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Discussion Starter · #1 ·
Noticed today that the mechanical fuel pump is squirting fuel out of this hole when running:
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Does anybody have any idea as to what that hole is even for? I plugged it up for now to stop the leaking, but would certainly like to find a permanent fix.
 

· 47 Plymouth Special Deluxe
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Noticed today that the mechanical fuel pump is squirting fuel out of this hole when running:
View attachment 628473

Does anybody have any idea as to what that hole is even for? I plugged it up for now to stop the leaking, but would certainly like to find a permanent fix.
That is called a weep hole, it is there to indicate a diaphragm failure. Time for a new fuel pump.
 

· 47 Plymouth Special Deluxe
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Ok. Will get right on it. Pump is probably 6 months old. I thought that Made in USA stuff is supposed to last.
Also, what a brilliant design - let's start squirting fuel all over the rad fan whenever the diaphragm starts to fail. That will get their attention!
I feel your pain, I replaced two defective/failed 'weepy' Holley mechanical pumps in a six month period on my 56 Chevy. Fortunately my local speed shop (Gotellis in SSF, CA) covered them both under warranty. Still mighty ridiculous.
 

· More for Less Racer
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There should be no fuel above the line where the upper and lower halves of the pump body are screwed together.....so obviously the pump diaphragm is leaking / torn / pinhole.
If it is managing to come out that small hole , that means it is also being pumped into the crankcase since the opening to the pushrod side is a hundred times bigger.
Check your oil for being fuel contaminated now.

The parts of the diaphragm edges you can see outside the housing do look a little swollen and ragged.
Possibly ethanol exposure incompatible?

it's a rebuildable pump, you can get a kit to replace the pump diaphragm.....rather than just replacing the pump.

Pump looks like it follows the original Carter design. Everybody makes a clone of it. Originally based off a early Corvette pump.

Carter 888562 Carter Fuel Pump Rebuild Kits | Summit Racing

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When you tear apart the pump check the inside for casting defects/cracks.

Lets say there are 6 in a mold and a ram injects aluminum into the mold. If there are any voids CRACK, then the thing is pulled from the mold and thrown into a vat of water/oil if it slams the side of the vat on the way in CRACK, up some type of belt to a press where the channels between the pumps that allowed the liquid aluminum to flow to all the pumps are sheared off, if the 6 are not set into the press correctly two may be destroyed but that will also pull the other 4 making a less noticable CRACK, removed from the press they are sometimes set in a box but usually thrown into a bin(more dent then crack) .

The tops follow the same basic pattern and the two pieces (5-7pieces total) are usually assembled off site. There may be some slag/trim removal or cleaning but for the most part stress cracks can easily happen.

If the part is coated so it looks like chrome thats may reveal cracks or voids before assembly. But if just raw aluminum things can get overlooked.

So it could be a cheap easy to replace diaphragm. But I am leaning towards the posiblity if a casting crack at or near that weap hole or next to the edge of the diaphragm. If you bolt a new diaphragm in and it still leaks then that will confirm a crack even if it is easily overlooked.
 

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Discussion Starter · #13 ·
Does anybody know what fitting I need for this? The thread is 1/2 - 20 and the only way I was able to figure it out is by finding a bolt at a hardware store that threads in. There are no 1/2 - 20 to hose fittings. What am I missing?
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Did the brass 90 (from the old pump) not thread into the new pump?

Use a bit of #2 permatex aviation sealant on the threads. Let it get "tacky" then install it before letting it sit 24 hours before putting fuel through the pump.


If you need a new fitting then most manufactures or sellers of the pump list the thread on the specifications page. Just need to know the model number etc and it is a simple search in most cases.
 

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Discussion Starter · #17 ·
Does anybody know what fitting I need for this? The thread is 1/2 - 20 and the only way I was able to figure it out is by finding a bolt at a hardware store that threads in. There are no 1/2 - 20 to hose fittings. What am I missing?
Did the brass 90 (from the old pump) not thread into the new pump?

Use a bit of #2 permatex aviation sealant on the threads. Let it get "tacky" then install it before letting it sit 24 hours before putting fuel through the pump.


If you need a new fitting then most manufactures or sellers of the pump list the thread on the specifications page. Just need to know the model number etc and it is a simple search in most cases.
The old pump is an edelbrock and has a bigger fitting. Does not fit. No auto parts store knows what fitting it uses.
 

· More for Less Racer
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Does anybody know what fitting I need for this? The thread is 1/2 - 20 and the only way I was able to figure it out is by finding a bolt at a hardware store that threads in. There are no 1/2 - 20 to hose fittings. What am I missing?
View attachment 628490
The tapered face in the back of the hole identifies this as an inverted flare, like steel brake or fuel line.
5/16" steel fuel tubing has 1/2-20 threads on the nut.

Original application would have had a steel hard line, bent 90° as close to the nut as possible, so that the line goes up the front on the engine in front of the passenger side head / behind the alternator.

If you want just a hose barb, it will be 5/16" male inverted flare to 5/16" hose nipple adapter fitting..
Any place that makes hydraulic lines should have the fitting.

Any auto parts store decently equipped should have also had it......but things today aren't what they once were as far as inventory on hand....
 

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Looking at the old pump in the first picture I don't think he has room for a straight barb.

He may have room for a piece of 3/8 tubing that turns around 120 degrees back towards the crank then goes up and after a few more bends goes into a carb. Need the flaring tool and highly recommend 3/8" nicopp due to all the bending that will be required.

Or just use a stock line which probally has the correct fitting and bends for a stock intake/carb. I would make room for the stock line with a BFH. But that's me.
 
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