As a new owner of a 1986 4.9L with a 4.9L with a feedback carb I've been reading several posts here about various conversion options. While my truck runs fine as it is, I do feel its running a bit rich. Its fine as far as driveablility and makes good power, maybe even more power than the one I owned years ago.

One of my main questions about doing the conversion to the earlier carb and DSII distributor is what to do with the therm-actor and EGR solenoids? Are they not controlled by the ECM? Without proper upstream and down stream flow from the smog pump, won't the catalytic converter overheat?
EGR can be made to work on it's own simply by routing the vacuum lines as they are on an non feedback motor.
Do you need to do the same with the smog pump circuit and vacuum?

Also, on older Ford vehicles with DSII there was a built in ballast resistor in the harness, on most this was located under the dash. If you convert to DSII, and run a round coil, do you need to add a ballast resistor or do you just run a 12v round coil such as a Bosch Blue coil?

Also, does the 1986 throttle cable work with the older carb? How about the air cleaner from the feedback carb? Will it attach using the same hardware?

While mine don't have AC, if a truck is so equipped, do you have to add some sort of electrical idle stepper to up the idle when the compressor is running? (The Feedback carb's stepper motor or idle solenoid is controlled by the ECM and increases the idle roughly 200 RPM when it sees AC input from the switch.

With all of this in mind, the one wire ignition from Davis (DUI), looks to be the best solution, needing only a 12v feed to run and a vacuum hose to the carb for advance.

Apparently the feedback system was problematic in these, it was certainly a short lived option, and years with the feedback system were also rated at a lower hp then prior models.

Has anyone had any experience with the one wire DUI distributors?
Is a ballast resistor needed with the DSII module on a 1984-86 truck?

 

If your truck is running fine "as is," and all the parts are still intact and functioning correctly, you won't really gain anything by doing a conversion. Why do you feel it is running a bit rich? Have you tested it, and if it is, have you done anything else to try to correct the problem? By doing an ignition conversion, you are also going to have to replace your carburetor and remove or re-engineer all of your emissions components. This is all considered illegal and will not pass a vehicle inspection if you have testing in your area.

https://www.ford-trucks.com/forums/1...ky-thread.html

The EGR is controlled by the engine computer, but I don't think the thermactor system is. I am pretty sure it is just belt driven. I could be wrong, though. Catalytic converters came out quite a few years before smog pumps, so the catalytic converter shouldn't overheat without the smog pump.

Yes. To make the EGR functional again without an engine computer, you will need to get a ported vacuum switch and run the EGR to a ported vacuum source, like the older models did. Running it on ported vacuum will ensure that the EGR only works off idle and not at wide-open throttle. The ported vacuum switch will only allow the EGR to work after the engine has reached a certain temperature, that way it won't turn on when the engine is cold and cause driveability problems. The ported vacuum switch you need will be rated for 150 degrees or so and is usually blue in color. The evaporative controls will operate in the same way. For that you will need an older canister purge valve to replace the computer-controlled canister purge solenoid you have now.

No, you do not need to add a ballast resistor, as your truck already has a ballast resistor wire in your stock wire harness, just like the older 1980-1983 models. The reason is because some 1984 - 1986 models still used Duraspark ignition, like the 351 H.O. and 460 engines. So Ford used the same basic engine wire harness from 1980 - 1986, and simply plugged in either the Duraspark ignition harness or the EEC-IV wire harness. The ballast resistor wire is located in the engine bay in the wire harness that comes from the firewall on the driver's side on ALL gas 1980 - 1986 models. It will be a fat red or pink wire. The Duraspark ignition wire harness plugs into your trucks existing wire harness (after the TFI ignition harness is removed) and activates the ballast resistor wire. The ballast resistor wire is simply bypassed when the computer-controlled TFI ignition harness is plugged in and the feedback carburetor system was used.

https://www.ford-trucks.com/forums/9...wontt-run.html
https://www.ford-trucks.com/forums/1...on-how-to.html

Yes and yes.

The electrical idle kicker is not absolutely necessary, although it does help. If you don't have one, you could simply tune your carburetor with a higher curb idle speed to compensate for the extra load when the compressor turns on. The idle kicker solenoid is not controlled by the engine computer.

It certainly is the most expensive solution. And yes, there will be less wires. It is a GM design though, and is not really an "improvement" over the stock Duraspark II ignition on a stock or even mildly built street engine. The DUI is a high-performance racing ignition that will be better if you plan on spinning your truck 5,000 RPMs or higher on the race track, though.

No. I wouldn't say the feedback systems were "problematic." However, they are more complicated, and since they were only used for a few years, most mechanics do not know what to do with these models. To make matters worse, there isn't much support for the average home mechanic to understand how these systems work. Parts can also be expensive and hard to locate at times, but otherwise it is a good system that yields better fuel mileage and less emissions than the earlier models. Think of it as a bridge between the older carburetors and early electronic fuel injection. The feedback systems were rated the same as the older non-computer controlled systems.

The DUI distributors are a good product, but very expensive. If you insist on getting a one-wire GM designed HEI ignition with everything piled on top of it, keep in mind that your stock air cleaner will not clear the distributor, as it is quite a bit larger than the Ford distributor. A ballast resistor is needed with the DSII module, but the stock ballast resistor wire is already in your truck's existing wire harness. See my earlier comments about the ballast resistor wire with the links above.

 

In addition to what Lariat has said, why do you feel the carb is running rich?

Have you verified this with a sniffer test? This is the best way to know for sure.

Have you pulled the computer codes?

Fuel Injection Technical Library » How To Run a Self-Test

 

I third staying with what you have if it is, like you said, "fine as far as driveablility and makes good power, maybe even more power than the one I owned years ago". As Chris said, check the codes and if the computer is happy then you should be as well.

In my opinion, the only time it makes sense to remove the factory stuff is if it isn't working and getting/keeping it working will be difficult and/or expensive.

 

Josiah has one in his truck.

https://www.ford-trucks.com/forums/1...300-build.html

https://www.ford-trucks.com/forums/9...ld-thread.html

The ballast resistor is in the trucks harness already. If you get a DSII engine harness it will connect up and everything will function as it would if your truck came that way from the factory.

 

Good job on thinking ahead and trying to pinpoint all the potential problems that might need to be dealt with in the retro-swap back to non-feedback. You mentioned using the "older carb" and the stock air filter housing in the swap. If so, another component that would have to be retrofitted or rigged somehow would be the choke hot air tube. It attaches to the carb on opposite sides depending on feedback versus prior carbs, for reasons unknown (to me). The choke hot air tube sustem may also have different components down on the manifold where it routes to pick up heat. These components are wont to rust out like most things made out of thin steel and exposed to exhaust heat, and may not be highly salvageable from junkyard trucks.

 

When I bought the truck, it had just came from the dealer, the last owner spent big money reviving this from a long sleep. The dealer told him that the feedback system should go and that it would pass State Inspection easier with the older system.
The idle is a bit choppy on this, as was the idle on my first 1986 4.9L back in 1986. It was one of the reasons I traded it for a newer truck after only a year and 50K miles.
I scanned the EEC system and get an all pass code 11, ... most of the time, every so often it spits out a code 41 in memory, system always lean, meaning that the ECM is trying to enrich the system or simply not 'leaning' out the carb. The dealer replaced the carb, ignition stator, module, ECM, O2 sensor, EGR valve, ECT sensor, and installed a new intake manifold under some recall program which from what I can tell was for a rough idle. They at the same time tuned the engine, replaced the exhaust from the manifold back, including the cat conv. installed a new fuel tank, new filters, as well as four new shocks, all new brakes with new drums and rotors, and four new tires.
I have the invoice from the dealer, they hit the guy for big bucks.
It runs fine, it is a bit hard to start after a short hot soak after a short ride. Once it's warm, its perfect. It basically runs the same as my new one did back in 1986.
The tailpipe is clean, no black soot, no smoke, but it does put out black smoke when it experiences the hot soak issue.
To make the problem occur, I would have to start the engine, drive less than 1/4 mile, shut it off, and try to restart it 10 to 15 minutes later, it will then flood and crank 5 to 10 times before clearing out and firing up Once its warm, you can do it time after time, and its fine. When the problem occurs, it also cranks hard, as if the timing was too far advanced for a split second. I did find that if I turn on the key, tap the starter but not long enough to crank the engine, then cycle the switch, it will fire up without touching the gas just fine in that situation.
The carb has no heater tube, the choke is electric and wired into the alternator circuit as on most Fords, the intake is heated by attachment to the exhaust manifold in between. There's a tube that goes from the choke housing to the air cleaner, but none going from the choke housing externally. My guess is that it draws from within the carb body? I see no signs of rusted off metal tubes and not fittings missing any connections.

The Thermactor solenoids appear to be controlled by the EEC system, the wiring is part of that harness that goes to the ECM. Disconnecting a solenoid produces a code, so my take is that the ECM controls the ground using the O2 readings to determine when the converter needs downstream flow?

I should also note that this truck has a Ford badged 'Multiple Spark" "Extra Performance Ignition Module" added. It has a Ford part number and Ford oval logo on the lable, its marked Motorcraft, not MSD or Motorsport. It looks like an MSD 6A box but with Ford style connectors. The inner fender has a flat area and four holes that fit the box like it was made to be there. Its not new, its been there for a long time. I've owned many Fords, but have never seen one of these installed this way or look so much like factory equipment. It sits on the right inner fender and has a Motorcraft tagged harness connecting it between the plugs on the left fender and the TFI module. Even the plugs on the harness are marked Motorcraft.

 

Sounds like a time-capsule of working emissions equipment. From what I've heard there aren't that many of them around, but I may be judging unfairly as I live out here where no one runs that stuff on the older vehicles. So, if you do pull it off you might want to do so in a controlled fashion to ensure it can be used again.

I think you are right that the computer grounds the devices it controls, although I haven't looked at wiring diagrams to make sure that is correct. But, the reason I believe that to be the case is that solid state circuitry is good at sinking current, meaning taking something to ground, but poor at sourcing current. And, if pulling a lead off one of the relays throws a code then they are obviously working.

I pulled all of the emissions equipment off of a 351W and it was a chore. But, in this case it had to be done because someone took the feedback carb off and literally threw it away. Without that the system goes into limp-home mode and runs very poorly. So, I had to decide whether to buy one of those carbs, which are expensive, or remove it all. I chose the latter because it was less expensive and easier to maintain. However, if the system had been working I would have left it on as I believe it gives as good performance and fuel mileage as you are going to get with the vehicle - until it fails.

Anyway, if you are going to pull it off then this is the place to get help. While I've not worked on that engine, there are lots here who have and they will be free with their advice. In the end, you should do with it what you want to do with it - it is your truck.

 

How does your truck start up when its cold? Does your truck have a Motorcraft or Carter 1 barrel carburetor? If so, the choke tubes are missing. The carburetor should have a thermostatic "hot air" choke and a secondary electric choke. The hot air choke should have two tubes: the "fresh air tube" is attached to a rubber hose that is attached to the carburetor air horn and routes to the bottom of a chamber located on the exhaust manifold. Filtered air is drawn through this tube, enters the choke stove chamber on the exhaust manifold where the air is heated, and then the hot air routes up to the choke cap assembly through an insulated "hot air tube" that is located on top of the exhaust manifold chamber. The electric choke that connects to the back of the alternator is an electric assist choke that is secondary to the thermostatic hot air choke. The electric choke only works above 60 degrees and is there to help the choke come off sooner for emissions reasons.

This is an issue. I would like to see a picture of this Ford Motorcraft "Extra Performance Ignition Module" that is attached to the TFI ignition module. The inner fender is where the stock Motorcraft Duraspark II ignition module bolts up to, so someone may have already attempted to do an ignition swap. And if that is the case, the TFI ignition distributor is not going to work right, and neither will the feedback carburetor. If that is what you have. it's hard to tell from your description.

Someone has definitely modified your engine. With the computer-controlled feedback models, that is a big NO-NO. You need to take some pictures of your engine, specifically the carburetor, distributor, and the ignition module you have mounted to the inner fender and post them here so that we can see what you have.

 

LARIAT 85,

I tried yesterday to "rep" you for your very detailed input and was reminded that I have to share the wealth. Thanks for yesterday and today's input. It is appreciated by others than just the OP.

 

X2 on everything Lariat 85 said. I have a bone stock '86 4.9L F150, and some of your Carb and ignition components do not sound like stock components. Pics would be a big help.

 

Thanks, Chief!

 

The carb says Motorcraft on it, and has the small silver feedback solenoid on the side along with a huge stepper motor that sticks out on the passenger side. It's a one barrel Carter carb badged for Motorcraft. (I've never seen any other type carb on an 1986 4.9L from the factory).
The Multispark module sits behind the battery on the passenger side, the wires run across with the other wire loom and battery cables, they attach to the coil, TFI and main wiring on the driver's side inner fender. The coil is connected directly to the unknown module, there are three leads connected into the TFI, they are crimped into the harness, not spliced. The harness has no connection at the box, there is no plug there. The box itself is identical to a common MSD box but has all Ford markings and a part number. I looked to see if I could unplug it and run without it but without it, there's no coil connection, it basically is going between the coil and the TFI and taking its power from the wiring on the left fender were older trucks would have had a DSII module. The TFI is still being used. I tried to check timing and see if there is any advance but the timing light jumps all over the place with erratic flashes. It appears to be advancing with RPM but I can't seem to get a stable reading. If it is a form of MSD ignition, this could be why the timing light acts funny.
The module is attached with Ford type hardware, not generic nuts and bolts.
Here's a pic, its not much but its the only one I had here on this computer right now.
http://i43.tinypic.com/k49f6w.jpg

The choke element is electric, it says Motorcraft right on the choke cap, there is one compressing type fitting and tube that connects to a short metal tube with a few loops which connects to an orange rubber tube beneath the air cleaner, it enters the air filter inside of the element and draws filtered air directly. There is no other port or tube, and no heater tube on the manifold.

The truck starts cold fine, two pumps of the gas and it fires right up. The choke seems to work fine and backs off just fine.
It starts fine cold and fully warmed up, it's only when I stop for coffee in the AM about a block down the road that it gives any hint of a problem.
If I don't tap the gas, it won't start at all then, if I give it a full pump, it floods and smokes. If its warm, I give it a bit of gas and it fires right up, doing so when its only been running for a minute or two floods the engine.
When it acts up, there's basically no heat in the engine compartment, the carb is still cold. It only does this when its below say 40 degrees or so.

 

Hmmm a puzzle. I don't doubt that your "Multispark module" is Ford-made, I just haven't seen that mentioned as an ignition component on these trucks before. I don't think it appears anywhere in my Ford '86 Shop Manuals or EVTM. And it seems odd to me that your carb is a Ford single barrel but lacks a (or even fitting for) hot air choke tube. Is your truck a U.S.A 49 states - made model?

81-F-150-Explorer can probably shed some light on this, if anyone can.

 

Yeah, Ralph would probably know more.

All I know is, I've seen those apparently-Ford-branded modules on eBay before 'cept for the DSII variant.

What I saw certainly looked like a Ford part, perhaps these are from Ford Motorsport:

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