Best Fuel Pump Advice for Newb...

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7milesout

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Guys,

Without going into a book of details, my 1972 Scamp is in need of a new pump. Let me provide a few details to point me in the right direction.

It is a 360 that was replaced in the vehicle in about 1996. I am running an Edelbrock 1405 (600 CFM with mechanical choke). It has a worn out / dead / whatever mechanical pump on it now. It allows the bowl to empty after about 6 seconds of full throttle.

I want a simple, effective and reliable pump. Whether your recommendations are electric or mechanical I have no preference. But I will say this. If the ole Scamp sits in the garage for a few days without being started, it takes probably 7 seconds or so to get it to hit a lick. Which I believe is totally normally. The gas in the bowl is probably all gone or mostly gone, and the accelerator pump is pumping dry for the first 7 seconds. So I pat the throttle during the first 7 seconds until I hear it hit a lick. Then I change to a more thorough pump and it starts right up. Sounds normally to me. Just needs the bowl and accelerator pump primed. After that first dry cranking, even if it sits at work for 9 hours, it fires right up.

I mention that because I'm thinking, if I were to use an electric pump, I would imagine I could turn the key to ON, hear the pump buzz as it is filling the bowl and pressuring the lines. And then once the pump stops buzzing, I would imagine the bowl and lines are primed at about 6 psi. At that point I have to believe the engine would fire right up, even if it has sit for a month. No ~7 seconds on the starter to get it to crank.

Other than that, my ears are open and I'm willing to learn.


7milesout
 
7milesout said:
Guys,

Without going into a book of details, my 1972 Scamp is in need of a new pump. Let me provide a few details to point me in the right direction.

It is a 360 that was replaced in the vehicle in about 1996. I am running an Edelbrock 1405 (600 CFM with mechanical choke). It has a worn out / dead / whatever mechanical pump on it now. It allows the bowl to empty after about 6 seconds of full throttle.

I want a simple, effective and reliable pump. Whether your recommendations are electric or mechanical I have no preference. But I will say this. If the ole Scamp sits in the garage for a few days without being started, it takes probably 7 seconds or so to get it to hit a lick. Which I believe is totally normally. The gas in the bowl is probably all gone or mostly gone, and the accelerator pump is pumping dry for the first 7 seconds. So I pat the throttle during the first 7 seconds until I hear it hit a lick. Then I change to a more thorough pump and it starts right up. Sounds normally to me. Just needs the bowl and accelerator pump primed. After that first dry cranking, even if it sits at work for 9 hours, it fires right up.

I mention that because I'm thinking, if I were to use an electric pump, I would imagine I could turn the key to ON, hear the pump buzz as it is filling the bowl and pressuring the lines. And then once the pump stops buzzing, I would imagine the bowl and lines are primed at about 6 psi. At that point I have to believe the engine would fire right up, even if it has sit for a month. No ~7 seconds on the starter to get it to crank.

Other than that, my ears are open and I'm willing to learn.


7milesout
Click to expand...
I tried using a eddy carb and didn’t have any luck. As far as a mechanical pump, I’m using a Carter strip super mechanical pump no complaints.
 
If you put a new pump in, especially an electric unit, one thing to be aware of is that Edelbrock carbs want fuel pressure of 4 - 6 lbs. (I think the official spec is 6.5 psi max) and don't do well at higher pressures. Many people report that they run best at 3.5 - 4.5, which is about where I have mine set. So you might need to plumb a fuel pressure regulator and gauge into the system as well.
 
If the vehicle has been sitting a while, the carb and lines may empty, but it is not nec to continue cranking for several seconds.
After 2 crankshaft revolutions the cams one revolution has cycled the pump's lever once, compressing a spring/diaphram inside the pump.
Stop cranking, wait a sec. and the spring/diaphram maintains suction for a coupla seconds moving fuel. Give it another short crank,wait a sec. the lever once again cycles the pump, fuel moves after key released.
I usually gently pump throttle on 3 rd try, and it usually fires pretty quick.
Helps when you have a weak battery to understand pump function.
Cheers
True on all manual diaphram pump vehicles to my knowledge.
 
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I've played the fuel pump game many times. Here is one that worked for me. Holley Mighty Mite Electric.(K&N, Mr.Gasket same pump different name) Jegs part# 510-12-426. Around $50. 1.5-4 PSI. Good for 300 HP they also make a 4-7 PSI and a 7-10 PSI Good to 400 HP stated by Holley. I installed one in my 1979 360 Chrysler 300 (Thermo Quad)as a primer pump with a switch to limit cranking and fill the bowl. After awhile I removed the mechanical pump as a test to see if it would handle running the engine on just the electric pump.Now I used the 1.5-4 PSI pump and the car ran just fine.Even full throttle bursts from first to high gear.The car was equipped with 3.21 gears so it was no slouch.The car also had the normal go fast goodies too. Since then I have installed them on several cars.I still run a mechanical on the daily drivers along with this cool little pump as a booster. Just something to think about.
 
All the pump needs to do is fill the bowls. The bowls are atmospheric pressure. Pressure in the line only needs to be enough to refill the bowl as the float drops and the valve opens. And not too much or the pressure will push the inlet valve open. Mechanical pump is all that's needed for what you're doing and you'll save yourself a headache with an electrical system design not really appropriate for running loads on the battery.
 
If you want to buy a new pump, Holley's 'Keith Dorton' 110 mechanical has been pretty good and probably the same as it was when they first came out with it.
p/n 12-260-11
From the Holley catalog. Free flow is zero psi on the outlet.
f110GPHchrt.jpg
 
It's not easy for me to reply at night. But one thing is for sure that goes against something mentioned earlier. My fuel filter is laying horizontally and the output side is on the same level as the input side.

Sounds like I need to lower the input side, and turn the filter up vertically with the output side of the filter high.

That would help wouldn't it? It seems it would keep the filter full at the very least.


7milesout
 
Of course PSI is important, what you are looking for is gallons per hour or GPH. That Carter mechanical pump that was recommended is an excellent one. That should be all you need. This is it:

Carter Strip Super Mechanical Fuel Pumps M6270

I recommend a regulator with it, as the Edelbrock carburetors don't like a lot of pressure on the needle and seat. 5.5 PSI would be plenty. I also recommend a good return line as well and plumbing the regulator in the return line as that will regulate the entire fuel system and use the regulator as the return orifice. Of course you will need a return style regulator. If you do it right, you will have a very nice fuel system.
 
Because 6 seconds at WOT is a very long time, enough to drain the bowls perhaps several times over, and NOT just once. The fact that it made it to the 6 second mark points to restrictions, possibly in the supply side, and after all it's a 72, so the entire supply line could be heavily rusted up inside. Or the tankvent could have failed.Or it's sucking air at the rear jumper. Or the sock is severely gummed up.Or the eccentric has failed.
I just hate throwing parts at a problem and crossing my fingers. I like to know that when I spend 100 or 150 on a customers car, that the problem will be cured. The volume test takes a couple of minutes.
If the supply side turns out OK, then I move to the pressure side. And remembering that debris stuck inside the fitting at the carb , or an incorrectly installed filter there has in the past made a fool of me, that is now my next check.

He wanted the short version, so I complied
 
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And that's why I recommended a complete fuel system upgrade. I gave the short version too.
 
The Holley has (had) the right spring as did the Carter 6902 ( NLA) so proper regulation is built in. Simpler, cheaper. Also less restriction unless using a fuel log and return side regulator. A stock pump should have been enough for the fuel consumption, but I can't guarentee that so didn't suggest it.

Anyway I'm with A/J. Spend the time on hunting down the issue. Check the sock, the rubber hoses, condition of the lines. If the filter is metal, cut it open to see if its clogging up. Pump can be tested like A/J posted, or if its an aftermarket pump, open it up to see if the diaphram or valves have failed.
 
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7milesout said:
It's not easy for me to reply at night. But one thing is for sure that goes against something mentioned earlier. My fuel filter is laying horizontally and the output side is on the same level as the input side.

Sounds like I need to lower the input side, and turn the filter up vertically with the output side of the filter high.

That would help wouldn't it? It seems it would keep the filter full at the very least.


7milesout
Click to expand...
It will help let any vapor bubbles burp out. On a system with a vapor return in the fuel filter, the return nipple should be clocked at to be at the top. Those sometimes were run horizontal because the relief was in the return. A '72 car came with some version of the 'vapor saver' systems. Its worth seeing which one is on your car, read up on how it works, and then figure out how to adapt or modify it so it works with, not against your current needs.
 
I'm attaching some pictures I took this morning on my way out the door. I pulled the hose off the breather, it doesn't run open like shown.

upload_2018-9-25_10-6-9.png


upload_2018-9-25_10-6-19.png


upload_2018-9-25_10-6-32.png


7milesout
 
Any comment on the fuel line / filter set up? Do I need to change it to make the filter stand up vertically?
 
7milesout said:
Any comment on the fuel line / filter set up? Do I need to change it to make the filter stand up vertically?
Click to expand...

That alone shouldn't be a problem. I run a horizontal inline filter before a regulator/gauge and then into the carb on a couple different cars. Personally, I try to avoid plastic and rubber in my fuel systems to the greatest extent possible, due to the corrosive crap that passes for gasoline here in California.

IMG_20180926_101628.jpg
 
I wouldn't worry about the air-pocket in the filter, the fuel will pass thru just fine,and and eventually most of the air will get picked up as well.

But one thing I would do is remove the line and the fitting from the carb and have a look in that cavity.
 
In the cavity, in the carb, right? If so, the carb is less than a year old. I'll do it, but I doubt any pinch point in the fuel delivery is in the carb itself.
 
I'm feeding 410cid. Full ported heads ,solid roller, 750 carb, tti step headers, 4 spd, 3" pipes 3.73 gears....I rev it 6800


I use a stock 340 replacement fuel pump.

Think about how long you hold it at wide open throttle. Save your money for good headers, cam, heads, Etc and don't buy the fancy water pump, fuel pump, alternator and all that because the stock stuff works Beyond stock stuff
 
I went ahead and pulled the fitting off the inlet. The fitting itself was wide open, clean as a whistle. Somebody mentioned some kind of strainer / filter on the inlet side of the carb. I got some pictures of that as well. Clean as a whistle. See the pictures at the bottom.

So I went ahead and pulled the pump off. I haven't torn into it, but it seemed kind of "catchy" when pumping the arm. It wasn't smooth at all. It did spurt some fuel out.

This is my thinking: The carb is new. The inlet is clear. The filter is new and clear. The tank is new. The sender is new (the sock is still clean and pretty). The fuel flowed like a geyser from the fuel tank, through the fuel line all the way to the fuel pump when I pushed air from that line into the tank. The only thing I'm not certain about, is the fuel pump itself.

I'm going to keep it simple, and purchase one of the mechanical ones mentioned here. And also follow the short start (let the fuel flow) starting procedure described above, when I estimate the fuel bowl is low to empty.

upload_2018-9-28_13-37-56.png


upload_2018-9-28_13-38-6.png
 
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