Author Topic: unusual fuel leak problem (Read 1124 times)

SAC69 · « **on:** August, 03, 2009, 08:22:18 PM »

A few months ago, I installed a dual-feed Holley carb that I rebuilt. The other day I noticed fuel leaking from the inlet-to-carb fittings so I removed the carb, removed the inlet line and resealed the thread connections. After reinstalling the carb and starting up the engine, fuel began to spray out the connection from where the rubber hose meets the hard line coming up from the fuel pump. The worm clamp was tight but fuel somehow worked its way backwards out. The fuel pressure gauge at the inlet to the line reads a steady 5psi.

I walked away, came back a 1/2 hr later and restarting the engine, the leak was gone. A test drive of several miles did not produce the leak and everything seems ok now.

Was there a air bubble in the fuel inlet line that occurred, somehow forcing the gas out the inlet connection, yet still allowing the engine to run? Or is there a significant problem with the carb itself that warrants replacement. I don't want to be driving and have the leak start up again spraying gas over a running engine.

Thanks for any info.

AzPete · « **Reply #1 on:** August, 04, 2009, 06:00:26 AM »

I would say that leak may come back. Sounds like you need a flared bubble on the pipe to get a better seal. I would fix it for sure. I don't see a carb problem....

SAC69 · « **Reply #2 on:** August, 04, 2009, 06:51:43 AM »

Thanks for the response. The metal line is the original piece (fuel pump to carb area) with the flared end.

AzPete · « **Reply #3 on:** August, 04, 2009, 06:54:19 AM »

I would replace the rubber line and clamps as a minimum.

95GT · « **Reply #4 on:** August, 04, 2009, 07:39:15 AM »

If it were me I would not take a chance. I would replace both the hard line and the rubber line. Burning gas can make a real mess out of an engine compartment. :yikes

70_Fastback · « **Reply #5 on:** August, 04, 2009, 09:16:58 AM »

What, if any, are some other alternatives to the standard hard line to rubber line set-up?

That's what I have right now, a rigid 3/8" line from the fuelpump up to with-in 1" of the carb dual-feed, flared, inlet. With a piece of 2" or so flexible fuel line connecting the cut (not flared) hard line to the flared Holley dual inlet. It's all double clamped as well.

I just don't really like the look of it that much.

silverblueBP · « **Reply #6 on:** August, 04, 2009, 10:23:27 AM »

Here's what I did

Bought the T and gauge from Jegs and found the brass fitting at the local hardware store.

70_Fastback · « **Reply #7 on:** August, 04, 2009, 10:45:11 AM »

I thought I remember seeing that Pete had some cool braided line or something coming up from the fuel pump?

AzPete · « **Reply #8 on:** August, 04, 2009, 11:10:26 AM »

PO had installed this cool braided line .......until you look close and find it to be rubber line with the fake braid over it and fake ends. I still am running the rubber line, just removed the fake braiding.....

70_Fastback · « **Reply #9 on:** August, 04, 2009, 11:28:17 AM »

Oh.

Well dat ain't so cool now. :mj

SAC69 · « **Reply #10 on:** August, 04, 2009, 11:55:13 AM »

I replaced the 3" of rubber line and the two clamps already. Unfortunately the '69's do not have a threaded nut attaching the hard line to the carb, it's a small section of rubber hose so to eliminate that, I'd need to run braided hose up the carb feed line.

silverblueBP · « **Reply #11 on:** August, 04, 2009, 12:12:41 PM »

Quote from: SAC69 on August, 04, 2009, 11:55:13 AM

I replaced the 3" of rubber line and the two clamps already. Unfortunately the '69's do not have a threaded nut attaching the hard line to the carb, it's a small section of rubber hose so to eliminate that, I'd need to run braided hose up the carb feed line.

That's why I made the line.

Fast68back · « **Reply #12 on:** August, 04, 2009, 04:03:29 PM »

Bought mine as a kit from Summit

mach514 · « **Reply #13 on:** August, 07, 2009, 07:07:11 PM »

I use the same set-up as fast68back and it has never been a problem and it looks cool to!

KBMWRS · « **Reply #14 on:** August, 17, 2009, 01:31:51 PM »

Mine is like 68Fastback's...with in-line filter.

Meyer65 · « **Reply #15 on:** August, 17, 2009, 01:48:46 PM »

Is it possible that the hose is not slid back far enough on the hard line?

lethal289 · « **Reply #16 on:** August, 17, 2009, 05:12:23 PM »

Quote from: KBMWRS on August, 17, 2009, 01:31:51 PM

Mine is like 68Fastback's...with in-line filter.

And a piece of duct tape too. Thats trick mike :rofl :pep.

SAC69 · « **Reply #17 on:** August, 17, 2009, 07:57:40 PM »

Well, the leak stopped on it's own accord and after further reflection, I realize (like an idiot) why it occurred. I was using a 3/8 rubber line to mate a barbed 3/8 carb inlet line to the stock 5/16 steel line. The 5/16 is, of course, slighly smaller diameter than the 3/8 rubber line and the fuel was able to move backward (!?) past the clamp. Fortunately, it stopped for now but I spent a better part of a day futilely hunting for a barbed reducer 5/16 to 3/8. I need a full 3/8 hard line or braided line from the pump to the carb at some point and will do a custom (aka "trick") routing along the driver valve cover around the back of the carb and move the dual inlet feed to point at the firewall. It will thus keep the fuel line from snaking across the front of the engine and clean up the appearance a bit.

Thanks for the tips.

KBMWRS · « **Reply #18 on:** August, 18, 2009, 06:25:54 AM »

Quote from: lethal289 on August, 17, 2009, 05:12:23 PM

And a piece of duct tape too. Thats trick mike :rofl :pep.

Actually that's heat wrap around the heater hose. I had been having problems with fuel vaporization and I was trying anything to keep the heat away from the fuel line. That's why the fuel line is not the stock hard line against the block. Final fix was heat wrap around the exhaust pipe under the drivers side. The hard fuel line is within an inch of the exhaust there pre-heating the fuel nice and toasty. :expl

70_Fastback · « **Reply #19 on:** August, 18, 2009, 07:55:52 AM »

Does it work?

KBMWRS · « **Reply #20 on:** August, 18, 2009, 08:03:07 AM »

The wrap around the exhaust finally fixed my stalling problems when the outside temps exceeded 90F. The engine ran fine but if you dropped to idle it would starve. My guess all along was fuel being too hot (390s put out a lot of heat). I started with a carb spacer, move the fuel line, add the piece of heat tape near the heater hose. Last fix was the wrap on the exhaust. That did the trick. It idles now even when its very hot outside and its been running highway speeds. Starting again still is a chore but its manageable.

70_Fastback · « **Reply #21 on:** August, 18, 2009, 10:26:54 AM »

Interesting. When I R&R'd my 347, this last round, I formed and installed a new hardline from the fuel pump to the dual carb inlet lines. But I changed my routing and ran the line up, behind the power steering pump right next to the block & heads. I now notice a miss, or sudden "drop" when it starts to get pretty hot udner the hood.

Could this be a similar issue? Causing this little "miss" or hicup as one may call it. It's like it loses fuel for just a nano-second, causing a little noticeable sputter.

KBMWRS · « **Reply #22 on:** August, 18, 2009, 11:08:25 AM »

That's it.
Does it idle okay when hot or after a long run in the heat?
check to see how close the line gets to the exhaust on its route.

70_Fastback · « **Reply #23 on:** August, 18, 2009, 11:16:39 AM »

No, I don't notice it at idle at all.

silverblueBP · « **Reply #24 on:** August, 18, 2009, 11:24:49 AM »

Quote from: 70_Fastback on August, 18, 2009, 10:26:54 AM

Could this be a similar issue? Causing this little "miss" or hicup as one may call it. It's like it loses fuel for just a nano-second, causing a little noticeable sputter.

That or your timing chain is coming apart :boo

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Author Topic: unusual fuel leak problem (Read 1124 times)

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