Hello all I have a 1982 F-100 and it is not running so well. It used to quit for no reason while driving down the road when you least expected it. I think I have nailed that down to fuel hoses that I have changed and at least have the front tank feeding fuel. Now it runs incredibly rich at idle and I have not been able to correct it. I have installed a shop overhauled carb (Carter YFA) 72786 and no soap I have check the all the vacuum hoses but if you pull one off it runs better. The idle speed screws is all the way in and so is the idle mixture screw just to keep it running. The plugs are black as night after idling for a short period. I have since taken a spare carb and reset the float level with very little improvement.

Is it possible for the fuel pump to be putting out too much pressure? It is new.

 

You can buy a fuel pump regulator at napa to lower the fuel pressure.

Or just put some vise grips on the rubber hose... to choke it off a little to see if it runs better.

 

I did the water pumps on the fuel hose and it smoothed right out. I will be getting a regulator tomorrow. I wonder why it ran for so many years without one?
Thanks Jim

 

First of all, welcome to our forum!

Did you replace the fuel filter? Maybe a dirty filter was restricting the flow previously, which is what you have done by pinching the fuel line.

 

I would look at the fuel filter because it could be letting little specks of rust into the carb and not letting the float needle seat. While the truck is running, take a flashlight and look down the carb throat. If you see liquid fuel dripping into the engine, then the float level is too high. If you keep resetting it and it still does this, I would suspect dirt is entering the carb.

 

Hey guys
Heres the update I purchased a fuel regulator from Checker. I tried Napa but they did not have one. Installed it with a new filter and it is doing exactly the same thing. There is fuel drops coming out in the venturi. I suppose I have to go to plan B What that is I am not sure. I guess I will have to go through the carb again or have someone else do it. It is frustrating.

 

Does the fuel come out a small brass pipe, it is about as big as a pencil lead? What I am talking about is shown at the end of the scribe in the first photo. This is the output of the accelerator pump. The second photo show the accelerator pump held in place by the 4 screws. Fuel travels out of the accelerator pump through the black hose past the check ball/weight and out the little brass pipe. There is vacuum on the bottom side of the diaphragm and fuel on the top side. As engine vacuum change, the diaphragm moves up and down. High vacuum pulls it down and the spring moves it back up.

I just failed my emissions test, it was to rich and still is…. I do understand the frustration.

 

Hello Jim
Great pictures. Mine is coming out of the orifice in the center of the venturi that can be seen in your pictures. My problem must be different I did not look at that brass tube. I want to do a proper rebuild myself and went to my local NAPA store where they never seem to have what I need. I was going to have them order the rebuild kit but they did not carry Berryman's Chem Dip carb cleaner which by the way is the only stuff that works. I have tried there brand of cleaner and if you immerse the parts in it overnight they come out with varnish and soot still on them. The damn stuff does not work. If I can't clean the parts then there is no sense in getting the kit.

I am sorry you live where they impose that ridiculous emission testing on you. I live out in the boon docks. When the tree buggers finally get their fee collecting emission station set up here I will be giving the truck to Junk for Jesus and buying a 1940 or 1950 vintage truck that is not required to be tested. My daily driver car is a 1960 Sunbeam Alpine. I will never buy a vehicle that is required to be tested ever again. If you look inside the carb from a vintage truck it has half the gizmos to go wrong.

Good luck with your carb I hope you can get through that ridiculous test.

Before I die I would like to rig a smoke oil system in a car and when they have me run on the testing drums that spin the wheels I'll hit the smoke oil pump and turn there station into an opuim den at rush hour.

 

On your carb it could be something as simple as a dirty needle and seat… or maybe a float adjustment

Thanks for the tip about the carb cleaner, as you might have noticed from the pictures I have not cleaned the carb I just got at the junk yard. I was thinking about attempting an MEK soak as I have a gallon of the stuff on hand.

The carb I currently have on my 1986 F150 is off an 84 I think as it doesn’t have a Throttle Position Sensor (TPS) like the original carb did. I had to replace the original carb as it was spitting/pissing gas out the accelerator tube. Never did figure out why, the diaphragm looked good.

I have not fully given up on the 1984 feedback carb I am currently using. It is freshly rebuilt carb that I bought off Ebay for $50… that was before I realized I didn’t want another feedback carb and it also explains why no one else bid on it. I might try lower the needle into the main jet to see if the reading on the O2 sensor get better.

I have been experiment with the solenoid on the feedback carb that controls rich/lean. When the solenoid is energized it is lean, too lean. I have installed a push button switch to energize the solenoid and I can then rapidly push the button while I watch the voltage reading of the O2 sensor to control the mixture.
I have order some parts to make pulse width modulated signal generator circuit which will pulse the feedback solenoid. The end result should be an adjustable mixture control from the cab.

This is my last emission test as they are only done ever 2 years and they only go back 25 years. We are the only county in eastern Washington that does testing so there is still as resale market for cars that fail in the other counties. In Western Washington most all of the counties do testing and the car is basically worthless if it fail as it is not usually cost effective to fix it.

Jim

 

The adjustable mixture sounds like fun, Will it adjust during cruise power settings on the long stretches of highway? I have always thought I'd like to have a EGT (exhaust gas temp) gauge and a mixture control coupled with a cruise control. On long flat stretches of highway one could lean to peak and get the best MPG.

 

I mostly plan on using the mixture control on those long flat highway trips, kind of like you would do in an piston engine airplane in cruise.

It will also be helpfull to lean out the engine in the high mount passes.

 

I finally got it fixed. I took the latest rebuilt carb apart and cleaned it and blew out the passages then lower the float level slightly and it runs better than it has in years.

I searched and searched on the web for the published float level. It seems it is a top secret ultra classified bit of info. I cannot believe someone has not published the specs and overhaul data on these carbs. They just want us to buy the bloody manual that we don't need. Full of valuable info like don't squirt gas in our eyes. Don't smoke around gas. Arrrggg!!

Why don't we publish these manuals on this web site?