Ford Sierra manual gearbox EEC IV vehicle speed sensor substitution

[Kenl40009]

Hi all, 

is there a replacement for the vehicle speed sensor that would be in the Ford gearbox?, or a way of utilising it in a RX8 box? I ask as I’ve replaced a auto box with a Mazda manual gearbox in my kit car which doesn’t have one, and have read various thoughts as to wether it’s needed or not, apparently Mazda use the wheel sensors, I have the ECU and loom for the EEC IV system and have all the other sensors fitted

thanks in advance

Ken

[Grim]

what engine are you using? If it's pinto with the eec iv, it wont be interested in the speed, the sensor was only for the speedo. What speedo do you have?

[Kenl40009]

It’s the 2.0 8v DOHC

[Kenl40009]

I have a separate Hall effect speedo setup using the prop shaft bolts as pickups, I’ve read that the ECU uses the VSS to shut the fuel to the injectors during throttle off deceleration

[Grim]

Have you got a wiring diagram to show that the speedo wires go to the ECU? I haven't got a later haynes manual to check.

I would be surprised if it needed the speedo output to do this as the pinto eec iv system can manage this with the throttle position/engine speed information alone.

[Sparepart]

I am fortunate to have a copy of the Haynes FORD SIERRA Service and Repair Manual 1982 to 1993 4cyl Petrol.

The wiring diagrams are not easy to use as all the major components have numbers on the diagrams, so you have to go back and for between several pages in order to see whats what. On page 13-54 (Diagram 1) the "Speed sensor" item number 150 shows a yellow/brown wire going to Diagram 4a (square H8). If I turn to Diagram 4a, I see this yellow/brown wire going to pin 4 of item 58 (which turns out to be EEC IV Module) .... So in answer to your question, it appears that the speed sensor input is required by the EEC.  I do not have this engine or EEC (I have SOHC carb) however on mine the speed sensor is a detachable part of the speedo cable which is driven from a mechanical output on the Type 9 gearbox. It was also used by the "Fuel Computer" on up market versions of the Sierra equiped with a Graphical Display.

Edited March 18, 2021 by Sparepart
Typo correction

[Kenl40009]

Thanks for the replies, the Speedo output was mechanical flex drive so the VSS was not for that, purely for the ECU, I’ll be taking it out for a short test drive next month when I get it taxed, staying very local!, see what happens without it

Ken

[Kenl40009]

Well, just had it out on the road for the first time and it would seem that the speed sensor isn’t required!, engine ran and behaved as it should, next step will be to get on a fast road just to be sure 70 mph is also as it should be

Ken

 

 

[Kenl40009]

Well, all is well!, speed sensor officially not required, no issues at speed so happy as Larry!