The dash gauge has nothing at all to do with the computer - two separate sensors, two separate functions.

The sender for the dash gauge has a single wire - either red/white-stripe or white/red-stripe, I forget which (one is for the oil pressure, the other for the water temperature). You have a straight-six, I *think* this sensor is mounted in the block back by the firewall but I may be confusing it with the oil pressure sender.

The computer's temp sensor is typically on the radiator hose neck and has multiple wires.

I don't have a wiring diagram for your feedback carb setup so can't verify or discount what you're seeing on other diagrams.

Wish Ralph was still around...

 

I'm late to the thread, but I was having driveability problems with my 85. My truck was eating O2 sensors, had poor performance, and got less than 10mpg. I have a Haynes manual for mine. I followed through each section and checked things one by one. I found a few problems, but kept having the issues. I finally was all set to chalk it up to a bad PCM computer. I pulled it out, cracked it open, saw nothing obvious, and put it all back together until I could come up with some extra cash. I started it back up, the check engine light unexpectedly went out, driveability problems were solved, and my MPG went up to 17+. I can't prove it, but I really think it was a bad connection...maybe even a ground.

It may be worth going through each of your sensors and checking them to make sure they are all within range. Cleaning all the connections may help also.

 

The temperature sensor for the gauge [six cylinder] is located on the passenger side of the engine, under the exhaust manifold.

 

Thanks again for the advice..

KsCop- Your probably correct but I am already headed down this path and want to figure out whats up with the origination system. Glutton for punishment?

Chris and Dave- Sure enough, that sensor was melted in the middle. Changed it and sure enough the gauge works. Now it shows that its running a little hot. Sitting on the L or normal. Probably just change the thermostat, I bet its old.
Red-white stripe is temp
White-Red stripe is Oil Pressure.

Ill run some more tests to ferret out the KOEO codes. I hope its just the black-wht stripe wire and not the computer.

Thanks Craig

 

This is the wiring diagram that I am using.

 

The fuel, oil pressure and temperature gauges receive their electrical power from the ICVR. This little device has a track record of malfunctioning as it ages [How old are our trucks? ]. When it does, all three gauges will read incorrectly. See if your oil pressure is higher than expected or your fuel level is higher than expected.


This is why many suggest the addition of after market gauges.

 

Havent had time to work on the truck much lately. So, here is what I have done. Since all of these sensors had a common wire I placed a duplicate wire from the computer to the MAP sensor to see if this would eliminate the error for the MAP when checking codes. It did not. I kept thinking that the problem was in the EEC module. So I removed it and opened it up. There are stickers on there saying that its a warranty item so I probably voided that . This is what I found:



The pin that say GND coming through is completely burned out and there is a fine white frost on the circuit board at that connection.

So looking at getting a refurbished computer. I dont have a "Tune" sticker on the B pillar of my door. Oreillys has 5 options that say they fit my truck. There are two numbers stamped on my EEC; E43F-CA and E43F-AB. Neither of these match exactly with the options at Oreillys. (I have a 1984 f150, I6, manual transmission, carburated)

So my question is - How are the EEC's programmed differently?

Thanks guys.

Craig

 

PatinaTruck,


My truck is a 1986 with 4.9L and manual O.D. I removed the computer and converted to Duraspark. I saved the computer in case my son's 1984 with same engine and transmission ever needs it.


Since the numbers on yours does not match up with the O'Reilly offerings, would it benefit you if I check the numbers on the original 1986 computer? It is in storage [easy to get to] and I cannot get the ones from my son's truck.

 

If its easy to get to, I will take you up on that offer. Thank you.

 

I will get back with you, tomorrow.

 

Thank you. I have an email in with Cardone also to see how the computers are programmed differently. That should yield some interesting information.

 

This WILL be interesting. I had an early 80s Buick with a bad computer. I ended up on the phone with a GM engineer that told me they used whatever they had on the hand at the time. I had to buy an ECM, a blank EProm chip, find someone with an EProm writer, GM sent me the latest and greatest code on floppy discs!

 

Wow, your picture shows a pretty dramatic failure!

Looks like pin 46 of your ECU which should be SIG RTN. Probably that black/white wire you mentioned back in post #29. I don't have a good print of an 84 4.9 ECU for the feedback carburator, so I can't confirm much more than your pictures and schematic show along with some generic info from the Ford Fuel Injection Technical Library.

Now, it looks like the wire link from the connector pin to the board has blown out entirely, just like a fuse element. Since the function is a return, (ground) inside your ECU, I would suspect some sort of external event placed a high current battery + source onto this pin. Could be a wiring short, or some type of failure amongst the sensors sharing this circuit. Looks like you have already replaced the MAP and the ECT sensors and noted damage described as "melting". A quick look at your schematic shows a carburetor stepper motor which could have been the culprit, but likely was replaced with your rebuilt carburetor. All the other sensors work from a 5V reference which is designed to be pulled to ground via pullup resistors built into the ECU. I would recommend a careful check of the sensors and wiring to eliminate the possibility of frying your replacement ECU.

Now, there is not much to lose by trying to repair your existing ECU. Can be a bit of a delicate operation, but no more so than replacing capacitors as is often suggested. It would seem that your ECU continues to function as evidenced by the fact you can still pull codes. The damage in the pic is dramatic, but does not extend into the board outside of the residue you noted and that looks like it would clean up fine. If your soldering skills are up to it and if you can still see a bit of the contact for pin 46, I would try replacing the burnt connection with a piece of wire. You may be able to salvage a contact from the connector of another ECU, but I think what you have may be salvageable. Another option would be to replace the connector entirely with one scavenged from another ECU. At any rate, the programming in an EEC IV ECU for a feedback carburetor will be significantly different than for an EFI V8, so finding a replacement may be a challenge.

Good luck!

 

I concur with NotEnoughTrucks, it looks like some sort of major wiring malfunction transpired someplace in the underhood wiring at one time, and I would locate and repair that before installing any computer again.

Like he says, that *looks like* it could be repaired from what can be seen in the picture, but soldering will be necessary.

As for programming of the things, the major classifications are: California emissions or not; high altitude or not; automatic or manual transmission; Calibration Code used by the factory.

 

Well, NotEnoughTrucks, you've given me a bit of encouragement to try fixing what I have. I took the ECU further apart to look at the bottom for damage. Just some signs of heat there. Checking the "Stump" that is left on the connection side indicates its good. Ill head to radioshack and get some parts and equipment. Ill let you know what happens. With pictures of the repair.

And yes, all of the sensors attached to the black/white wire have been replaced. I have checked the wire in the harness to see if it is shorting on something and it looks intact. Ill inspect the other wires involved.

Thanks, Craig.