EFI Accumulator Fuel Pump Problem?

[Viperwolf1]

To me this seems like this might be a return issue.
I'm not sure how to plumb in a return line on a return less system.
Are you using a Mustang or 1997-1999 explorer fuel rail? The returnless ones just had a damper on it.
I'm not sure where your issue is, but the mixing and matching of return and retrunless parts could be part of it.

Returnless systems do have a return. It just isn't at the rail. I see no inherent problem with the way it's plumbed.

Running more than one pump can cause problems like the OP is seeing. If the LP pump can't flow at least enough fuel to keep up with the HP pump flow (high speed and uphill demand is much greater than idle), eventually fuel gets too low in the accumulator and the HP pump goes into vapor lock. It goes into vapor lock because the a partial vacuum is created in the accumulator and that lowers the boiling point of the fuel. Heat and high altitude exaggerates this and causes the fuel to boil even sooner. This is one advantage of the returnless rail. If the return is positioned prior to the engine, the returned fuel doesn't absorb heat from the rail and then heat the remaining fuel in the tank. Bottom line is you need to use a good LP pump with a system like this.

 

[ntsqd]

Which is why I'm still waiting, likely in vain, for what the pressure is at the outlet of the LP pump when the engine lays over. Gotta cover the simple stuff first.

 

[Killer Frogs]

I am running the Mustang fuel rail with a return line. Garry (EFI Guy) had me set the fuel pressure just above 63 psi. I am going to try running the return straight to the tank and capping the T on the accumulator. I'll let you know if this fixes things.