Technical Ongoing fuel problems

< insert BIG exasperated sigh here >
Try as I might, I cannot get adequate fuel to my engine. I'm a reasonably intelligent fellow, but I believe that the fundamentals of fluid dynamics escape me. The Romans could make water flow uphill, but I seemingly cannot get fuel from the rear of a '50 Mercury to the front with any degree of reliability.
The equipment I have is a new fuel tank, with a 6-volt Carter fuel pump like this one:

It is (currently) mounted on the frame just ahead of the rear wheel on the driver's side. It was previously mounted on a bracket under the car just ahead of the fuel tank, but more on that in a minute. Up front I have a new Edelbrock 600CFM carb mounted on an Edelbrock 452 manifold.
I have had fuel issues with the car ever since I got it 2 years ago. When I got it, it had the original intake with an old Holley 94 that leaked everywhere and a different type cylindrical 6-volt electric fuel pump (which went out in short order). I replaced the fuel pump with the one above, and that caused the Holley to spray gasoline out of every orifice like a lawn sprinkler. I ran across a 452 manifold for sale here on the HAMB and paired it with a new Edelbrock (the model escapes me) carb. Voila! Off and running! Sort of.
The problem I have is that when the car is under a load or heavy acceleration the car bogs. I believed the problem to be (and still do) is that the engine just isn't getting enough fuel. After I installed the Carter, I noticed the pump sounded like it was laboring -- or more specifically, like maybe there was air in the lines -- which caused me to think that maybe there was either trash in the fuel filter or that the pump kept losing its prime. I replaced the fuel filter. No difference. So I moved the pump to what I thought would be a lower point on the car in order to hold its prime--its current location on the frame. The problem improved somewhat (sort of confirming my fuel-starvation theory), but it still exists. I can "put my foot in it" a little more than I could before I moved the pump, but it still falls on its face if I push too much.
Also, and I don't understand this at all, when I first crank the car, the clear fuel filter ahead of the carb inlet will be FULL of fuel, but after running for a bit, it looks like it's empty...yet the car continues to run.
I checked the fuel pressure and I'm getting about 4-5 PSI, but the needle surges and you can hear the pump surging too. Is that normal? Also, it seems like I should be getting more like 7 PSI out of that pump...has this one gone bad too??
I have never had any luck with electric pumps though people swear by them. I'd like to just go back to the mechanical pump, but I can't seem to find one for a '50 Merc (but there seem to be plenty for '51 and up...???)
Sage advice greatly welcomed. I've had this car now for, as I say, going on two years, but I've never gotten it any further than the corner store...
Thanks.

 

Some things that immediately come to mind are a plugged sock or strainer on the fuel pickup or sucking air somewhere before the electric pump, much like trying to drink with a broken straw. Old rubber fuel line can look ok on the outside but be swollen or collapsed on the inside causing a restriction in the system, modern oxygenated fuels play havoc with older rubber compounds.

 

Suggestion...T in a fuel pressure gauge, mounted near the windshield outside the pass compartment, so you can see it when you're driving.

Watch the gauge, when the car acts up. my guess is you don't actually have a fuel starvation problem. The reason? the carb you have has huge float bowls, and it takes a while for them to run dry.

Might be that you have twice as big a carb as you need. When you open the throttle, airflow is at such a low velocity that it can't generate enough vacuum to pull fuel into the nozzles, so you get a lean bog.

But that's just a wild ass guess...there could be any other problems. But to know for sure whether or not you're getting fuel starvation, you need to know what the fuel pressure does when things go wonky. Put the gauge on so you can see it when you're driving, see what happens, and you'll know one way or the other.

 

Your new pump should have a G.P.M. ratting as well as pressure. Pull the line at the Carb, put a length of hose on it and into an empty 5 gal can. Turn on the pump and let it run for 30 seconds and measure the volume in the can. Fuel delivery may not be your real problem but at least you'll know if it is. New don't mean Good anymore. It could be in the pickup tube inside the Tank. Heck it could be a plugged vent line.

 

What BLACK-Sheep said sounds like your Problem, I have been running Carter Electric
Fuel Pumps for over 50 years & I swear by them I run one in
My Merc. ( 327/300 hp ) & it Never l;et me Down

Just my 3.5 cents

Live Learn & Die a Fool

 

Tank vented?

Oops...Mr. Wizzard covered that

 

- or vented cap?

 

I forget to Ask if this is a Stock Engine ( flathead ) or what.??
If it is Stock & your running a larger Carb. than I Think that could
be the Problem.!
Give some Spects on the Engine.!

Just my 3.5 cents

Live Learn & Die a Fool

 

If you have a starvation issue it will lean out under load and I don't know that I would describe it as a "bog". If you put a load on the engine and it lays over and doesn't recover until you lift I would agree it may be starvation. If you load the engine, it bogs but recovers I wouldn't be looking at fuel volume. As I remember, an Edelbrock/AFB style carb only wants 4-5 psi and more will be too much for the needle valve.

 

Like all others have suggested, I would start @ tank , checking to make sue the sock / outlet is free flowing .
Connect a hose from tank outlet , use air to pressurize gas tank 1-2 psi ( A quick tap of air) , to check flow from tank into a seeable container.
Move your way forward ,
Or you can for just as a test after checking flow from lank , Run a temporary hose from fuel pump to carb & see if problem still exist.
Try witch gas cap removed or cracked if not tried yet .
like ""Squirrel"" said Carb to big or adjustments need to be made to the secondary side.
But start from tank & move forward.

 

This is a long shot...but it happened to me. Check the rubber "connector" hose coming off gas tank to the steel fuel line.

Years ago I stuffed a 425 dual quad Buick engine into a 48 Ford Pickup. I could drive it about 3 miles and the carbs would lean out, and eventually stall.. Let it sit 5 minutes, pump the hell out of it and it would drive 3 more miles, lean out and die...would do that all day long. Figured the mechanical fuel pump couldn't keep up with the carbs, so I added an inline electric pump. That made it worse...could only drive 1 mile at a time before it would lean out and die.
It ended up being the 6 inch long rubber "connector" hose from the gas tank to the steel fuel line. With the mechanical fuel pump, it would suck closed after about 3 miles driving. Adding the electric pump just made it suck closed faster.

 

I thought of that -- it may actually be a 500 CFM -- anyway, I know it's got too much throat for the flattie but it's the smallest I could get. I did disconnect the secondaries and I still get the same problem. I don't know what the CFM is with just the primaries, but its got to be more in-range with the displacement.

 

The secondaries on those carbs have an air valve, which only opens when needed. So I would not expect much improvement by disconnecting the secondary throttle blades.

look at the number stamped on the bottom front of the carb, it will tell you CFM. 1406 is a 600

 

I thought about a plugged pickup tube...don't know if this is copacetic or not, but blew air into the tank from the outlet to knock loose any crud. Didn't make any difference. Of course, it could've just sucked the same crud back into the sock...In any case, I can't see the sock/pickup, and if there is a sock or screen, I can't see it from the sending unit bung. And if it is a clogged screen, I don't know how the hell I'd get it out.
I'm about ready to just put a milk jug in the back seat.
Kidding.

 

Return line is pretty much a need with todays gasoline... Dead heading electric fuel pumps isn't a good thing to do...

 

Yes, that's exactly what it does. It leans out, doesn't recover until I let off the throttle.

 

Yes, it's a stock Merc flattie. I'll find out what the CFM is...I can't remember offhand. I just know I got the smallest 4-bbl I could find,.

 

Does the "bog" happen as soon as you open up the throttle? or does it take several seconds, for it to use up the available fuel in the float bowl, before it "bogs"?

Think about what's happening...I've driven some cars with real fuel starvation problems, they are not consistent at all. It takes a while for the carb to run low on fuel, and lose power. It does not happen right away when you open the throttle. Usually, you will notice it when the car loses power going up a hill, or after you get moving, it stumbles, coughs, or just loses power.

 

That's the kind of $#!+ that'll drive ya nuts!!!

 

I have wondered if I've got WAY too much carb for the engine -- and to be clear, I know it's a little too big, but I didn't think it was so big that it'd negate its venturi. But if it is...what carb would someone have set atop an Eddy 452 back in the day?

 

It takes some time; I wouldn't say several seconds, but its not immediate either. And it depends on how I get on the throttle. If I floor it all at once, she'll start to wind up and then falter before she gets going good. If I put the throttle down more slowly, she'll get going good, but then start to sputter and falter. I don't know if I'm describing it correctly. It feels almost like the parking brake is on...it's like the car wants to go, but it runs out of fuel or wind or timing or something. But I'm *almost* positive its not spark.

 

I suggest again that you put a fuel pressure gauge on the car, so you can see what the pressure is when it's acting up. The pressure should hold steady, but if it drops, then you know you have a starvation issue.

 

Maybe an engine vacuum gauge hooked up and taped to the windshield too, could help with diagnosis while driving. Just more info to work with if anything.

 

Seems like a decent video here. No more than 6psi fuel pressure sounds like.

 

Yep, I'll do that.

 

It does sound like a fuel system problem, but if your testing doesn't reveal any problems don't discount the possibility of a restricted exhaust system. A vacuum gauge will show engine vacuum falling as the symptoms begin, and drop to near nothing as the power drops off.

 

Wonder if the pump is getting a full six volts. It may work but not be able to keep up....?

 

I hate problems like this it sucks you try everything but problem still exist. Honestly I had a problem like this once on my truck it would bog going up a hill and when you put your foot in it. I replaced the pump the lines the filter the gas cap checked the vent everything still same problem. Drove me crazy for about a year and I drove this truck every day. I So one day I got pissed off I took a small gas can hooked up a duct tape a hose in the spout to a 12 volt pump to a jump box ran a switch through the window took it out for a spin and for the first time in a year the truck ran great the only thing I did not replace was the fuel tank and that was my problem. The pick up tube inside the tank had a pin hole in it the tube was rotted a little rust spot in the middle sucking air. I'm not saying this is your problem but by bypassing the fuel system I was able to find the problem and fix it.

Sent from my LM-Q720 using The H.A.M.B. mobile app

 

That exact thing happened on my T Bird , New sender ,good as new again. It would fill the bowl but not for long.

 

Every time I hear a story like this it reminds me of my Childhood and my Dad. I remember being on Vacation in his Packard when we had some kind of an issue. We found a city park and left Mom and the rest of the family and walked around this strange town to many Service Stations. He would talk to "The Guy" on duty explaining the issue. Then we'd just walk on to another. After several places and still walking I asked him why he didn't have one of them fix us. He said "when I find an actual Mechanic I will" "Those guys all are just Parts Changers and I can do that myself". I was 9 years old and that stuck. That walk with him taught me a very good lesson and I've never forgotten it.