I have an 84' F-150 with a 351W and a Motorcraft 2150 Carb. I have been experiencing issues since I got the truck. The engine runs great at idle (set a little high) from cold start, but if i turn it off at the gas pump, I can't make it more than 3 feet without being towed. I thought it was a choke issue, so I adjusted the choke and even with the engine warm, if I open the choke even a crack, the truck just dies. I am an absolute NOVICE when it comes to anything before fuel injection. I am at a complete loss. Even something that seems basic knowledge would be appreciated. I'm missing something.

What I've already done:
*Rebuilt Carb
*Changed Distributor Cap
*Changed Distributor Rotor
*Removed/Reinstalled the Rebuilt Carb with some RTV on the paper gaskets to ensure a good seal (I let it cure for 2 days before starting it up.

 

The choke should be completely open when the engine is warm. It's very common for the choke tubes to be rusted away on a 34 year old truck.

The first thing you need to understand is what you are working with. Or *should* be working with. Your 1984 F150 with a Motorcraft 2150 carburetor (great carburetor) came from Ford with a feedback system. In other words, you have a computer on your truck that controls the ignition timing, emissions, and to a lesser extent, the air/fuel mixture at the carburetor. Think of it as a "bridge" between traditional mechanical carbureted systems and electronic fuel injection. Like EFI, if ALL of the components aren't on your truck and functioning properly, your truck will never run right.

Like an EFI system, you should have an O2 sensor, MAP sensor, and EEC-IV test port. Make sure you have the correct TFI distributor, feedback carburetor, and all of the emissions are still in place and working correctly. If any of these parts are not the correct items or are missing, you are going to have problems. Your truck is now 34 years old. It's not uncommon for things to go missing during that long stretch of service. I have seen trucks come through here over the years that are completely original with all the correct parts still in place, and others are hacked up with an older, non-feedback carburetor and aftermarket ignition system.

Can you post pictures of your engine? That will be a great place to start.

 

Sounds like a massive vacuum leak, opening the choke adds even more air and stalls.

The leak is "supplying" the air, opening the choke "as it is supposed to be" is adding even more.

Capp off ALL hoses going to the carb and see if it acts the same or suddenly gets happy.
Now you can plug things back is and see if it goes south.

Best remedy: strip off the whole top end and get a 4-v intake and new carb.

This is what I did, tore 54 pounds of emissions crap off, and got a Edelbrock 4-v and non EGR intake, very smooth now.
Remember, if you have vacuum controls in the dash, those too can have leaks that go back to the carb.
If you get it running, listen for hissing coming from just about anywhere, Power brake booster, under the dash, master cylinder push rod......
Look for any rubber hoses that are plugged, or going "nowhere" the plugged one may be leaking and actually went somewhere, hoses going nowhere are a major problem...

 

Hold on there, Hoss.

If Superzero220 does this, he will also need to replace the entire ignition system. That is, if he is still running the stock TFI ignition system. The TFI ignition and aftermarket carburetor are not compatible with each other.

He will also fail an emissions test. We need to know Superzero220 has emissions testing in his area.

That is why I asked for pictures of the engine.

 

I agree that it is a vacuum leak. One or more of the hoses may have cracked or a rubber cap has split and/or fallen off. Start it and listen closely for hissing. You may want to use a piece of hose to your ear. Another way is to spray brake or carb cleaner on various potential leaks and see if the engine speeds up - which indicates you've found a leak.

 

Very true Lariat, didn't check to see if he needs to do emissions. Converting to duraspark would be his answer if "allowed" to trash the emissions.
I tried to get mine running with all the emissions stuff and was told By the Ford dealer, not to, you could top over $800 to get it running right.

"If 1 piece of the emissions system goes down, other parts try to compensate, if they can't it just wont run right, now if you fix one component and it throws more errors, other components have gone south, replacing more components may work, but figure, the TAD and TAB solenoids are rusted, the bottom of the Vac. reservoir has a hole in it, and most check valves are frozen, since they have not moved in years.
ALL the rubber lines need replacing, O2 is carboned over, carb needs a re-build. And that's just the beginning."

"This stuff really didn't work right (for the long run) when it was designed, do youself a favor and Get a 4-v and new intake and call it a day"
That statement from the dealer......

 

I don't have to worry about any inspections, this engine is not the original, and I don't think the Carb was originally a 2150 on the engine either. I won't be able to get pictures up until tomorrow. I was thinking of possibly going with a normal 2 barrel for now just to get the monster back on the road, but by the sound of it, there is a lot that goes into it. I will plug up the vacuum ports on the carb to see if that helps. I will inform either way. Thank you for the tips and tricks so far.

 

I agree with you. In fact, I did a Duraspark II conversion on my own truck, which also had a feedback system.

Except for this:

That dealer is full of it.

The EEC-IV/feedback carbureted system worked absolutely fantastic when it was new. When functioning correctly, it was the smoothest and most efficient carbureted system ever devised. The only problem is, you couldn't remove anything or modify anything that had this system. Everyone with modern vehicles equipped with EFI know and understand this NOW, but hardly anyone pays attention to this fact when they see a carburetor. Many people felt that they could remove all of the "smog junk" and it would magically run better. (My own truck was a victim of this.) As a result, most of the trucks around today that have the feedback carbureted system have been hacked up because people don't understand them. It can be difficult attaining the correct replacement parts. And like you said, it is usually not cost effective to keep the system as it was designed when a lot of parts are missing. To make matters worse, finding someone who understands is rare - including the Ford dealer.

 

And that may be true WHEN NEW but add 15 to 20 years and see what the dealer has to say then.
Also how well you know that dealer and they know you and what oyu know will also change to answers you get.


My 02 Dodge I take to the dealer for any work, no time or right tools for me to do it, and it is getting tuff getting factory parts so the dealer has had to go thru local parts stores.
When that dries up then what? And they know I know cars/trucks so they can not push me to some thing that may only last a year as I will call them out on it.
Dave ----

 

My Dealer specializes in repair of older ford cars and trucks, This guy still has parts on the shelf for Mavericks, Granada's, Cougars, and trucks back to the 1940's, He is also a Mustang Cobra, and Juggernaught dealer.
Check him out
Bowens Garage.
He had all the parts needed for getting my 85 "back to spec" and priced it out for me, 4 new 4-v and intake was less that a quarter on the cost...

When I go into his wooden-floor garage with the analog gas pumps (where you have to multiply the price on the pump x2 cause the analog dials don't go that high) and he has just about every year mustang, and working on customers, 74 F-100, a 77 Bronco, has a running '48 F-5 out back, still has ALL the shop manuals to the 30's, all the microfiche, and points and condensers on the shelf and all the "antique diagnosis equipment", along with a 2016 Cobra, and building a 17 Mustang Juggernaught, If he tells me to scrap the emissions cause it did not work (again in the long run) I'll do it.

Remember all that crap was on the engines not because Ford thought
"this is much better for performance and mileage" this was mandated buy the government EPA standards. It had to be done fast, now and profitable.
Give it 5 years and it went haywire.

Dealer full of it??? .....Hardly..

 

If the engine isn't original, you could have *anything* going on. We need to see pictures of what you have before going any further. (Some 1984 5.8/351 models had a Motorcraft 2150A 2V feedback carburetor with EEC-IV engine computer, and others had a Motorcraft 4180 4V carburetor with a Dura Spark ignition.)


The dealer will say ANYTHING to get you into a newer model, Chief.



The difference is, feedback carbureted systems were only in use for about three years, 30+ years ago on selected models. So, modern mechanics don't know much about these systems at all.


I. - Carbureted engines didn't change all that much from the 1940s to the 1970s. There were changes of course, but it was very gradual.

II. - In the mid 1980s, suddenly Ford added an engine computer to control the emissions controls, ignition timing, and the very old and familiar carburetor that hadn't changed very much in almost 30 years now had a feedback solenoid on it that was connected to the EEC-IV engine computer - the same engine computer that Ford later used on the EFI engines.

III. - Then, the feedback carburetor was replaced with modern electronic fuel injection that didn't change all that much for the next 15 years.


So, it's easy to see why this system is often scoffed at and dismissed as being inferior.


I agree with this. Except the feedback carburetor with EEC-IV *did* improve mileage.


Do you and the mechanic at Bowen's Garage know that the 4.9/300 engines from 1984 - 1986 that had a feedback carburetor produced less emissions, better fuel economy, and about the same power as the 1987 - 1988 vehicles that had EFI?


1986 F-150, 2wd, 4 speed manual:OD, Feedback Carburetor:
MPG: 23 highway, 20 combined
CO2: 9.3

1987 F-150, 2wd, 4 speed manual:OD, EFI:
MPG: 20 highway, 17 combined
CO2: 11.0

Source: fueleconomy.gov


1986 was last year for Feedback carburetors, and 1987 was first year of EFI for the 4.9/300. According to the website, not only was fuel economy down 3 MPG, the engine with EFI was dirtier with 1.7 more Co2 output than the engine with the Feedback carburetor just a year earlier!

If you keep going forward, 1988 is even worse:

1988 F-150, 2wd, 5 speed manual (the four speed OD was dropped), EFI:
MPG: 18 highway, 16 combined
Co2: 11.6


Yes, the dealer is full of it.

 

As Promised, here are some pics

 

I have decided, with all the trouble I've gotten with this carb, I would like to convert to a standard 2 Barrel and eventually work my way up to a 4 Barrel. I have a 2 Barrel on hand or I would go straight for the 4. Thoughts? what do I need to change over to make the switch? this 2150 is just too much trouble for my dumb brain.

 

Your carb isn't that complex. The feedback carbs will work w/o the computer controlling them. But, if you replace the carb you will need to replace the ignition and go DS-II.

 

So, if I were to convert to DS-II, what would be involved? Am I missing it in FAQ or HowTo's? Don't be afraid to break it down barney style for me.