what is this little black box?

[1lowf150]

i am working on my 70 ranger. i bought the truck no motor and trans. someone had stole the cluster and collum from it.i have been working under the dash to figure out the plugs and i have to the right of the gas pedal on the firewall a little black box. it has two vacuum lines going out through the firewall,and two wires go out the firewall up and to the left of the fuse panel. the other set of wires run to the drivers side door jamb and are connected to a plate. i have now idea what this does, the front end was off when i got it so i don't know what the wires hooked to, and the plate in the jamb, no idea what that would do. the plate is stamped with a ford logo and has a part number. this is my first bump side truck, so i am new to the parts, i have never seen anything like this in any dent side i ever worked on. any help would be great. thanks

[seattle67]

There is a picture here of that somewhere. I dont have that on my 67, but I believe it is for emissions.

[Joshpow]

Saw the same thing on the 70 I parted out. I dont know what it is unless it works the choke for better emissions. If anyone knows, clue us in.

[FORDification]

That black box is a NOx (emission control) device, part of a system called TRS, or 'Transmission Regulated Spark', that only allows the vacuum advance to work under certain conditions. When the outside temperature is below 60 degrees or so the vacuum advance is allowed...when it's above that temp, the vacuum advance is only allowed when the vehicle is traveling around 30mph or faster. The hardware and wiring to do this varied from '70-'72 but basically you have a temperature sensor on the driver's door pillar, a sensor on the transmission and a control module with a solenoid valve for the vacuum. For automatics the transmission sensor is a line pressure switch and for manuals it's just a mechanical switch that tells when it's in high gear. The control module switches the vacuum source on or off to the vacuum advance depending on the temps and/or speed. This emission system is a 'tack-on'Â

[Joshpow]

I have the temp switch in my driver's door jamb, but no box or vacuum lines to my knowledge. I know it isn't operable, because my vac adv line is directly off the ported line on the carb. Does the temp switch operate anything else?

[1lowf150]

thank's everyone for the help. this site is the best, always get great help.

[ezernut9mm]

cool. now i know what the piece is that the speedo cable ran through on the 70 i parted. it's the "speed sensor". thanks keith.

[OldGuy]

Hey everyone,
I have been struggling with a stumble off idle and decided to buy a rebuilt 2100 2bl carb on my 360 w/auto trans just to minimize the frustration of chasing down the problem. Over the last couple of days I have seen a few "warnings",similar to above, to make sure the distributor vacuum lines go to the carb port not the manifold port.

My distributor has 2 lines coming off of it. I noticed today that the vacuum line off of the "front" of the distributor goes to the carb, but the other line goes to the manifold port.

I have not switched to the rebuilt carb yet and wondered if this was the correct set up or part of the problem with stumble? Any easy way to check?

PS I have already put new ignition wires, plugs, MSD coil to try and get rid of stumble (I was realy hoping to leave the darn carb alone!) Pertronix upgrade is next.

THX

[rjewkes]

thge back port on tyhe dist. goes to manifold vaccum tohelp with deceleration. Mosdt have taken it off with todays crummy gas it sometimes cuases an over retard on the advance.

[OldGuy]

thge back port on tyhe dist. goes to manifold vaccum tohelp with deceleration. Mosdt have taken it off with todays crummy gas it sometimes cuases an over retard on the advance.

OK thanks for quick reply. At least I know that the vacuum lines aren't crossed with each other.