ENGINE WON'T RESTART AFTER RUNNING NORMAL. Engine will restart when you let cool down. Fuel rail pressure is 46 psi when not starting (hot) and 50 psi when running (cold). I replaced the fuel pump. I took the pressure tester back and did not test new pump pressure.(I know) Engine cranks normal. I don't think it's a ignition problem but could be wrong. HELP!!!

Vapor lock is caused by fuel getting too hot in a fuel line or fuel rail and is rare since modern fuel system circulate fuel fro the tank to the fuel rails and then excess goes back to the tank. Are you sure you have vapor lock? Please describe all symptoms.

Could be a weak fuel pump in the tank.
Depending on the year and engine, 30psi may be a bit low for normal running. Most multi-port fuel injection runs at 35psi or more.

You hook up a fuel pressure gauge to the test port on the engine's fuel rail, and see if the pressure is correct with what is specified for the car. If the pressure is correct, the pump and filter are good, doing what they are supposed to do. Some stores loan or rent fuel pressure gauges. Multiport fuel injection systems usually have high pressure requirements-about 40-50 psi. Check the specs for your car. Usually, the specs call for a pressure with just key on, no start, and a second pressure (maybe 3-10 psi lower) with the engine running.

When it dies, can you immediately restart it, or do you have to wait a bit? Probably fuel or spark related, Any trouble codes present?

need to check fuel pressure before trying to start and see if it's bleeding down or staying pressurized hook gauge on and check periodically before trying to start, seems like mine done that and it was a b ad fuel pressure regulator on the fuel rail, 5.3 ? it's on drivers side rail with vacumn line erunning to it about the size of silver dollar diam.

BAD CRANK SENSOR ON TOP OF ****** HARD TO SEE FOLLOW WIRES, OR FUEL PRESSURE LOW BAD PUMP IN TANK..RENT TOOL AT AUTO ZONE HOOK UP TO FUEL RAIL SHOULD HAVE AT LEAST 45 50 PSI OF PRESSURE IF GOOD THEN CRANK SENSOR.WHEN IT DOESNT START CHECK FOR SPARK IF NO SPARK GOOD CHANCE ITS BAD.ITS ABOUT 45.00 BUCKS FOR NEW ONE AND ABOUT 35MIN TO PUT ON.GOOD LUCK

Fuel pump worn out and is weak, when the fuel is warm the pump expands and the fuel pressure is good. When the colder gas is added or when the gas has cooled down the fuel pump.
The pump can not create enough pressure to run the fuel injector due to the piston and sleeve in the pump are worn out, you might get another year if you lucky by replacing your fuel filer.
Start with the simple and replace your fuel filter and check your fuel pressure readings at the shredder valve on your fuel injector rails. You should have i think 56 PSI to run them properly.
Thank you for using fixya and be safe.

I have been working on a simular problem on my daughter's vehicle. with the following additional symptoms. It only fails while hot. Runing fuel preassure checks, I noticed that the preassure rises from 30 psi while running to 40 psi after turning off the hot engine. This is caused by the expansion of the fuel in the rail. I believe that this hgh preassure is causing the regulator to stick closed preventing the fuel to get to the rail during a restart, (as the preassure drops to 0 while the fuel pump does whirrrr during the startup proceedure). It seems to free up after it has cooled then works normally. We ordered a new regulator but haven't received it yet to see if this fixes the problem. There is a possibility that the problem is a weak pump that cannot overcome the stuck regulator but since all the checks are in spec, I'm leaning toward the regulator at the moment.

Fuel pump is bad. At idle pressure should read 50 PSI. Replace with original manufacture fuel pump after market pumps will burn out fast and are unreliable from my experience. Also could have a bad fuel regulator but that only works while driving down the road full throttle. You can unhook the fuel rail pressure regulator and that will give it full fuel and the pressure reading should read 60 PSI while it is running. If you turn the engine off and turn the key to run position it should read 50 PSI and hold for 60 seconds, if it drops below 30 PSI after 30 seconds Pump is defective. Many pumps are going bad here of late as people have been running them less than ¼ tank and this kills the pump. The fuel cools and lubricates the pump so the lower the fuel level the worse it is on the pump below ¼ tank. Not to hard of a job to do if you want instructions let me know.

Has Neon do same, I ran fuel at low level, on hot day, ran engine until it started to act up & threw a fuel pressure gauge on it. Was at approx 5 psi. Cold next morning, 48-50 psi. Always hot day about 30-40 miles into work in morning, o.k. Sit in hot sun all day & would happen 3-4 times on way home. Sit and let cool, 20 minutes or so & go again for a while. Cool day, no problem. Change pump I would.

It does sound like fuel. I needs at least 55 psi. You need to know exactly what the fuel pressure is.