You've heard the phrase that the sum of all parts is greater than the whole, well when it comes to fuel injection this adage is a motto to live by. All of the requisite components work together as a team. So when you are planning to build your machine, you need to plan a package that will work together before you even start to bolt it on. A little planning in the beginning stage will save you a lot of headaches during the building process and provide you with a vehicle that will be trouble free and a pleasure to drive.
One of the most important things in this plan is the fuel delivery system. Keep in mind that the easiest way is not always the best way. In the long run the easy way my cause you a lot of problems. Two of the first things to consider are the gas tank and the fuel pump. You want to put the pump in the tank if at all possible because external pumps are not designed to suck, but primarily to push.
Most people don't realize that external pumps that were used on Ford trucks, vans and 500ci engines had a low-pressure pusher pump in the tank that pushed fuel to the high-pressure external pump. A problem with external pumps, if they are not installed properly, is that you will not get the proper fuel pressure to the injection system, which, in turn, will eventually burn the pump up because of the lack of fuel to lubricate the pump. If you must use an external pump, a good pump to use is the '87-89 Ford Truck or Van, Mercedes, older Cadillac or Datsun 280ZX external pump. On these vehicles the tank had a good baffle inside. The pick-up port should be 1/2-inch NPT and close to the bottom of the tank. If the tank is not baffled fuel will run away from the pick-up port when going around a corner or accelerating.
If you pull out of the top of the tank, you should use an external pusher pump that is designed to suck fuel from the tank and push fuel to the high-pressure pump. You should also have a minimum of 3/8-inch line from the external pump to the pusher pump. Do not use a pre-filter with external pumps because as the filter gets dirty, it makes it more difficult for the pusher pump to push thru the filter. If using an external pump it needs to be mounted within 18 inches of the fuel tank. When installing new fuel line make sure that you flush the lines with fuel before connecting them to your injection unit. Blowing air through the lines will not remove some of the fine particles left in the lines from when they were cut. These particles will get trapped in the injector screens and stop the fuel flow through the injector.
If your external pump starts to make noise it is best to pick up a spare. External pumps are not the least expensive way to go. The Ford external pump is more than $400, and by the time you buy the fittings and other hardware you will have to spend as much as you would if you had a pump put in the tank. If you have a good tank, there are companies such as Rock Valley who you can send your tank to and they will install the pump. Additionally, Rock Valley, Tanks, No Limit, and other companies can provide a tank to fit your application with pumps already installed inside.
For later-model vehicles, it's even easier to put the pump in the tank. For instance, a fuel pump assembly out of a '86-87 Monte Carlo 4.3 throttle body will fit in '78 and later Monte and El Camino gas tanks. On '78-81 Corvettes all you have to do is use an '82 Corvette in-tank fuel pump assembly. On Blazers, Suburbans, and pickups you can use the same body style '87 and later gas tank or sending unit in earlier vehicles. If it is a throttle body-sending unit and you are running a TPI or multi-port, all you have to do is put a Corvette pump on the unit. For your application, you can call one of the Street & Performance tech staff for help (479/394-5711).
Vapor Lock is another problem that can plague a fuel injection system. Every year in July and August we get calls from people traveling long distance with their vehicle and experiencing vapor lock.
Vapor lock is the heating of the fuel to a point where it turns to a vapor. Internal pumps will help keep exhaust heat away from the pump, lines and tank. Making a heat shield between these parts and exhaust will also help. High altitude will also accelerate the vapor lock problem. Another way to prevent late afternoon vapor lock is to top off your gas tank with cool fuel.
You should also keep fuel lines from coming down by the back of the headers, because hot air coming off of the radiator and the headers and blowing over the fuel lines acts like a heat exchanger. Using an improper fuel filter such as a billet style designed for carburetors restricts fuel flow and puts extra backpressure on the pump. Fuel Injection works better than a carburetor because it circulates cold fuel at the injector. In contrast, the fuel dead heads with a carb and is warmed by the engine heat, which takes away horsepower.
Having an improper size injector that is too small or too big for your application, or incorrect fuel pressure, or a computer chip that has not been programmed correctly for you application can also cause overheating or vapor lock.
Additionally, you have to take into consideration the cubic inches of your engine and horsepower when choosing components. A 305-inch small-block's injectors operate at 19.9 lbs per hour, while a 225- to 275-horse 350's use a 21.9 lb injector. For 300-375hp engines such as a, ZZ4, 350 Ram Jet, LT-1 or LS-1 a 24.9-pound injector is employed. The New LS-6, which cranks out 405 ponies, uses a 28-pound injector and the big-blocks churning between 425 and 550 horses, use a 30-pound units. The new 502 Ram Jet uses a hefty 38-pound injector. If you have a used engine or injection system, it is best to have a professional clean its Injectors with an ultra sound cleaner and flow them so that they will be clean and matched evenly.
If your vehicle is running and you would like to check its system, one of the best tools you can have is an infrared heat gun to check the exhaust temperature of each header tube. If all injectors are in good shape, they should be within 35 degrees of each other at idle (normally between 225 and 300 degrees). For example, if you have one or more with a higher temp, you usually have a lean injector or one that is dripping. Most injector's will clean up without a problem but '89 and later Tuned-port and LT-1 Injectors are the worst. If you have a problem with the multi-tech injectors it is best to replace them. With the correct parts and clean injectors you'll have a great running engine that offers good power, drivability and economy.