Why two vacuum lines from distributor?

Been a bit, but I’m FINALLY within a few days of getting the Bronco running with the Sniper EFI set up. Right now I’m running vacuum hoses and noted that I have two vacuum lines (one red, one yellow) coming off the distributor. I assume one was tied to the emissions system, but that was a bit of a mess when I got it.

Just hoping for a little confirmation that I can remove/cap one and still be good to go. I should note it’s a duraspark II set up.

Also, there’s a few electrical wires that used to go to the carb - one coming from the distributor area. Any thoughts on what that could be (pic attached). I looked at the wiring documents, but I’m really terrible with them. I’m hoping I can maybe tap into it when I’m wiring up the Sniper (last big step!!!).


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1983 Bronco 4.9 300 I6
Current Name: Whitney

1983 Bronco 4.9 300 I6
Current Name: Whitney

The vacuum lines probably were for advance on the backside of the distributor and retard on the front side.  Under some conditions they used one vs the other, usually decided by the ECU.

Not sure what the wires to the carb are, but if you gave me the wire colors I could figure it out.  I'd need both the primary as well as the secondary color.

Some are for the stepper motor for leaning the air/fuel ratio.  Some are for throttle solenoids.  There were several combinations and the wire colors are the key.

Either way, it’s probably not switched power, right? I think it went to the IAC before...

I should have taken a picture of how they are attached to the distributor - they both come off a plastic tree. One behind the other. Seemingly double sourced vacuum? I’ll get a picture tomorrow.

Don't think there's an idle air controller on a YFA.  Those are for EFI.

You know what, I think it might be for the choke... I’ll get you those colors though.

OK - Here’s the wire as well as the two vacuum hoses coming off the distributor.

Looks like the wire is red with yellow or orange hashes.

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Gary,

I think the hoses to the dist. are the other way around.
Most I have seen the front port is advance and the rear retard.
Easy way to tell is use a hand pumpor put vacuum to them and see what way the pickup plate moves when vacuum is put to it.

Now this brings up a question (or 2).
Was this a feed back system or not?
I ask because the feed back dist. did not have vacuum to it and I dont know of the "before feed back" having 2 ports on the dist., mine dose not, unless it was a Cal. truck maybe?

For the wires to the dist area it would not be the choke as I believe that was 1 wire off the"S" lug of the ALT.
Do we have a little better picture of the plug and the other end where the wires go to?

Just my .02 on them
Dave ----

I’m having real trouble with images. Here’s the vacuum set up.

1983 Bronco 4.9 300 I6
Current Name: Whitney

1983 Bronco 4.9 300 I6
Current Name: Whitney

I can follow that red and yellow wire to this connector that then goes into the firewall.







1983 Bronco 4.9 300 I6
Current Name: Whitney

Heres the connector on the other side, which definitely previously went to the carb.







1983 Bronco 4.9 300 I6
Current Name: Whitney

FrazerJames wrote

I’m having real trouble with images. Here’s the vacuum set up.

Are the 2 lines Tee in just below what I think is a check valve?
And if so does the 1 line then connect to the dist. just out of the picture to the left?
Or is there 2 ports on the dist. vacuum can just out of the picture to the left?

If they do Tee in to 1 vacuum port on the dist. vacuum can then use only 1 line to go from the TBI unit to the dist. vacuum can.
Dave ----

FrazerJames wrote

Where dose the other end of that wire go to and the wire colors?

Did this truck have a feed back system or not or a Calf. truck?
Being I see the dist. vacuum can (I think) in another picture I am guessing non-feed back system?
Truck have AC and if so dealer installed? Factory AC had the idle kick up wire coming from the other side, at least on my 81 with a 300.

I am also having issues with "quoting" and my answers showing up and I think I am answering to fast before you get the full story posted

Let me see if I can make out what you got.
Dave ----

Yep, it’s teed. No double ports. Does it matter which one? There that check valve on one of them...


Here’s a better pic of it.


1983 Bronco 4.9 300 I6
Current Name: Whitney

Carb end

other end

I am thinking if the other wires in that plug don’t go to anything you could just un-plug that harness as I think there is 1 of 3 plugs on the inner fender not used.
If the other wires go to something what is it?
Dave ----

It’s definitely not a California truck and I don’t believe it has feedback. It does have AC and it was factory installed. The wire originally came up and over the engine.


In some pics before I removed the carb, I’m pretty sure it was attached here:

Yep, you got that set up right. From that plug all the wires feed into the firewall. I’ll see if I can spot where they go to from there inside the cab.

Really, what I was hoping for us that red/yellow wire might be live for the key switch.

FrazerJames wrote

Yep, it’s teed. No double ports. Does it matter which one? There that check valve on one of them...


Here’s a better pic of it.

Well being the red & yellow are that plastic line I would not use either in the long run as they will break so replace it with rubber from the TB unit to the dist.
But for now I would pull the check out of the short rubber hose and plug the hose (small screw or bolt works) and use the yellow one.
Dave ----