Greetings, all. I have a 1983 ford F100 I6 300 that I am working on with my grandfather. We had the engine rebuilt, a remanufactured carb installed, and it was cherry until about a month ago. It began idling very rough, black smoke would exit the exhaust and the cat got red-hot. So we sent it back to the mechanic, and he fixed it well enough to get it to idle, but he blamed the carburetor for being too rich. However, we took it to the carburetor shop, and nothing was wrong with it, and it was properly adjusted. All the vacuum lines are connected/there is no vacuum leak, yet when I remove plugs from the tree, the engine smooths out, and the revs increase. We are now stumped as to what to do now. We will take It back to the mechanic once he returns from vacation, but we are trying to see what we can do here. I have searched the forums but all that I could find were members suggesting to check the vacuum lines. Perhaps it is the EGR valve? Any advice would be much appreciated.

 

Welcome to FTE

You'll have to get into the carburetor, it may be flooding out (float level?) Hard to say from a distance. Crud in the lines may have caused the carb needle and seat to fail?

 

Check vacuum source for distributor, it should be on "manifold" ...

 

We had the carb-mechanic take a look at the carb, and he couldn't find any issues with it. He believed the timing may have skipped a tooth however, I do not believe these motors can do that, unless I am mistaken?

 

I have it connected to the "manifold", which is right above the vacuum tree on this CARTER YFA. It is NOT connected to the tree.

 

has anything on the engine ever been modified to your knowledge? how much high do the rpms increase once you've pulled plugs? does the engine temp increase in addition to the exhaust? any noticeably foul smell from exhaust? what do the spark plugs look like?

 

Only general maintenance: Plugs, wires, dizzy cap. The new plugs in there and the new wires are set properly. The plugs are black, carbon fouled. The engine warms up, as for the exhaust temperature, I do not know. The exhaust smells of unburnt petrol.

 

like others have said...its running rich, hands down. something is clearly wrong with the carb. I wouldn't spend any more money on a "carb mechanic." Purchase order a guaranteed/warrantied refurb carb, and be done with it.

 

This is true. The carb-mechanic said he'd rebuild my old carburetor, free of charge, and put it back on. I will take him up on this offer and report back to you all. Thank you so much for your inputs, and quick replies.

 

Well the mechanic on the one hand sez the carburetor is OK, but then sez it is "too rich", why didn't he adjust it then? How much did he charge for that nugget of wisdom?

This is a perfect example of why if you're going to drive a carbureted truck you have to get in the manual beforehand and study it thoroughly so you, the operator, have a good understanding of how they work. Carbureted engines went bye-bye 30+ years ago, so unless this good old boy has gray hair, forget it. Nobody is usually willing or able to troubleshoot.

It is also tough to troubleshoot remotely over the internets, but it's running super rich obviously. It "could" be a timing issue. Start from scratch, assume nothing and check everything. Valve timing. Distributor timing. Ignition timing.

How much engine manifold vacuum is indicated on the gauge at idle? Check fuel pump for correct pressure and volume. Check Carburetor fuel height in the bowl. Adjust idle RPM and idle mixture screws. Etc.

 

exactly what I was gonna say. The single barrel carters are super simple. There is a mountain of information on the world wide wed about these carbs and their adjustments.
like tesdter9 mentioned, eliminate other variables like valves, ignition, etc. first. Then get into the carb. you'll be lucky to find someone that is willing and able to accurately dial in your carb locally. speaking of which, where are you located?
Don't be afraid to get your feet wet in the realm of carbs. That's part of the fun of owning an older vehicle is the learning process.

 

this is one of a 4 part series available for your viewing pleasure...for free! be sure to take notes.

 

On the passenger side, look at the base of the carburetor just above the EGR spacer. You should see an adjustment screw and a vacuum port. On a YFA that is the "spark" or S port and you should have an vacuum line from that port to your vacuum advance on your distributor. Make sure your timing is set correctly, then when the truck is warm, turn the adjustment screw IN until the engine starts to slow, then back it out 1/8-1/4 turn. That is your idle mixture adjustment screw. Try that before you start ripping the carb apart.

 

that may work...good point. although if its pig rich, and the float isn't set properly...it wont run right no matter how you adjust it.
simply judging from his comments made by the "carb mechanic."
it's definitely worth a shot...I'm merely saying that I wouldn't trust someone that says the carb is fine, when it clearly isn't.

 

Hey All. I had the factory carb rebuilt (wanted to make sure it was done correctly) and she's running well once again! Only issues I have now is the fuel gauge and temp gauge not reading right. Ran out of fuel taking it for a spin earlier today!