Adding an elec fuel priming pump

62 Dart Convertible · Jul 24, 2015

Hi Guys. I've seen a few threads where some have thrown this idea around, but I have not found definitive results or conclusions, so I'm asking for educated thoughts or experiences.

I usually only drive my car every few weeks, and when I go to fire it up, the carb bowls are absolutely bone dry. The mechanical pump takes an age to fill the carbs and the poor starter gets a hammering before the engine finally fires. (Having dual quads I imagine makes things worse compared to a single carb as I have 2 carb bowls to fill up ...)

So, I have bought one of these Holley Elec pumps to install by the fuel tank in order to prime/fill the carbs before cranking -

My plan is to only energize this pump prior to cranking for long enough to prime the whole fuel system so the engine starts instantly.

As usual, I have been perhaps over-thinking it all and have concluded there are 2 different plumbing options to fit it. A simple way and a more complicated way -

I'm sure the simple way would work, but is it possible that at full throttle, the de-energised elec pump could restrict flow on the suction side of the stock mech pump enough to starve the carbs of fuel? (If so, that's why I thought the more complicated way with the elec pump in a TEE branch would minimise suction side restriction. The non-return valve is a necessary addition so the elec pump flow doesn't just recirculate when it's energised.)

Proposed non-return valve -

Also, to energise the elec pump for only a pre-set time when I turn the key to 'ON' and before cranking, I would use a small electronic timer like this hidden under the dash -

Thoughts?

miller · Jul 24, 2015

A priming pump? I've had a few thoughts on those lines, since reading about all the good fuel stuff these days. If I get mine together, probably have about the same set-up...two fours, and going to 3/8" lines from the tank.

On the big radial motors (airplane), they have an engine driven fuel pump mounted on the rear case. Also have a electric 'boost' pump, that's mounted right at the fuel tank, and is operated by a momentary switch. Before you fire the motor, simply hold that boost pump switch, until you get a reading on the fuel pressure gauge.
But...without digging into my AC books, I'll have to add, not sure on all the plumbing, for the fuel flow from tank to the engine pump, AFTER the boost pump is off. All that boost pump does is 'prime' the system, before start.

Right now, I'm simply (?) thinking on just an electric pump, and be done with it.

badlite · Jul 24, 2015

I used to have a 440 with an AVS, that had the same problem. I did what you are proposing with great results. I installed a switch under dash, and would shut pump off after engine fired. I used the setup with check valve. It worked great.

Darter6 · Jul 24, 2015

your simple diagram is how I have it set up on mine.Same thing,,a switch to prime the carb and for spirited driving. A.K.A full throttle bursts but being completely legal........:happy7::happy7::happy7:

69a100 · Jul 24, 2015

Cr8crshr has done 2 of them, on his Satellite and a 66-300. I have one on my van and need to install another on my 300. Yes they do work great for priming after sitting, KISS don't over think this! Don't make more work for yourself if not needed!
It's either do this or keep a squeeze bottle with some gas and do it the old fashioned way, both work but after awhile the bottle becomes a pain. Good Luck

cr8crshr · Jul 25, 2015

Thanks Bro for the lead. The only thing I would change on your simple version is to place the priming pump closes to the fuel filter in the front rather than by the tank. I mounted mine to the frame rail and wired in a single throw toggle switch under the dash wired to a circuit bus I installed form my extra gauges. I turn it on while starting and then turn it off when it gets running. I also have a metering valve so as to not over prime the carb bowls. But it is a very simple addition that I wonder why it took so long to do it???cr8crshr/Tuck

62 Dart Convertible · Jul 25, 2015

cr8crshr said:
Thanks Bro for the lead. The only thing I would change on your simple version is to place the priming pump closes to the fuel filter in the front rather than by the tank. I mounted mine to the frame rail and wired in a single throw toggle switch under the dash wired to a circuit bus I installed form my extra gauges. I turn it on while starting and then turn it off when it gets running. I also have a metering valve so as to not over prime the carb bowls. But it is a very simple addition that I wonder why it took so long to do it???cr8crshr/Tuck

Hi Tuck

Thanks for the response mate.

So you mounted yours on the frame rail by the engine and plumbed it in before or after the stock pump? (I'm sure either will work, but I'd think before would be better.)
I just had a look at how much room I have to mount it on frame rail - it will fit well but drilling the holes will be tricky. Might need to remove stock pump to make room for drill.

What is the metering valve that prevents over priming your carbs? (My elec pump only supplies 4psi so I don't think I need it.)

383man · Jul 26, 2015

Why not just eliminate the mech pump and use just the electric pump. Thats what I did and it works great. I even carry a spare electric pump in my trunk incase the electric pump went bad on the road but I have never had to use it. And there is no worry about the mech fuel pump rod. I mount my pump back near the stock gas tank. It also helps fight vapor lock as fuel under pressure wont cause vapor lock as easy as fuel being pulled by vacum. Ron

62 Dart Convertible · Jul 26, 2015

Hi Ron

I really don't want the noisy electric pump running all the time in my cruise car....

1962polara · Jul 26, 2015

Frank didn't you have issues with your mech pump a while ago ? Why is your fuel evaporating so quickly? (Need to drive more buddy

)
Maybe you need to look again at your mech pump Not saying a "priming pump is not a solution" you would know.

62 Dart Convertible · Jul 26, 2015

1962polara said:
Frank didn't you have issues with your mech pump a while ago ? Why is your fuel evaporating so quickly? (Need to drive more buddy )
Maybe you need to look again at your mech pump Not saying a "priming pump is not a solution" you would know.

I did have issues with the car when I got it, but I could find no problem with fuel pump/pushrod. Mind you the carbs were full of crap and all the secondary jets 90% blocked at that time too. All my problems were related to fuel vaporisation when the engine was heat soaked. When I rebuilt the engine I added more insulators under the carbs and (touch wood) I have no more of those issues.

The problem of all the fuel evaporated from the carbs is common in cars not driven every few days. It sure isn't just me! Having 2 carbs means it takes twice as much cranking to fill them as if I had 1 carb so the poor starter cops it more than it deserves.

You're dead right in that I should drive it more often!:icon_lol:

miller · Jul 27, 2015

Going to guess the 'right' electric pump will cure all that, pressure and such. Even if it's deadhead. Gonna find out.
Anybody try one of those Carter electric pumps?

While back did a search on boost pumps...and found one. Real spiffy looking, too, with the by-pass and such. Heck, it was only $400! I'll use a hand pump first.

Derwud · Jul 27, 2015

I would do it with the timer and a WOT switch and the simple plumbing.. Every time you turn on the key, 15 seconds or so of fuel pump and then every time you do "Timed" acceleration runs!

coloradodave · Jul 27, 2015

Also, check with the manufacturer of any electric pump you are considering using. Most pumps are designed to PUSH fuel and therefore should be mounted close to the tank and below it.

dave5237 · Jul 27, 2015

383man said:
Why not just eliminate the mech pump and use just the electric pump. Thats what I did and it works great. I even carry a spare electric pump in my trunk incase the electric pump went bad on the road but I have never had to use it. And there is no worry about the mech fuel pump rod. I mount my pump back near the stock gas tank. It also helps fight vapor lock as fuel under pressure wont cause vapor lock as easy as fuel being pulled by vacum. Ron

Yeah. I posted a lot about this issue. I just eliminated the mech. pump too and have a switch interupting the key ignition on to the electric pump. The switch is under the dash and acts as a theft deterrent. The only problem I have is to remember to turn the switch on to get power to the pump when the ignition key is turned on.

miller · Jul 28, 2015

Separate switch sounds like a good idea.

Meep-Meep · Jul 29, 2015

I like the idea of the primer pump on a timer and I have the same concern as you regarding the restriction. You can easily install it the simple way and make a test run. If it doesn't pose an issue then clean up the installation and let it go. Otherwise you will need a check valve.

Speaking of which, what is the cracking pressure of that check valve? Seems to be designed for this purpose but it would be nice to know it won't cause a restriction by itself on the suction side. Perhaps install the check valve first (on the pressure side) and see if that cures/helps the issue? Then install on suction side to see if it also cures the issue without causing a restriction. In my experience it's the engine heat that dries out the carb and evidence to that would be strong gas smell in the garage after you shut it down. In that case you will need the primer. I guess your gas isn't carb friendly either, huh?

X2 CO Dave. Electric pumps typically push not pull.

62 Dart Convertible · Jul 29, 2015

Meep-Meep said:
I like the idea of the primer pump on a timer and I have the same concern as you regarding the restriction. You can easily install it the simple way and make a test run. If it doesn't pose an issue then clean up the installation and let it go. Otherwise you will need a check valve.

Speaking of which, what is the cracking pressure of that check valve? Seems to be designed for this purpose but it would be nice to know it won't cause a restriction by itself on the suction side. Perhaps install the check valve first (on the pressure side) and see if that cures/helps the issue? Then install on suction side to see if it also cures the issue without causing a restriction. In my experience it's the engine heat that dries out the carb and evidence to that would be strong gas smell in the garage after you shut it down. In that case you will need the primer. I guess your gas isn't carb friendly either, huh?

X2 CO Dave. Electric pumps typically push not pull.

Hey Meep

I know little of the check valve. I will install pump, simply for now, and cross the other bridge if needed.

Fuel is definitely not draining the line back to tank as I tested the check valves in the stock pump, and they are fine.
It's engine heat evaporating the fuel off in the carbs as the garage does smell for a day or 2 after parking. In Australia, we can still buy ethanol free fuel, but it still seems much more volatile now than in the days all cars had carbs.

Meep-Meep · Jul 29, 2015

62 Dart Convertible said:
Hey Meep

I know little of the check valve. I will install pump, simply for now, and cross the other bridge if needed.

Fuel is definitely not draining the line back to tank as I tested the check valves in the stock pump, and they are fine.
It's engine heat evaporating the fuel off in the carbs as the garage does smell for a day or 2 after parking. In Australia, we can still but ethanol free fuel, but it still seems much more volatile now than in the days all cars had carbs.

That's what I figured. Fuel these days is designed for fuel injection, meaning it must turn into a fog state as it leaves the nozzle in a relatively cool intake (no exhaust heat) so the chemistry must be altered to make that happen. Add insult to injury, many modern intakes are made of a glass resin material for the purpose of maintaining near constant temps, but this is all part of controlling emissions and providing good efficiency. So for all this to work the fuel must be different.

The era of carbs is over and short of converting to FI we either suffer of take measures to deal with it. You have two pots of gas boiling on that stove! Start by blocking the heat cross over then add the 1/2" thick insulated carb spacers. I know your setup uses the stock 1/4" bakelite spacers but increasing the insulating properties can only help. Still won't be perfect until you make it EFI!

Mebsuta · Jul 29, 2015

If mine has been sitting, I spray a little starting fluid, or take off the air cleaner lid and pour a few drops of small engine fuel into the carburetor, and it fires right up.

Adding an elec fuel priming pump

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