| 47Jack | -- 02-15-2011 @ 9:06 AM |
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I drove my 47 truck yesterday as the weather was quite mild. The carburator floods when the engine first shuts down. I've asked about the carb before and tried suggestions about tightness of the power valve and TomO's suggestion of letting the carb sit overnight to see where it leaking from. No leaks when sitting. The power valve gasket is correct and torqued to 15 ft. pounds. My question:, is it possible to be overpressurized by the fuel pump? The only time this floods is when the engine is first shut off. I'm running a 91-99 carb and I believe the engine is a 39-41 as it had a double dome dist and generator with fan on it when I got it. Thanks in advance........Jack
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| supereal | -- 02-15-2011 @ 10:59 AM |
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The normal fuel pressure to the carb shouldn't exceed 3.5 to 4 lbs. Most mechanical pumps won't exceed that, but some electric pumps produce 5-6 pounds. As your problem seems to occur after the engine is shut off, and you smell gas, it is likely that "heat soak" is causing the gas in the carb bowl to boil. You can minimize that by being sure the float level is correct, and the float needle is seating properly. If you see gas on the outside of the carb, check to see that the gsaket surfaces are clean and true, and the screws holding the carb together are not so tight that they squeeze the gasket out of place. Also be sure that the internal parts of the carb are in place, and not overtightened. We have lessened heat soak somewhat by placing a couple of extra gaskets between the carb and the manifold, and by blocking off the heat passage under the carb. Finally, it is possible that hard starting after shutdown may not be fuel related. The heat soak also affects the coil, reducing the spark. Be sure the choke is fully off, and avoid pumping the gas pedal before starting. Poor spark will produce flooding that may be blamed on the fuel system.
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| 47Jack | -- 02-15-2011 @ 11:42 AM |
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Thanks Supereal for your reply. I forgot to mention that there is a governor but I removed the throttle plates in it some time ago. I also didn't mention that the fuel is running over on the outside and probably on the inside. It seems to be coming out of the axle for the throttle plates. After about fifteen minutes and the gas evaporates it starts right up. I'll double check the float height and needle valve. This carb did the same thing before I rebuilt it and I was hoping that the rebuild would correct the problem. Thanks again
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| JM | -- 02-15-2011 @ 8:21 PM |
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It would be a good idea to actually check the gas line pressure between fuel pump and Carb. Some of the new replacement mechanical fuel pumps put out too much pressure, sometimes much more than the stock carbs can handle. Also, some FP rebuild kits have springs that cause much higher gas pressure than stock carbs can handle. JM
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| TomO | -- 02-16-2011 @ 9:06 AM |
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If your fuel is running over on the outside, your float could be too high or the needle valve could be sticking. When you check your float, make sure that the gauge is held perpendicular to the casting and check both sides. If your float level is correct, check the float for leaks by dropping the float in water that is close to the boiling point and watch for tiny bubbles. If you see any, your float is leaking. The tang on the float could also have a indentation that will keep the needle valve from seating. Ford fuel pumps provide 2 /12 to 3 lbs of pressure at the output. More than 3 lbs can cause flooding problems. Less than 2 lbs can cause vapor lock. Pressure is controlled by the diaphragm return spring. Tom
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| supereal | -- 02-16-2011 @ 9:31 AM |
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Fuel leakage outside the carb almost always indicates a fault in the casting such as warping or cracking. Any leaking around the throttle shaft confirms wear. We always rebush that when we do a rebuild. You can check for warping by placing a piece of fine emery paper on a sheet of glass, then rub the gasket surface on the paper. Any voids will quickly show up. Internal cracks are not rare, as the body of the carb is made of diecast metal. Gasoline has a very low surface tension, and will easily leak from places that water wouldn't. The surest way of narrowing down your problem is to try a known good carb.
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| 47Jack | -- 02-16-2011 @ 3:13 PM |
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Thanks all of you and I will use your advice when it gets warmer and let you know the results. Jack
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