Please help, I am at my wits end. I have a 78 F-100, 302, motorcraft 2150 2bbl. I have just rebuilt the carb, and while the truck is sitting in park idle, does fine. It idles fine and the ports open when you step on the gas. As soon as you put it in drive and drive down the road, the truck acts like it is starving for gas and dies and is impossible to crank back up. Please give me some insites of what to try. Thanks

 

Dihydrogen monoxide!!!

 

I'd suggest laying off this "joke." It is getting in the way of people trying to discuss legitimate topics.

As for the carburetor problem, what do you mean when you say the "ports" are opening? Your problem sounds like the accelerator pump is not set correctly, or not functioning. With the truck shut off, get under the hood and pull off the air cleaner, hold the choke plate open, and push the throttle. You should see two nice streams of gas spray against the venturi assemblies.

It also sounds like your float height is too low. Did you properly measure the float height when you put the carb back together? This is absolutely necessary because different carb kits have different size of needle seats, so often times you must adjust the float height for the rebuild. To double check your work, you should do a "wet check" - with the truck in park at hot idle, pull the air horn off of the carb and measure the distance between the fuel level in the bowl, and the machined surface of the top of the throttle body. The spec for this distance should be in the carb rebuild sheet. Be really careful if you do this - keep in mind the engine is running, beware of the fan, and be alert that you have an open source of gasoline exposed.

 

I just did a quick look through some of your posts and I found this! fmc400
Elder User Join Date: Apr 2004
Location: Austin, TX
Posts: 652

Quote:
Originally Posted by Centurionclassic
Could it be possible that the points are going out?



Points on an EFI?

__________________
Yes you did a one line sarcastic post. Not offering anything to the original posters question and not offering any help!!

Mtf3877 just rebuilt his carb so, I am sure he didn't rebuild it for fun! Water in a jet will cause the above problem it has a higher surface tension and when not under vacum will probably let some fuel by (enough to idle and free rev) but put it under load and the water starts getting all swirled up in the bowl and more of it blocks the jets! Mtf was the problem that lead you to rebuild the carb similar to what is happening now also? Try a couple of bottles of a dedicated gas line dryer each bottle treats 10 gals. If I were you I would double up the dosage!

 

That post of mine has nothing to do with this thread, and was made a long time ago. It wasn't sarcasm - it was meant to clarify if his system really had EFI or not. That is strange that you would look through all of my old posts like that. None of this is helping the original poster. I'm here to share my knowledge and learn from others, not get involved in arguments that make no sense. Let's get back to the topic.

 

Yes the same problem led to me rebuilding the carb. A problem I saw the I forgot to mention is when I tore down the carb there was like this dark syrupy substance in the bowl where the float is at....could this be old gas or a foriegn substance mixed in with the gas. Thank you for the quick response and I will try the tech you suggested.

 

Are you sure you don't have any enemies (sugar in the tank!) Dark syrupy could be alot of things water and rust, Dirt, old fuel. Take off the fuel filter and dump it out see what comes out of it, Get a new one and install. when the used one dries out cut it open and see what is in there. You could suction some fuel out of the bottom of the tank and put it in a glass jar see what settles out.

 

Fmc400 yes I have too much time on my hands, I just skipped around and found that.
Did you read the rest of my post, It did help the poster here. My original comment was right on topic, Water will cause the above problem! Post #5 here had nothing to do with his problem! Everyone wants to go right to the most difficult thing to prove how much they know about this part or this system, When usually it can be the simplest things, But nobody goes to that. I was not arguing at all. You attacked what I posted because you are looking to argue. I was hoping he would go read my post so I don't have to keep repeating it.

 

thank you, I will try that.

 

The dark syruppy substance can be normal in a carb that hasn't been rebuilt for a while. It is varnish caused by fuel sitting in the fuel bowl. Ironically enough, gasoline is pretty tough on neoprene and rubber carburetor parts which leads to the rebuild. Has this truck sat for a while? The carb could be pulling junk and sludge from the tank. If the truck sat for a long time and recurring debris in the carburetor becomes a problem, I'd suggest having a radiator shop flush out the gas tank, or at least changing out the fuel filter a couple times to start out with.

However, your problem sounds more related to the accelerator pump diaphragm or the float height. Did you investigate the issues I said in my first response? Bogging down off-idle is a tell-tale sign of acc. pump issues.

 

Yes the truck has been sitting up for about year. No I have not tried the what you suggested in your first response. I plan on working on the truck this weekend and try all the pointers that ya'll have suggested. Thanks

 

Did it happen to be sitting with less than a full tank? If so just do the gas line dryer might want to do a double dose or more of both types (methanol and isopropyl) Each bottle treats ten gallons. The tank sucks in outside air(with the humidity in it) overnight when it cools, the liquid in the air changes phase and sticks to the tank walls, that process repeats day after day, multiply say 2/10 of an ounce a day over 365 days and it adds up!! Just like when people say my vehicle doesn't use oil!! That is totally untrue!!
The reason the level doesn't change is because ring blowby(unburnt fuel) and condensation(if you don't run it long enough to get it hot enough to vaporize out the water) all motors let some oil by the valve seats and oil control rings!!! Another supposed myth that people ignore!! On older trucks if your dip stick has got scale rust on it you ain't runnning it long enough leading to the oil getting contaminated, change it even if it has only 500 miles on it and three months! Unless you like rebuilding that is!! Sorry for the semi hijacked thread MTF but water is a big problem especially if the vehicle isn't a daily driver. A couple of bottles of gas line dryer during oil changes(in the gas tank) will end headaches before they begin.. Whats that saying an ounce of prevention is worth a pound of cure!!