Well, if you still can't get a computer diagnostic, then it has to be wire related, assuming the new JY computer and EEC Relay are good. $20 isn't much for a computer at all, and is a good investment for the future as these parts go obsolete. I try to have two of everything, engine computer related for my truck as example, as those parts are extremely hard to find.

As for the problem, I'd start with power wires from the EEC Relay, to the EEC, and also the self test input and output wire connections. Might have to disconnect the EEC and TFI-IV harness and do a continuity test between each wire color with a ohm meter.

 

well i got a friend who knows someone who has all the stuff i need to do to swap the ignition system back to the duraspark 2 with the vaccum operated timing, to eliminate all the electronic stuff. i might do this and then i can just take the other wiring harness and i can go through it on a bench and test it or take a look at it and just keep it for future use if i still have the truck.

 

You can also give it to one of the guys here who might need it (it that situation comes along)....

 

A DS-II conversion would probably get you back on the road quicker, I do have to admit.

Just make sure you do everything that is involved with the swap. This includes replacing the carb with a non-feedback type carb.

 

i already am running a carb that has a non-feedback port on it. when i bought the truck the carb. wasnt on their and i had an engine that i bought from the guy that has the stuff for the swap that i bought from him for $40, he was just going to take it to the junkyard and i just took the carb off of that to get the bronco going, and its been running good since.

 

i found this on the website when i did a search. i might try testing the PIP and see what i get. it is possible that this is a bad new part because the old icm was putting a little to much current through the one wire i tested.

https://www.ford-trucks.com/forums/6...running-2.html

 

If you are running a non-feedback carb, then fixing the computer controls wont fix all it's problems. The computer will still operate in limp home mode. A new Feedback carb, with the right calibration for your engine would be needed to fix it right.

 

actually i meant i am running a feedback carb(with the distributor port on it).

now what does a MAP sensor do for a carburated engine? does it help control spark? i know it does something with the air/fuel mixture.


i now have the truck out of my storage and at home now i have time to mess with the wiring and stuff

 

Here is a "Cut and Paste" from Wiki:

MAP sensor function is to sense air pressure or vacuum in the intake manifold. The computer uses this input as an indication of engine load when adjusting air/fuel mixture and spark timing. Computerized engine control systems that do not use a MAP sensor rely on throttle position and air sensor input to determine engine load.
Under low-load, high-vacuum conditions, the computer leans the fuel mixture and advances spark timing for better fuel economy. Under high-load, low-vacuum conditions (turbo boost, for example), the computer enriches the fuel mixture and retards timing to prevent detonation.
The MAP sensor serves as the electronic equivalent of both a distributor vacuum advance diaphragm and a carburetor power valve.
The MAP sensor reads vacuum and pressure through a hose connected to the intake manifold. A pressure sensitive ceramic or silicon element and electronic circuit in the sensor generates a voltage signal that changes in direct proportion to pressure.
MAP sensors should not be confused with VAC (Vacuum) sensors, DPS (Differential Pressure sensors), or BARO or BP (Barometric Pressure) sensors. A vacuum sensor (same as a differential pressure sensor) reads the difference between manifold vacuum and atmospheric pressure (the difference in air pressure above and below the throttle plate). A VAC sensor is sometimes used instead of a MAP sensor to sense engine load.
A MAP sensor measures manifold air pressure against a precalibrated absolute (reference) pressure. What's the difference? A vacuum sensor only reads the difference in pressure, not absolute pressure, so it doesn't take into account changes in barometric (atmospheric) pressure.
A separate BARO sensor is usually needed with a vacuum sensor to compensate for changes in altitude and barometric pressure. Some early Ford EEC-III and EEC-IV systems have a combination barometric pressure/MAP sensor called a BMAP sensor, combining both functions.
Anything interfering with accurate sensor input can upset both fuel mixture and ignition timing. Problems with the MAP sensor itself, grounds or opens in the sensor wiring circuit, and/or vacuum leaks in the intake manifold.
Typical driveability symptoms include detonation due to too much spark advance and a lean fuel ratio, and loss of power and/or fuel economy due to retarded timing and an excessively rich fuel ratio.
A vacuum leak can cause a MAP sensor to indicate low manifold vacuum, causing the computer to think the engine is under more load than it really is. Consequently, timing is retarded and the fuel mixture is enriched.

 

I don't know if this applies to your year model, but I learned something interesting yesterday.

The fender mounted starter relay does more than just shuttle voltage to the starter on later model trucks (like my 92). On Ford trucks, when you engage the start circuit (key in start position), your ignition module retards the timing for easier starts. When you return the key to the run position, there is a diode in the relay that bleeds off the current and allows the ignition module to return to normal advance mode.

If that diode is burned out, the ignition module will get stuck in start mode for the whole run cycle, thus not applying proper advance.

I found that interesting, as I didn't know the relay had any other function other than the obvious one. Just something to consider when chasing down weird timing issues, right?

 

I've read about the EVTMs on this site and how good they are, this thread inspired me to get my own for my 1981.

Cost was around $20 including shipping, got it on eBay from this guy: eBay My World - davesbooks who BTW was a great seller, he even e-mailed me on Sunday and delivery took less than a week.

I agree with the others, these things are pretty good! They tell how how the circuits work, the tools you'll need to test them, exactly what to test, and exactly how to test them:











If you're at all interested in fixing stuff covered in this book, at $20, this is a GREAT book to help you do that.

 

well thanks for all the help guys. since i brought the truck home from my storage unit it was easier for me to work on it longer after work..

for the evtm i searched ebay and couldnt find one for the bronco. but i didnt search f150 either so i will do that next time.

but i found the problem. the + on the coil when i would test it between the ICM wire and on the coil + i wanst getting any thing through it. then i had a spot where i spliced something for the tach but then found out it was the wrong wire but i stuck the lead from the multimeter and i got power, so i pulled the connector end on the wire and notcied it was bending so i just popped the terminal out of the connector and the wire was broke underneath the coating so i re-soldered it and had power and then turned the key and it ran.

its just one of those things that you have to track down and could take a while. i will have to go pick up another connector tomorrow and put it on.

 

Here's one I found via Google:

1986 Ford Bronco, F-150-350 Series Electrical and Vacuum Trouble-shooting Manual

eBay is just one source, there are a variety of places selling used auto repair manuals.

The original publisher for Ford - Helm, Inc www.helminc.com - sometimes even has brand-new ones.

 

EEC wiring diagram from 1986 EVTM for 4.9L F150/Bronco