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I have a retrotek speed EFI and procharger on a 454. It has a regualtor mounted up next to the throttle body. We had some high temps last weekend. My engine stayed relatively cool. 180 to 195 ish . Two different days after warming up the fuel pressure went from 45 to 20 and leaned the engine out. After stopping it started back up. Cody at Retrotek suggests it may be vapor lock. Any other ideas? Bad fuel pump? Regulator?

I wouldn't think you would get vapor lock with 45psi.I would think pump may be going bad.

I agree with chad. bypass regulator (those with a return line) systems do not vaporlock ever. Pump (or pump driver if it is electronic) is going out

It has a Walbro 255 LPH pump. It is only a few months old. Yes it has a return line and regulator at the throttle body. Pain to change also. Would it work then fail all at once or would it come and go? What are the failure modes?
If I change the pump I am thinking of going to a new EFI tank. Ricks has a nice unit. Anybody have experience with it?
http://www.rickscamaros.com/camaro-gas- ... -1969.html
Anybody know if you can buy the insert for the sender and fuel feed and return separately?

My only similar experience was with a bosch external efi pump. It didn't like to suck air, and it didn't like to get hot. Failure took a couple weeks. After the third time, I knew exactly when to order a new one.

I have noticed when I started it the pump would make a certain sound when it would prime the line. I started to make a different tone when it was hot and was about to lean out. I guess this could either be caused by vapor lock or a failing pump.

Again, a bypass reulator system cannot vapor lock. When you turn the key on and the pump runs to pressurize the system, most of what it is pumping is flowing right out the return back ot the tank.
At idle, 95% of the pump output is being bypassed.

Vapor lock happens on the suction (negative pressure) side of a mechanical pump system when the fuel in the line vaporizes and refuses to be "sucked" into the pump.