Fuel Tank, Lines and Pump with Instructional Video
Fuel delivery in a TBI system is CRITICAL to achieving optimum performance. Any deviation from these instructions or the parts supplied can result a number of problems at first start up.
Before adjusting fuel pressure be certain the gas tank is at least half full. If the fuel pressure is not steady chances are that air is being picked up from the fuel tank because the level is too low.
Installation of the regulator (preferred location and new style regulator),fuel lines and the fuel pump. Your fuel pump may differ from the one shown but the installation principle is the same.
TBI Fuel Pump & Fuel Line Routing
A dirty fuel tank and/or dirty fuel lines can have a major impact on how your car performs with TBI. For that reason I strongly recommend that you remove your tank and have it professionally purged, cleaned and tested. This would also be the perfect time to have a bung for the return line fitting and for the tank outlet. Both bungs should be 1/4″ NPT.
Tank Outlet Bung 1/4″ NPT
Return Line Bung 1/4″ NPT
Now that you have a clean tank, you’re ready install the correct sized fittings and plan the best way to run your fuel lines. With the tank in place, install a shut off valve and the return line fitting. The shutoff valve will make working around the fuel lines much easier in the future, including a yearly fuel filter change.
Shut Off valve screws directly into the tank outlet.
The fuel filter hangs directly below the shut off.
DO NOT USE your existing steel fuel lines as the supply line from the tank to the regulator. They are TOO SMALL and won’t deliver enough fuel to the regulator and the injectors. I recommend 5/16″ for both supply and return. Nickel aluminum tubing is easy to bend and lasts forever but is expensive, NAPA BK 641-3352. Steel brake line tubing may also be used.
When using AN connectors or braided hose it must be 5/16″ or 3/8″ inside diameter or larger.
How you ultimately decide to run the fuel supply hose from the fuel pump to the regulator is up to you but keep in mind the following:
This is as sharp a hose radius as you should make.
The return line is run from the regulator back to the fitting that was installed in the tank. This allows any excess fuel not used by the injectors to be returned to the tank. The return MUST go to the tank and NOT to the supply line.
This right angle fitting was put in the top of the tank on the driver’s side. It could also have gone on the side of the tank.
The easiest way to run the return line is to re-use the old steel supply line that already runs from the fuel tank to the old mechanical pump. IMPORTANT: if you plan on re-using the old steel line, you must remove & replace the few sections of existing rubber hose that connects sections of steel line. The old rubber pieces gave probably deteriorated with age and must be replaced. Before replacing them, blow compressed air through the steel lines to make sure they are clean and clear of any debris. The return line is a low pressure line so 5/16″ fuel hose can be used for the connection from the end of the steel line at the mechanical pump to the regulator.
Plumbing the fuel system consists of four parts; suction, high pressure, return, and regulated pressure.
Suction: The section of line that supplies fuel from the tank to the electric fuel pump.
High Pressure: This section of line is from the electric fuel pump to the fuel pressure regulator. Line pressure in this section is 30 to 40 psi and the fuel filter is located here.
Return: This smaller line returns excess fuel from the regulator back to the fuel tank. This section is usually very low pressure at less than 2 psi.
Regulated: This is the regulated pressure out of the fuel pressure regulator that supplies the TBI injectors. Pressure in this section is typically 14 psi.
Shown below is the system used on Aaron Cropley’s 1971 TR6. Another example from a 1975 TR6 can be seen here.
The original fuel line from the TR6 tank is 5/16″ steel line coming out the bottom of the tank. Because the source is at the bottom, gravity will drain the entire tank if there is a leak, we added a fuel shut off (must be a full flow type). A short section of hose connects the shut off to the plastic filter. The valve pictured is available from most marine suppliers. The electric pump used for TBI has a 5/16″ supply nipple.
Even though the fuel pump has a filter screen, it’s best to install a filter between the tank and the fuel pump. Best to mount the filter vertically so any entrapped air gets returned to the tank on shut down. There’s no telling what’s collected in the bottom of a 30 year old gas tank! Replace fuel filters every other year for most classic car driving, regular intervals if daily driver.
Shown is an early installation using 3/8” tubing. We now find that 5/16” line is sufficient and a much easier line to work with. This is the section that carries the high pressure output from the fuel pump. Steel 3/8″ brake line connects to the pump’s output and heads forward along the left hand frame member. A 3/8″ coupling joins another section of steel tubing and connects to the fuel filter. The filter used is a common GM fuel injection filter, NAPA 3481. The steel tubing requires adapters to mate with the filter, 2 of a NAPA WH 1446 fitting. The 5/16″ line crossing over the top of the pump is the return line back to the fuel tank.
In place of the steel lines, copper/nickel alloy tubing in 5/16″ OD is now my favorite. Although a bit pricey it’s easy to work with and lasts virtually forever. It’s available from most auto parts stores and online. A 25’ spool is enough to run both lines.
A filter after the fuel pump can also be added for extra security. In this case a GM filter has been installed.
Fuel Pressure Regulator
NOTE: Installation Requirements
The fuel pressure regulator adjustment screw should be backed off before pressurizing so the pressure can be brought up to the target amount. Over pressure will instantly destroy the 0-30 psi gauge. Pressure setting differs depending upon the make and model car but if that is unknown 11.psi is a reasonable starting point. Components are tested up to 25psi- do not exceed that limit without contacting Patton Machine or Affordable Fuel Injection.
The gauge is liquid filled so it must be mounted with the little rubber plug at the top to allow for expansion and contraction of the liquid with temperature. The rubber plug needs to be pierced with a pin making a tiny vent hole. Mounting instructions are on the gauge itself or in the box.
The return line returns excess fuel from the regulator back to the gas tank in the trunk. There is little or no pressure in this section so regular fuel hose is perfectly suitable. Starting at the regulator 5/16″ fuel hose connects to steel 5/16″ tubing. The steel line drops down from the regulator, runs across the backside of the front frame cross-member and is connected to the original TR6 steel fuel line. The connection between the two steel sections is made with a short piece of 5/16″ rubber hose at the same location as there was a short hose splice in the original line.
The yellow arrow shows the new return line from the regulator connecting to the old steel fuel line which was reused for returning gas to the tank. Fuel returns in the original TR6 supply line and back near the new pump, is coupled to 5/16″ plastic line with a short section of rubber hose. I prefer to use fuel injection style hose clamps whenever possible. The plastic tubing squeezes up through a rubber grommet in the trunk floor alongside the tank vent hose. It continues up to the the top of the gas tank and connects to the vent nipple at the left end. The hose that originally attached to that vent nipple is plugged off. If you don’t have a connection at your tank for the return line, you’ll have to have one soldered in.
If your tank doesn’t have these vent nipples, you will need to make provisions for the return. Either have a repair shop add a 5/16″ nipple or contact me for a sender unit with the return built in. The tank connection is something you will need to take care of on your own. Provisions can be made long before starting the conversion.
Here we are at the end of the line where all the previous plumbing delivers fuel at 12 PSI. Two regular 5/16″ hoses (minimum size), connect from the regulator to each of the fittings on the carb bases. Best to have the regulator within 18″ of the injectors.
The regulator show here is an older style than the Aeromotive that we currently provide but the connection concept is the same.
There are many other ways to run this plumbing, especially the high pressure section. Some suppliers recommend a high pressure “push lock” hose. High pressure plastic tubing could be run the entire way or even high pressure rubber hose. Personally I like to use steel lines under the car but newer cars are using plastic or Teflon lines.
Safety is a concern with the fuel pressure regulator so an off the shelf alternative is best. The regulator must be the recirculating type to work properly. Most of the aftermarket regulators have a small line used to sense intake manifold vacuum. In case of a ruptured diaphragm, fuel would escape down that line and flood the engine. Those same regulators when used with TBI should NOT be plumbed to sense manifold vacuum. That line could be piped to the carb’s temperatures compensator port, run back to the fuel tank, or vented in a non smog application.
Fuel filters are also open to change. For Aaron’s car the GM filter was chosen as it is available anywhere and suitable for connection with steel line. Ford uses a filter that is designed for quick disconnects but works well with hose.