Leaking Fuel Pump Diaphragm?

[BRL]

Originally Posted by IT Cowboy

Can someone explain the electric fuel pumps to me like I am a 3rd grader...

I went to YouTube videos for inspiration, of course the pump isn't working yet and I'll toss in a fuel pressure regulator if necessary.

Wiring that stuff up under the dash was another adventure.

Love it LockDoc, I'll look into the heavy duty version.

My Sister got me one of those flashlights that clip to the bill of a baseball cap and I don't know how I ever lived without one.
The bill kept bumping into everything though so I broke out the scissors.

[dmjlambert]

Originally Posted by IT Cowboy

Can someone explain the electric fuel pumps to me like I am a 3rd grader. Are they connected to a relay and the ignition so that is how they come on and what keeps it from just flooding the carb if you turn just the ignition or a pumps switch on.

The carb does not get flooded with an electric fuel pump or mechanical fuel pump because the carburetor has a float in a bowl connected to a needle and seat valve that shuts off the incoming supply of fuel. Pretty much just like a toilet tank shuts off incoming water when the tank is full. If that piece is working correctly, the carburetor only lets in enough gas to fill the internal bowl. The needle and seat and sometimes the float are some of the items typically replaced during a carburetor rebuild.

[IT Cowboy]

Originally Posted by dmjlambert

The carb does not get flooded with an electric fuel pump or mechanical fuel pump because the carburetor has a float in a bowl connected to a needle and seat valve that shuts off the incoming supply of fuel. Pretty much just like a toilet tank shuts off incoming water when the tank is full. If that piece is working correctly, the carburetor only lets in enough gas to fill the internal bowl. The needle and seat and sometimes the float are some of the items typically replaced during a carburetor rebuild.

OK durr, like a gravity fed motorcycle tank and carb

[BRL]

Originally Posted by IT Cowboy

OK durr, like a gravity fed motorcycle tank and carb

Sorry about that IT Cowboy, I'm in no position to explain that stuff to anybody.

[Steeveedee]

Originally Posted by BRL

Sorry about that IT Cowboy, I'm in no position to explain that stuff to anybody.

It's entirely possible for the scenario you asked about to happen. The fuel just doesn't come through the carburetor- and is actually a worse situation. It is unbelievably rare, but I've seen it...and in the case of a bad needle and seat or float, much less of a problem, unless someone just leaves the engine running. I've seen crankcase oil dilution from that, too.

[BRL]

Originally Posted by IT Cowboy

OK durr, like a gravity fed motorcycle tank and carb

That's exactly what I was looking at.

Years ago I had a really nice '69 Nova with the deluxe trim and the wrong year rally wheels.
One day I noticed fuel dripping out of a bad mechanical fuel pump through a weep hole in the pump and of course replaced it.
That tank is located way in the back under the trunk and under the frame and who knows if any fuel flowed into the crankcase before I caught it, didn't know enough to check the dipstick level.
Now picture a 20 gallon gas tank essentially turned sideways behind you up in the cab, well above the frame and a leaking fuel pump with open access to your engine crankcase and your garage floor.

[BRL]

Getting ready to try to figure out the fuel line routing to my electric pump.
Thought it might be too close to the transmission crossmember but a short piece of rubber fuel hose will slide right over the top of the crossmember to meet a hard line.
...so far so good.
Pinched the short rubber fuel line from the tank to the beginning of the hard line with vicegrips and cut the line.
Fuel started pouring all over me and the floor?!?
Thought it was just residual fuel in the line from the mechanical pump up front so I allowed it to drain out...but it continued.
Turns out I cut the fuel line on the wrong side of the vicegrips and the tank was draining out all over me.
Decided right there and then that I don't want a woodstove in the garage for heat and I'm done tinkering for tonight.

[Papa Smurf]

I put a carter fuel pump on my big block with quadrajet and the pressure was too much and caused it to flood out. Put a 3# pressure rgulator on it and it works fine.

[BRL]

Originally Posted by Papa Smurf

I put a carter fuel pump on my big block with quadrajet and the pressure was too much and caused it to flood out. Put a 3# pressure rgulator on it and it works fine.

Good to know thanks.
The Carter P4070 is supposedly putting out between 4-8 psi and will be feeding a Edelbrock 600 cfm model 1405 (I think) so it might or might not need a regulator in the end.
Should be interesting if I get my lazy tail up to the garage and continue installing the dang pump.

[IT Cowboy]

My 72 has a mechanical pump with a return line. If I put a pressure regulator on the feed line to the carb will the pump handle the "back pressure" or do I need to plumb in a return T from the carb supply line to the pump return line and put a check valve in there too. I think my return is 3/8

[BRL]

Went to remove the hard line that goes from the tank to the mechanical fuel pump that runs along inside the frame, and all went well except for that last clip which of course is hidden in the most inaccessible place on the truck.

There probably is a simple technique for removing that clip but I don't know what it is.

Spent about 2 hours fighting with that stupid thing with every feasible tool I could come up with in my toolbox until finally it broke free from the frame.

I'm taking the rest of the evening off.

[LockDoc]

-
Not only is it hard to get to but you can't see in there either....

[BRL]

I figured if you replied at all it would go something like: "You big dummy, all you gotta do is...

I appreciate the sympathy and understanding, that thing was a nightmare!

[BRL]

Ok, I really am in the market for one of these babies!