When it comes to fuel pumps, there are two categories: in-tank or external. The in-tank pumps are more complicated to install, but they tend to last longer, hold higher pressure, and run quieter. Retrofitting an in-tank pump costs more, but the cost is worth it in reliability.
There are two ways to add an in-tank pump to a 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.
An in-tank pump that can supply the 72 psi at 45 gph fuel-pressure requirement is required. The Aeromotive Phantom 340 in-tank retrofit pump has the capabilities to support the LT fuel system and is quite easy to install.
Another option is to use a factory GM fuel-pump module from one of the LT-powered vehicles from 2014-and-up that were used in 1/2-ton trucks, Corvettes, and Camaros. The Camaro fuel module is fairly tall, so it does not fit in most car tanks, but the 2014-and-up GM truck fuel modules fit quite well. Installing one of these pumps requires some fabrication on the fuel tank. The nice thing is that if you use a factory module, the wiring for the pump is basic plug and play.
This Tech Tip is From the Full Book, HOW TO SWAP GM LT -SERIES ENGINES INTO ALMOST ANYTHING. For a comprehensive guide on this entire subject you can visit this link:
LEARN MORE ABOUT THIS BOOK HERE
SHARE THIS ARTICLE: Please feel free to share this post on Facebook Groups or Forums/Blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https://www.lsenginediy.com/how-to-install-the-right-fuel-pump-on-an-lt-swap
New tanks can cost $600 to $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 Antique Auto 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.
For the 1987 Camaro, we went with option C, which is to install a new pump in place of the original in-tank pump. If the vehicle had EFI from the factory, such as almost any 1987-and-newer GM vehicles (and a few older models), then it already has a fuel pump in the tank. This upgrade begins by knocking out the retainer ring for the pump assembly.
We went with a DeatschWerks DW300 pump kit. This pump can flow the required 75 gph at 45 psi and is capable of using a PWM signal. It is also the same size as the original in-tank pump.
The new pump is shown next to the old. There are a few things that we won’t be using, including the wiring, connectors, and the return line.
First, we removed the old pump and disconnected the wires. The black connecter is also removed.
On the underside of the pump assembly is a little vapor line. We removed the cover and the keeper. This will be the wire run.
Up top, the line that went to the vapor filter was cut off. There is still a vapor line attached, but we needed one of these for the port.
This connection must be soldered, do not crimp this. This is a PWM signal wire, and it must be a proper connection.
The solder joints were covered with shrink tubing and then sealed with fuel-resistant silicone for an extra layer of protection.
We routed the pump wires out of the top of the assembly and coated the entire area with some more fuel-resistant silicone.
The pump comes with a plug pigtail. We need to lengthen this and seal it from the gas.
Don’t forget to put the filter sock onto the new pump. We set the pump in the stock location, so there is no concern about the filter not reaching the bottom of the tank.
We mounted the new pump to the assembly with a section of fuel line and a worm clamp. The pump will be secured with a couple of hose clamps to the no-longer-used return line, which is also the support stem.
The unused lines get capped with silicone caps.
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 the engine. For the most popular vehicles, Aeromotive and Holley offer replacement tanks that are closer to the $600 price range, and they use nice reproduction tanks with their own proprietary pump systems.
Ambitious builders can choose to modify the stock tank themselves. Note: The following procedure requires welding on a gas tank. Serious injury or death can occur if the utmost care and preparations are not followed. There are a several ways to alter a 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 1½ 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 won’t work for all tanks, especially shallow tanks, and it may be hampered by the diameter of the stock assembly. Additionally, the fuel-level sending unit may be in the way, depending on the application. This method keeps the stock feed lines in place and eliminates any floor pan 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.
The next option involves welding on the tank. This 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, do 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 offer their services for retrofitting tanks, so employ their services if you can.
Installing a custom in-tank pump in the top of the tank often requires a recessed panel on the top. The fittings clear the floor pan and provide a flat surface to mount the new assembly. If you place the top sump to the side of the original, the stock sending unit can be used, simplifying the process. This requires a boxed section 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 piece should have a bar or rod on the inside portion of the tank for the pump to mount to.
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 don’t leak. The entire assembly bolts to the sump. In addition, by installing baffles to the inside of the tank, fuel will surround the pump at all times. These should be added before the top sump is installed.
The other option is to weld a sump into the bottom of the tank. This sump would be placed directly below the pump, but the pump would be installed in the lowered section, with the filter sock on the floor of the sump.
Tanks Inc. offers an upper tank mount, complete with a fuel pump and a baffle. This option reduces some of the legwork in building this piece and ensures the pump will be covered with fuel at all times.
There is one more option that allows you to 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 systems.
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, hook up the lines, and you are done. 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. 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 for carbureted engines. Installing these systems takes slightly more effort than the Phantom kit, but not much.
Next, we need to make a flex line to connect the fuel line to the engine. We are using Earl’s Performance Plumbing fittings and Super Stock hose, which is a push-on style. It can handle 250 psi, good enough for our LT. We also have an adapter that will push onto the stock LT fuel rail. As a side note, always use swept tube–style fittings like this for fuel; the block-style 90-degree fittings cause turbulence in the fluid flow.
Then, the hose is just pushed onto the fitting until it won’t go anymore. These may not seem like high-pressure hoses, but they work very well. Be sure to use the Super Stock hose with Super Stock fittings for this to function correctly.
A little assembly lube makes pressing the hose onto the end much easier.
One end of the hose was threaded onto the adapter on the hard line. AN fittings do not require much torque, just hand tight and then a slight tightening is enough. Too much torque will damage the seal.
External or inline pumps offer a simpler installation and are usually cheaper. Inline pumps are much easier to change, making roadside swaps bearable. The main gripe over inline pumps is the noise. Drivers may hear the whir of the electric pump over the engine with a stock-style quiet exhaust. For most builders, the added noise is merely an inconvenience. However, for a show car, a noisy pump might be considered a serious drawback.
The real drawback for an inline pump is that the fuel line is only pressurized after the pump, so 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 in the 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 inline electric fuel pump.
Inline fuel pumps also require a more substantial return line system. This is because of the long distance between the regulator and the fuel tank. Inline pumps are also subject to failure through heat. The only thing that cools the pump is the gas flowing through it.
Not all inline pumps are created equal. External pumps come in all different shapes and sizes with the majority of the market consisting of low-pressure units designed for carburetors. These pumps deliver 6 to 14 psi, and they are not close to the 72 psi required to operate an LT engine. Inline pumps are more susceptible to overheating, and most are not capable of PWM returnless operation. So, running this in a return-style system with an LT engine will result in more complications due to overheated fuel.
Installing an inline pump is pretty simple, but there are a few caveats. The first is to always install a prefilter before the pump, so the pump does not get clogged and ruined. A prefilter is 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 will impede the gravity feed, and there will not be enough force to push the fuel through the micron filter.
This Tech Tip is From the Full Book, HOW TO SWAP GM LT -SERIES ENGINES INTO ALMOST ANYTHING. For a comprehensive guide on this entire subject you can visit this link:
LEARN MORE ABOUT THIS BOOK HERE
SHARE THIS ARTICLE: Please feel free to share this post on Facebook Groups or Forums/Blogs you read. You can use the social sharing buttons to the left, or copy and paste the website link: https://www.lsenginediy.com/how-to-install-the-right-fuel-pump-on-an-lt-swap
Make sure the prefilter is large enough to free-flow the fuel. A small prefilter will restrict the flow to the pump, causing cavitation that will burn up the pump. A stock-type metal canister prefilter works great, but they are not pretty. Most aftermarket fuel pump makers have large-capacity prefilters if you want a good-looking filter. Most of the aftermarket prefilters are rebuildable as well.
We don’t want to chop off the quick-release fitting on the fuel rail, so we are using a push-on adapter. This will connect to the fuel rail and leave a -6 AN connection on the other side.
All done, the fuel system is now complete.
The most important aspect of any electric fuel pump is the wir- ing. In addition, it is 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 there is 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 cur- rent. Running a relay circuit from the pump trigger lead, along with 12-gauge positive and negative wires to the fuel pump, provides ample capacity. This ensures that the pump gets the required amperage without overheating 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 12-gauge power wire, and the larger pumps need 10-gauge wire. This includes both power and ground wires.
Fuel Control Module Pressure Sensor
Regardless of how the fuel sys-tem is plumbed, the factory fuel module is required for an LT-series engine to operate correctly. The ECM must know the inline fuel pressure coming into the DI pump—without it, the engine will run erratically. To send this information to the ECM, the fuel module is needed. Because of this, running the factory-style PWM control is a matter of three wires. It is easier to use the PWM system than a regulator with return line system. The factory fuel module is a learning unit; it has the ability to slightly adjust the fuel trims to match the pump it is controlling. This technology is still fairly new, so the aftermarket has not quite caught up yet. It is possible to tune the fuel module to match the pump being used in the system. A special pressure sensor in the fuel line monitors the pres-sure of the fuel, which is main-tained at 72 psi. Rather than use a regulator, the pressure is man- aged through PWM control of the pump. Essentially, the ECM uses PWM to control the speed of the pump, ensuring full pres-sure at all times with no delays. This complicates the fuel system for the LT-series engine swap. Don’t use just any old pump. The pump must be able to be PWM controlled. Before purchasing a pump, make sure it is PWM capable. Installing the PWM control- ler is relatively simple, but the fuel pressure sensor is a bit tricky. First, an inline adapter with a pressure sensor port positioned at 90 degrees or 5 to 85 degrees to the flow of fuel is needed, accord- ing to the GM manual for the fuel controller. This means that the sensor itself must be mounted either 90 degrees vertically or between 5 and 85 degrees from the vertical position. Essentially, the sensor should not be horizon-tal or below the flow of fuel. As long as the sensor is angled upward (with the terminal sitting above the fuel port) at least 5 degrees, fuel cannot pool in the sensor. This is fairly easy because there are plenty of fuel sensor adapters out there. The problem is that most of the adapters are for 1/8-inch NPT fittings and not the 10-mm threads required for the GM sensor.
Finding a 1/8-inch NPT male to 10-mm male adapter is difficult. It is easier to find a -6 AN male to 10-mm adapter. To use this, you need an aluminum fuel log or Y-block fuel splitter and a -6 to 10-mm male-male adapter. This allows you to connect the sensor into the fuel system. We made one with a leftover piece of fuel rail from another project.
Wiring the PWM pump controller is a plug-and-play affair, but the pump wiring itself is not. There are three wires coming off the pump module: yellow with a black stripe, gray, and a smaller-gauge black wire. The yellow/black wire is the ground, the gray wire is the power side, and the small black wire is the shield. If you are using a GM pump with a shield pin, connect the small black wire to that pin, but if you are using a pump without a shield pin, leave the wire unterminated and tape it to the other wires.
Because of the nature of PWM control, there is a very real potential for electromagnetic interference (EMI) from other electronics in the car. To eliminate this from interrupting the control signal, the two main power control wires are twisted with a third shielding wire. This wire is grounded to the chassis near the pump.
If you want your LT engine to run like it is supposed to, use the fuel control module (FCM). This small computer controls the fuel pressure your engine receives based on demand.
There are three wires that run from the FCM to the fuel pump, and they must be twisted with a shield ground wire. We braided our wires, but the minimum is 27 twists per 8 foot. The cleaner and more consistent the twist, the better the signal wires are protected. A loose braid is best because a really tight twist or braid can stress the wire itself.
There are several versions of the fuel pressure sensor that can be used with LT-series engines. Upper left is the Corvette and truck sensor; bottom right is the sensor used with Camaro LT engines. They are the same internally, but the Camaro sensor has hose barbs, while the other requires a 10-mm male threaded adapter.
The FCM must be mounted between the engine and the fuel tank; the Chevrolet Performance wiring harness has a very short pigtail for the FCM to fuel pump run, so it may need to be extended. On the Buick GS, we mounted the FCM under the car to the transmission crossmember.
Depending on the fuel system plumbing, the Camaro sensor may work better because the truck/Corvette sensor can become a bit clumsy if you can’t find a direct fitting adapter. If you are using AN fittings, the Corvette sensor works better.
The Chevrolet Performance wiring harness only comes with a certain length, about 6 feet. To maintain the shielding, the wires must be twisted at a minimum of 27 twists per 8 foot of wire. The best way to ensure that the wires are correctly twisted and won’t unravel is to braid the three wires together. It does not need to be a tight braid, rather a consistent loose braid, wrapping the wires around every 3 inches or so. Do not use crimp connectors for these wires. Instead, make sure to solder them well and use shrink tubing.
Return Lines
If you decide to go with a regulator/return-line setup, then you will need to run a new line. The minimum requirements for EFI fuel lines are 3/8-inch line for the feed and 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.
Many people assume you can use the 1999-and-up Corvette filter regulator with an LT engine, but this is not the case. While the engine will run, it will be starving the pump on the top end. This unit has two lines (an input and an output) on one side for the fuel tank, and one output on the other, which 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. This is not recommended for an LT engine swap. For a full dual-line system with the pump in the tank, a filter between the pump and the fuel rail is the preferred method if you are not running the factory PWM system (the filter is required for all fuel systems). It is best to filter the fuel as soon as possible, keeping the fuel lines clean.
Installing new lines is a fairly simple process, but it can be nerve racking at the same time. There are three ways to accomplish this task: run braided hose, bend new hard lines, or install pre-bent hard lines. 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 will be frustrating at best for the novice. There are tubing makers, such as Classic Tube, that offer custom bending services using coat hangers or other wire. A pattern is bent by hand and sent to the maker. They, in turn, will bend a set of hard lines to your specifications and ship them to you. This ensures quality bends with proper flare where you want them— without kinks—and without the aggravation of doing it yourself.
The other option is to use flexible hose for the long runs. This works, but braided hose should be used rather than plain rubber hose to protect from road debris damage. The chance of road 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 will have to replace the rubber lines eventually.
The Camaro has good hard lines up to the engine bay, so we chose to use them for the fuel feed. The larger line is 3/8 inch, which will work perfectly.
We used a tubing cutter and removed the flare because we will make our own.
AN fittings require a 37-degree single flare (never a double flare), which we made using this portable tool from Matco. The standard 45-degree flare commonly used for brake and non-AN fuel lines will leak with AN fittings.
We are using a tube sleeve and nut to create an AN flare for the pressure sensor. These are from Earl’s Performance Plumbing and are -6 AN, which is the correct size for 3/8-inch line. The tube nut goes on first, then the sleeve, then flare the line.
Once flared, the sleeve slides up to the flare. The nut will thread onto the fitting, creating a tight seal.
We installed the fitting, which is an adapter port for the pressure sensor.
Written by Jefferson Bryant and republished with permission of CarTech Inc
LEARN MORE ABOUT THIS BOOK!
If you liked this article you will love the full book!