FoMoCo Cruise and Vacuum

[cushjbc]

So I went down the rabbit hole of trying to fix/replace the very leaky FoMoCo cruise control actuator on my car. Found the MB recall campaign and pursued replacements from them. MB abandoned all association with FoMoCo in favor of the VDO cruise control system (two generations). The current MB recall solution is to remove the actuator. I did this myself.

MB manuals and classic center (Irvine) says the VDO system is not compatible with pre-1975 cars (chassis number available in EPC). I'm not ready to fly that white flag yet and have 2 complete VDO systems in hand for experimentation.

Meanwhile, I found a cool vacuum pump made by Hella to help diagnose my original cruise control system. This Hella pump is used by VW, Audi, Volvo, Saab and others; widely available on eBay. It keeps a chamber evacuated to a range of -11 to -15 inHg.

I mounted it on the side of my cruise control bracket (no holes in the car). I wired it to terminal 15 at fuse 9 through the passenger side wiring grommet. I grounded it at the chassis point aft and above the fuse box. An I routed the vacuum line, with a check valve, to the manifold at the rear left corner of the engine compartment (where climate control and central locking lines break out). I also split off another line from the same area for a dedicated vacuum gauge which I placed on the firewall behind my battery. The pump is automatic. It augments my leaky intake manifold system and helps me find those leaks. I have been chasing those for a year now and am getting closer to a tight system. When I am testing I, simply turn the ignition to position I, and let the pump do its trick.

The pump runs for about a minute when I start the car after it has been parked long enough for all vacuum to decay. In this time, it takes a no vacuum system down to -15 inHg. The pump will not run after that because the engine picks up the load.

I will keep charging the windmill of vacuum and let you know if I ever succeed with the VDO cruise control conversion. Meanwhile, I hope this little pump might appeal to some of you.

Regards,

[RadioTek]

Do you have some info for the price range and part number? I've been thinking about a vacuum pump as a troubleshooting aid for a while, myself.

Thanks,
Scott

[cushjbc]

I can't find the part number until I get home. I paid $89 on eBay from ptcfactory outlet in Atlanta. They don't have one on auction right now but maybe you could call them for info. If you search eBay for vacuum pumps you will see one like item 220799368830 which looks like the same pump.

I think this pump is actually sold as several part numbers by different companies. I see VW and Volvo pumps just like it also on eBay.

[97 SL320]

" MB abandoned all association with FoMoCo in favor of the VDO cruise control system "

You do realize that FoMoCo is the parts arm of Ford Motor Company?

[engatwork]

I had a guy come by in a 1980 300D the other day that had a Sears cruise control unit installed. Needless to say it did not work.

[Strife]

Originally Posted by engatwork

I had a guy come by in a 1980 300D the other day that had a Sears cruise control unit installed. Needless to say it did not work.

I wonder how many times it was fixed under warranty while it still didn't work.

[cushjbc]

97 SL320

Yes - I did recognize the Ford Motor Company connection. Ford Philco, FoMoCo, etc. - I read somewhere that the same actuators were used on Pintos and pickup trucks. I did some searching in the Ford world to see if I could find parts for the system - no luck.

I found a company in the UK that stocks the actuator and amplifier but too much $$ for me. MB Parts Center stocks it too according to their online parts catalogue; I have not verified this by trying to order.

Honestly, the recall made me loose interest in the Ford unit. I am interested in making a VDO system work in my car. I am pretty sure the only limitations are mounting brackets, bowden cable, and the speed sensor. These can be solved in time.

[cushjbc]

Update - I found two 74 450 SELs at U Pull & Pay; both had Philco cruise actuators. One of those was vacuum tight. I installed it, tested it and have an operable tempomat cruise control that has been recalled by Mercedes Benz.

I am going to delve into the amplifier circuit to see if I can install a kill switch to put in series with the brake switch.

I have not given up on the VDO retrograde.

[compu_85]

You might look into the VDO system Audi and VW used. In my experience it is more reliable than the motor driven system MB used. Really the only thing that goes wrong is the little vacuum motor tears, but they used it on so many zillions of cars it's not hard to find a good one. The only real bummer is it doesn't have a coast function.

-J

[cushjbc]

-J

Thanks, I'll check that out

[compu_85]

The computer is generally mounted in the dashboard or to the center console. The brake and clutch have combination electrical / vacuum valves. The control motor is in the engine bay. On the older cars the servo is under the hood near the throttle, on newer cars it's mounted near the go pedal inside the car.