signal TF signal TD
 

Hello

Does someone know what it means "signal TF" on the KE injection circuit (ECU to fuel pump relay). and what kind of signal it is (12 V continuous, square, sinus, other).

Same question for the "signal TD" (between the ECU and the ignition electronics module)

The car is W124 1988

Thank you in advance

IF I understand correctly, you try to find the problem between Fuel Pump relay (N16) and CIS-E control unit(N3).

I'm not expert on CIS-E control unit (any experts out there feel free to correct me) but from my book (M103 engine (US)) this is what I found...

TD signal is rpm signal. Measuring volts on plug of control unit (N3) terminal 25 (green/yellow line) (engine start. Voltage should between 6 to 12 volt.

TF signal...No idea but If you mean TF terminal on Fuel pump relay (Jack 2)
This is what I found,
Test voltage on fuel pump relay, jack 12 (terminal 50) and jack 2 (Terminal TF) to ground, engine start.
Voltage jack 12 min 10 V
Voltage jack2 = 3-5 volts at 10 kohms, simulated. (This I never do it but book said done by simulate 10 Kohm w/ ohm decade (part # 124 589 09 63 000) on coolant temp sensor.

The TF signal is the temperature signal from the ECU. It goes to the FPR and the idle control processor behind the passenger floor false bottom. I experimented with this by soldering a wire to the FPR pin 2 connector and measuring it. Here is a copy of most of my post on the MBCA forums.

Voltage vs Temp in centigrade.

2.1 v - 2
1.1 v - 6
0.5 v - 60
0.46 v - 70
0.35 v - 80
0.31 v - 87 (running)

There is a gap due to my checking the temp gauge and the outside thermometer.

I measured this DC signal by soldering a wire to pin 2 of the FPR and hooking up my voltmeter to it.

Thanks to all for the quick replies,

wbain5280 this is much more than what I expected

George560sel. what I am guessing is that the connection quality at N3 on ECU connector is ageeing and not of good quality anymore. Some erratic misfunctionments occurr. Nevertheless when engine is at working temp it runs like silk.

Hello wbain5280

Have you have made the similar measurements on the cold start injector signal? or is it just the normal battery 12V?

thanks in advance

Hello to all,

Made measurement on TF signal wbain5280 found same values as you.

But still need to know what tention is on pin 87V of the fuel pump relay. My guess is that this should be activating the coldstart valve by the mean of a signal on TF. Is it square, normal 12V, other

thanks for reply

The cold start valve is turned on by the fuel pump relay. It's a 12v signal, you can think of it as a square wave of some duration proportional to the temp.