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Discussion Topic:
Dual Carbs & vapor lock
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nelsonford |
04-21-2013 @ 1:03 PM
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Member
Posts: 52
Joined: Nov 2009
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I have had Dual Carb (94's) with the Ford mechanical pump on my 48 Merc for years and resently started having trouble with Vapor lock. With clear plastic fuel lines I can see the bubbles form and not allow gas to flow. I am trying to eliminate all the possible problems. I have a fuel regulator and am wondering if I need it and whether it may be plugged. I don't want to use an electric fuel pump unless absolutely necessary. I am installing a pressure gauge between the pump and fuel block. I will insulate fuel lines better and put shields where needed. Any suggestions?
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supereal |
04-21-2013 @ 2:24 PM
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Senior
Posts: 6819
Joined: Oct 2009
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Most "vapor lock" isn't. It is more likely that you have an air leak between the tank and the engine. We are seeing more fuel problems with ethanol added, and if you have any non-resistant rubber parts in the system, one or more may have been attacked. This includes the fuel pump diaphragm and valves. If you have any inline fuel filters, particulary made of plastic, look for cracks. Even though you see bubbles in the line, a failing coil or condenser will produce symptoms oftem mistaken for "vapor lock", as will a cracked flex line at the firewall
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nelsonford |
04-21-2013 @ 2:33 PM
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Member
Posts: 52
Joined: Nov 2009
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Thanks Supereal, I will look for possible leaks...One thing that comes to mind is the glass fuel pump bowl gasket. I understand it should be neoprene rather than cork.
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supereal |
04-22-2013 @ 6:15 PM
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Senior
Posts: 6819
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Could be either. Most were originally cork, which tended to dry out and split. If rubber was substituted, be sure it is nitrile, which is alcohol proof. If the gasket is leaking, you probably found the source of bubbles.
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TomO |
04-24-2013 @ 7:31 AM
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Senior
Posts: 7256
Joined: Oct 2009
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The rubberized cork gasket material sold by Fel-Pro works great as a gasket for the sediment bowl.
Tom
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nelsonford |
04-25-2013 @ 4:37 AM
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Posts: 52
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Tom Rubberized Cork sounds like a great idea. I'll give Felcro a try. Thanks again
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nelsonford |
04-25-2013 @ 4:52 AM
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Member
Posts: 52
Joined: Nov 2009
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I also checked and found the line runs within a few inches of the exhaust pipe and muffler. I am ordering some tubing good for 750F from Napa made by "thermosleeve" ($7/ft) which I will slide over the line. I can also put heat shields on the pipe.
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joe b |
04-25-2013 @ 6:39 AM
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Member
Posts: 389
Joined: Oct 2010
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While you are at it you should replace the plastic fuel line to the carbs. Plastic fuel lines are just waiting for an under hood fire.
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Old Henry |
04-25-2013 @ 8:13 AM
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Senior
Posts: 738
Joined: Apr 2010
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The way I finally diagnosed vapor lock as my problem was every time I had a problem I poured cold water on my fuel pump and it fixed the problem. As soon as I became a "believer" in that phantom vapor lock I installed a backup electric pump back by the gas tank to switch on whenever the engine sputtered, died, or wouldn't start and it fixes it every time. It could be any of the other things suggested but don't discount vapor lock as the real problem easily diagnosed and easily fixed. Old Henry (The older I get, the better old looks.)
This message was edited by Old Henry on 4-25-13 @ 8:16 AM
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supereal |
04-25-2013 @ 9:44 AM
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Senior
Posts: 6819
Joined: Oct 2009
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I went thru that whole thing OH. As the problem got progressively worse, I decided to check the only part of the fuel system that I hadn't tackled: the fuel line between the tank and the firewall. I found it to be almost completely blocked with dirt and rust. What fuel did get thru seemed adequate, but on a heavy pull, it wasn't. My electric pump would smooth out the bucking, etc, until there was no more room in the line. Twenty bucks for a new line finally fixed it.
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