TPS connector

[FiatFan]

So I bought a used connector from Midwest, I cut the old one off and now I don’t know which wire goes to which? Help they are all white wires

[spider2081]

If you strip the black jacket back there might be wire numbers on the wires. These wire numbers correspond to the ECU pin numbers which are the same as the TPS pin numbers. So Pin 3 of the ECU goes to pin 3 of the TPS as 2 to 2 and 18 to 18.

[kmead]

It is an on off switch on these cars so it doesn’t matter which wire attaches to what.

What matters is proper adjustment of the switch.

[spider2081]

It is an on off switch on these cars so it doesn’t matter which wire attaches to what.

I believe the 81 spider has 2 separate switches inside the TPS assembly. One switch is engaged at idle and the other switch engages at full throttle. Hence 3 wires are used.
18 is common to both switches
2 is the idle switch
3 is the full throttle switch
I think the position of the wires is important for the engine to idle and accelerate properly.

[kmead]

Dang, right you are.

The center is indeed the common which supplies the power, with the wires to either side being idle or wide open throttle.

Under no circumstances use a continuity tester on the wires leading to the ECU as you could damage the ECU.

On the switch itself, using a continuity tester, you can place the one wire onto the center contact and assuming the switch is properly adjusted and the throttle is closed, the “left” contact will now have continuity when you touch it with the probe.

Next keeping the center contact being the common touch the other probe to the right contact of the switch and then rotate the throttle shaft fully to open. Just as you get to fully open, the continuity tester will show the circuit is open.

This will tell you what the wires are in the connector.

To identify the 3, 18 and 2 you will need to travel farther up the existing wires to find the numbers printed onto the wires it it isn’t immediately obvious.

If the switch doesn’t show the throttle closed (this is the most important of the two switches), ie continuity between 18 and 2 you need to adjust the switch so that only as the throttle plate is closed does it have continuity. Anything movement off fully closed should break the continuity of the switch.

My apologies for stating it was a 2 wire single switch solution, I had forgotten the WOT function in these. Thank you for the correction.

[RRoller123]

My understanding (I think it came from either Csaba or Brad Artigue) is that our FIAT version of Bosch L-Jetronics is quite stripped down, and does not use the WOT function. The closed throttle function IS used, as an anti-backfire system, when pulling one's foot off the pedal and engine braking. It has been awhile, though, and my memory may be wrong on this.

[stuartrubin]

We need to talk about your TPS report.

[rridge]

Unlike Throttle Position Switches (TPS) used on later Bosch injection systems, the switch used on the L-Jet system in the Spider is indeed quite basic and provides no inputs at part throttle. However, when the throttle is closed, a switch in the TPS closes and signals the ECU to do two things. First it basically cuts off the fuel flow to prevent backfiring at high rpm on the overrun. When the rpms drop to near idle, the ECU again provides fuel but takes the oxygen sensor out of the loop to stabilize idle rpm. When the throttle is pressed full open a second TPS switch is thrown which provides additional enrichment. All of this is done with analog circuits.