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Thread: Cruise control w/carb?

  1. #1
    Gonna buy me a Mercury BoulevardRide's Avatar
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    Default Cruise control w/carb?

    On the early models with carburetor... how complex is the cruise control system? Is there a computer module, or is it just vacuum lines and switches? Is it basically the same as the cc in the 1970s big block Fords?
    96 MGM

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  2. #2
    I'm an air-conditioned gypsy gadget73's Avatar
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    Not real complicated. Ford used the same system from the 60s through the 90s. There is a control module with a half dozen odd pins on it to make it all work. Speed sensor in the trans or speedo or somewhere in between, buttons to control it, power, ground, input from the brake switch, outputs to the cruise servo for vent and pull. Through 87 it was stand-alone, and it was stand-alone again from 92-94 or so.

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    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

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    Thanks for the explanation. I understand the basics but the finer points still elude me. Is the servo where the vacuum lines go?

    And how much vacuum does it take to lug a 5,000lb tank uphill at 55mph, say pulling a trailer... i'm guessing the firewall coffee can is part of this...?... how about the air pump aka smog pump? are these needed for proper cruise funtion under heavy load... i'm thinking about a full-size 70s 4-door, not just the slimmer Panther...
    96 MGM

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    Beater gonna beat sly's Avatar
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    if you can maintain, I think, 6-8 inches of vacuum, I think it'll hold cruise. But if it has to open wide, vacuum will bleed off and cruise will fade. The smog pump does help supply vacuum under loads to augment that though, so if equipped, and functional, it should maintain cruise up-hill.

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    ... and it should all work like magic and unicorns and stuff.
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    Quote Originally Posted by sly View Post
    The smog pump does help supply vacuum under loads to augment that though, so if equipped, and functional, it should maintain cruise up-hill.
    I am not completely certain, but I believe this was a later 80s introduced feature (in the SEFI years maybe). I don't believe there is a vacuum source on my 83 or 84 smog pumps (85 pump is not present).

    My 83 is factory carb, no computer, with factory cruise, manual climate control. Manual climate control cars have a smaller vacuum can than ATC cars (mixed nuts can vs coffee can), but they do still have one. With manual climate control, temp blend is done with a cable, so there are less vacuum powered things in the car. Point of mentioning that is I am unsure how significant it is to the cruise system as I believe the check valve isolates the reservoir from the cruise system and keeps it dedicated to the climate control vent selection system.
    Last edited by kishy; 03-23-2020 at 04:29 PM.

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  6. #6
    Beater gonna beat sly's Avatar
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    That's easy enough to check. If the smog pump has a vacuum line going up over to the cruise servo, then it has the vacuum helper function.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
    rides: 93 Crown Vic LX (The Red Velvet Cake), 2000 Crown Vic base model (Sandy), 2003 Expedition (the vacation beast)
    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  7. #7
    I'm an air-conditioned gypsy gadget73's Avatar
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    The climate control reservoir doesn't have anything to do with the cruise anyway tho. I think the bigger can for ATC is because the ATC temperature regulator thing has some amount of vacuum leakage just as part of it's design.


    And yes the cruise servo is where the vacuum line and the throttle cable goes. Its basically a diaphragm with 2 valves in it. One opens the diaphragm to vacuum, one vents. Thats how it applies and releases throttle. Inside of the cruise servo is what amounts to a throttle position sensor to provide feedback to the controller about what the servo is doing. Thats the only difference on 80s models between stand-alone cruise and ECM cruise. ECM ones don't have the TPS inside, but the actual servo is identical. Pop the cover off and you can mount a TPS inside to put a later servo in an early car if needed. Its not the same one the ECM uses, but it does the same job.

    for whatever it may be worth, I haven't had a smog pump in a long time on the Towncar and I've never had issues with the cruise control because of it. I've only ever had 2 real CC problems. Mark VII had surging issues, it was a leaky vacuum dump valve. The Conti had really bad surge problems, it was a bad TPS inside the cruise servo. I have a book from the late 60s somewhere that actually has a very in-depth explanation of the cruise control system. If I can dig it up I'll scan the pages.

    totally unrelated, officially the Ford system is Speed Control. Cruise Control is GM.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

  8. #8

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    Ford Speed Control is simple system. From the 1960s to the early 90s, the brain box was very similar in concept. From the end of the 70s until the years when it was integrated into the computer, it barely changed. The major changes between vehicles were whether or not it had the "resume" feature, what the switches looked like (and, if it was a dealer add-on, whether the switches were on the steering wheel or the turn signal stalk), and the vacuum servo. The vacuum servo had differences of which I am not entirely sure, but I suspect that they had some changes for vehicle size/power. Or maybe it was just how the thing mounted, but I _think_ there's more to it than that. The brain boxes may also have minor programming differences (rate of acceleration or allowable speed difference) but I am also not entirely sure of that.

    Even in the years where the cruise control was programmed into the vehicle computer, the dealer add-ons used the same brain as the cars from earlier (and briefly, later) years.

    I have a box of Ford cruise parts for various projects; it's not real hard to modify to put in other cars as long as the speedometer cable or transmission speedometer gear housing are similar.

    There are 3 styles of speed pickup. One uses a sensor mounted to the transmission that goes between the speedometer gear and the cable end. The other goes in the speedometer cable (the sensor is in the dash); there's a long cable from the sensor to the transmission, and a short one that goes into the back of the gauge cluster. In the 80s and later the transmission mounted style was more common, but either style is available. The kind behind the dash is most common until the late 70s, but was often included in the dealer add-on style (but it could be either, and you can still buy either). The third arrangement is for later cars without a speedometer cable; it's wired in the vehicle speed sensor circuit. All the styles send the same type of signal so any of them will work with any of the cruise brains.

    Interestingly, from the early 60s until the early 2000s, the wiring is similar enough that switches from one car can be transplanted to another; and for many of them you don't even need to change the wires.

    In the 2000s, the vacuum servo was replaced with a stepper motor. I believe the electrical signal to the stepper is compatible with the vacuum style servo and vice versa.

    These things are really mix-and-match and really easy to make work with very few exceptions. One exception is that the "resume" function requires that both the controller and the switch be wired for it; and the other (not so much an exception as a caution) is that you should use a servo that is compatible with the engine you're using (or at least have a bracket that fits the vehicle in a way that allows smooth cable motion). Also, in a retrofit, be sure to include the vacuum dump at the brake (and clutch, if you have one) pedals; that will prevent you from fighting the speed control (or blowing it up when you push in the clutch and the car tries to accelerate).

    All you need is box, servo, switches, and the vacuum plumbing, for a carb or EFI.

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    Would adding an additional vacuum canister be of any benefit when pulling a trailer at higher speeds especially up hills ?

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    It could maybe give longer bleed-off, but if you want to truly maintain cruise on long uphill runs, add an electric vacuum pump for brake boosters. It will self regulate vacuum between I think 10-12 and 15-17 psi.

    Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. -- Albert Einstein
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    Quote Originally Posted by gadget73
    ... and it should all work like magic and unicorns and stuff.
    Quote Originally Posted by dmccaig
    Overhead, some poor bastards are flying in airplanes.

  11. #11

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    Also make sure the check valve is in good shape, between the vacuum canister and the intake. The lines to the HVAC and cruise should be AFTER the check valve.
    Adding a second check valve to JUST the cruise can help (so the HVAC can't bleed off all the vacuum), but eventually there's just no vacuum left.

    I've been playing with the servo motor design, as no vacuum is required. I'm not sure what years those were on, but I suspect 5.0 Explorers had them. I'm not sure about the 94-95 Mustangs and the last of the F-Series trucks, and I'm not sure that the cable ends are the same on the 4.6 Panthers, but it's worth looking at if someone has a junkyard around them.

    My experiments have mostly been using early (standalone) controls and switches on later engines, for engine swaps.

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    Thanks for the responses. A standalone speed control system sounds like the way to go for someone with limited diagnostics.

    Are the necessary parts still available going back to the 70s/early 80s? Junkyards, ebay, etc. Or does it come down to some part I should have stashed away 5 years ago before they all disappeared?

    Anybody ever run aftermarket cruise with a magnet that glues to the drivesahft, etc? or do those become junk after 5 years and parts nla.

    Also is the quality that bad on the 70s Fomoco? I remember the 12/12 warranties and how bad Dodge sucked back then, didn't realize it was bad at ford too.
    Last edited by BoulevardRide; 03-25-2020 at 10:45 AM.
    96 MGM

    Cruisin up and down the road...

  13. #13

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    I've installed the dealer add-on cruise and 3rd party aftermarket units.
    The magnet-on-the-driveshaft style work fine, but I would not do it. Your car may already have the vehicle speed sensor in the speedometer cable. The wire you need is under the dash. If not, you can buy a speedometer cable and vehicle speed sensor for your transmission (tell the counter monkey a 1986 Crown Vic or a 1987 Ford F150 with the sensor at the transmission, there's only 1 option and it's probably under 25 bucks, the last one I bought is still in the F150 and it was $12).

    https://www.rockauto.com/en/moreinfo...21724&jsn=2265 9 bucks on Rock Auto.
    https://www.rockauto.com/en/moreinfo...21724&jsn=2324 The connector for 4 bucks (if you don't have a connector that fits).

    That's the style: speedometer cable goes on one end, the speedometer driven gear goes on the other. If you're changing axle ratios you'll be doing all the work of installing this anyway.

    You could use the Ford VSS with most aftermarket kits, but I would instead suggest finding any late 70's or '80s V8 Ford with cruise control; preferably another Panther or an F-series.
    The module is under the dash, along with the vacuum dump parts. The vacuum servo is under the hood and the end fittings will "probably" fit what came with your engine already (assuming it's a Ford carburetor or Ford fittings on an aftermarket carb).

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    Gonna buy me a Mercury BoulevardRide's Avatar
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    Thanks Wolf. At this point I'd only buy a car with cruise installed, I'm past the point of grafting a complete junkyard 90s truck system into a 70s sedan, and so forth. with help here i feel i can troubleshoot an existing system but definitely lack the ability to install one from scratch.

    basically i'm gathering info in case a nice old car pops up that is well maintained, etc, but if the cruise isn't working won't be a deal breaker with the info i am getting here. nice to know i can still get stuff new from rock.

    My question about the 3rd party glue-on cruise was actually in case i find a nice 70s motor home that has everything i need except the cruise. so good to know those things actually work too. but that is another story. thanks again


    sorry i meant to say "speed control," not "cruise"
    96 MGM

    Cruisin up and down the road...

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    fomoco panthers !
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    By BoulevardRide,
    "Also is the quality that bad on the 70s Fomoco? I remember the 12/12 warranties and how bad Dodge sucked back then, didn't realize it was bad at ford too."

    Ford quality started going down badly in 1969. So did most other American made vehicles. Styling may have been good, motors and transmissions were generally good. Body and interior body fit finish and mechanical durability really was bad. It did not help matters that the federal regulations forced car makers to comply with smog and crash safety features. The foreign car makers flooded the market with smaller, better quality vehicles that got better gas mileage. By about 1980 Detroit finally woke up and began the climb up the quality ladder. Many customers fled American cars never to return. Today the American auto industry has to produce higher quality vehicles or go under.

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    Gonna buy me a Mercury BoulevardRide's Avatar
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    Yeah it's amazing there are still some 70s cars for sale running, back then 100,000 miles was pretty much the death knell. Just last year prices on 70s cars were still pretty cheap but they seem to be spiking all of a sudden.

    I'd go 60s but Lincolns were unibody then and i hear the vacuum windows, etc are a frig. Trying to keep things as simple as i can. Might end up with a 50s shoe box now that i know i can add cruise to the driveshaft without much hassle. I hear those old transmissions weigh a ton tho, would be hard to find someone around here to rebuild one, let alone pull it out. Plus seats back then didn't have headrests, i need a headrest. Hard to beat the 70s for styling, they had it all.
    96 MGM

    Cruisin up and down the road...

  17. #17

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    Just as a note, here's a link to the dealer supplied cruise parts. Look at the picture; these are all the parts you need for any Ford from about 1983 to 1995 that doesn't have cruise (or to repair the cruise on a car that didn't have it integrated in the ECM).
    Note this is for a Tempaz, but the differences are in wire and hose lengths, mounting brackets, and the part numbers on the servo and the controller; it won't fit a Crown Vic but if you changed the bits around to where they physically fit, it would operate. Also note that the speed sensor mounts on the back of the speedometer; if it physically fit behind a Panther dash it would work (but it would be a pain to get to).

    https://www.ebay.com/itm/NEW-OEM-For...gAAOSwwD1eAlHF

    The switches are all the same electrically, only the plastic is different. Use the one you like.
    The speed sensors are all the same electrically, only the mounting location (speedometer head, speedometer cable behind dash, or at transmission) is different. Use the one you can reach (I prefer the transmission because it's easy to reach and it's the cheapest new).
    The control box is the same but may have different programming based on the engine/car combo?.
    The servos are different mainly because of the brackets to mount them, but may have different orifices to control rate of acceleration on different car/engine combos. A serious mismatch could result in sluggish acceleration or flooring the pedal at the slightest slowdown.
    I suspect that if the engine/vehicle weight are similar, the servo and controller will do just fine.
    Again, the switches and sensors are the same (even the same as cars where it's built into the ECM, so if your ECM loses cruise function, or you switch to an ECM without the cruise function, just move the wires over to a standalone and you're done).

  18. #18
    I'm an air-conditioned gypsy gadget73's Avatar
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    ^^ what he said, its just not that complicated of a system. If you can physically attach and mount the stuff, the electrical side of it really isn't any big deal. Power, ground, 2 wires to the switches, 2 to the speed sensor, and 5 or something to the servo.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

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    Quote Originally Posted by gadget73 View Post
    ^^ what he said, its just not that complicated of a system. If you can physically attach and mount the stuff, the electrical side of it really isn't any big deal. Power, ground, 2 wires to the switches, 2 to the speed sensor, and 5 or something to the servo.
    2 grounds actually. Ground is accomplished through the brake lamps and vss-. 87+ is the 3rd brake light specifically, which is why cruise disengages on 86 and down when the hazards are on. and doesn't work with conventional LED bulbs. Remember all the crap we went through trying to get my cruise to work only to find out it had no ground signal.

  20. #20
    I'm an air-conditioned gypsy gadget73's Avatar
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    ah right, the brake switch stuff.

    86 Lincoln Town Car (Galactica).
    5.0 HO, CompCams XE258,Scorpion 1.72 roller rockers, 3.55 K code rear, tow package, BHPerformance ported E7 heads, Tmoss Explorer intake, 65mm throttle body, Hedman 1 5/8" headers, 2.5" dual exhaust, ASP underdrive pulley

    91 Lincoln Mark VII LSC SE, triple black (Timewarp) - poly front bushings, KYB struts and shocks, Holley SystemMax1 lower intake, SilverFox AOD valve body,

    1984 Lincoln Continental TurboDiesel - rolls coal

    Quote Originally Posted by phayzer5 View Post
    I drive a Lincoln. I can't be bothered to shift like the peasants and rabble rousers

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