in-line elec fuel pump not pushing through mechanical pump

[dbdevkc]

Originally Posted by Flathead Fever

I had a '66 Mini Cooper S with an external adjustable fuel regulator. This was 30-years ago but they look exactly the same today. Every once in a while, the regulator would just shut the fuel off. I have to get out, reset the regulator and then I'd be good for maybe a month, and it would happen again. So, I bought a new one and then anther different brand regulator, and it did exactly the same thing. I think they are designed more of a 5-6 lb. system, because at around 3 lb. they seem to have issues. No manufacturer uses an external fuel regulator. They design a pump with the correct pressure required by the carburetor. If you're just priming the system, then use a low-pressure electric pump that is open in the off position.

Well, what we have is the electric pump from shoebox central - it is 4.5 psi max, and a regulator just upstream from it. We'll stick with that until we see it not working.

[Gene1949]

Originally Posted by dbdevkc

I am going to check the regulator on it - it might be set to 3-ish - because the Carter WCFB carb we have on there uses a lot of fuel when those 4bls open up.

I’ve been running a “vintage” SW pump on my WCFB for 25-30 years. Fired with a relay and a bump [safety] switch. Ignition switch does pilot duty only. I would suggest bypassing the mechanical altogether. Lot less grief.
The WCFB is very happy with 3 not to exceed 5lbs.

[69a]

I know how the regulator works when you are using the electric pump, but I have no idea how the fuel gets through the regulator when it is being sucked through by the mechanical pump. It may or maybe not cause a resistance. I guessed by your original post that it works ok. The first sign that your mechanical pump is not up to the task is low revs and open throttle. ie going uphill in 3rd gear

[ford38v8]

Going back to the subject of the leaking cork gasket, You may find that it leaks fuel when the electric pump is running, but not when only the mechanical pump is running. That is because it is either under positive pressure from the electric, or negative pressure from only the mechanical. Negative pressure anywhere in the fuel system will not leak gas, but rather, will introduce air to the system, sometimes seen as bubbles in the glass bowl. Common sense sometimes needs a little reminder.
For a cork gasket to seal, it must be pliable, which can be easily achieved by soaking it in hot engine oil. A dry cork is most difficult to seal, and can distort without actually making a seal. Lubrication softens it to conform to the mating surfaces correctly. An additional advantage of using motor oil on the cork is when it sits for long enough to evaporate the fuel, the cork is still soft and pliable having been prepped with oil. Don't use any gooey glue, just hot motor oil.

[69a]

Originally Posted by dbdevkc

I understand what you are saying. And do not plan to run the electric while running. But would having the regulator set to 2 while the mechanical is delivering 3 to the carb - would the regulator constrain the mechanical pump's ability to suck enough fuel to continue delivering 3 to the carb? In other words, might the regulator set to 2 be a bottleneck?

The setting of the regulator will not effect the fuel pressure from the mechanical pump.
What pressure does the electric pump run at? Anything less than 5 PSI and just using it for priming, you could probably ditch the regulator. Too much pressure can bust the fuel bowl gasket or the fuel pump diaphragm, or it can be too much for the needle and seat in the carburetor, causing it to flood.
The only way to tell is to road test it. I have a hand held Fuel pressure/vacuum gauge. It will read pressure or vacuum to 30PSI. you could tee this into the fuel line
(1) Between mechanical pump and carb
(2) Between pressure regulator and glass bowl.
I have a fuel pressure gauge under the dash, it is actually a boost gauge where the sensor is mounted high up on the fire wall, and a single wire goes inside to the gauge. I don't have a mechanical pump, but run two flow through electric pumps mounted in tandem, but only one is alive. If I lose one pump it is just a matter of laying on my back under the car and swapping the wire.
I also have a digital rev counter, so makes diagnosing a problem easy.
I turn on the ignition, wait till the fuel pressure is "2" pull the choke and hit the starter, if I have spark the rev counter will read over 200 RPM.

[Mart]

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If you are only using the electric pump to prime you probably don't need the regulator. Just run the pump for a few seconds and turn it off. My electric primer pump makes a ticking noise. when the ticking stops it means the system is full and I turn off the pump.

[glennpm]

I have two 97s and use a Holley 12-804 regulator to keep my fuel pressure at ~2psi. I use an electric fuel pump only. I modified the regulator to dump fuel below the engine if the diaphragm leaks, keeping it off the top of the hot engine. This is the thread.

https://www.fordbarn.com/forum/showt...ight=regulator

[dbdevkc]

Originally Posted by ford38v8

Going back to the subject of the leaking cork gasket, You may find that it leaks fuel when the electric pump is running, but not when only the mechanical pump is running. That is because it is either under positive pressure from the electric, or negative pressure from only the mechanical. Negative pressure anywhere in the fuel system will not leak gas, but rather, will introduce air to the system, sometimes seen as bubbles in the glass bowl. Common sense sometimes needs a little reminder.

After our latest test drive and not running the electric pump at all, just the mechanical, and after shutting off the motor there was a slow but steady drip from the glass bowl and we could see the fuel was running down from the gasket. Makes sense that would be under negative pressure. Maybe it is not leaking while running, but after shutdown with heat expansion and all, and a very bad gasket - we'll be taking the bowl off today to take a look. maybe try your oil soaking idea. We do have a ne gasket on the way.

[tubman]

You should make sure the rim of the glass bowl is perfectly flat with no chips. After closely inspecting mine, I make sure it's even by sanding it on "Wet-r-Dry" paper on my surface plate. (A dead flat 2" thick piece of granite made purposefully just for such things.) Also, though it goes counter to to what I would initially think, I've always had much better results with cork over neoprene gaskets. A slight vacuum leak at the sediment bowl can cause a lot of hard to find tuning problems, since there is no leak to see.