NZCOBRA Posted May 4, 2020 Share Posted May 4, 2020 I decided, to see if i could get the cruise control to work , i found a broken wire on the speed sensor which on my truck is where speedo cable fits into the transmission , i had to refit the servo which had been out for quite a while , i also found two plugs exactly the same ! but there is only one long enough to reach the servo , I fitted a new throttle cable , and clipped the servo cable in . On the first test run it worked ok, but it didn't work all the time ? I had asked some questions on ford truck forums , and asked Gary a couple as well , so i removed the servo to check the condition of what ever was inside it . ,This my version of how it works The port beside the plug on the servo is basically sealed shut , it has a (electric valve ) until you turn on the cruise (set cruise) that then allows vacuum into the housing , there is a second electric valve which lets the vacuum to the back side of the diaphragm ,that's the hose which goe's across the servo with a tee going to the dump valve on brake pedal , so when setting accel speed it lets more vacuum into the back of the diaphragm, it has a potentiometer pot on the arm pivot, that pulls the throttle cable ,so your truck accelerates to your speed setting , coast must let vacuum bleed out of back of diaphragm, and the brake dump drops the vac quickly to stop the cruise , so the combined effort of the , speed control on the speedo cable, the servo pivot arm potentiometer and computer part , of it, adjusts the vacuum on each side of the diaphragm to maintain the set speed . well that's what i gather from looking at all the internals . Hope this helps someone , I made a Vacuum canister( Maybe i should have used a dog food can) ! to help the system have more volume, it has a non-return valve ,also i had weak accel and i tried lifting my brake pedal while setting the accel and truck pulled good to set speed , my dump valve was bleeding vacuum , so with torch in hand , turned it about 2 turns toward the pedal i think the nylon tip gets worn and not sure how it seats but if it was rubber, it could be hard , also I think that when you turn cruise off on the pad, it takes longer to bleed the vacuum down and the dump valve is more of a noticeable off. white arrow to servo , yellow arrow from engine ,supply vacuum , Cheers Link to comment Share on other sites More sharing options...
Gary Lewis Posted May 4, 2020 Share Posted May 4, 2020 Good job, Vaughn! Thanks for the write-up. It will surely help someone at some point who is struggling getting one of these things going. Who know, it may be me! Is the yellow arrow pointing to your vacuum canister? That's pretty! But it looks like it is mounted on the rare aux battery mount. Is that what it is? Link to comment Share on other sites More sharing options...
grumpin Posted May 4, 2020 Share Posted May 4, 2020 Good job, Vaughn! Thanks for the write-up. It will surely help someone at some point who is struggling getting one of these things going. Who know, it may be me! Is the yellow arrow pointing to your vacuum canister? That's pretty! But it looks like it is mounted on the rare aux battery mount. Is that what it is? That’s great! Link to comment Share on other sites More sharing options...
NZCOBRA Posted May 4, 2020 Author Share Posted May 4, 2020 Good job, Vaughn! Thanks for the write-up. It will surely help someone at some point who is struggling getting one of these things going. Who know, it may be me! Is the yellow arrow pointing to your vacuum canister? That's pretty! But it looks like it is mounted on the rare aux battery mount. Is that what it is? Hi , Gary, didn't come out too bad , quite pleased and it works, the yellow arrow is the hose coming from my motor to the new canister , i used an old brake booster check valve , I dont know about the battery mounting tray ,there was sort of a flat spot, with three holes.............????? , so to find out about my truck , what do i look up, door code , vin , i have the usa plate, cheers Link to comment Share on other sites More sharing options...
NZCOBRA Posted May 4, 2020 Author Share Posted May 4, 2020 Hi , Gary, didn't come out too bad , quite pleased and it works, the yellow arrow is the hose coming from my motor to the new canister , i used an old brake booster check valve , I dont know about the battery mounting tray ,there was sort of a flat spot, with three holes.............????? , so to find out about my truck , what do i look up, door code , vin , i have the usa plate, cheers Also my truck is an 86, but i put the late model air box and washer/ coolant container, because the air box wouldn't fit over the cobra rocker covers , which were required as it has got comp cams steel rockers on 7/16 screw in studs, I didn't like the hot air box anyway , I always keep all my parts. Cheers Link to comment Share on other sites More sharing options...
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