Is an electric fuel pump reliable? Yes, they are. Hey, there is about a billion cars running around right now with them. All new cars have them. An electric fuel pump is small and thermally insulated to prevent sparking. It consists of a 12-volt electric motor attached to a pump assembly that pulls fuel in as the motor spins and pushes it out through a different line that goes to the engine compartment. The fuel may pass through a fuel filter after it leaves the pump, or it may be filtered before the pump. The assembly runs at a constant pressure to allow for optimum fuel delivery to the engine without interruption and to prevent air from getting into the fuel lines and causing problems.
The motor inside the electric fuel pump, starts to spin and runs for a few seconds to build pressure. On new cars you will find that electrical fuel pumps are in the fuel tank; to use the fuel in the tank to cool the pump and ensure a steady supply of fuel. Electric fuel pumps can be heard as, a quiet whine or hum in most cars. Most fuel pumps are built to last a long time. When in doubt, test it.
With aftermarket mechanical vs electric fuel pump though, you must install them. That is where some problems can start.
Electric Fuel Pump – How Do They Work:
- Fuel is drawn into the pump, through an inlet tube and filter system.
- The fuel then exits the pump, through a one-way checkvalve; (which maintains residual pressure in the system when the pump is not running). And is pushed toward the engine, through the fuel line and filter.
- The fuel filter traps any rust, dirt, or other solid contaminants, which may have passed through the pump.
- Fuel then flows to the fuel supply rail, feeding individual fuel injectors.
- A fuel pressure regulator on the fuel rail or on the fuel line, maintains fuel pressure, and routes excess fuel back to the tank.
- On newer vehicles with return less (EFI) systems; the fuel pressure regulator is in the fuel tank.
- There is no fuel return line, from the engine back to the tank.
- Fuel pumps run continuously once the engine starts; and continues to run if the engine is running.
- The pump may run at a constant speed; or variable speed depending on engine load and speed.
- If the engine stalls; the (PCM) will detect the loss of the (RPM) signal and turn the pump off.
Electric Fuel Pump – How Can They Fail
Fuel pumps should last the life of the vehicle, but can fail because of:
- Contamination inside the fuel system (dirt or rust)
- Fuel starvation (running out of fuel)
- Overheating (always driving with a low fuel level)
- Low voltage (wiring problem)
- Overwork (trying to overcome a restriction caused by a plugged fuel filter)
We are Here to Show You the Right Way to Do It!
So, what do I use? For a stock or performance car, I like mechanical vs electric fuel pump. They are quiet and work well. For higher performance or fuel injection I will go with the electric fuel pump and do so without any issues.
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 is 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 and below the bottom of the fuel tank. 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 do not have a good ground from the body to the frame or to the engine. This will kill pumps quick.
Tip: Screw into 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 is just 1 extra wire…
Once, a friend 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…
Hmm…
What happened was the older metal of the frame simply was not 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…
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 extremely dangerous.
But They Do Not Have to Be.
If something let us go in your engine bay like a fuel line, the engine will eventually quit. However, if you do not 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 do not 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 To 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 am trying to start the motor and the oil pressures not up yet?
You use a three-prong switch.
The switch will also let the pump run when you hit the starter because the engine does not have oil pressure yet.
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.
Do not worry, it is easy to wire…
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 are going to have a long run of wire. So, you need to have good wiring going back to it. Wiring that will carry enough current. Running the current through your ignition switch is not a good idea since it’s probably already overloaded and will kill the voltage. That will kill the pump. However, it is nice for convenience. That is why a relay is 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 plumb your pump for a carbureted engine:
Fuel Pump – Failure Signs
So, how can you tell if a bad fuel pump is causing, your no-start problem? One way is to listen for pump noise, after turning the ignition key on. No pump noise would tell you; the pump is not running. The fault may be a bad pump; or it could be a bad fuel pump relay, fuse or wiring connection.
On most vehicles, a failed fuel pump will not set any diagnostic trouble codes or check engine light. The engine will crank normally; and it will have spark, but it will not start, because of no fuel.
One way to tell if a no-start is due to no fuel is to; spray some starting fluid into the throttle. If the engine starts, runs a few seconds, then dies, it has spark and compression. But is not getting any fuel from the fuel pump.
Pump Failure Symptoms:
- Loud Whining Noise from the Fuel Tank
- Difficulty Starting
- Engine Sputtering
- Stalling At High Temperatures
- Loss of Power Under Load
- Engine Surging
- Poor Fuel Mileage
- Engine Will Not Start
NOTE:
Overheating is among the top factors in, causing a fuel pump to wear out. Mounting the fuel pump on the bottom of the tank helps. This keeps the pump cool, but only if there is enough fuel to keep the pump covered. Additionally, if the fuel level gets too low, the pump can begin, sucking in air with the fuel.
This creates further problems, by throwing off the correct mix of fuel and air in the engine. For these and other, non-pump-related reasons, many experts recommend; never letting your fuel level get down below a quarter-tank full.
Finally
Most times fuel pump problems are hard to diagnose. Specially, because some symptoms, are like those produced by problems in other systems.
So, by understanding the basic process of the fuel pump, you will have a better understanding of what happens; when a fuel pump goes out — and how to recognize when it is happening. Reliability of the electric fuel pump has certainly improved over the years and obtaining the correct pump for your vintage car is possible thru a variety of aftermarket and specialty part shops.
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