector dtc or running rough

 

sorry it took so long. I had to put a jdm tranny in the acura for the kids. The missing was the injector, so now when I run it and let it sit for an hour or two, I have to crank it to start it. It seems like I'm priming the line. Once it get fuel it start right up. I'm think that could be related to the vapor line. What pictures would you need to help you figure this out? Thanks

 

if you have a long crank time...it probably is loss of fuel prime in the fuel rail. to confirm...prime the rail before cranking by turning the key to run for 3 seconds and repeat 3x before starting. if it start normally after priming the fuel pressure is leaking down.

it can leak down from either the injectors, fuel pump check valve or fuel pressure regulator (if it has one near the manifold). the check valve is the most common cause. it is part of the fuel pump assembly.

not related to the vapour line. the purge valve should be sealed at start up. if the purge valve was open...you would have a hard start after refueling

 

sorry, let me state it better. It starts fine every morning. If I run it to temp and then let it sit for an hour or 2, it's like it lost prime. It seems more like a vapor lock condition to me. That is why I thought maybe the vapor line. If the system was losing pressure it would start right up in the AM, as far as I know. Everything is in the tank on this. I am going to look at it tomorrow.

 

that is a symptom of leaking past the injectors. it creates a flood condition that disappears after a long sit as the fuel evaps and the engine temp is cold the next morning...cold starts need rich mixtures.

 

to test this....mechanics...ie me...put a fuel pressure guage on the fuel rail and close off the return line(if it has one) and feed line...prime the system. if the fuel still leaks down...its the injectors. you could also pull the fuel rail out of the manifold leaving the injectors connected to the fuel rail. prime the rail and see if one of the injector drips fuel.

vapour lock is a thing of the past in carb systems. returnless fuel systems i have never seen do this. the system only pumps what you need so the fuel doesn't get hot. the volume and pressure of modern system is also a deterrent.

the evap vapour line should be sealed to the engine at engine off by the purge valve. you can't vapour lock a line that doesn't carry liquid fuel. if you have liquid fuel in an evap line...you have other problems.

to test the hard start after a hot soak problem. start the truck in clear flood mode. gas pedal to the floor and start motor...this shuts off the injectors during cranking. if it starts better...you have a flood condition.