I hope this is the right forum to ask this so here goes. I am installing an 04 mustang gt 4.6 into my 52 Ford f1. Question is, do I need a fuel regulator and a return line to make this work? I am trying to use the original tank. I have a holley terminator Eli kit ordered, a holley fuel pump. I believe that fuel is regulated on the fuel rail. I also think that a return line isn’t necessary. I believe the 04 mustang didn’t have a return line originally. Is this correct. Any feedback is appreciated.

 

OK, here is some! 4.6 in '96 Mustang used RETURN type fuel system. Later it became returnless, so used both systems successfully. Return type system relied on fuel pressure control by a REGULATOR mounted on the fuel rail, controlled b y engine vacuum. The pump delivered it's full output to the rail ALL THE TIME, the unused amount being returned to the tank. This system caused engine compartment heat to be transferred to the returning fuel, heating the fuel in the tank. This was good under certain circumstances, bad in others. But simple in operation, easy to employ in conversions like yours.

RETURNLESS was done in two ways. For a couple of years it was done by the fuel pump dumping it's excess output directly back into the tank via a relief valve built in. This system experienced several drawbacks and was abandoned, followed by the now current RETURNLESS system in which the FUEL PUMP SPEED is constantly controlled to maintain the desired pressure. This is done using information from a FUEL PRESSURE AND TEMPERATURE SENSOR, mounted on the fuel rail. It has both vacuum and electrical connections, data from which are used by the computer (PCM) to control pump speed. This system has the most benefit of all, including very long pump life. (mine has 176,000 miles on it). However, it is also the least "forgiving" compared to the old return type; all appropriate sensors and the proper PCM must be employed. Early modules used a FUEL PUMP DRIVER MODULE which processed the data to control the pump. Later, this function was built into the PCM itself. All these considerations are part of the game of conversion.

"Question is, do I need a fuel regulator and a return line to make this work?" Yes, and it depends.

"I am trying to use the original tank. I have a holley terminator......" Original tank may always be modified for use with either return or returnless. In fact, conversions I've done used the OUT of TANK pump used by Ford in late 80s F-150s, pump mounted on the frame, saving internal tank mount. EFI tanks are specifically baffled for pump in tank use; you don't get that with a stock tank. I have no knowledge of the Holley product you mention.

"I believe that fuel is regulated on the fuel rail." Fuel PRESSURE is what is regulated; this controls VOLUME flow. I cannot confirm which system 2004 Mustang used, but that's not too important except that if all 2004 components are used, the type of fuel system is determined by it.

 

Thank you for your response. His information is very helpful in determining how I plan to proceed with my project. We holley terminator efi pcm should arrive in the next week. I already have the holley fuel pump that the holley suggested I use. Thanks again