hello All,

I have an 84 F-150 with a 300 straight six in it. It has the Motocraft single barrel. I've put 2 kits in it as well as replaced the fuel pump.

When I let the truck sit overnight all the gas seems to drain out of the carburetor so it takes forever to start. If I manually add a little, it fires right up.

My thinking is for whatever reason it's allowing the gas to drain out and I just don't seem to be able to find why. Also, I really don't care for not being able to do any adjusting on it and It's always ran way too fat.

I was thinking about getting another carburetor that would just bolt on to my current manifold, that is both reliable and fairly inexpensive, but also includes some adjustments. Any Ideas? Maybe a single barrel Holley of some sort?

Thanks
Eric

 

One question comes to mind and that is , the automatic choke. Is it closing completely when the engine is cold?

 

Thanks for the response hanky,

No it isn't. I have played with that damn thing, but I just don't seem able/competent enough to get it to behave like it should. It is either closed and won't open, so it lopes like hell after it starts, or it's open and won't close, but it's not sticky in the least and the little vacuum pod on the side moves the butterfly like it should.

The pipe that heats the spring in the choke seems intact.

Maybe I'm setting it wrong. With the engine cold I loosen the 3 screws on the plastic cap at the back, then turn it just till the butterfly closes, but it never opens. I've tried backing it off a little bit, but once it opens, it never closes. Again, it's not sticky in the least.

However, should the carburetor be running dry after one night? The damn thing runs fantastic once it starts, it's just stubborn as hell trying to get it there.

 

I'm not sure the carb is running dry.
When cold, the choke should snap shut when the throttle is opened. If it doesn't loosen the three screws and rotate the black bakelite piece until it does. If the choke heat tube is open then there is an opening in the choke body that pulls the heated air through the choke housing and causes the spring to open the choke.
I don't remember if the choke is heated electrically, but if it is, then maybe there is a problem either with the electric heating element or the supply of voltage to the heating element. Which system do you have ? In either case the choke pull off when adjusted properly will crack the fully closed choke open to allow the engine to run smoothly as the choke warms and opens. The pull off is vacuum operated and could have a leak and be defective.
I've given you plenty to check, let us know what you have and found.
If you remove the black plastic choke cover you will see a hook on the end of the spring.That hook has to catch the choke arm in order to work properly.

 

To be honest with you, I'm not entirely sure it draining either, but I do know that if I dump a little gas down the Carb it fires right up.

As far as the choke goes it's not an electronic heater I don't think, I'll have to check to make sure, but I'm pretty sure it get's it heat from the exhast manifold, but again, I may be completely wrong, I'll have to trace it.

I probably didn't make it clear in my first post, but yes, the hook is positioned properly to catch the choke arm.

Here's how I've been setting it.

I loosen the 3 screws on the choke spring cover, while it cold I turn it just until the choke snaps shut, then I re-tighten the screws down. If I do it like that the choke will never open once it warms up. Is that the proper way to set it?

Thanks for the help
Eric

 

Every time we write this we find something was left out.
You need to open the throttle slightly for the choke to be free to set when cold. As long as the choke butterfly is free and can rotate freely , slightly open the throttle then rotate the black plastic cover until the choke is closed against the opening. There is a suggested setting for the choke pull-off . It is usually listed in the overhaul sheet for that particular carb #. If you bottom the diaphram of the choke pull off it should open the choke butterfly to the desired opening listed on the sheet. The pull off is stronger than the choke coil and should open the choke so the engine will run smoothly until it gets heated and opens from the heat.
If the heat tube isn't open to allow heat from the manifold to open the choke there may be a blockage in the choke body because engine vacuum pulls the heated air from the tube into the intake and that is how the heat gets to the coil. Does the coil get hot at all?

 

sounds like maybe the fuel pump is not holding the pressure up to the carburetor !

 

I was wrong, the carburetor was not draining like I thought. After much tweaking this weekend, I finally got the choke to work. It runs a little crappy for the first minute or so while the choke is warming up until the butterfly opens (probably need to back it off just a weebit,) but it starts right away even after it's sat for several days.

Thanks for the help on that Hanky.

One more small inquiry, I have always had a problem with this carb loading up and destroying my ability to lug worth a crap. I notice there aren't any Jet screws on it, or at least I can't find any, and from what I've read that's by design. It's in desperate need of leaning out but I have no idea how I'm supposed to do that.

Is there a way?

Again, thanks for all the help.

 

I think what you are referring to is the idle mixture adjustment screw. There should be a mixture screw to adjust, you just need to look around to find it. It should be located on the lower part of the carb very possibly on the rear. Some had plastic caps on them to prevent tampering, but they can be removed with a pair of side cutters. I wouldn't try prying the plastic off because you can damage the screw which has a very fine thread to get a decent adjustment. If you still have the ovhl kits there should be a pix of the carb and it may even point to the location of the mixture screw.
The screw is adjusted by turning it in until the RPM drops some then turning it out until the RPM is affected then placing the screw at the midpoint of those two positions.

 

If this is the original carb, they had a metering rod if memory serves correctly. This was a common complaint (low/no power) when the rods were adjusted too low. If they go to teh other extreme, they run too fat.
Another problem that ALL these engines had (which were probably one of the best ever built) was that the intake and exhaust manifolds would crack and leak under the carb (it's where the two manifolds bolted together), and this would cause low vacuum and many of the problems you've mentioned. I've replaced many of these manifolds and solved a lot of problems that people kinda 'always had' with the truck. It's worth a look.