I headed up towards Eetes Park to wheel Pole Hill last week and just before I got to the trail head it bogged way down and sputtered out like it was out of gas. I got out, popped the hood and I heard hissing coming from the rear tank. I listened to the gas cap and also heard bubbling/boiling coming from the inside the tank. The tank was hot to the touch. I slowly removed the cap and released a lot of pressure and I could feel the heat coming out. My fuel pressure gauge on the rail read "0". After 15 minutes I primed the pump and it started right up. I parked it at the trailhead and wheeled in my buddy's jeep for a few hours. When we got back to my truck (9 pm) it had cooled down and ran just fine back home.
I'm guessing the culprit are the errands I ran all day in 95+ weather. The constant on/off and parking it on the black asphalt heated the fuel up more than usual. Heading up the canyon wasnt cool enough in my engine bay to reverse it but actually made it worse.
Oh- my engine temp never read more than 200 degrees.

My current set up is 3/8 steel line from 22 gal main tank -to filter- to external HP pump-to engine- to 3/8 return line, back to main tank.

I put an extension on my shroud to channel more of the air flow, heat shielded the fuel lines in the engine bay, and deflected any heat from the headers where it is close to the fuel line. Is that enough?

What about tank venting? After I added my big tank, I realized that the "vented" gas caps only vented a little, and couldn't keep up with actual pressure (positive or negative) changes. I added a tank vent directly to the filler neck, and never had the tank pressurize or gain vacuum. You are returning a lot of unused fuel to the tank, and its had time to heat up on the way to & from the engine compartment. I haven't had vapor lock on my EFI, just thinking out loud.

What was your fuel level when this happened ?

The less fuel you have the quicker it heats up from the heated fuel returning to the tank from the fuel pressure regulator.

If your tank was hot / warm to the touch.....that seems like a lot of fuel had to be by-passing. Might check your FPR too.

I was more than 3/4 full. How do you test a FPR?

I'd say you're probably on the hairy edge of vapor lock. That vapor lock is occurring between the tank and the pump though. You could try to insulate the lines there but the fuel is already hot, picking up heat from the fuel rails. There are a couple things you could do to make things better.

1) Plumb a cooler into the return line to get rid of some heat before it gets to the tank.
2) Move the HP pump closer to the tank. This would give you less fuel volume under vacuum. Vacuum and heat are causing the fuel to boil.
3) Install a LP pusher pump near the tank to pressurize the long line that is now under vacuum. An in-tank HP pump would be an even better idea.

If you need a in tank hi pressure pump I have an extra.

Explorer trans coolers might be a good option.

I think something like this would be better. https://www.summitracing.com/search/bra ... ner=SREPD5

I had a couple other thoughts about limiting the fuel heating. Unless you're willing to make big changes in the plumbing, it would apply more to someone in the build stage.

1) Use metal supply and return lines and route them where air can move freely around them, outside frame or top of frame with a body lift. The long metal lines would work nearly as well as a cooler with hoses.

2) Use a returnless fuel rail. The returnless rail still needs a pressure regulator and a return but it can be mounted further back near the tank. This would prevent engine heat from getting into the fuel.