I have looked all through the threads and found nothing that can relate to my issue. I have recently completed a new build for my 2002 TA with original LS1 motor. Here are some details.Original long block built at Texas Speed. Wiseco Forged Pistons all new strong internals etc. I got the long block, but the rest of the build I did myself.


Gen Info.
LSA 111 cam 231/234
Compression 10.33:1
Heads PRC 2.5 5.3l CNC Ported
Bosch 42 LB Injectors with plug and play adapters
Fast 92MM Intake
Fast Fuel Rails
Nick Williams 92MM Throttle body
85MM MAF
Standard AC coil packs
Fuel Pump Racetronix FPA-001C 255 LPH Turbine Pump
2-7/8 headers with 3" Texas Speed true dual exhaust
3600 RPM Stall with RPM Transmission Level V

Fully Tuned by Pat G tuning in Victoria

Ok, here is the issue. Car runs great. Have had it on the road now 8 months and now issues. EXCEPT 1. First noticed when needing gas. I would take the gas cap off and notice a rush of air. Like a vacuum was released. Then after gasing up, hard as hell to start. Like it was out of gas/not getting gas for about 8-10 seconds, then catches and starts, but runs rough for about 20-30 seconds. Then all is fine. As well, I live in Houston, and during the cooler months, no issues while driving. drive all over town, stop and go and nothing. Now that it is hot, I drive around for 30 minutes and the car starts acting like it is starving for gas. Let the car sit for about 10 minutes, runs fine again for about 20 minutes ( again I am driving in the heat ) and it starts acting up again. It almost like a vapor lock in the old carb days, I sure there is something in the fuel supply, but I am looking for suggestions on where to start looking to fix this.

I am hoping to get the community help on this one.

Thanks
James

 

How about starting with a look at the fuel pressure when this is going on?
A data log would help, too.

 

Mine did something like that ended up be vapor lock. Couldn’t start the car after shutting it off when it was hot. Had to wait until it was nearly cool. Only thing I did to fix that was insulate the fuel lines in the engine bay. Never had a problem since. Is the f body fuel tank vented? Wouldn’t think you would be getting and pressure positive or negative. Unless something is plugged up.

 

Start with verifying good fuel pressure and I take it you've replaced the fuel filter. Hard to see from the picture but is your EVAP connected or capped off? You could also have a defective gas cap but my EVAP is still entact and I've never noticed any pressure build up in the tank when I open the gas cap.

 

Try leaving the cap off.

 

thanks for the help...I have done a couple things. First, started up and then took gas cap off. the car barely Idles or dies. After dies, it hard to start again, turns over 7 or 8 times before catching. Fuel pressure stay around the 55 PSI range. I put the cap back on, once it starts up idles just fine.

New fuel filter put on after the first 500 miles on new build. I just cant help to feel this is something to do with the fuel supply system. I could insulate the fuel lines in the engine bay, but not feeling that is an issue.

Any thoughts this could be a tuning issue?

thanks again on the comments

 

Not familiar with the smog plumbing on this car. However, if it's still there, is it plumbed correctly?
It appears that the engine is going lean when exposed to atmospheric air with the cap off.
If the smog system is plumbed so that it pulls a vacuum on the tank, causing the rush of air you mentioned,
and you cut off that supply of air, by putting the cap back on, the issue goes away, and the afr gets back to a reasonable ratio.
Just a "SWAG".
Data log it to help with locating a tune issue.
If you have a WB O2 on the car, what's it saying when this occurs?