# Electric Fuel Pump



## PontiacJim (Dec 29, 2012)

Most of us have experienced this problem - hot engine start-up or hard starting after the car has sat for an extended period of time. Generally, it is the ethanol blended gasolines that are the cause as the modern formulas seem to evaporate quicker than the older leaded fuels. There of course can be other reasons such as timing, electrical, or a fault somewhere in the fuel delivery system. But if you know all is good with the engine and fuel system, then it is most likely the gasoline giving you a fit.

Did a little online research to options. It is said, and done, that you can add an electric fuel pump coming off the fuel line in back at the tank. Then push the fuel down the lines to the mechanical fuel pump which acts as a regulator and then of course up to the carb. This seems to work and my brother has done this on 2 of his cars and the hot start problem in the heat of summer went away and hard starting was greatly improved. Of course, a little common sense in selecting how big an electric pump you plan on installing.

HOWEVER, it was pointed out in a post that an electric pump could pump gas past a leaking or ruptured fuel pump diaphragm - which then goes directly into your engine. You could put gas in the oil and if not detected soon enough, damage the engine by diluting the oil or as was experienced, build up gasoline fumes within the engine that when it was first cranked up, the fumes caught a spark and blew the valve overs off and luckily did not start a fire or burn to the ground.

I read many forums from an assortment of websites having Chevies, Fords, Mopars, etc.. There were many opinions as to the practice of using an electric fuel pump back at the gas tank along with the engine's mechanical fuel pump as the regulator - ie enhancing the mechanical pump and eliminating vapor lock or to aide in getting the gas to the fuel bowl of the carb quicker eliminating hot start problems, or to fire up the engine faster and eliminate long cranking times after sitting for longer periods of time.

Mixed results seemed to support adding the electric pump to a engine's mechanical pump. There was indeed the mention of the diaphragm in the fuel pump developing a tear or rupturing and fuel being pumped into the engine by the electric pump. However, this happening seemed to be more of a concern and something to think about rather than "this happened to me" experience. A number of persons had successfully ran their cars for years and others going back to the 1980's like this without incident.

The concern could indeed be a concern only because we know that the ethanol laced gas will deteriorate/rot the older type rubber used in days past - which would likely include that rubber diaphragm in the fuel pump. So if it is an original fuel pump or one that was replaced prior to the introduction of ethanol fuels, it might be of concern if adding that electric fuel pump. If you have installed a newer version of your fuel pump, it should have a diaphragm that has been upgraded to be compatible with ethanol fuels. You should also have all rubber lines replaced with ethanol friendly lines if you have not already done so.

So one line of thinking is that you can add an electric pump to work along with your mechanical pump.

The next line of thinking is to eliminate the mechanical pump and use electric only. Today's electric pumps can do the job, but read several instances were some pumps seemed to be better than others as some would quit being run all the time for street use. A regulator would also be needed to set the correct PSI line pressure to match the carb manufacturers specs on fuel pressures. Of course a fuel filter still needs to be incorporated in any fuel system.

The third line of thinking was to use the electric fuel pump only to prime the carb when the bowl goes dry after sitting long periods or for hot start issues. This is accomplished by creating a bypass line and using an inline check valve. The electric pump would push gas to the mechanical pump for the "start," but once the engine is running you could shut off the electric pump. A check valve would then open to allow fuel to bypass the electric pump and let the mechanical pump draw gas from the tank as it normally would. 

I included a picture that shows a bypass system which is the first one I pulled up, so no doubt there are better pictures or diagrams - but this gives you an idea of the bypass operation. Of note is the bypass valve and the fuel line loop. The gas comes in from the tank and would be pumped by the electric pump. The gas is pushed out the outlet side, but to keep the gas from being pushed back around the loop and back into the tank, you see the check valve which closes under pressure and won't allow the gas through. Gas goes through the line to the mechanical fuel pump. Once the engine is running, the electric pump is shut off. No gas can be drawn through the pump. The gas is then drawn from the loop that goes around the electric pump as the check valve is now pulled open and gas is supplied from the tank. This set-up is a little crude and you won't use the fuel regulator as shown, so the loop would run parallel rather than go all the way around the bottom of the pump as shown.

The BIGGEST concern, and one that should be mandatory if you add an electric fuel pump anywhere in your system, is a SHUT-OFF pressure valve. Here is what I pulled of the web. 

*How do you keep an electric fuel pump safe?*

If something lets go in your engine bay like a fuel line, the engine will eventually quit. BUT 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 and cause a fire. And, in a crash your pump can continue to run feeding a fire if you don't have a way to stop it.

The easiest way is to use an oil pressure switch. This switch will automatically turn off and shut down the pump whenever the oil pressure in the engine goes away due to any mechanical or electrical failure or in the event of a major crash that affects the fuel system.

*How do I get the pump to run when I'm trying to start the motor and the oil pressure's not up yet?*

Use a three prong switch like the Standard Ignition PS-64. The switch will let the pump run when you hit the starter because the engine doesn't have oil pressure yet.

*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 seems simpler and it's nice for convenience but that's why a relay is really a better choice to use.

It lets the ignition switch activate the pump, while not overloading the ignition switch by running the power wire to the electric pump 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 and get the power from there. Then connect your power wire back to your electric fuel pump.


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## cij911 (Oct 25, 2017)

Great read Jim.

My car always starts great when the engine is cold. The fuel is still in the bowls after sitting a few weeks (I rebuilt the carbs a while ago and had to dum the fuel out).

I have experienced the long cranking / hard to start symptoms others have mentioned. In my case, and I suspect others, it is an easy fix - while cranking the car have the gas pedal pressed ~ 1/3 of the way in (don't prime the motor before cranking either).


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## 11th Indian (Feb 15, 2018)

I was planning on using an electric fuel pump in conjunction with my mechanical pump, however the electric pump would have a spring loaded heavy duty toggle switch. I would just run the pump for a few seconds to pressurize the line see if that filled up the fuel bowl. Pressure from the electrical pump would be regulated to be low enough as to not unseat the needle valves. Would be fully manual, hold the switch to pressurize, release - start car.

(assuming the electric pump is passive to fuel flow when off)


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## PontiacJim (Dec 29, 2012)

cij911 said:


> Great read Jim.
> 
> My car always starts great when the engine is cold. The fuel is still in the bowls after sitting a few weeks (I rebuilt the carbs a while ago and had to dum the fuel out).
> 
> I have experienced the long cranking / hard to start symptoms others have mentioned. In my case, and I suspect others, it is an easy fix - while cranking the car have the gas pedal pressed ~ 1/3 of the way in (don't prime the motor before cranking either).


Agreed, sometimes is is a matter of learning what position to get the throttle plates into and it'll start better. 

I would do this with my '73 Fury when it got hot, but, much of my hard starting problems were actually a combination of a hardened and dried gas line from the fuel pump to the the filter ( Plymouth set-up is right off the fuel pump down low on the engine) that was no longer pliable and a weak spring style hose clamp which did not in any way have enough tension to clamp such an old hardened rubber line tight onto the fuel line. When hot, the gas would heat up of course, and the pressure would push it out the connection because it was not tight and I would have to crank the car a bit to get gas back into the line. All looked good and nothing was really evident until I grabbed the line one day checking the fuel filter. Gas poured all out into my hand. I knew something wasn't right and that's when I found the real problem to my hard starts when the engine was hot. Once new rubber lines, fuel filter, and clamp were installed, my hard start problems when hot were gone. I still do hold the carb open just a little when starting it hot and this seems to be what my car wants.

Here is something interesting as well and this was with a stock fuel pump & 2 bbl carb. I installed a clear body fuel filter so you can see the gas. As the engine was running at an idle, the gas would fill into the filter so you could easily see it. Then the filter would appear completely empty, I mean no gas. The engine was still running fine, then I would see some gas trickle in and vanish again. Thought, ut-oh, fuel pump is going bad on me. Nope. I did a web search and this seems to be a common/normal occurrence - it's just that most filters you cannot see into. What was said is the the engine heat can boil the ethanol gas creating a vapor and the vapor is enough to pressurize the fuel filter so it appears as if no gas is filling in. As the pressure is diminished, you see the fuel pump pressure overcome the vapor pressure and gas fills into the filter until the next round of vapor pressure. This would make sense in that the gas fills the carb bowl until the float shuts off the needle and seat and the gas flow to the carb. Until the float drops down enough to let gas flow back into the carb to fill the bowl, there is enough heat in the engine as the line runs up along the block to boil the ethanol blend gas and turn some of it into vapor which has enough pressure to slow/overcome the flow of the gas being pumped by the fuel pump. Once the float drops, the needle valve opens, and the gas and vapor that is in the line gets pushed into the carb bowl as the fuel pump pressure is now able to overcome the vapor pressure. Keep in kind that carbs have a vent or even a hose on some of the emissions year carbs so the vapors can be released or drawn out. With the vapors being released/drawn out, gas then fills the bowl until the float shuts down the needle and seat - as the process continually repeats itself. So what I was seeing was normal, but did not seem like it. Never a problem running the car this summer.


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## PontiacJim (Dec 29, 2012)

11th Indian said:


> I was planning on using an electric fuel pump in conjunction with my mechanical pump, however the electric pump would have a spring loaded heavy duty toggle switch. I would just run the pump for a few seconds to pressurize the line see if that filled up the fuel bowl. Pressure from the electrical pump would be regulated to be low enough as to not unseat the needle valves. Would be fully manual, hold the switch to pressurize, release - start car.
> 
> (assuming the electric pump is passive to fuel flow when off)


The spring loaded toggle switch sounds like a good alternative to the oil pressure switch for this application. The key to making this work is as you stated, "passive" fuel flow in that the pump when shut off allows your mechanical pump to draw through it. I read this, but it also seems many of the new electric pumps are of the vane style and won't allow this. So it would be a question to ask the supplier or manufacturer before purchasing the pump. Otherwise, the bypass line and check valve seem to be the answer in making a non-passive style pump work.


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## PontiacJim (Dec 29, 2012)

OK, so how do we figure what electric fuel pump to use? Now this is essentially related to using an electric fuel pump by itself, but it can also let you know if the factory stock mechanical fuel pump or if one of the aftermarket mechanical fuels pump will work for your build. Keep in mind that there are replacement gas tanks, and even retro-fitting kits, that allow an in-tank electric fuel pump. The prices on some of these set-ups are not too bad if you need to replace your tank anyway - and some have baffles to prevent fuel starvation on those hard launches. So again, you have options on how to go, but the important part is fuel pump GPH flow based on the HP requirements of your engine build - so this is loosely a guideline that can be used.

*Choosing the Correct Fuel Pump
*
Different fuel pump manufacturers rate their fuel pumps in different ways. Some manufacturers for instance rate their fuel pumps at free flow. The problem with this rating is that no fuel system operates at zero psi. Other fuel pump companies may rate their fuel pumps at a given psi. For example the Walbro fuel pumps that we sell are rated at 40 psi. Our most popular fuel pump we sell is the 4 series fuel pump assembly. These assemblies use a Walbro 255 lph fuel pump. 255 liters is the volume of fuel that the pump will flow at 40 psi. While this is a more accurate rating than a free flow rating, the 255 lph rating is only accurate if you are running your engine at 40 psi and your pump is being supplied with 13 volts.

Sometimes pumps are rated based on pressure. For example the Walbro 255 lph pump is capable of producing a pressure in excess of 100 psi. While this information may be relevant, it only provides one detail about a fuel pumps capability.

The better way to select a fuel pump to use in your fuel system is to consider three factors:

How much horsepower your engine will produce.
What fuel pressure is required for your engine.
How much voltage is supplied to your fuel pump when the engine is running.

*1. Horsepower*

The amount of horsepower that your engine has will determine how much fuel flow is required to support that engine. As horsepower increases so does the volume of fuel required to support that power. A good estimator of volume to power is approximately 10 hp per gallon or 2.64 hp per liter. For example if your pump flows at 50 gph it should be able to support a 500 hp engine (50 x 10 = 500). However, to actually know the gph you must also consider the fuel pressure required for your engine.

*2. Fuel Pressure
*
Different engines require different fuel pressure. For example a carbureted engine typically requires between 4 to 7 psi.

It is important to know what the max pressure your engine will require because fuel pressure has a large effect on how much flow a pump can produce. A fuel pump will flow at its highest volume when there is no pressure (free flow). As fuel pressure increases, fuel flow decreases. Every pump has a different flow volume at a given pressure. Because of this it is important to look at a flow chart of whatever pump you decide to buy. As free flow, or even flow at a given pressure is only part of the equation.

*3. Voltage*

Fuel pumps have different flow rates at different voltages. As voltage increases so does the speed of the fuel pump which will increase the flow of a pump at any given pressure. Because of this it is good practice to see how a pump is rated at a given voltage. Most cars will produce about 13.5 volts when running. However, if your alternator does not produce 13.5 volts, or you simply want to plan conservatively simply look at the flow ratings of a pump at 12 volts.

Info from: Choosing the Correct Fuel Pump

*Feeding a Carbureted Engine with an EFI Fuel Pump*

It is becoming more and more common for people to use an in-tank electric pump to feed a carbureted engine. Many new engines simply do not have the provisions to use a mechanical fuel pump. Sometimes there is no room to have a mechanical fuel pump in the engine compartment. Others simply want to clean up the look under the hood and do so by removing the mechanical fuel pump.

Any of our in-tank pumps can feed a carbureted engine provided that a bypass regulator is used. Because an EFI fuel pump can produce a large amount of flow, a bypass regulator is necessary in order to return the excess fuel back to the fuel tank. When shopping for a bypass regulator make sure that you buy one that is specific for carbureted applications. This is because most carburetors only require around 6 psi to operate. Typical EFI bypass regulators run between 40-80 psi while most carbureted bypass regulators are adjustable from 4-10 psi. Keep in mind that since the pressure requirements of a carbureted application is lower that an EFI application the flow rate of your pump will be higher. This means that the fuel pump is capable of supporting higher horsepower. For most applications our TBI or 2 series fuel pumps provide enough flow for a carbureted engine.

Info from: Feeding a Carbureted Engine with an EFI Fuel Pump


The *Aeromotive 13301 Bypass Fuel Pressure Regulator*, 3-60 PSI Universal Fit, Gasoline Fuel Type is one option in using a bypass regulator when using a high pressure electric fule pump. https://www.speedwaymotors.com/Aeromotive-13301-Bypass-Fuel-Pressure-Regulator-3-60-PSI,40596.html

Here is a kit that uses an *Edelbrock brand *Bypass Fuel Pressure Regulator, Fuel Line Kit for Carbureted Engines with Bypass Regulator

The Aeromotive piece has 3/8" outlets which I have read is clost to AN-8 size and what you typically want and would work with our GTO's 3/8" gas line. The Tanks, Inc set-up uses the smaller AN-6 size lines & fittings and may work better with those earlier GTO's with 5/16" gas lines. In either case, a little research would be needed in meeting your gas line size requirements. The key here I believe would be how many gallons per hour your engine needed and how many gallons per hour either the 3/8" or AN-6 lines/fittings can provide.


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## BearGFR (Aug 25, 2008)

I like the idea of using an oil pressure switch as a safety cutoff. I avoided the need for an electric pump by running a RobbMc mechanical pump. I also already have one of his regulators that can be configured to run in either dead-head or bypass mode. The one thing that I don't have in place already (other than the electric pump) is a return line that would be large enough to support an EFI system in bypass mode. I do have a vapor return line, but it's the original small factory size and not large enough to use as a bypass. 100% of my fuel lines are either hard lines or braided stainless hose both on the 1/2" feed to the pump and regulator, and the vapor return. I've always avoided electrics because of the need for the larger return line and the safety issue, but I might consider it one of these days. A run of teflon-lined braided hose long enough to make an adequately sized bypass return would be pretty pricey, and I'm not sure there's enough room in the frame openings to snake an additional 1/2" hard line through there, how hard that would be to do. The factory routing comes up over the top of the frame near the rear spring perch so following that route exactly without lifting the body would be very hard if not completely impossible. ...Maybe one of these days...

Bear


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## geeteeohguy (Feb 2, 2008)

I've had a small in-line pusher electric fuel pump on my '67 since 1988. It's connected near the tank. Hooked up to a toggle switch on the dash. It used to help out on hot days with vapor lock issues. Then I re-installed the stock vapor return set-up on my car and haven't needed it since. It does help if the car sits for a long time, and you want to fill up the fuel bowl quickly without cranking the engine. Still, I tend to not use it at all, and just crank the engine in two or three cycles to fill the carb and start it up. The disadvantage to this is increased starter wear (but I have not had issues with this, and my starter is a 40 year old GM unit). The advantage of cranking a bit to start a dormant car is that when it lights off, it already has oil pressure to the bearings. YMMV...........


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