Mechanical vs Electric Fuel Pumps: How to Do It Right

Want an electric fuel pump to last forever and work right? We’re going to show you how to install it and wire it up to the correct way!

Ok, let’s talk about the mechanical vs electric fuel pumps. There is a lot of confusion and misunderstandings about them. There is also a lot of potential danger when people don’t do it right because they don’t know the right way to plumb them in or wire them…

So, let’s break it down:

  • When do you need an electric fuel pump?
  • Is an electric fuel pump reliable?
  • How do you keep an electric fuel pump safe?
  • How should you wire an electric fuel pump?
  1. When do you need an Electric Fuel Pump?

    Usually, a mechanical pump is preferred over an “aftermarket” electric fuel pumps. They tend to be more reliable. However, sometimes that won’t work. In my old ’47 Chevy, the engine I had swapped in had an issue. The cross member was in the way of the mechanical fuel pump.

    So, I ran an electrical fuel pump and had many trouble free miles. Sometimes, people will plumb them inline with a mechanical fuel pump to add more volume and pressure. This is more for a full on drag car though…

  2. Is an Electric Fuel Pump reliable?

    Yes, they are. Hey, there’s about a billion cars running around right now with them. All new cars have them. With aftermarket mechanical vs electric fuel pump though, YOU have to install them. That’s where some problems can start.

    We’re here to show you the right way to do it!

    So, what do I use? For a stock or performance street car, I like these Facet/Purolator mechanical vs electric fuel pump from Napa. They are quiet and work well.

    A lot of people complain about some aftermarket electric vs mechanical fuel pump being junk, but usually, there is a reason they go out. It’s often the way the person installed it. There are a few things that kill them.

    • Do not run them dry.
    • Always run a filter before the mechanical fuel pump.
    • Keep them as close to the tank as you can. Electric fuel pump pushes fuel much better than they can pull it.
    • Mount them away from heat sources such as exhaust.

    Electrical Fuel pump power to them is everything. You must have the correct wire size to it. A relay is preferred. You may be getting the proper voltage to it, but not enough amps. Remember, the longer the run the more the power will drop.

    Also, the grounding of it is critical. Many people will scrape the area where they mount it or even add a ground wire. However, they forget that they don’t have a good ground from the body to the frame or to the engine. This will kill pumps real quick.

    Tip: Screw into the metal to the ground, not through it. “Star” washers are your friends…

    Preferably, run a ground wire to the front. Many professional auto electricians will run ground wires from a unit to a common grounding point in an older car, just like in a fiberglass car. That way, there is no question if your ground is good, and it’s just 1 extra wire…

    Once, a buddy and I were going to a show in his ’26 Buick roadster. It was built much like a T-bucket and it had an electric fuel pump. It was wired incorrectly and grounded by screwing into the frame by the electric vs mechanical fuel pump. We were about 50 miles out, and the pump quit…


    What happened was the older metal of the frame simply wasn’t carrying the current well enough. The mechanical fuel pump overheated and shut down. Fortunately, he had some extra wire and we screwed one end to the ground wire at the back and ran it to the front where we attached it to the negative side of the battery.

    The pump started back up after it cooled down and we were trouble-free all the way there and back. When we got home he wired it in neatly and never had a problem after that…

  3. How do you keep an Electric Fuel Pump safe?

    The electric fuel pump can be dangerous?

    Yep, without some way to automatically shut them off, they can be VERY dangerous.

    But they don’t have to be.

    If something lets go in your engine bay like a fuel line, the engine will eventually quit. However, if you don’t have a way to automatically shut off your electric fuel pump you will keep spraying raw fuel all over your hot engine and wiring.

    Also, in a crash, your pump can continue to run feeding a fire if you don’t have a way to stop it.

    Note: Never mount an electric fuel pump in an enclosed area such as the trunk or interior space…

    Ok, so how do I do it right?

    The easiest way is to use an oil pressure switch. The switch will stop the pump whenever the oil pressure in the engine goes away. So, whenever the engine is off, the pump will turn off automatically.

    Some switches just do that. But how do I get the pump to run when I’m trying to start the motor and the oil pressure’s not up yet?

    You use a three prong switch like this Standard Ignition PS-64:

    The switch will also let the pump run when you hit the starter because the engine doesn’t have oil pressure yet.

    Electric Fuel Pump

    One wire goes to the pump, one to the start circuit, and the other to the ignition circuit. So, when there is no oil pressure, the switch connects START to PUMP, and as soon as you start cranking it runs the pump. When the oil pressure comes up, the switch connects IGN to PUMP, for normal running. When oil pressure goes away (because you just hit that rock and tore the pan off the engine, for example) it again connects START to PUMP and disconnects IGN from PUMP, so the pump shuts off.

    Don’t worry, it’s easy to wire…

  4. How should you wire an Electric Fuel Pump?

    Since you need the fuel pump back by the tank and at the same level as the fuel or lower, that usually means you’re going to have a long run of wire. So, you need to have really good wiring going back to it. Wiring that will carry enough current. Running the current through your ignition switch isn’t a good idea since it’s probably already overloaded, and will kill the voltage. That will kill the pump. However, it’s nice for convenience. That’s why a relay is really good to use.

    It lets the ignition switch activate the pump while keeping the power from having to run through it. It will keep your pump alive and happy because it is getting full voltage. A good way is to mount a relay beside a power distribution block on the firewall (see Improved Power Circuit) and get the power from there.

    Here is a diagram on how to wire and plumb your pump:



Our Picks

All four of these manifolds serve their purpose in the performance community. The GT manifold is probably best suited for road race and autocross cars looking for the power coming off the corners. If all-out high horsepower for drag racing is your thing, then stick with the Cobra Jet manifold. The BOSS 302 is a cost effective upgrade as a mid-level upgrade for the 2011-14 GTs and the GT350 respectively for the 2015+ GTs.


  • 1 hp at 6,900 rpm
  • 2 lb-ft at 5,400 rpm
  • Average Power: 373 hp, 376 lb-ft – 2,800-7,500 rpm

BOSS 302

  • 4 hp at 7,600 rpm
  • 4 lb-ft 5,400 rpm
  • Average Power: 376 hp, 361 lb-ft – 3,000-7,800 rpm
  • +/- to GT manifold:+19.3 hp, -30.8 lb-ft

Cobra Jet

  • 2 hp at 7,600 rpm
  • 6 lb-ft at 5,400 rpm
  • Average Power: 386 hp, 370 lb-ft – 3,000-7,800 rpm
  • +/- to GT manifold:+40.1 hp, -20.6 lb-ft


  • 8 hp 7,500 rpm
  • 6 hp 6,100 rpm
  • Average Power: 381 hp, 365 lb-ft – 3,000-7,800 rpm
  • +/- to GT manifold:+24.7 hp, -26.6 lb-ft

More OEM Goodness from Ford Performance

When we asked what’s in store for 2015+ 5.0 enthusiasts, Kershaw remarked, “We are really close to releasing our Power Upgrade kits for the 2015-2016 Mustang GT and Power Upgrade 3 that includes the GT350 manifold. This is the first time we’ve offered one of our manifolds with a CARB EO. You can now rev over 7,000 rpm and it picks up huge of the stock manifold, nearly 70 hp at 7,500 rpm!  However, it loses some mid-range and is pricy. The Power Upgrade 2 uses the GT350 throttle body and CAI picks up 21 hp peak, over 40 lb-ft at 1,500 rpm and will be a very reasonably priced.”





Development for the 3rd Generation engines by Chevy began after the short-lived LT1/LT4 engines which in the year 1992 to 1997 that failed to meet GM’s expectation.

General Motors then created Generation 3rd V-8 engine that has replaced a small-block LT1/LT4 platform.

After that Generation 3rd LS1 engines designed by GM showcased modern engine technology retaining traditional valve mechanical system. This engine was first appeared in Corvette 1997. After that whole series of high performance engines followed it.


In the last 10 years,

The LS engine exploded the market and we see them nestled between all show cars to all racing cars.

There are some reasons for this!

Their downward price and the market continued to make their transplants into all variety of vehicles with the fact that they are not simply going away.


Whether you are planning to drop this magical engine into your legendary ride or you are buying a car for your college going child. I want to give a small introduction about them, focusing on the part that why LS engines are called GREAT in hot road culture!


What is an Engine??

It is just an air pump.

Air goes in, fuel added, mixture blows up and horsepower happens. Vroom-Vroom…

We all have heard some shorts about this technology on how engine works. But, the process is not quite easy as I have explained in one sentence. There are lots of processes undergoes inside the engine. And these

LS engines add quite more to advance these processes.

For starters,

The pistons are made up of alloys that are more stronger and more thermally stable than the cast iron pistons used in Generation 1 engines. These pistons are fitted with a thinner metal ring packs that reduces friction and also helps bore sealing.

Coming to the connecting rods, LS platforms use powder-forged design. They have cracked cap providing irregular mating surface allowing rod to align precisely with a large end, helping equalize bearing wear. They are very much stronger than production rods used earlier.


LS crankshafts are tough pieces with relocated thrust bearings have been proven to quadruple horsepower outputs.

So till now, I have established that the bottom end to this engine has got few things which are different from traditional small blocks. So, why to change SBC engine combo for few things when bottom end is less than $1000? It doesn’t make sense.

Now, here comes the master piece of LS engines…

The master piece of LS family engines is the cylinder head and valve mechanics components. This is what makes LS engines to deliver outstanding performance with few changes made.

The head of the engine is designed with a 15 degrees valve angle.

Research about a 15 degree small block head and you’ll come to know about the biggest win for the LS engines. In addition to improved geometrical valve design, the LS engines have replicated ports. Something different from Gen 1’s mirrored port configuration that have different runner sizing for cylinders 3 & 5, 4 & 6.

The new LS engine style allows every runner to be more symmetrical and gives every cylinder equal opportunity for airflow. The ported LS heads have proven to move over 300cfm of air.

The valve mechanism design for LS engines retains the pushroads. No more pinning rocker studs, or adding rocker girdles. The LS valvetrain is 7000 rpm capable right out. Engineers also integrated beehive springs which reduces overall valvetrain mass.

One more thing!

With LS, there’s no need to spend $1,000 on a retrofit kit.


I can go more on and on LS engines but till now you probably get the point that why LS engine are great stuff. But you are still hanging on Gen I small block death grip.

Not yet ready???

Just fine. Knowing that there is some better options available in the market can’t reduce the things we love.


MSD Performance  Atomic Fuel Injection System  has been granted an Executive Order Number from the California Air Resources Board. This E.O. Number makes the Atomic the only aftermarket EFI system that is legal on 1987 and older GM vehicles in California. The Atomic EFI system received E.O. Number D-722 which permits the system to be installed in place of the factory carburetor on 1987 and older  passenger cars and trucks originally powered by a V8 engine. This Executive Order also means the Atomic EFI system provides “reasonable basis” for satisfying the anti-tampering requirements of the Federal Clean Air Act, thus allowing its use in all other states. This is terrific news for enthusiasts with an ’87 and older  car or truck as it means they can finally do away with their old carburetor and take advantage of the driveability benefits of a modern, self-learning EFI system such as quick starts, consistent idle and smooth power throughout all driving conditions. MSD will supply an information label with the E.O. Number and details that must be affixed on the vehicle for inspection purposes. Great news for all you Hot Rodders and Replica cars that faced restrictions with Emmisions.