This might belong in electrical, but it seems pretty specifc to early '85's. I have a feedback carb with EEC VI on the distributor and PCM under the dash. What looks exactly like the Data Link connector and test wire are located near the battery. Hooking it up like the manual shows, clutch in or out makes no difference, I can't raise a trouble code on either a meter or the emissions light.

The Haynes manual is discussing EFI systems when it goes into trouble codes while mine is carbureted. So, I;m wondering, does this model F-150 even have trouble codes or do I have a problem with the pcm?

Thanks for any help!
-Smoky

 

If you have a feedback carb you should have a computer and be able to get codes. No matter what you do in the test you should be able to get codes. The computer should tell you if you do the test wrong too. Code 33 or 77 if I remember right.


Some possible reasons why you wouldn't be able to trigger them...

The self test trigger or self test output wires have broken connections. Hence the signals not reaching the computer or the meter.

The computer itself not working properly, due to a bad relay or loss of power to computer, or the computer itself having a fault. Some of the earlier computerized control units would still let the engine run even with total computer faliure, on carb models. MCU computers mostly. But the engine would run bad.

I would check to see if the computer was getting it's required power supply. Then I would check for continuity in the wiring harness between the self test trigger and self test output wires and the computer connector on the other end of the harness. Repair wires as nessessary.

If that all check out, then you will have to Check the computer relay or relays. (forget what ford calls it) and the computer itself. The only way I know how to check these is by substitution. Hopefully somebody may be able to tell you more.

Good luck.

 

Thanks for the help! I'd done the disttributor EEC VI module to computer PCM voltage and harness checks, all sensor voltages are present too. I see a low, constant voltage at the Data link when I place a meter there for the test, but no fluctuations or dash lights.

The system does have an intermittent. One state, emission light's always on, which it should be, if it were really working right. The other condition, emission light goes on, then extinguishes after a few seconds, as though all were well with its world. I can't get codes in either of these states. Switching between gas tanks or hitting a bump can make it change states.

I don't really need the codes, I presume they'd be yelling at me "the smog pump's missing, my egr is blocked off with plumbing fittings, half my sensors are gone and the pcv hookups are bassackwards" or something like that. But I'd like to see what's stored just the same! Might be something I don't know!

After reading your reply, the intermittent probably needs to get fixed first, then see if codes are there.

Despite all that's "wrong" the engine seems to run great and must have some sort of vacuum advance happening to handle uphill under load and high revs as well as idle smoothly. A friend gave me a timing light but it has a blown scr so I haven't been able to verify timing or advance yet.

Last real issue to conquer is what the heck is that solenoid on the side of the Carter YFA carb? A bowl vent or fuel mixture control? That's what I'm hoping the trouble codes might help with.

Thanks!
-Smoky

 

>>>The system does have an intermittent. One state, emission light. >>>

This light on this year was just a reminder to do routine maitenance. there is a module under the dash that you trigger to turn the light off. It should come on every so many 1000s of miles. Most prople just remove the bulb.


You might have a "electric dashpot" on the right of the carb that can control idle speed, for air conditioning, or when the computer does a run diagnostic. The solonoid on the Left side of the carb is the Fuel mixture control solonoid. It is linked up to the computer and the O2 sensor. The computer reads the O2 sensor and adjusts the fuel rich or lean depending on the reading from the O2 sensor. The YFA model of carb, when the ignition switch is in the on position, engine off, you should hear ticking noises coming from the solonoid. If you don't then there is a definate problem going on there. Also on the YFA that you are working on there should be one vaccume hose coming off of the carb and that should go to the EGR valve, "and/or" on some models the vaccume advance. Some of these models also have spark retard solonoids that block vaccume to the vaccume advance when the computer senses knocks.

If everything is running alright and the feedback solonoid on the cab is working, I would say you have a intermittent conection with the self test trigger and the self test output, or self test input, or one of the relays. On my 1981 F-150 with the YFA Feedback carb, and MCU, the computer uses the TAB (Thermactor Air Bypass) solonoid as the relay for code retreval. I had a bad TAB valve once and couldn't get codes to save my butt. After I replaced the TAB I could get codes. On your system ford was smarter and put a seperate computer relay for such code retreval than a actual solonoid. . Its a blue, black or Green or Brown or other color box on a fender somewhere. About the size of a childs wooden letter block, with wires attached to the bottom. On some models, (the computer systems changed yearly) if the relay was out, the truck wouldn't run. This is usually on fully controlled computerised distributors, etc. TFI. ETC...

Hope this helps.

 

Yes, that is most helpful! I've looked for these relays, TAB, TAD, etc., but they aren't located where the Haynes manual says they should be. Discussion in there on this particular system is sorta limited.

I've tested the fuel solenoid for continuity and voltage is present to it. I haven't heard any clicking, but its connector is flaky to say the least. O2 sensor seems ok but I can't really say I've gotten repeatable, conclusive tests.

It has the idle dashpot but the idle solenoid is missing, both would be on the linkage. It does have the throttle position sensor and the fuel mixture solenoid.

With the egr stopped off, the pcv is just jury-rigged to vent the crankcase. When I got it, it was venting backwards into the air cleaner. I got some pics of how egr and pcv are supposed to connect but haven't had time to change it.

I've read about the light coming on at 60,000 miles. Indeed, the emissions bulb was missing when I got the rig. Wouldn't disconnecting power clear this? I've had the EEC and PCM out of the rig as well.

At one point, when I first connected the fuel solenoid back up, I heard a buzzing coming from under the dash. Should there be a relay under there?

Thanks!
-Smoky

 

I don't see any relays anywhere under the hood, but there is one attached to the computer bracket under the dash. I get a single click turning the key, so the relay part of it works at least. There's another larger module of some kind about the size of what you describe on the left side of the steering wheel. I'll have to have that out for a looksee. My underhood sticker says I should have a TAB, TAD and EGR solenoid.

Thanks!
-Smoky

 

Ok, As I've said each year is different, and I also forgot to mention, that California has different smog than the othe 49 states. So the two systems are usually different. I'm more used to the california versions.

It sounds like you found some of the relays. If one of them is malfunctioning or burnt out that could cause the no code problem. If your Tab and Tad solonoids are gone I know that on my 1981, the removal of those would prevent code retreval as well.

If you live in a state that doesn't have smog control, I would suggest replacing the Carb with a non-feedback type, and distributor with one out of an earlier truck, that uses Duraspark II (if not already equipped) and get rid of the computer control alltogether. That would probably save you a lot of heartache in the future. It sounds like a lot of it's missing or not working anyway. Hope this helps.

 

Yeah, they must all be under the dash, unless one's mounted right on the engine, unlikely, but that's the only place I have empty sockets under the hood, and there's nothing like the size and number of conductors a solenoid would need.

Found a loose ground where the black module is mounted under the dash. Another step closer to seeing if I can get codes.

I had a new distributor all ready to go in, but a little voice told me to check out what was under the hood first. I started making some headway with the setup, other than it being a bit rich, and wondering how the fuel solenoid might affect that, I'm really very pleased with how it's running. No smog checks to pass or fail here at least, just trying to understand the system a bit better. I can always rip it out, but since it seems so close, I'd like to see if it can run any better by playing a bit with the parts that are still here.

I appreciate the help and comments. Every time I get a reply like yours, it brings me another step closer. Looks like it would probably take a near-identical truck to finally see for sure how mine should be hooked up.

-Smoky

 

Sorry I can't be of more help. Would have to see the truck in person.

It could be the computer itself why it wont release any codes, or as I've said before, so many missing parts might cause the computer to get confused. You may have one of the relays missing etc...

It is no doubt running on stand by mode, a limp home mode as it were... A factory preset when different components are not working or unplugged from the computer. The only way that I can see to get it to run any better without replacing all the computer parts that have been taken off (costly and probably impossible due to parts deletion), is to go to a non feedback carb, and distributor etc..

You could try adjusting the fuel mixture by hand using the mixture screw on the right side of the carb. If it is original it possibly still has the tamper proof cap over the screw, that will have to be removed.

I can't think of anything else you can try.. If I do, I'll speak up.

Good Luck and Hope this helped.

 

Hey '81, would you happen to know the action of the fuel solenoid? My guess is it would make it richer when it clicked on. Or, at any rate, if it's disabled, some sort of baseline adjustment can still be made using just the mixture screw? That hopefully would remain constant?

I have an older non-feedback carb, but it's pretty sad. Besides needing a rebuild, it looks like the throttle shaft is sloppy and no doubt leaks. I don't think a kit alone would fix it. On the feedback carb that's on the truck, the only thing in the way of using it in a non-feedback mode is this fuel solenoid. If leaving it unhooked or blocked off would bypass the solenoid where it isn't enriching the mixture, I'm good to go.

Before I started this journey, the computer's power wire was unhooked. Timing could be set for fair idle or good timing at road speed but not both. The mechanic I took it to said there was no timing advance. That's what also happens in "limp home" mode. Timing is set to some default value and does not advance.

He was as stumped as I, I guess it's because he was totally unfamiliar with this particular setup. They put a lot of time on it, installed a used intake and that worn out older carb and called it good. It actually ran worse and cost me $240. They were obviously very glad to see it go. It sat at their shop so long somebody sideswiped it with a snowplow! Needless to say, I'm not going back!

So I just started reading the manual and playing with it. I've hooked up all I can without springing for new parts. I took off the crapped out carb and rebuilt the original feedback carb, connected the computer and set mixture and timing as best I could without benefit of lights or gauges.

It now runs well at all throttle positions and gear loads with just a hint of a miss at idle, a bad valve or lifter is my guess. This tells me the computer must at least be working well enough to handle timing advance.

I guess I'm trying to find out what all else it might still be controlling, i.e., that dad-blamed fuel solenoid. Mileage has gone from 7mpg to about 12mpg, so I know I'm making good headway.

I also picked up a point distributor, not a Duraspark, but I laid out big bucks for it and I'm stuck with it. As I said, I'm holding off sticking it in till I understand the computer system well enough to know I've taken it as far as I can without a complete overhaul of it. I've read here the point system isn't the best alternative, that's why I'd really like to discover just what the computer is handling. Otherwise, I have no basis of comparison when I make the swap. I may just want to swap back, or if this system can be made to work just a bit better, why make the swap at all?

I need to spend a full day on it. All I've done lately is conduct one little test or another as I have time and good weather. I also really need a timing light and vacuum gauge.

If you're interested in looking, I can add some pics to my gallery.

Thanks for all your help! Hope it's not bordering on the rediculous! I can get pretty single-minded on things like this, I won't let go till the bitter end. Drives my wife nuts! There's just one or two things I don't understand yet, then I'll be ready to try the swap. Hopefully this point distributor and feedback carb can be made to serve. If not, I'll just stick with what I've got, as it's really not that bad, cobbled as it is.

-Smoky

 

Well, the feedback solonoid on the carb can be disconected, and you can try to get a fair fuel mixture with just the mixture screw. It may work, and it may not. Never tried that before, but it would be easy to try and test, then switch back if it doesn't work.

The computer on my 1981 controls Fuel Mixture, Air to the catalytic converters, or the exaust manifold, Wide open throttle, closed throttle modes, Spark retard, charcol canister purge, and also regulates engine settings depending on what tempurature the engine is.

I would say by 1985 the computer would control, Fuel Mixture, Air to the cats, or exaust manifold, EGR valve, Timing of distributor, spark advance and retard, Charcol canister purge, Wide open, and closed throttle positions, Idle speed, and would also do various adjustments depending on how hot or cold the engine is, or if the air conditioner was on, etc...

Parts on this engine that it would need for this type of control would be...

TAB and TAD solonoids - Controls Air flow to cats or exaust manifold.

Throttle position sensor - Tells computer if you are in wide open or closed throttle positions, and adjusts timing and fuel mixtrue appropriately.

EGR solonoid - Lets vaccume from the carb activate the EGR only when the engine is warm, or beyond just idle speed.

Fuel Mixture solonoid - Fuel mixture rich or lean, is adjusted by the computer using the O2 sensor as a base for control. The computer also uses the tempurature sensor, and throttle position sensor in conjunction to control fuel mixture. Richer mixture when cold, or when you are in wide open throttle positions.

O2 Sensor - Tells the computer how rich the engine is running, and then the computer can control the Fuel Mixture solonoid appropriately.

Electric Dashpot - Controls idle speed. If the air conditioner turns on, or the computer is in a run diagnostic, or the truck is cold, this solonoid is used.

Tempurature Sensor - Tells the computer which mode to be in. Hot or cold mode. In hot mode the computer is in closed loop and adjusts everything to optimum. In Cold mode, the computer adjusts everything to make the engine warm up faster, and run better cold. Richer fuel mixture, faster idle, more advanced timing, etc...

Canister purge solonoid - Operates to burn the trapped gasses from the Charcol canister. Mostly gas fumes from the gas tank or carb.

If parts of the computer are missing it will run in open loop, and adjust everything at predetermined factory set level.

This is just my two cents... I wouldn't recomend using a point distributor on this engine. I would get a Duraspark II distributor with module and that would help with vaccume advance and things to start working proper. I would also recommend getting a Non-Feedback Carb, that is in good shape.

It would gain you some MPG, and some horse power as well. It would also probably eliminate some of the miss you are describing.

With the Non Feedback Carb, and the Duraspark II distributor, you could throw the computer away.

Just my opinion,

Hope this helps,

 

Nice to see all that in one spot instead of splattered through a manual. Thanks much for taking the time!

It's missing enough of those sub-systems that it's gotta be suffering from it. I guess I'd never track all that down without a donor vehicle.

One last question before I go shoot the computer and put it out of my/our misery. What's the issue with going to a point distributor that hardly anyone recommends it?

Thanks!
-Smoky

 

It's harder to adjust the points and condenser to optimum without special equipment. A Tach/Dwell meter, timing light, etc... You can get the gap close with a feeler guage but really need the diagnostic equipment to get it tuned right. In California, anything that uses a breaker ignition system with points and condensers from the factory are smog exempt, 1975 and older, cause it's so hard to tune them up right, without high dollar diagnostic equipment, that even the repair shops don't have anymore. The points and condenser have to be changed often, about as often as a cap and rotor, some people just regap them once and change them every other tuneup but I don't recommend that. You don't get quite as hot of a spark either.

With the Duraspark II there isn't any of the tedious adjustments, you get a hotter spark, tune up is just a cap, wires, rotor and plugs, and they very rarely ever fail, except the module itself, and that is very few and far between. And I always keep a spare module for that scenerio myself.

Hope this helps.

 

Wow, I've never owned a timing light or set points by tach/dwell, though I understand why you should. I mostly go by feeler gauge and feel, what seems to run best. Worked on everything I've owned with points the last 35 years or so. I borrowed a light once to set my MGB, but ended up going back to my hands-on method. I guess that's why I felt comfortable with going back to such an early system.

Since I've already popped for the dist, cap, rotor and wires, I can't see the harm in trying. Meanwhile, I can keep my eyes open for a Duraspark II and carb.

The rig spends most of its time on the property hauling rocks or logs with a 6-mile round trip to town every now and then. The farthest it's been since I've owned it is 35 miles to the next town and back a half-dozen times. My wife and I barely drive a total of 5,000 a year between three vehicles. What I guess I'm saying is I don't usually need to change points very often on my MGB, and this rig will be used about the same or less.

Thanks again for all the help! I'll report how the change-over goes.

-Smoky

 

If you already have the distributor, and you are comfortable with points etc.. I don't see anything wrong with using it. I'd check to see if the coil is compatible, or get another coil that goes with the distributor your changing. What ever year the distributor is, get the coil and carb to match the year for best compatibility. You can check part numbers at motorcraft.com for compatibility issues, etc... You may have to convert the ford part number to Motorcraft part number, but not too hard. Only thing I can think of that may cause a problem with the exchange.

You will need the non feedback carb to get proper working vaccume advance once the swap is done, preferably the same year as the distributor. You can use the EGR port on the feedback carb for vaccume advance (but it won't be quite right) until you get a non feedback carb swapped in.

Hope this helps.