Why two vacuum lines from distributor?

[FuzzFace2]

FrazerJames wrote

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:

If the wires from the plug on the fender go inside the cab then it would not be easy to just unplug and remove the harness.
That also looks like it goes to the choke, it is a little different than my 81 that has 1 wire from ALT to choke with hot air asst.

As for using it for keyed power you could turn the key on and see if hot then but dose it also need power when cranking also? If so you would need to check for that at the ssame time.

The other question is what will it power and how much power (amps & volts) dose that part take to make it work and will that wire in the plug be able to handle it?
Dave ----

ps them pictures you post really mess up trying to quote a post  
Had to remove the pictures.

[FrazerJames]

Yeah, just checked and this plug leads to a mess of wrapped wires heading into the firewall and who knows from there unless I start unwrapping the factory set up. Either way, I do need to figure out a place to tap into keyswitch that also has constant 12 volts while running.



1983 Bronco 4.9 300 I6
Current Name: Whitney

[FrazerJames]

Yeah, I think the image issue has something to do with the float - it’s driving me a bit nuts too.

It’s going to the Sniper EFI system - It definitely needs 12 volts at key ON, but needs power when starting as well. It sounds like it’s ok if it only gets 10 volts for starting though. They don’t give any amperage requirements, and from the research I’ve done no one seems to have a problem with the stock wiring.

[FuzzFace2]

FrazerJames wrote

Yeah, just checked and this plug leads to a mess of wrapped wires heading into the firewall and who knows from there unless I start unwrapping the factory set up. Either way, I do need to figure out a place to tap into keyswitch that also has constant 12 volts while running.

So I get this right the plug has 2 wires a yellow and a red one.
They go down to the plug in the other picture that has 2 other wires on the same side of the plug the 2 wires are on.
The other 2 wires on the same side go back into the harness and into the cab.
The other side of the plug has 4 wires coming from the harness that is also from the cab.

If so I dont know why they would send wires out and then back in only to have 2 go to the choke?
I would post up all the wire colors on each side of the plug so someone can look them up for you.
Dave ----

hate this quote

[FrazerJames]

Here’s the thing Dave - If I’m reading this correctly (found in another thread looking for the same thing but they didn’t say where they tapped into), that Red/Yellow wire going to the choke may actually be hot for both. There’s an excellent chance I’m very wrong...

[FrazerJames]

Sorry for the confusion. No, it’s one red wire with yellow hashes. At the plug it just goes into another red with yellow hashes and into the cab. No weirdness that I can tell.

[FuzzFace2]

FrazerJames wrote

Here’s the thing Dave - If I’m reading this correctly (found in another thread looking for the same thing but they didn’t say where they tapped into), that Red/Yellow wire going to the choke may actually be hot for both. There’s an excellent chance I’m very wrong...

So it is EEC and has a computer in the cab?
I hear the EEC systems can be a tuff cookie to work on or with.

I dont see the choke set up in there or my eyes are that bad?
Is the wire you are looking at on the right upper side of that?
It looks to be 1 wire R/Y and not 2 wires a R & Y.
Or I have the wrong colors and still thinking of the vacuum lines LOL
Dave ----

[Rusty_S85]

Gary Lewis wrote

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.

I've always been curious about the non computer setups myself.  My original distributor I pulled from my '82 to replace with a new one actually has the dual advance can with the inner line plugged and using just the outside terminal for advance.  I think the inner was for retard and the outter was your typical advance.  Sort of like on my dual advance can on my '56 292 Y8, the outter is to venturi vacuum for advance and the inner is to manifold vacuum to pull advance out.  When you go full throttle manifold vacuum drops but venturi vacuum stays so you lose this retard feature of the advance and you get more advance under load.  This was done as there was no mechanical advance on this distributor.  On my '82 I question how it would work cause you couldnt do the same thing as ford did on my '56 as the '82 has a mechanical advance to take over when vacuum is lost.

Mine was not hooked up and my original emission decal is so faded I dont know if it even shows how it hooked up in the first place.

[FuzzFace2]

Rusty_S85 wrote

Gary Lewis wrote

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.

I've always been curious about the non computer setups myself.  My original distributor I pulled from my '82 to replace with a new one actually has the dual advance can with the inner line plugged and using just the outside terminal for advance.  I think the inner was for retard and the outter was your typical advance.  Sort of like on my dual advance can on my '56 292 Y8, the outter is to venturi vacuum for advance and the inner is to manifold vacuum to pull advance out.  When you go full throttle manifold vacuum drops but venturi vacuum stays so you lose this retard feature of the advance and you get more advance under load.  This was done as there was no mechanical advance on this distributor.  On my '82 I question how it would work cause you couldnt do the same thing as ford did on my '56 as the '82 has a mechanical advance to take over when vacuum is lost.

Mine was not hooked up and my original emission decal is so faded I dont know if it even shows how it hooked up in the first place.

Rusty,

Looking over his pictures I found he did not have a 2 port vacuum can on the dist. but 2 different vacuum lines going down to a single port can.
The lines Tee'd in close to the can and 1 line looked to have a check valve in it.
I have no clue where the 2 lines got hooked up to but a guess with the check valve they wanted 1 side not to pull vacuum from the other and only on the dist. can?
Crazy set up for sure
Dave ----

[Rusty_S85]

FrazerJames wrote

Yeah, I think the image issue has something to do with the float - it’s driving me a bit nuts too.

It’s going to the Sniper EFI system - It definitely needs 12 volts at key ON, but needs power when starting as well. It sounds like it’s ok if it only gets 10 volts for starting though. They don’t give any amperage requirements, and from the research I’ve done no one seems to have a problem with the stock wiring.

If you are doing sniper I havent confirmed it but lots of people swear holley recommends using the key hot in run and crank as a trigger for a relay then provide straight battery voltage to the sniper through the relay.

Im tempted to do this myself as I could in theory splice into the key hot wire for the ignition system as it has to be hot in the run and crank position.  In theory it shouldnt harm the ignition system using it as a trigger and should take nothing away from the voltage to the ignition system.  But I think I will try to drop my column and find a wire from the ignition switch itself that is hot in key on as well as crank and splice a jumper wire into it to run as a trigger for the sniper.  Think it would be easier as I can run this wire along the dash and out through the firewall with the wiring for the passengerside lighting harness to my auxiliary fuse/relay box that will be mounted by the battery.

For the sniper itself there is no amperage rating but they do want more than 11 volts though otherwise the sniper cant fully function properly.  The FiTech goes a bit further to 10.5 volts as a min.

[Rusty_S85]

FuzzFace2 wrote

Rusty_S85 wrote

Gary Lewis wrote

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.

I've always been curious about the non computer setups myself.  My original distributor I pulled from my '82 to replace with a new one actually has the dual advance can with the inner line plugged and using just the outside terminal for advance.  I think the inner was for retard and the outter was your typical advance.  Sort of like on my dual advance can on my '56 292 Y8, the outter is to venturi vacuum for advance and the inner is to manifold vacuum to pull advance out.  When you go full throttle manifold vacuum drops but venturi vacuum stays so you lose this retard feature of the advance and you get more advance under load.  This was done as there was no mechanical advance on this distributor.  On my '82 I question how it would work cause you couldnt do the same thing as ford did on my '56 as the '82 has a mechanical advance to take over when vacuum is lost.

Mine was not hooked up and my original emission decal is so faded I dont know if it even shows how it hooked up in the first place.

Rusty,

Looking over his pictures I found he did not have a 1 port vacuum can on the dist. but 2 different vacuum lines going down to a single port can.
The lines Tee'd in close to the can and 1 line looked to have a check valve in it.
I have no clue where the 2 lines got hooked up to but a guess with the check valve they wanted 1 side not to pull vacuum from the other and only on the dist. can?
Crazy set up for sure
Dave ----

I wonder if that Tee took out the temperature controlled vacuum switch that ford used?  Looking at the diagram when I was working on my emission decal to replicate how my truck looks it shows that you had ported and manifold vacuum through a three terminal vacuum temperature switch, from my understanding there would be no vacuum supplied when cold to take vacuum advance out till warmed up then above I believe I read 140 or 150 degrees it would apply ported vacuum to give you advance when driving.  Then above 210* in what was believed to be a overheat condition the switch would switch the distributor to manifold vacuum to idle the engine up to spin the fan faster in an attempt to cool the engine down if idling in traffic.

That is what I planned on doing with my sniper in a sense having the idle speed setup to increase by 100 to 150 rpm above 220 degrees which I may have to play with as I dont know what would be normal for my engine build since I am running a NOS 190/192* thermostat if I remember right so my engine may very well run at 200 - 220 normally but with the optional 7 bladed flex fan I am throwing on that was used with A/C equipped trucks I may not have that issue with the HD cooling radiator my truck came with.

I dont think my truck how ever has this temperature vacuum switch hooked up either I would have to look under my hood one day but I really have no desire to open the hood till its time to pull my old engine out and drop the new one in lol.

[FuzzFace2]

Rusty_S85 wrote

FrazerJames wrote

Yeah, I think the image issue has something to do with the float - it’s driving me a bit nuts too.

It’s going to the Sniper EFI system - It definitely needs 12 volts at key ON, but needs power when starting as well. It sounds like it’s ok if it only gets 10 volts for starting though. They don’t give any amperage requirements, and from the research I’ve done no one seems to have a problem with the stock wiring.

If you are doing sniper I havent confirmed it but lots of people swear holley recommends using the key hot in run and crank as a trigger for a relay then provide straight battery voltage to the sniper through the relay.

Im tempted to do this myself as I could in theory splice into the key hot wire for the ignition system as it has to be hot in the run and crank position.  In theory it shouldnt harm the ignition system using it as a trigger and should take nothing away from the voltage to the ignition system.  But I think I will try to drop my column and find a wire from the ignition switch itself that is hot in key on as well as crank and splice a jumper wire into it to run as a trigger for the sniper.  Think it would be easier as I can run this wire along the dash and out through the firewall with the wiring for the passengerside lighting harness to my auxiliary fuse/relay box that will be mounted by the battery.

For the sniper itself there is no amperage rating but they do want more than 11 volts though otherwise the sniper cant fully function properly.  The FiTech goes a bit further to 10.5 volts as a min.

So if you can find a hot key on supply and not when cranking could you tap off the starting solenoid small post marked "I" like they did for points motors when starting for a hotter spark?
Dave ----

[Rusty_S85]

FuzzFace2 wrote

Rusty_S85 wrote

FrazerJames wrote

Yeah, I think the image issue has something to do with the float - it’s driving me a bit nuts too.

It’s going to the Sniper EFI system - It definitely needs 12 volts at key ON, but needs power when starting as well. It sounds like it’s ok if it only gets 10 volts for starting though. They don’t give any amperage requirements, and from the research I’ve done no one seems to have a problem with the stock wiring.

If you are doing sniper I havent confirmed it but lots of people swear holley recommends using the key hot in run and crank as a trigger for a relay then provide straight battery voltage to the sniper through the relay.

Im tempted to do this myself as I could in theory splice into the key hot wire for the ignition system as it has to be hot in the run and crank position.  In theory it shouldnt harm the ignition system using it as a trigger and should take nothing away from the voltage to the ignition system.  But I think I will try to drop my column and find a wire from the ignition switch itself that is hot in key on as well as crank and splice a jumper wire into it to run as a trigger for the sniper.  Think it would be easier as I can run this wire along the dash and out through the firewall with the wiring for the passengerside lighting harness to my auxiliary fuse/relay box that will be mounted by the battery.

For the sniper itself there is no amperage rating but they do want more than 11 volts though otherwise the sniper cant fully function properly.  The FiTech goes a bit further to 10.5 volts as a min.

So if you can find a hot key on supply and not when cranking could you tap off the starting solenoid small post marked "I" like they did for points motors when starting for a hotter spark?
Dave ----

I guess you could do that, just be extra wiring but you would have to take and run both wires up to a relay as a trigger though.  You also would have to make sure the two wires dont back feed being tied together that could cause other issues as well.

But on the ignition switch there should be a wire coming out that has 12v on it when the key is on as well as in the crank position.  There has to be as the ignition system has to have power in crank as well otherwise the engine will just sit there and spin over and not run till you let up off the key.

[FrazerJames]

Yeah, they do mention a relay as an option in the instructional videos. It’s beyond my know-how at the moment, though. I have real trouble wrapping my head around electrical - I just don’t do it enough to retain the science of it.

Having this one choke wire be hot for crank/run would be insanely lucky... I’ll likely have to find another source, but I’d prefer not to have to run it from the inside of the cab.

[Rusty_S85]

FrazerJames wrote

Yeah, they do mention a relay as an option in the instructional videos. It’s beyond my know-how at the moment, though. I have real trouble wrapping my head around electrical - I just don’t do it enough to retain the science of it.

Having this one choke wire be hot for crank/run would be insanely lucky... I’ll likely have to find another source, but I’d prefer not to have to run it from the inside of the cab.

Well the factory choke wire was only hot after the engine was cranked up and running.  That way you can go to accessory mode and listen to the radio without the choke opening up fully.

On the relay its not really that hard.  On a 5 pin relay you have pins 30, 87, 85, 86, and 87A.

Pin 87A which is the middle pin is normally hot then when the relay is activated pin 87A loses power, this pin if you decide to use the AC cut out function of the sniper will require your compressor clutch wire to clutch come from this pin 87A.

Pin 30 would be your power wire being triggered.  It can be power or ground, in the case of the sniper for AC cut out it would be battery hot.

Pin 87 would be your triggered output going out to what is being powered or grounded by the relay.  In the case of the AC cut out this would be left empty.  In the case of powering up your sniper this would go to your key hot on the sniper wire.

Pin 85 is one leg of the trigger.  In the case of the AC cut out this would go to output #6 which Holley uses grounds for triggers.  In the case of the key on relay for the sniper this terminal would be grounded.

Pin 86 is the other leg of the trigger circuit.  This one in the case of the AC cut out would go to battery hot for the sniper to apply ground to activate cutting the AC off.  In the case of a key hot relay this pin would be the key hot circuit you are using that is hot in crank and run position.

If it helps below is the wiring schematic I created for my truck for my auxiliary fuse/relay box.  The sniper related relays are numbered R4, R5, R6.  My plan is to not use a relay for the key hot trigger seeing as I have no more relays if I follow through with using R7 and R8 for auxiliary roll bar lights (two spots/two floods).  I could get a larger fuse/relay box but then it comes with way too many relays/fuses.  Only way I could add an extra relay for the sniper key hot would be to try and run 400W worth of halogen lights off a single 30/40A relay.  In theory I should be able to as at 12.8v nominal battery voltage 400w worth of lights is 31A and at 14.0v which is what the 3G regulator is set to, 14.3V to be exact drops the amperage requirement down to 27A/28A.  So I should be able to run both sets of lights off one single 40A 5 pin relay.

But maybe this wiring diagram can help you with planning out your hook up as far as the sniper goes.

[FrazerJames]

Ok, yeah, I think I follow that. So I’d need an auxiliary fuse box connected directly to the battery, then potentially use that choke wire for crank and run?

[FrazerJames]

Ok I’m digging more into this, Rusty, and I feel much more confident I can do this.

I’d be interested in where you got your set up. I have some decent relays ready to go in my cart on summit, but do I want to be building out a true auxiliary fuse box? I’m not sure I’ll need any future accessories or anything. Maybe just get some relays and drop some in-line 100amp fuses before them?

Here’s what I’m gathering from your post aside from the AC kick down notes:

87A - nothing

30 - constant battery positive

87 - key hot on sniper

85 - ground

86 - ignition keyed power (assuming I’d connect that to the ignition wiring that I just set up for the new alternator)

[Rusty_S85]

FrazerJames wrote

Ok I’m digging more into this, Rusty, and I feel much more confident I can do this.

I’d be interested in where you got your set up. I have some decent relays ready to go in my cart on summit, but do I want to be building out a true auxiliary fuse box? I’m not sure I’ll need any future accessories or anything. Maybe just get some relays and drop some in-line 100amp fuses before them?

Here’s what I’m gathering from your post aside from the AC kick down notes:

87A - nothing

30 - constant battery positive

87 - key hot on sniper

85 - ground

86 - ignition keyed power (assuming I’d connect that to the ignition wiring that I just set up for the new alternator)

The auxiliary fuse/relay box you wouldnt have to have unless you are going to have a large number of auxiliary circuits you like to consolidate into one unit.  Currently I have individual relays mounted all over which is why I am going to rewire it all and consolidate it into one auxiliary box to clean things up for a more OE look.

Correct, the center pin or pin 87A is seldom used as it is powered up long as the relay is not energized.  majority of uses of the relay will result in 87 being used instead where it is only powered up when triggered.  If your alternator excite wire is hot in key on as well as key crank then yes you can use that as your trigger as well.

[FrazerJames]

Ah, I think I found where to tap into - the wiring from the key switch to the ignition coil should be run and start, which I think you mentioned above, but now that I’m getting everything to sink in it’s coming together.


This diagram helped a lot.

[Rusty_S85]

FrazerJames wrote

Ah, I think I found where to tap into - the wiring from the key switch to the ignition coil should be run and start, which I think you mentioned above, but now that I’m getting everything to sink in it’s coming together.


This diagram helped a lot.

Correct and running it to trigger a relay shouldnt have an adverse effect on your ignition system.  It may be what I try on my setup if I dont feel like dropping the column on my truck to find the wire at the ignition switch itself.