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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

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Old 07-12-2014, 09:23 PM
tylerz71 tylerz71 is offline
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Way too much fuel!

81 F100 4.9 1bbl carter yf. Truck ran great til I changed fuel filter it seems like. Then it started dumping fuel. We rebuilt the carb with a new accelerator pump and all the other small items in the kit. Took the time and thought it was done right. We did not set the float because it seemed to be in good position. New needle and seat. Reinstalled and now still getting way too much fuel. It's spitting it out of the tube on the top of the carb while I pump the throttle to get the truck to start. Took plugs out and cleaned them and cleared cylinders.
When I pinch off the fuel line the truck runs decent. I drove it around the yard like that.
Can you guys tell me what to try next? I am a paycheck away from chunking the carb and getting a reman for $200 off rock auto. I don't want this thing to wash my rings out.
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Old 07-12-2014, 11:41 PM
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Gary Lewis Gary Lewis is offline
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I wish I had a silver bullet for you. But I don't. However, if you are getting way too much fuel the there aren't that many possibilities. Here are some:
  • Float sinking: Sometimes the floats sink. Brass ones can get filled with gas and plastic one can absorb gas. That causes the float level to raise and fpgas goes everywhere.
  • High pressure: YFA's aren't known to be finicky about pressure, but your trick of squeezing the fuel line suggests the pressure is high. Perhaps a bad pump can do that, but I don't see how.
  • Float level: Maybe you didn't get the level right?
  • Wrongly assembled:
  • Dirt: Dirt on the needle will do it, but you changed the needle and seat. Right?
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Old 07-12-2014, 11:51 PM
tylerz71 tylerz71 is offline
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This float is brass; we water tested it and there were no holes no bubbles so it seemed to pass inspection. Needle and seat are new yes, and new spring inside the needle which felt better than the original one. If the pump was new I would say that is likely the cause too much pressure but it looks old and has been there since I bought the truck. I went from a see through dirty filter to a $.80 metal Delco filter and its like I removed the form of fuel regulation from the system. Lol I will have to probably disassemble it yet again and look for any issue but I doubt I am enough expert to find anything.
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Old 07-13-2014, 05:01 AM
oneowner83 oneowner83 is offline
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From your description it sounds like you're pumping the throttle too much. All it should need is at most one or two pumps, then let it alone to try to start. That's if all else is ok. I'm just thinking you're introducing too much gas and flooding it. You do know how to start it if flooded??
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Old 07-13-2014, 07:48 AM
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I hate to tell you, but it is something wrong with the float system. You are going to have to keep messing with it till you figure it out.

I have done the same as you, and had the same problem, and after I took the carb apart and pulled the needle out, I looked down in where the needle went and there was a little chunk of rubber down blocking it from closing. The fuel line I had made had a sharp place on it, and just by sliding the new piece of fuel line up on the metal line, it had shaved a little chunk of rubber off the line and that had gotten up in there and fouled it up.

I would take it apart again, for some reason the float/needle system is not working.
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Old 07-13-2014, 08:40 AM
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It really has to be something simple like Dave is saying. And you are going to know it when you find it.
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Old 07-13-2014, 10:03 AM
tylerz71 tylerz71 is offline
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Alright I will tear it back down. Do I need to take it off of the intake again or is it common to disassemble it while attached?
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Old 07-13-2014, 10:14 AM
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Alright I will tear it back down. Do I need to take it off of the intake again or is it common to disassemble it while attached?
If you are VERY careful and don't drop any screws down in the engine, you can take the top off on the carb on most of them while it's still on the engine.
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Old 07-13-2014, 01:24 PM
tylerz71 tylerz71 is offline
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I pulled it off while on the motor it was easier that way it seemed. Inspected everything involving the needle the seat and float. Found no trash or obstruction. Even bent the float downward to make it float higher.? Put it back on the truck and same condition as soon as I un pinch the fuel line it sprays fuel out and dies. This thing is beyond me
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Old 07-13-2014, 02:43 PM
Widetrack455 Widetrack455 is offline
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Look down the throat of the carburetor while it is idling. If you see fuel dripping from the accelerator pump output port there is something wrong with the accelerator pump circuit. When idling there should be no fuel coming from this port. The possibilities are: bad accelerator pump, linkage or output check ball and brass weight. There is a possibility like what I just experienced that the check ball is not seating. In my case the wrong size check ball had been installed at sometime before my ownership and wouldn't seal the port. Take a look at the exploded view from the carburetor kit to see where these parts fit. Fortunately the NAPA carb kit I bought had the correct check ball. The NAPA kit was $29.00 vs the typical $18 to $19 cost at other parts places. I'm not saying that the kits from other places have incorrect parts. Just saying the NAPA kit had the correct parts.

If your accelerator pump diaphragm is ruptured the manifold vacuum that is present on the bottom side of the accelerator pump diaphragm and which pulls the accelerator pump down into the pump well will pull copious amounts of unmetered fuel straight into the intake manifold. There is also the possibility that your accelerator pump isn't properly seated in the pump well and thus leaking. Any time you mess with the accelerator pump you need to properly readjust the metering rod and insure all parts are in their correct position. Again refer to the carb kit instructions for your application. There is a youtube video demonstrating how to test the accelerator pump function while the carburetor is on the bench. It is very helpful.

Credit Mike's Carburetor for this very instructive video!!

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Old 07-13-2014, 02:56 PM
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Reps to you, Poncho. . I'm guessing accelerator pump. Blown or a check valve missing.
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Rusty: '81 F150 Ranger XLT 4x4 w/a 351M, RV cam, Performer carb & intake, C6, & 3.50's
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads, Weiand intake, Street Demon 750/ZF5/3.50 gears w/Kevlar clutches
1969 Super Bee awaiting restoration
1950 Chevy 3100 in queue
Worst fear: I die and my wife sells my rides for what I've told her I have in them.
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Old 07-24-2014, 09:43 AM
tylerz71 tylerz71 is offline
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Guys... I just spent $200 on a reman from rock auto. It looked good, I installed it and same old thing. Truck ran smooth for about 3 seconds then it spit fuel everywhere and there was a puddle under it on the manifold. What the hell? Now that carb is ruled out (aside from minor adjusting) what should I look at next? Fuel pressure?
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Old 07-24-2014, 09:58 AM
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Check the return line to the tank. Might be plugged or pinched shut. Fuel pumps put out volume not pressure. All good fuel pumps will create more volume than the engine needs to operate. The excess has to be returned to the tank or it will create sufficient pressure to lift the needle off the seat. That's why pinching the fuel supply line "fixes" the problem. Let us know how it turns out.
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Old 07-24-2014, 10:56 AM
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Quote:
Originally Posted by cliff_mennenger View Post
Check the return line to the tank. Might be plugged or pinched shut. Fuel pumps put out volume not pressure. All good fuel pumps will create more volume than the engine needs to operate. The excess has to be returned to the tank or it will create sufficient pressure to lift the needle off the seat. That's why pinching the fuel supply line "fixes" the problem. Let us know how it turns out.
No return line on his truck. Only some of the 460's had a return line system.
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Old 07-24-2014, 10:56 AM
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Quote:
Originally Posted by cliff_mennenger View Post
Check the return line to the tank. Might be plugged or pinched shut. Fuel pumps put out volume not pressure. All good fuel pumps will create more volume than the engine needs to operate. The excess has to be returned to the tank or it will create sufficient pressure to lift the needle off the seat. That's why pinching the fuel supply line "fixes" the problem. Let us know how it turns out.
Fuel injection uses a return line to tank. Carbureted does not need one. the Fuel pressure is much lower (5 to 6 psi is all that is needed).

You should have a vent tube on the carb (at the top of the bowl). Remove this line and make sure it is not clogged (also if fuel comes out this tube while engine is running it tells you the float is not working/set properly). If the bowl vent is clogged air above the fuel level in the bowl can't move properly and this can cause problems.
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Old 07-24-2014, 10:56 AM
 
 
 
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