I hope this isnt a repeat of an older thread, but I just bought myself my first truck with a carburetor and so far the only problem it has is throwing me for a loop. It's a 1984 Ford F150, and on the first run of the day, it gets stuck in high idle (about 3000rpm) and won't return to normal until a while later in the day (typically by the second run). I figure from some basic research that the carburetor is getting stuck in fast idle and isn't warming properly to reach curb, but I'm not certain.

Thoughts?

 

Lube up the choke linkage and make sure it is working properly and moving freely. This will also mean pulling the choke cap to make sure the vacuum pull off piston is freely moving also.

Matthew

 

A picture of the carb with the air cleaner off will show us what you've got.

With the air cleaner off check out all the springs on the outside of the carb. If they're really dirty spray them with carb cleaner to clean them up and then give them and the choke pivot points a little lube.

The choke opens when the bi-metallic choke spring gets hot and some carbs use electricity to heat the spring and others use heat off the exhaust manifold.

If it's an electric choke it could be as simple As reconnecting a loose wire.

 

Ford used a electric assist choke just for this reason. When its warm outside the assist kicks in and opens the choke fast

 

Thanks for the fast response. I actually don't have the truck in my possession yet (owner is out of town, waiting on the title sign off). When I do have it, I'll get some pictures up and go through the springs and joints as suggested. I believe I remember the owner saying that it is an electric choke that he couldn't figure out, but I'll have the truck sometime next week to open up and take a look through.

 

So I finally got my truck. Opened up the hood and took the air cleaner off and the first thing I notice is all the hoses and vacuum lines that are severed and missing! Now I'm no expert, but I believe I have found my problem.

 

Looks like some one has taken all the emissions off and done a poor job at it.
It needs to be finished and sorted out.

Also that Emissions Holley should be replaced with an aftermarket non emissions carb. They were not a great carb in that sort of calibration to start with and with all the emissions gear half gone it will never really run properly.

 

Well the way I see it the vacuum lines that have been removed would not have anything to do with the idle staying high for a long time.


We will look in to any of the vacuum lines to the air filter at a later time as you will need them to help when it gets colder out.


First it loos like the choke is electric only. Check to make sure you have power to the choke when running and if you can what the voltage is.
If no power you will need to trace back that wire going to the choke to see why no power.


If it does and everything is clean & lubed and moves freely lets try adjusting the choke. There are 3 screws around the outer ring that holds the black choke housing tight. Before you go and loosen the screws mark the black housing so you know where it was before starting to adjust.
Loosen the 3 screws and turn the black housing a little. you should be ableto tell what way you need to turn it as the choke would close tighter or open a little.
If you try and push it open before adjusting when you turn it you should also be able to tell if going the right way.


Just go a little bit and give it a try and see if it is ok now or needs a little more adjusting. If you have to go back to where you started you have that mark to go back to.


Let us know how you make out and if it works we can help with the air filter hoses.
Dave ----

 

I checked the voltage to the choke and it does have power to it. At peak it gets 14.5 VDC but will occasionally drop to 0 or somewhere in between.
I haven't adjusted the choke yet (I don't have a lot of time during the week days), but all the linkages are moving freely and are lubricated.
As for the picture above, I found this Holley carburetor behind the seat. Not sure if it would be any better than the Holley that's currently installed.

Matthew - would you be able to recommend a carburetor that is not emissions based? I was just going to buy some vacuum hose and start reconnecting what was removed, but if a new carb would be more desirable, then I think I might shift towards doing that.

 

IMO the 4180 carb you already have is a good one and the only thing emissions about it are the big external vent holes on the fuel bowls.

Speaking of which, the big round open vent hole on the front fuel bowl needs a cap, otherwise dirt can get into your carb and gas can slosh out which it does as evidenced by the fuel residue.

At a glance I'm guessing your extra carb is a 4160 and externally about the only difference between it and the one on the vehicle is the fuel bowls don't have the vent holes. Edit: the choke on the spare carb looks different and it doesn't look like it has the vacuum choke pull off ("vacuum break" I think it's called).

For the unfamiliar carbs are mysterious things and they wrongly get a lot of blame when things go wrong and people mistakenly think a new carb will magically transform an old truck into a high performance hot rod.

Your best bet is to become one with the carb that's on it, put a cap in that big open hole on your front fuel bowl, figure out your choke issue (which could be as simple as loosening three screws and adjusting the choke housing) and then go from there.

Otherwise changing carbs will require you to re-engineer the mounting base and linkages and then you'll still have to learn how to tune it. Much easier to figure out how to tune the one that's on there already.

 

Carbs can give a lot of trouble. It's not their fault, it's the fuel they sell now, it goes bad in as little as a month, gumming up the carb. I would not even try that carb behind the seat without putting a kit in it and cleaning it up. Or put a kit in the one you have. If you are not up to using a kit, then a new one would be the next option.

If you are going to let this truck sit around for any length of time before you drive it on a regular basis, it's worth the money to find a station that sells non-ethanol fuel and use it in the truck. You should already be using non-ethanol fuel in your mowers, chain saws, boats, etc.

 

What is the list number on that carb that was behind the seat? It should be stamped on the choke housing. That will tell us the CFM ,applications and calibration.

If you are going with a non emmsions carb all that crap under hood can be removed and you will basically end up with a late 60's sort of set up.

The carb that is on your truck the calibration is not shall we say "not ideal" I have never seen one of these later emissions holleys run well or to full potential with all the emissions gear removed, short of a ground up rebuild, changing the metering plates idle air jets etc etc and then you are still left with an ugly looking Holley.

If the carb behind the seat is not useable.

The what I would use is

https://www.summitracing.com/int/par...00vs/overview/

or the 500CFM unit.

https://www.summitracing.com/int/par...00vs/overview/

Or the Holley

https://www.summitracing.com/int/parts/hly-0-80457s


Alternatively lots of guys have good success with the Carter (Edelbrock carbs) personally I never liked them, but that is me.

Performance Carburetors and Accessories - Thunder Series Carburetors - Edelbrock, LLC.


All of thse carbs Except maybe the Carter should be a drop in bolt up that require no modification of linkages and just basic tuning.
The summit carbs come with a handy little how to DVD and there are extensive videos on Youtube on tuning and setting these carbs up.
Plus they are the lowest price and cost in the long run. I'm partial to the Summit but I might be biased as it is based off the Autolite/Ford 4100 and it was as far as I'm concerned the best 4BBL ever designed in terms of reliability and simplicity and efficiency.

 

Franklin2 - With where I live, I would not have access to a gas station that sells non-ethanol fuel so a kit may just be something I would have to look into. I'm assuming this "kit" is supposed to help with the fuel combustion?

Matthew and Brnfree - I'll try adjusting the choke on the Holley that's installed and see what kind of results I can get. After driving the around for a little while now though I've discovered a few patterns in how it runs.

The first start of the day it starts up no problem and actually idles pretty decent for about 7-10 min. After that, the engine just sounds choppy like it wants to quit (it doesn't quite get to the point of quitting though) and stays that way despite how much gas I give it for about another 10 min. After that the choppiness goes away and the carburetor is warmed, but the revs jump around going between 1000 and 2000 RPM. At times, I find myself not even having to touch the gas pedal on my drive to work. I've noticed that quickly stomping the gas will lower the revs for a minute, which I typically do before I go to park.

I also notice that it doesn't start up right away like it does in the morning (I give it three pumps and turn) on the next time I run it. I usually have to give it a little gas while turning despite giving it gas to start it beforehand.

I hope these details help to paint a better picture to my issue. Anyways, I'll start by messing with my current carb and finish the emissions removal, and if it seems like I'm getting nowhere I'll probably just switch to a summit when money is available.

All markings on the spare Holley carb have been worn away so I have no idea what it is other than Brnfree's assessment.