Rev counter on an F75

[nid]

hello everybody

I have an F75 2.8 intercooled TD fourtrack (rocky) and I would like to attach a rev counter. Does anybody know how it connects to the injector pump?

Thanks

Nid

[Sneezing7]

I am pretty sure a Tacho does not get its input from the injector pump.

With that said, most tacho's have 4 wires:
1) Ground
2) Positive
3) Sensor pickup (connects to the coils or EFI computer output wire)
4) Light

Alternatively some brands of tacho's do not have wire 3. Basically it runs off of the pulse in the elctric system.

Hope that helps

[HotFourOk]

But a Diesel has no coil or similar...

When revs increase, the pump is increased mechanically isnt it? So that would be how to tell how many revs the engine is doing yeh??

On petrol vehicles they sometimes use the ignition coil for a signal.. I'm not sure with Diesels though

Thats why we can go underwater

[Hatsu]

I don't know if the rocky's are different, but on my F50, the tacho signal comes off some wiring for the altenator or voltage regulator.
If you need more info let me know and I'll go out and figure it out for you.

[Big-Stu]

Well I've had a look through the useless Daihatsu wiring diagrams and all it mentions is a 'pickup coil'. I can find in the drawings where the tacho connects into the dash connector but not the other end of the wiring loom. I can't find any special components in the gearbox or motor that would be the 'pickup coil' so I think it connects into the alternator. Also I can't find anything special on the fuel injector pump.

Stu
92 intercoooled turbo diesel.
Only gets driven on Sundays.

[HotFourOk]

Yeh in a lot of VW's they use the 'W' terminal off the back of the alternator...

I'll keep an eye out for you.. if all else fails, i can trace my tacho back to where its from

Also found this from another forum..

Do you have a multimeter which can measure frequency?

The tacho drive on my alternator (and apparently most others) is a rectified 14v AC signal which results in a 7V pulse. None of the other leads should be 7v which makes it easy to pick.