Fully Primed: Not All Electric Fuel Pumps Are Created Equal

Electric fuel pumps are, for the most part, standard equipment in drag racing. Ditto with fuel injected applications.

But a lot of carbureted street cars use them too.

Fair enough, but street and street/strip cars present a whole new set of issues when it comes to using an electric fuel pump. For one thing, many electric fuel pumps must be mounted at the same level or below the level of the fuel in the gas tank or fuel cell. This is because they need gravity in order to first prime and then deliver the fuel. Basically, many electric fuel pumps like to push fuel rather than pull it (unlike a mechanical fuel pump).

That sort of installation layout is easy enough with a race application. The pump is typically mounted alongside the fuel cell in the trunk of the car. Unfortunately, this mounting arrangement isn’t easy in many street driven cars—if it’s even possible in the first place.

So, what’s the solution?

Meet the Self-Priming Fuel Pump

One good fix is to use an electric fuel pump that can actually prime itself (and not all can do this). An excellent example that fits our needs is the Weldon A600-A fuel pump featured in this article. According to Weldon: “The pump may be mounted in any position as it has high such capability—over 23 inches of mercury.”

In practical testing, it has a “dry lift height” of 15 feet. And that’s very stout.

There’s some practical experience out there too: One of Summit Racing’s customers (“Lennard”) tested the pumps at a dry lift of six feet. According to Lennard, the pump lifted Avgas with ease, and the flow rate was 79 GPH at 25 PSI.

As a result of all of all of the above, it’s much easier to mount a pump like the Weldon A600-A. You can mount it out of the way in a safe spot in a car and simply plumb it to the gas tank. When selecting a mounting location, it’s a really good idea to protect it as much as possible from road debris and direct exhaust heat. At the same time, you have to keep it away from moving suspension components.

Safe locations can include a spot alongside the frame rail or on the rear axle kickup beneath the trunk.

If you’re installing a fuel pump, you may find this article handy too: Fueling Around: Ideas for Routing Fuel Lines

Consider Fuel Pump Operating Temperatures Too

Pulling a prime isn’t the only issue you’ll encounter with an electric fuel pump, particularly one that’s used in a street application. Cooling is a huge obstacle.

Many of the big race pumps don’t like to run for hours on end. The large electric motors heat up with constant use and eventually fail. Certainly, some are better than others, but they aren’t the ultimate solution.

What resolves the heat problem is the way the pump is laid out. Several different pumps out there are engineered so that the fuel passes by the pump motor. With this setup, the pump motor is effectively cooled by the moving gasoline.

Understanding (& Preventing) Cavitation

When working with high power, high flow pumps such as the Weldon, you should always consider the potential for pump cavitation. Cavitation will limit flow to the engine and at the same time, it can also cause catastrophic damage to the fuel pump. Weldon notes that installing this pump in series with a stock in-tank fuel pump will cause the pump to cavitate. The reason is the OEM pump and small OEM fuel lines tend to be a real fuel flow restriction.

Pumps like our Weldon example have huge -10 AN inlet and outlet ports. Weldon advises you should not install fuel lines smaller than the ports on the pump. In addition, the 600 series pump is manufactured with full depth O-ring ports. That means you must use some form of straight thread (not pipe thread) such as AN, Mil Spec, or SAE designed for use with an O-ring.

Down the road, we’ll show you how we prepared a stock tank to work in conjunction with a high flow electric (or mechanical) fuel pump. The short version is, we cut a new tank apart, installed a Holley Hydramat inside the tank and plumbed it with a -10 AN outlet, a -8 AN return line and a -8 AN vent—which happens to coincide with Weldon’s recommendations.

Venting & Filtering

Gas tank venting is another concern. Essentially a stock vented cap will likely prove insufficient when using a high volume pump such as this. It’s far better to vent the tank externally with something like the -8 AN setup mentioned above. When dealing with AN hose for a vent, be certain you inspect it periodically. The line might look intact but the inner liner can collapse. Something to keep in mind.

When plumbing the system, Weldon advises you should make use of a 100 micron filter element before the pump as well as a 10 micron filter after the pump. Filter elements should be inspected and cleaned or replaced on a regular basis. Bottom line here is, gasoline is dirty stuff. Plus a clogged filter can lead to pump cavitation.

Electrical Demands of a High Performance Fuel Pump

Current draw is also a major consideration, particularly in a street or street/strip application. Some of the race electric pumps out there for carbureted applications mandate 20+ amps of electricity at full bark. (Some dedicated extreme horsepower race EFI pump setups can actually be more than double that!)

In contrast, a pump such as the A600-A draws approximately seven amps under normal carbureted use. This means, for many applications, you don’t have worry about increasing the size of the alternator in order to keep up with the draw on the battery.

With that said, when wiring a fuel pump such as this, it’s still a good idea to set it up with adequately sized wire along with a relay system. We’ll dig deeper into this in a future article.

Pump Performance with Carb or EFI

In terms of construction, the Weldon A-600-A pump is manufactured with a 304 stainless steel housing. The end caps are Mil-Spec black anodized billet aluminum. Internal components are 100% metallic (no plastic bits) and the electric connections are located on the outlet side. Inlet and outlet ports along with the electrical terminals (+ and -) are clearly marked. The pump includes two insulated aircraft style t-bolt mounting clamps.

Finally, the 600-series pump is very quiet and is compatible with gasolines containing up to 40% alcohol as well as most race fuels. For carbureted applications, it will meet the demands of engines up to 800 HP at 7.5 PSI, normally aspirated. For fuel injected applications, it will meet the demands of a 700 HP engine at 50 PSI, normally aspirated.

The bottom line here is, Weldon’s got a high quality pump that meets the diverse requirements of a street or street/strip car head on.

Take a closer look in the pics below.