Okay, so I have a couple issues here and I want to see what others have to say.

The truck is a '78 bronco, originally sold in Michigan, so it has the vented gas cap setup. I put a 460 in it years ago and it has an edelbrock 750 carb that was just rebuilt and seems to work well.

I have a new mechanical fuel pump and I installed an inline Mr. Gasket electric pump back by the tank. It runs off a switch.

I also installed all new rubber fuel lines this last summer. Oh, I also have a check valve installed right after the e-pump.

Now, I have always had a drain back issue with fuel, meaning, once the truck sits for more than a day, there is no fuel left in the lines. I figured the new lines and check valve would fix that (it didn't).

So what I have been doing, is using the e-pump to prime the system, then I just run it off the m-pump once it starts. That was working well. I could hear the e-pump gargle fuel, then push it to the carb, through the pressure regulator and gauge that I also installed under the hood.

But now, the e-pump doesn't gargle and it isn't pushing fuel and it takes a looong tome for the m-pump to get fuel to the carb. Once it starts, it runs great, but even after 1 day, the fuel drains out of the lines. How it's doing that, with a check valve inline, is odd.

So, it appears as though the e-pump is shot, I get that, but does anyone have any theories on why the fuel drains out of the lines and why it takes the m-pump so long to pressurize the lines? It takes like 20 seconds. The gas cap vent rattles as it should, seems to be good.

One other detail, I pulled the tank last year and put a new pick up in it. So basically, I have replaced everything but the tank. I even put a new filler tube in.

Any thoughts would be greatly appreciated.

 

Are you saying on cold starts you crank for 20 seconds before she kicks off ?

 

yes and that's after it's been sitting for only 1 day.

 

Have you verified that whatever choke you're using on your carburetor is closing when cold. If not, check that first, next time before you cold start. Post back with what you find. You may have the choke out of adjustment. Best to eliminate that possibility first.

 

Good idea, I'll check that out.

 

In my experience, some of which is with in the last few months, edelbrocks allow all of the fuel to evaporate out of the bowls within a day or two. Went from an AVS2 back to a Holley recently and that's no longer an issue

 

that would be fine if the lines didn't completely empty out too. I don't understand how it's happening, I mean, there are 2 filters, a gauge, a regulator, two pumps and a dang check valve and it appears to me that the fuel drains back into the tank.
As far as the holly vs Edelbrock thing goes, I have both, tried the holly for a while, but it was one thing after another, I couldn't ever get it to stay reliable, the edelbrock has been good. The carb shop that rebuilt them for me said he trusts the e-brocks a lot more, but then again, he breathes gas fumes in all day.

 

If it’s not a choke issue, or something unrelated, such as weak spark from the ignition, then you are also losing all the fuel out of your carburetor.
If you think about it, no matter how empty the pump and lines are, the engine will still start, and run for a couple of minutes, just on the fuel that’s in the bowl.
Depending upon where you live, that’s a common issue with carburetors of any type. Sounds like Holley has a little less likelihood, but it’s also possible that the different regions that you two live in might have less ethanol, or maybe a different mix of fuel that evaporates much quicker.
Not an issue in a sealed Efi system, but unfortunately, all too common with carburetors.
As you surmised as well, fuel pumps fail. Especially with modern fuels.
Doesn’t sound like yours sits too long, or for extended periods between driving, so that’s not your problem.
It is for a lot of our old trucks however, when, after sitting for a couple of months, their brand new fuel pump is dead.

We should be investing in fuel pump company stock because they keep selling the crap that’s not compatible with today’s fuels. 😩

 

I had to replace my Bronco's fuel line, original was full of pin holes from rust. I used tubing again as don't trust rubber hose as fuel lines. Only use minimum for connections. I cringe every time I see an engine with rubber hose coming from the pump all the way to carb.

 

Modern fuel will evaporate out of any carb it seems. If you have a correctly installed anti drainback valve it cain't drain back.. The valve itself can be a restriction and a non working electric pump also. drain back is not likely anyway as the two pumps both resist it. I recommend carter electric pump and ditch the mechanical one. The sock filter in the tank could also be clogged.

 

How is all this plumbed I wonder?
I thought my Edelbrock was evaporating all the fuel, but it turned out just one pump on the pedal with half choke (manual chokes only here) ... it fired off every time. I had just developed a bad habit. My Holley does the same. I like both, but can only use one at a time and my cruise control seems to favor the Holley.

 

i don't think the sock filter is clogged, because once it's running, it's solid and there is no studdering or hesitation and I'm able to maintain 7 psi.
But yeah, the drainback issue is odd. If there was any fuel left in the line, the m-pump would get it to the carb within a second or two, it's taking 20 seconds to get it there.
I'm nowhere near ready to ditch the M-pump, it's the most reliable part of the fuel system right now and as long as it provides 7psi of fuel, I'm good with it. especially since the e-pump seems ro have failed after just one year of very light use. I've probably only used it to prime the fuel system maybe 30 times.

 

okay, so I have a fuel filter on the inlet of the e-pump, which is mounted right in front of the tank. Then, the rubber line runs through a midship check valve at about the drivers door area of the frame rail, then the line runs to the m-pump. Comes out of the m pump to the regulator mounted on the drivers side fender. Then, there is a gauge mounted by the air filter housing, then of course there is a filter on the carb.

 

1Ton hit it on the head
There would / should still be fuel in the carb bowl it would start and run on till fuel got pulled back up.
Fuel in the carb is evaporating and why it will not start / run till the carb is filled again.
Now wither it is a Elde or Holley thing I can say as I have heard both do it.

I do have a question?
How are hot restarts? A lot of cranking, foot to the floor like it is flooded and it will then fire up?
This is a sign the carb is getting hot and boiling the fuel in the bowl. The vapors go out the bowl vent and down the carb flooding the engine and why you need to hold the throttle wide open. I think in your case when you shut it down all the fuel in the bowl is boiling out and when you have a hard time starting it after 1 day.

You also need to check that the choke is working as it should.
When checking it if it is closed hole it open look down the carb and move the throttle you should see fuel squirt.
If not then either the pump is bad or the bowl empty.

Either case it is best to get the carb away from heat. They make spacers that can do this.

BTW when you gor to start it after sitting a day you are pushing the throttle to the floor at least 1 time to set the choke and give it a squirt of fuel.
If it is really cold you may need to give it 2 pushes.
Dave ----

 

If the needle and seat at the carburetor loose their seal you're essentially, at that point, providing a vent through the entire fuel line to dump in the tank if no check valve is in place. Working backwards any hose clamp etc. which possibly provides that vent is suspect until eliminated. Also on a side note, your 460 transplant, what vehicle did it come from ? Some in the 80's were plumbed with a built in drain back "Y" right there where the fuel line passes between the dizzy and the driver's side valve cover.