Also, do not forget that many late model OEM apps use a PWM controller to drive the fuel pump only as fast as required to relieve stress and wear on the pump; they spin the pump just fast enough to deliver the correct volume and pressure at the injectors for a given load criteria. Some even control the fuel pressure via pump speed.
OEM apps with deadhead setups also tend to use pulsation dampers up near the injectors to even out the pressure given the uneven on-off-on fuel delivery of the injectors which is more pronounced in a deadhead setup.
A setup with the regulator at the tank and "deadheaded" rails can be prone to vapor locking after you shut the engine off. When you shut off the engine and the fuel flow stops the fuel in the rails can boil off from heatsoak creating a hard start condition. Simply cycling the fuel pump won't fix this since there isn't a constant flow of fuel through the rails back to the tank as in a system plumbed with the regulator after the rails which will have fresh fuel go through the rails and displace the vapor. Granted, if the regulator is working properly it will hold the fuel pressure in the rails after engine shut off which is to prevent vapor locking. Once that pressure subsides then vapor lock can be a problem. Most OEM manuals I've seen specify that pressure at the rails be maintained for a minimum of 20 minutes after engine/fuel pump shut off to combat vapor locking from heat soak.
Even putting the regulator back at the tank will still heat the fuel, although not as much as running it through the hot engine compartment and rails first and then sending it back to the tank. Regardless of where you put the regulator by pumping the fuel you are adding heat to it. As long as the fuel can shed its heat through the tank to ambient air faster than you can put the heat in everything's OK; once you start putting more heat into the fuel faster than you can dissipate it you are on your way to overheating the fuel and creating a vapor lock condition which can not only strand you on the side of the road but can lead to fuel pump cavitation and damage.
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1969 Chevelle
Old setup: Procharged/intercooled/EFI 353 SBC, TKO, ATS/SPC/Global West suspension, C6 brakes & hydroboost.
In progress: LS2, 3.0 Whipple, T56 Magnum, torque arm & watts link, Wilwood Aero6/4 brakes, Mk60 ABS, Vaporworx, floater 9" rear, etc.
Last edited by Blown353; 06-27-2006 at 06:24 PM.
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