Fuel Pumps - Electric vs. Mechanical

[Wbulk]

I am in the process of ordering parts for my car and one of the issues I am evaluating is electric vs. mechanical fuel pumps. What's your opinion on the issue. I don't see this discussed much.

I have a old school 71 Ford 302 which is a mild performance build. I am using an Edelbrock intake and 600 CFM performer carb and mild Comp cam. The motor will rarely see 5,000 rpms. Edelbrock says fuel presure should be 5.5 PSI. The inlet on the carb is on the right rear of the carb, (passenger rear).

Electric Pump
I like the idea of an electric pump, but I think it has to be done right. I beleive it should be set up with a relay and should be wired with an auto shut off, in case of an accident. I have seen pictures of the special oil presure swith that shuts off the pump if oil presure is lost. But I don't know how this works before you start the engine, when you don't have presure yet and need it to start the motor. Another option might be to get one of those impact switches from a wrecked car, that shuts off the pump on impact.
An electric pump would most likely require a presure regulator to get the presure down to 5.5 lbs. Even the Holley red pump runs at 7 psi.

An advantange to the electric pump would be the fuel line could be run on the right side frame and come up the right rear of the motor where the carb fuel line comes in. You also have instant presure when the key is turned.

Mechanical Pump
Mechanical pumps have been around forever and are pretty reliable. You don't need all the wiring. They shut off when the engine dies.
The cons are: low tech, and they are right in the heat stream which contributes to vapor lock. Also, if the car hasn't been started for awhile you have to crank it over several times to get the fuel up to the carb.

While most don't consider resale value of the car when they are building it, would one option over the other effect the value of the car?

Opinions please! Are you happy with what you have or would you do it different? Am I missing something?

[onefastmustang]

I have an electric fuel pump now.. I broke my first mechanical after about 1000 miles.. I needed to keep the pressure low so I went with a carter fuel pump.. It pushes 4-6 PSI and is super quiet. You never hear it running when the car is idling. I have a toggle switch in the cockpit to shut it down and an oil pressure switch in case of accident which then shuts down the relay. Be sure to go from hard line to rubber before the pump so you cut down on vibration.

[Ron61]

I did the same thing as mentioned above except I used a Holly Race pump and a regulator to regulate the pressure to the carb. The only drawback I saw to using the set up I had to what Onefastmustang uses is that I put in a return line to take the excess fuel back to the tank and with his pump that matches the needed pressure you wouldn't need the regulator or return line.

Ron

[madmaxx]

LISTEN VERY CAREFULLY, USE A MECHANICAL FUEL PUMP. Electric fuel pumps buzz, loose prime, fail unexpectedly, require more work to install. Complete utter waste unless you are fuel injected.

[onefastmustang]

Thats a funny comment considering a majority of all modern cars use electric fuel pumps. My mustang Cobra has two of them even.

Ultimately I think either one is the way to go. Depends on your needs and desires.

[ERA Chas]

Originally Posted by madmaxx

LISTEN VERY CAREFULLY, USE A MECHANICAL FUEL PUMP. Electric fuel pumps buzz, loose prime, fail unexpectedly, require more work to install. Complete utter waste unless you are fuel injected.

Unless this is your personal experience, use caution how you advise others. And if it is, say so.

I have had the same Holley red electric feeding the same Carter mechanical and dual quads running on the car for eighteen years. The reason for the electric is to provide a head of fuel for the mechanical on cold startup (which stopped killing the battery) and it runs all the time for the top end RPM feed. And you never hear it over the header noise unless it's really a mouse motor. Hearing it is not a bad thing, it tells you it's working.
That's my experience.

[FUNFER2]

Most or all the the factory cars having electric pumps are mounted in the tank, to keep them cool. Unless you want to drop your tank and install one. It's a lot of work, fabrication and expense, for really nothing. A mechanical should last you for years,..... on the street without problems

[madmaxx]

These are not modern fuel systems in the majority of 1965 cobra replicas. He has a carburator. Find any mass produced car equipped with a carburator and electric fuel pump regardless of year, you wont. I had an electric one and loathed the buzzing, the loss of prime, never ever trusted it. Roush sells there engines for $14K plus and if it has a carburator it has a mechanical fuel pump.

As far as helping on startup, you float bowls should be full of fuel so it will not start any easier with or without an electric pump. You have a bad battery or charging issue.

Originally Posted by onefastmustang

Thats a funny comment considering a majority of all modern cars use electric fuel pumps. My mustang Cobra has two of them even.

Ultimately I think either one is the way to go. Depends on your needs and desires.

[MadDog]

The only reason all cars now days have electric pumps is because of the higher pressure requirements for fuel injection. My advise would be to run a manual pump if you are not running a high hp motor 450+.
I have run both and they both work fine and are reliable but an electric pump will cost considerably more to install. If you plan on running nitros electric is a must. Just my two cents.MadDog

[ERA Chas]

As far as helping on startup, you float bowls should be full of fuel so it will not start any easier with or without an electric pump. You have a bad battery or charging issue.

We need the Mythbusters here.
Float bowls are not full of fuel after a two month or more layover for maintenance or weather. Ask me how I know. The Optima is now six years and is 12.7 at the terminals and 14.5 at fast idle.
The mount location of your electric was certainly the reason it would not 'hold prime'. No pump will 'hold prime' more than two or so weeks-the length of time for fuel to evaporate from the bowls.
This caused you to swear off electric pumps and advise others against them. A correctly mounted pump will pull fuel as soon as the switch is turned on even when the system has dried out.

[vector1]

i would prefer mechanical for carburetor, electric for injected.

you have a fuel pressure problem, which would you prefer to fix? think of all the possibilities with mechanical or electric, and simplicity of one over the other.

jmo

[onefastmustang]

Originally Posted by madmaxx

These are not modern fuel systems in the majority of 1965 cobra replicas. He has a carburator. Find any mass produced car equipped with a carburator and electric fuel pump regardless of year, you wont. I had an electric one and loathed the buzzing, the loss of prime, never ever trusted it. Roush sells there engines for $14K plus and if it has a carburator it has a mechanical fuel pump.

As far as helping on startup, you float bowls should be full of fuel so it will not start any easier with or without an electric pump. You have a bad battery or charging issue.

I guess you missed my point. Electric fuel pumps are not as unreliable as you claim. I like having an electric pump. The override switch might come in handy if someone tries to carjack me.

[madmaxx]

I agree my electric fuel pump was not mounted low enough and was an install issue, but if I were to have installed it below the fuel tank then it would have been ripped off the first speed bump i went over. a correctly designed electric fuel pump would be installed in the tank and not external. I agree after two months no more fuel. One blast of ether, or for you younger guys starting fluid would fire it right over, doesn't smell bad either LOL. All good points my never failed I just got so tired of trying to orient so it wuld not loose it prime in addtion to the constant buzz.

Originally Posted by ERA Chas

As far as helping on startup, you float bowls should be full of fuel so it will not start any easier with or without an electric pump. You have a bad battery or charging issue.

We need the Mythbusters here.
Float bowls are not full of fuel after a two month or more layover for maintenance or weather. Ask me how I know. The Optima is now six years and is 12.7 at the terminals and 14.5 at fast idle.
The mount location of your electric was certainly the reason it would not 'hold prime'. No pump will 'hold prime' more than two or so weeks-the length of time for fuel to evaporate from the bowls.
This caused you to swear off electric pumps and advise others against them. A correctly mounted pump will pull fuel as soon as the switch is turned on even when the system has dried out.

[ERA Chas]

Maxx,
I am certainly not the Fuel Pump Police and you are surely entitled to your preferences. Glad you found what works for you.

My intent is only to provide feedback to help the OP gather the facts he asked for to construct his system. I surely feel a combination similar to mine is of value in a climate like Utah, (unless he uses the car everyday) where the car resides and is not onerous in cost, fabrication or convenience.

[Jim Werth]

I like Wbulk's comment that the engine will rarely see 5000 rpm's. I know my valves start floating around 6700 rpm's. Run a mechanical pump its easier,quiet and reliable. Jim

[MrMagoo]

I agree with madmaxx based on my experience after running a holley blue for three years. I have two years on a mechanical pump now and I like it better.
I did this on the advice of joe lapine, who some of you may know as one of the most knowledgeable FE engine builders around. He told me in his gruff authoritative engine builder voice: "I'd never run an electric fuel pump on a street Cobra". That was enough for me, and I've never had to think about my fuel pump since. My electric setup worked although I did have a flukey ground once that caused the fuel pressure to be inconsistent. My reasons for doing the swap were safety, simplicity, and silence. At idle you definitely hear the whine and it's not a happy sound. Simplicity equals reliability.

Anyway, I just hook up the booster when I start with dry float bowls, and I'm good to go. Don at four seconds flat says when you get up in the 550 Hp range, you need a good electric pump just to keep up your fuel pressure, but if you are below that a mechanical works fine.



The original SC/427 cars did have electric pumps.

[RICK LAKE]

Wbulk Nice name Let me see if I can clear a little of the info up here. First off, what is your car setup for? If there is one fuel line running from the tank to the fuel pump, your car was setup for a mechanical pump. They are dependable and should last for years. The main thing with these pumps are what the diapham is made of and what fuel will not bother the material. We are getting into more fuels like E85 and this is having issues with some pumps and lines. This is why most auto companies have gone to plastic fuel lines.
The plus on the mechanical is, the simple way it runs, it's quiet, and overall dependable. Down side is that you have to crank the motor to get fuel into the carb to start the motor. If the car has been sitting for a couple of weeks, the gas will evaporate and you will need an extented cranking to start the motor. This is also when the most wear on the bearings happen. If you have taken the car for a good drive and it is hot, unless you open the hood or have a turkey pan seal around the carb, the gas will turn to vapor and again you are with the long cranking to get the car started. On some carbs you have to pump the pedal 2-3 times before trying to start the motor and this also sets the choke operation. Depending on the carb you can easily wash down the cylinder walls from this starting way. I have had mechanical pumps last 100K miles I have one on a car with 144K and still working fine.
Electric fuel pumps, there are a couple of different styles, Pulse and rotary pumps. You can get them to pump from 6 psi to over 100psi. Depending location is about how much noise you will hear. A pulsing pump is quieter than a rotary pump, pulsing pumps due cause problems with some carbs and the needle and seat for keeping the correct fuel level in the carb. If not careful the pulsing pump will bounce the needle in the seat and overfill the carb and whole motor. I have seen this happen. You should have a regulator on this system between the pump and carb. Set to 5 psi. I would also put a return line in if you can to ease the pumps working load and better control of the fuel pressure. You will need to wire a relay to the igntion switch or use a remote switch to turn on and off. This pumps is not used on FI systems in general. They do last a long time, I have one for 6 years on my jeep that goes off road and it took a beating and no problems but the flood issue.
Rotary fuel pumps, depending on location, in some cars they are noisy. Weldons come to mind on my friend cobra mounted in the R/R corner of the car. It is a race pump and you can hear it at an idle. 15 years and runs fine with 30K miles on it. This is for a Olberg setup with #10 lines to the the carbs and #6 line return with a fuel regulator between the pump and carbs. Down side of this setup the pump doesn't draft well from the tank. The pump is low as possible and the tank has a sump with 2 #10 outlets. After racing for 20 minutes the fuel is warm from running from the tank to the carbs and back. Up side of the system, able to fill the carbs without cranking the motor, little cylinder wash down from this setup. Down side is location of the pump and custom fuel tank outlets. This pump had problem lifting gas 12" above the tank. It doesn't have great sucking abilities. The pump is larger than in the ta
nk pumps and draws more amps. It is rebuildable.
In the tank pumps, I have 2, 255liter walbros for my FI system. They are quiet when the tank is half full or better, I can prime my fuel system and then turn them off before starting. No failures on 10 years of running the same pumps. I do have a fuel pressure regulator set at 44 psi at idle and 52-54 at WOT. These pumps in the tanks need fuel to help keep them cool and extend there lives. Mine I only here on priming the system, rest of the time, no noise. I do have 2 couple fuel supply systems going to the front of the motor and one return line. I have way more supply than the motor will ever use. It is nice to have too much than not enough. These pumps will not work with a carb to well, too much pressure even with a good regulator.
Bulk you are running a SB motor in the car. a 3/8" supply line from the tank to the motor will be more than enough for your setup. I do prefer to have a return line on all my cars to help with the dead heading of the gas. I don't like this way of fuel system because of the small debries that get into the system and through or around the filters. Over time this crap ends up in the float bowls and jets for carbs, and in injector rails and injector screens on FI systems. If setup right both pumps will work fine. IMO electric is better strictly for the cranking issues of the motor. I also run a accusump as a peroiler before start my motor. Cranking with 30 psi in the motor is better than 0. Regulator, a good one and return line would be my reccomendations. This is from 30+ years of racing and being a wrench turning mechanic. Good luck. Rick L.

[MrMagoo]

rick

Great post. I have a question regarding the issue of oiling at startup. After the first crank, I see pressure on my guage. Does this mean that (assuming no pre-oiler) after the first crank, the oil issue is irrelevant? Thanks.

[patrickt]

Now Rick, remember when you answer Magoo's question that Ford's own service manuals list 4 psi as acceptable at idle.... We're not talking revs, just the startup.

[Wbulk]

Thanks for the comments. A few things were brought up that I didn't consider.

Mechanical is reliable, easy and inexpensive. Electric will start that baby right up after setting for a few months, but at a cost.

Rick, thanks for the detailed comment.
I am thinking it would it be best to have an electric pump just to prime the motor and then shut it off. Is there an electric pump that when not running will allow a mechanical pump to pull gas through it ? Then second, would you do a return line by perhaps using one of the filters with two exit ports like the old Jeep 360 ci engine filters or what other return methods would you use?

Thanks !
Wayne.