Quote:
Originally Posted by RustyPile
I read through this old thread and most of the information is pure bologny and false, erroneous information.. The fuel pump has nothing to do with the EEC system. They are two totally separate systems not connected together in any way..
Starting at the fuel pump, there are 2 variations.. One pump has 2 connections - the rubber line coming from the sending unit in the tank, which is the pump suction line. This line draws fuel out of the tank. The other fitting (a flare type fitting) on the pump is connected to the line that delivers fuel to the carburetor. If you have only one line connection on the sending unit, this is probably the fuel delivery system you have.
The other fuel pump has 3 connections.. Two of the connections work as described above. The 3rd connection is a 1/4" nipple. it serves as a fuel return through a line back to the tank. This recirculation serves to keep fuel moving at a faster rate to help prevent vapor lock. This line runs basically parallel to the suction line all the way back to the tank sending unit.
The EEC system is a fuel vapor only system.. There is a nipple on the gas tank in the upper corner on the passenger side of the tank.. This nipple has a rubber hose connecting to a steel pipe that runs up through the B pillar and back down through the floor in the area where the liquid fuel lines pass through the floor. This line continues along the frame rail to the front and connects to the charcoal cannister located under the battery. Coming off the canister are 2 more vacuum lines connecting to vacuum control pieces on the engine.
The simple facts are:
#1- If you have 3 connections on the fuel pump and 2 on the sending unit, you have fuel recirculation plumbing..
#2- If you have that nipple on the upper passenger side of the tank, you have an EEC system. If the EEC system components are in place and working, you will need a non-vented gas cap for the system to properly function.
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Good stuff.
If you go by the parts book the recirculated system was installed beginning in 1972ish. I say ish because you know, sometimes they installed new stuff before the next year, sometimes even old stuff from the former year.
You say it has nothing to do with one another, fuel/vapor. Tell that to my former mechanic
After the canister and that were pulled he connected the vent line to where a return line would be on the fuel pump replacement. It worked somehow, couldn't tell you, though the replacement cap was vented.
You know what else is BS is vendors sell upper fuel lines varied on whether or not the truck has A/C. It has nothing to do with A/C, some people suggest it does. The difference is whether or not the fuel pump takes a return line. They figure a return line means it's A/C equipped
Here's a tank assembly for an EEC system for reference. Images of the two different fuel pumps too.