1984 Ranger 2.3 MCU?

[colefouche13]

hello, I have a 1984 Ranger with the 2.3 and I cannot figure out what the MCU does. so could someone help?

 

[Mark_88]

MCU? You mean the little mess of wires on the passenger side fender or do you have something else? Typically, that was an idle control module with the carbed engines...it was responsible for kicking the idle down after the engine warms up...

There was a little box on the driver side that controlled the spark along with the distributor and coil, so in no spark situations you need to check the coil output and then trace it to the distributor...then to the plugs...

So...I guess if you just need information to understand the parts that's what they are...if you are having trouble starting then it would help to know what you've done already...whether it's spark or fuel issues...

 

[colefouche13]

Haha yes the little box full of wires and a few vacuum lines. It has a ford sticker on it that says "MCU". well I just want to pull it out and I have a new carb coming with none of the electronic stuff on it. I'll check the wiring diagrams and vacuum diagrams to see if anything important goes through that, if not it's coming out.

 

[adsm08]

I'm no expert on carbs, but I thought the coil, alternator, and starter were the only important things that had wires.

 

[Mark_88]

Haha yes the little box full of wires and a few vacuum lines. It has a ford sticker on it that says "MCU". well I just want to pull it out and I have a new carb coming with none of the electronic stuff on it. I'll check the wiring diagrams and vacuum diagrams to see if anything important goes through that, if not it's coming out.

The one on the passenger side can be removed if you are using linkage controlled choke or kick down...mine was only connected for about the first six months until I burned the tip of my finger on a hot choke connection...lol...then I simply disconnected it from the carb...never actually had a functioning choke and my truck started without it just fine...most of the time.

I did put on a block heater in the winter and that eliminated the need for a choke or air warming attachments...

I know people have removed the module from the passenger side but I never did find out what needed to be left connected. It doesn't directly connect to the starter relay or anything that I can see, but a mass of a dozen or more wires meanders around in the engine bay and somehow connects to the firewall connectors...

I'm no expert on carbs, but I thought the coil, alternator, and starter were the only important things that had wires.

Pretty much that's all there is...and after driving a carbed truck for 14 years I thought I knew all I needed to know about them...I was wrong, of course...

They are not that complicated but certainly the fine points of them are worthy of study if you are gong to drive one...

 

[tomw]

Back then, there were no off the shelf injector sytems and EPA was breathing down their necks about emissions, and international problems with fuel supplies were pushing the need for better mpg. That all combined to multiple things on carbs, one of which was a movable metering rod that changed the fuel flow depending on ... phase of moon, price of gas, price of rice, temperature, weather forecast, and which way the cow stood when making patties... in other words - stuff - that was not disclosed in available readings.
So, you are left with a 'dithered' carb, modulated vacuum doing heaven knows what, and plastic nodules that have vacuum lines on either side. Some are temp sensors & switches, some delay vacuum signals, and some use a small vacuum signal to control a larger, more powerful, vacuum signal. The last is the EGR control, operated by carb vacuum near the plate, moving a diaphragm to operate a larger valve to move the EGR diaphragm... whatta mess.
If you do not have emissions inspections, you can go to older model stuff, such as the two-barrel holley-weber of the 1974 vintage along with a manifold if you can find one that matches intake ports. The one-barrel on the 2.0 was/is an emissions carb, some of which have electrical controls to diddle with the metering rod(s) to adjust the mix on the fly depending on 'stuff', but is not really a well-flowing carb to my knowledge.
Used to was you could get an adapter for a two-barrel regular old Holley that was similar to the old two barrel Ford used on so many V8's of the day. More than enough flow for a 140 cid engine.
The caution at the end of this writing is to know what you are doing, as disconnecting stuff from a carb, especially electrical stuff, can lead to very poor fuel mileage, or a very large loss of power, depending. When the stuff works, it does pretty good, but when it breaks, it is like searching for hens teeth to find the problem. IMO.
tom

 

[colefouche13]

So here's some pictures of the box itself. I got a new carb and it has nothing on it except a fuel inlet. But first I followed all the vacuum lines and there were only three that I still need and they aren't connected directly to this box. One is from the distributer to the temperature activated vacuum switch on the intake manifold for the vacuum advance for the distributed. Another is from the vacuum modulator on the transmission and the last one connects to a selenide on the a/c to a different vacuum switch on the intake manifold. The rest are all emissions related and go to the MCU. So there are a lot of electrical wires and I don't know if I can pull the unit out because they connect straight to the ecu and distributed but there are two connectors I can't use because of my new carburetor, they are for the throttle positioned and the feedback solenoid. So should I pull the MCU? I just hate unplugging electrical stuff, especially whe. It connects to the ECU.

 

[Mark_88]

I remember seeing that setup once...a long time ago...I've had nightmares ever since...but that's just my natural aversion to anything complicated.

l'd be willing to bet that there is so much corrosion on the bottom of that vacuum thingy that it probably isn't doing what it should or could do anyway...and although I agree mostly with what tomw said about removing stuff (that's why I still had the MCU in my truck 5 years after disconnecting it) I think you could probably get away with that here.

My truck had a smog pump, the old 2 bbl Asian carb, and about a mile of vacuum tubes that seemed to actually do something. I started with the smog pump removal since the bracket was broken anyway and just worked my way back to the carb, purge canister, and under the intake manifold vacuum lines...the rest was easy.

I don't expect anyone on here could or would want to step you through how to remove the MCU (ICM was what it was later called I think) so you're pretty much on your own...and I wouldn't volunteer any information without being there to trace every line and vacuum tube connection...because it just needs to be viewed and understood to make any sense.

I would say you could probably make yourself some money if you documented a complete system because nobody that I've seen yet has a complete system...but that's your call...

 

[tomw]

The contents of the box look like 1)vacuum canister, 2)EGR solenoids that control vacuum apply and hold to the EGR diaphragm, and 3)ignition module. In this case, ignition module also handles diddling with the carburetor mixture based on speed, temp and load.{as a guess}
If you replace the carburetor with aftermarket, the only thing I would be concerned with is vacuum to the distributor advance, other than carburetor stuff such as power valve, jets, mixture adjustment, and fitting an air cleaner that would keep out the abrasives that want to destroy the rings. Oh, and have hot air if needed for cold weather operation. Nothing like trying to drive with ice forming in the carburetor. You go slow, and eat a LOT of gas, until you pull over and let things melt.
tom

 

[colefouche13]

The contents of the box look like 1)vacuum canister, 2)EGR solenoids that control vacuum apply and hold to the EGR diaphragm, and 3)ignition module. In this case, ignition module also handles diddling with the carburetor mixture based on speed, temp and load.{as a guess}
If you replace the carburetor with aftermarket, the only thing I would be concerned with is vacuum to the distributor advance, other than carburetor stuff such as power valve, jets, mixture adjustment, and fitting an air cleaner that would keep out the abrasives that want to destroy the rings. Oh, and have hot air if needed for cold weather operation. Nothing like trying to drive with ice forming in the carburetor. You go slow, and eat a LOT of gas, until you pull over and let things melt.
tom

Well the distributor advance is defiantly temperature activated. There are three vacuum switches on the intake manifold that are part of the cooling lines. The switches are temperature activated and once the engine coolant reaches a certain temperature they open up. The vacuum advance on the distributor connects to one of these switches so that won't be a problem with the new carb, or even with pulling the whole MCU out.

 

[diver14_98]

i have a 2.0 with a one barrel so take this for what its worth. i cut and removed everything from that box. i had to get power to the choke and the coil after i did this. i then remove every vacuum line on the truck. i ran one vacuum line from from a ported vacuum port on the carb to one of the temp switches on the intake then to the dist. the truck runs 300 times better than it did before. i can take pic tomorrow when there is light if you want.

i, actually getting ready to rip all of the carb stuff out and put gm tbi on it( don't beat me. i work with this system a lot so i know it and it works well)

let me know if i can help in any way. i cant say i will be of any help but ill try

 

[Rizzo1130]

i have a 2.0 with a one barrel so take this for what its worth. i cut and removed everything from that box. i had to get power to the choke and the coil after i did this. i then remove every vacuum line on the truck. i ran one vacuum line from from a ported vacuum port on the carb to one of the temp switches on the intake then to the dist. the truck runs 300 times better than it did before. i can take pic tomorrow when there is light if you want.

i, actually getting ready to rip all of the carb stuff out and put gm tbi on it( don't beat me. i work with this system a lot so i know it and it works well)

let me know if i can help in any way. i cant say i will be of any help but ill try

Please take a picture so I can see that's exactly what I want to do to my carburetor

 

[Daniel Black]

I took it all out when I swapped my 2.0 for a modified 2.3. I did have to find a hot wire for coil power. The distributor wiring goes from the Duraspark box, to the computer, then back to the distributor. I took the two plugs I needed from the old harness and made a harness straight from the Duraspark to the distributor. The only thing that seemed crazy is the wiring for the backup lights went with the computer wiring for some reason. It was as simple as finding the two backup switch wires and jumping power back to it. My trucks a V8 now and I still use the same wiring setup I had with the 2.3. Same distributor harness, same Duraspark box and the same power wire running the coil. I've always had aftermarket mechanical gauges but I think the gauge wires had their own harness like the alternator. Just hook up the vacuum advance from distributor to carb and find vacuum for your trans and call it a day.