Fuel-injection systems require careful planning and component selection. There are many components that go into a fuel system (including tank, fuel pump, lines, fittings, and filters) and each one has multiple replacement/upgrade options. So, simply installing an electric fuel pump is not going to work. The fuel-pressure requirements alone necessitate some detailed planning.
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In-Tank Fuel Pump
When it comes to fuel pumps, there are two categories: in-tank and external. In-tank pumps tend to last longer, hold higher pressure, and run quieter. However, in-tank pumps are also more complicated to install, and retrofitting an in-tank pump costs more. Virtually any aftermarket EFI in-tank pump that can supply the 60-psi fuel-pressure requirement is suitable. Many builders suggest the Walbro 340 in-tank pump because it holds higher pressures and has proven to be very reliable for supplying LS engines. The key is to buy a pump that is suited for your application. The stock F-Body fuel-pump assembly can be purchased from GM dealers and used for retrofit applications.
There are two ways to add an in-tank pump to your vehicle: buy a tank with a preinstalled EFI pump, either custom or OEM from a different vehicle, or retrofit the tank. Both options can be pricey, but there are ways to keep it on the cheap as well.
Buy a New Tank
New tanks can cost upward of $1,000. Companies such as Rock Valley Antique Auto Parts build custom stainless-steel gas tanks for street rods, hot rods, muscle cars, and trucks. If your car is not on the list, Rock Valley can build a custom tank. These new tanks are very slick, well built, and easy to install, but they come with a high price tag.
Each Rock Valley EFI fuel tank features a dropped sump in the top of the tank. This allows for adequate floor clearance. Each EFI tank comes with a new high-volume, high-pressure fuel pump to feed your engine.
Refit the Current Pump
There are several ways to alter your stock tank to take an EFI fuel pump. The bargain-basement method is to take the stock sending unit assembly out of the tank, cut off a short section of feed line (about 11⁄2 inches, depending on the depth of the tank and the length of the pump), and fit the pump to the stub using fuel line and hose clamps. The important thing here is to make sure the pump is mounted about 1/4 inch off the floor of the tank, with a filter sock resting on the bottom of the tank. This keeps the impurities out of the pump while getting the most fuel out of the tank. The pump needs to be supported, so a piece of steel rod can be welded to the underside of the assembly plate. The pump is then clamped to the rod, so it remains stationary.
This method doesn’t work for all tanks, especially shallow tanks, and clearance may be hampered by the diameter of the stock assembly. Additionally, the fuel-level sending unit may be in the way, depending on application. This method keeps the stock feed lines in place and eliminates any floorpan clearance issues. One more drawback is the complete lack of a fuel sump feature, which traps fuel around the pump inlet, ensuring it does not run dry. Running an in-tank pump dry is very destructive; they don’t last long when run dry.
Modify the Tank with Welding
Welding on the tank is extremely dangerous and should not be attempted in haste or by novices. All of the old fuel must be removed and the tank thoroughly rinsed, drained, and rinsed again until there is absolutely no possibility of any remaining fuel vapor.
If you smell a hint of gas, clean it again. Some people even suggest filling the tank with water or inert gas, such as argon, while the welding is being performed. In any event, when in doubt, seek the help of a professional. Most fuel tank builders also offer their services for retrofitting tanks.
Installing a custom in-tank pump in the top of the tank often requires a recessed panel on the top. The fittings clear the floorpan and provide a flat surface to mount the new assembly. If the top sump is placed to the side of the original, the stock sending unit can be used, simplifying the process. This requires a boxed section to be built and welded to the top of the tank.
Then a fuel-pump assembly unit is built with both wiring and inlet and outlet fittings. This unit should have a bar or rod on the inside portion of the tank to mount the pump. Using 90-degree hose barb fittings is usually the easiest way to get the fuel in and out of the assembly. These fittings must be sealed tight so they do not leak. The entire assembly bolts to the sump.
In addition, by installing baffles on the inside of the tank, fuel surrounds the pump at all times. The baffles should be added before the top sump is installed.
The other option is to weld in a sump in the bottom of the tank. This sump is placed directly below the pump, but the pump is installed in the lowered section, with the filter sock on the floor of the sump. Tanksinc.com offers an upper tank mount, complete with a fuel pump and baffle. This option reduces some of the building legwork and ensures the pump is covered with fuel at all times.
Install a Pump Kit
You can install a truly high- performance fuel pump into a stock fuel tank without welding. Aeromotive offers two retrofit in-tank pump kits: the Phantom and the A1000 Stealth.
For basic street performance use, the Phantom 340 kit is suitable. This kit allows you to simply cut a hole in the top of the tank, drop in the pump, bolt it down, and hook up the lines. The kit comes with the seals, hardware, and a drill jig to ensure the holes are in the right place. The 340 supports up to 700-hp supercharged EFI engines, or 1,000-hp supercharged carbureted systems. That means there is plenty of room to power a stock 400-hp LS3. The Phantom system can fit in just about any tank, so this is a really good option that takes out the guesswork.
For more serious performance engines, the Stealth A1000 system feeds up to 1,300-hp EFI systems and 1,500 hp for carbureted engines. Installing these systems takes slightly more effort than the Phantom kit, but not much.
External Fuel Pump
External, or in-line pumps, are simpler to install and are usually cheaper than in-tank fuel pumps. In-line pumps are much easier to change, making roadside swaps bearable. The main gripe with in-line pumps is the noise. The relatively quiet and smooth-running Gen III/IV engines do not drown out many external sounds, including these in-line pumps. Therefore, drivers hear the whir of the electric pump sound over the engine with a stock-style quiet exhaust. For most builders, the added noise isn’t a problem but merely an inconvenience; for a show car, a noisy pump might be considered a serious drawback.
The real drawback for an in-line pump is that the fuel line is only pressurized after the pump, meaning the tank to the pump is gravity fed. Anyone who has dealt with a modern high-performance external fuel pump can tell you that life is really difficult when you lose the siphon feed in the fuel tank. Simply having the pump in the tank maintains a constant supply of fuel to prevent those hard-cornering and acceleration woes that come with a stock tank and an in-line electric fuel pump.
In-line fuel pumps also require a more substantial return line system because of the long distance between the regulator and the fuel tank. In-line pumps are also subject to failure through heat. The only thing that cools the pump is the gas fl owing through it.
Not all in-line pumps are created equal. They come in different shapes and sizes, with the majority consisting of low-pressure units designed for carburetors. These pumps deliver 6 to 14 psi, not nearly close enough to the 60 psi required to operate an LS engine. Any less than 60 psi and it leans out and does not run well, if at all. Thankfully, there are plenty of in-line EFI pumps to choose from. Many builders prefer the Walbro GSL 392 external pump. These pumps are well suited for Gen III/IV engines and can supply the pressure needed.
It’s pretty simple to install an in-line pump, but there are a few caveats. The first is to always install a pre-filter before the pump, so the pump does not get clogged and ruined. A pre-filter is basically a screen-style filter that traps the big stuff.
A micron filter should be placed after the pump to catch small contaminants. Do not install a micron post filter in front of the pump (between the tank and the pump) because it impedes the gravity feed and there is not enough force to push the fuel through it.
Make sure the pre-filter is large enough to free-flow the fuel. A small pre-filter restricts the flow to the pump, causing cavitation, and burns up the pump. A stock-type metal canister pre-filter works great, but they are not pretty. Most after-market fuel-pump makers have large-capacity pre-filters if you want a good-looking filter. Most aftermarket pre-filters are re-buildable.
Cavitation is a natural process that occurs when vapor bubbles are introduced into liquid under pressure. All electric fuel pumps are susceptible to this force. Its most common cause is installer error, where an inadequate fuel supply increases the suction on the inlet side.
Cavitation is literally boiling the fuel through pressure. Vapor bubbles form and then split, causing a micro-explosion. This is extremely damaging, as even a few minutes of cavitation can ruin a fuel pump.
Another cause of failure is over-heated fuel. Not running a return line (dead-head style) or attempting to plumb the return line into the feed line (not into the tank) causes hot fuel to cycle back through the pump, heating it up more. The hotter the fuel, the easier it is to cavitate or even vapor lock. Yes, EFI systems can vapor lock too. This is why a proper return system is so important for EFI.
The most important aspect of any electric fuel pump is the wiring. In addition, it is most difficult to get solid grounds because paint, rust, and scale inhibit the ground. Always be sure to remove the paint and anything else from the ground location so you have clean metal.
Electricity requires equal grounding and positive current flow. A bad ground is just as bad as a faulty positive feed. Electric fuel pumps require a lot of current, so it’s important to run a relay circuit from the pump trigger lead and to run 12-gauge positive and negative wires to the fuel pump. This ensures the pump gets the required amperage without over-heating the wires.
Do not run a 16- to 24-gauge primary wire to a fuel pump, because it will cause a fire. All fuel pumps require at least a 12-gauge power wire.
All EFI engines require return lines. This can sometimes be confusing because Gen III/IV engines use a single-line fuel rail. The 1997–1998 Corvettes and 1998–2002 F-Body LS1s used a dual-line fuel rail. In 1999, the Corvette LS1 went to a single-line rail, using a filter regulator near the fuel tank and running a short return line back to the tank. This configuration is much simpler and requires only a single line run the length of the vehicle.
Many builders prefer to run two lines the distance of the vehicle with the dual-line fuel rails. The benefit of running a full-length return system is cooler fuel. The fuel does not sit in the lines, heating up from the pressure. Instead, a constant flow of fuel is running through the lines, ensuring cooler fuel and therefore more power.
This of course requires two sets of fuel lines: a 3/8-inch line for the feed and a 5/16-inch line for the return. Some muscle cars and trucks came with return-style mechanical pump fuel systems, but these are not the norm for older vehicles; most were dead-head systems, meaning that the fuel simply stops at the pump until it is sent on to the engine.
If you choose the simple one-line route, you need the 1999-up Corvette filter regulator. This unit has two lines (an input and an output) on one side for the fuel tank, and one output on the other side that goes to the engine. This preset regulator provides the correct 60 psi to the engine, which pressurizes the entire fuel line while pumping the excess fuel back to the tank. This is typically mounted as close to the tank as possible to minimize the length of feed and return lines to the tank. For a dual-line system with the pump in the tank, a filter is needed between the pump and the fuel rails. It is best to filter the fuel as soon as possible to keep the fuel lines clean.
Installing new lines is simple, but it can be nerve-wracking at the same time. There are three ways to accomplish this task: install pre-bent hard lines, bend new hard lines, or run braided hose.
Using pre-bent hard lines is the simplest method if the vehicle has the fuel tank in the stock location. Pre-bent lines, such as those from Classic Tube and Tube Tech, are patterned after the original lines in the car and should fit just like the originals. That is not to say that there are not compromises and tweaks that must be made along the way.
Bending and installing custom lines most effectively transports fuel the length of the vehicle, but it is much easier said than done. This is a challenging task that requires some metalworking skills, and therefore the task is frustrating at best for the novice. Tubing makers such as Classic Tube offer custom-bending services using coat hangers or other wire, where a pattern is bent by hand and sent to the maker. They, in turn, can bend a set of hard lines to those specifications. This ensures quality bends with proper flare where you want them; without kinks and without the aggravation of doing it yourself.
The third option is to use flexible hose for the long runs. This works; however, braided hose is preferable to plain rubber hose to prevent road debris damage. The chance of debris snagging a long braided fuel line is much higher than with a hard line. Rubber lines are not the best option, either. Rubber lines dry out and crack much faster than hard lines corrode, so you have to replace the rubber lines eventually.
Feature Vehicle: 1966 Mustang
When Mike Magnuson was looking to build a new project, he knew it had to be an early Mustang. Growing up a Ford fan, Blue Ovals were at the top of the list. Then Mike saw a 1969 Camaro with an LS swap and became very intrigued. He then found the original version of How To Swap GM LS-Series Engines Into Just About Anything and was hooked. After a trip to the Holley LS Fest, Mike realized that any vehicle could be LS powered for far less money, time, and effort than just about any other modern engine. After some searching, he eventually landed a pair of LQ4 6.0L Vortec engines for $1,400. When it came to the car, Mike went back to his Ford roots. When he found a clean 1966 coupe that had been dismantled for restoration, the deal was made.
Mike began by reassembling the car with modern performance in mind. The front strut-style suspension was removed, along with the strut towers, in favor of a Total Cost Involved front clip. This opened up the engine bay for the wider LS engine to fit where the 289 once lived. The 2002 Denali LQ4 was stripped to the long block. A 2002 Camaro intake was installed, along with an accessory bracket from KWiK. The alternator is a 2002 Camaro unit, and the power steering pump comes from a 1994 Cavalier with a 1998 Pontiac Montana pulley. The truck oil pan was retained.
The 4L60E transmission was rebuilt with a Beast sunshell gear, Raybestos clutches, Corvette servo, and a stage two shift kit. The stock Mustang shifter was modified to control the shifts. Under the dash, the Mustang retains the drive-by-wire throttle. The exhaust is handled by a set of Hedman 2002 Camaro headers that were modified to fit around the steering shaft. To handle the increased power and torque, a 1996 Ford Explorer 8.8-inch rear was narrowed 3 inches and installed under the Mustang, along with a set of 3.73:1 gears on an Eaton limited-slip differential.
The fuel system uses the stock Mustang tank with a 2003 Ford F350 in-tank fuel pump and module. Mike built a custom sump to help keep the inlet covered with fuel. Outside the tank, the lines continue with -8 AN braided hose feeding a Corvette combo filter/regulator running to the factory fuel rails.
The results of Mike’s efforts are quite nice. The Mustang was driven to the 2012 Holley LS Fest, averaging 23 mpg on the 1,300-mile trip. This first-generation Mustang was the only one at the show and garnered a lot of comments. The car was even featured on Chuck Hanson’s television show, Horsepower TV.
Written by Jefferson Bryant and Posted with Permission of CarTechBooks