Fuel Injection wiring? Options

[mike_the_man]

Hi all,

I have a question regarding my fuel injection wiring harness. I pulled it on the weekend to have a look, and make sure there are no cracker wires, etc. It's off of a 74 2.0L. I'm wondering what all of the hook ups are? There was one wire not connected, and I'm not sure where it goes. The ones that I am sure of are the following:
4 fuel injectors
MPS
CHT
Manifold Temp sensor
Trigger Points
TPS
Cold Start Injector
Grounds
Connection to Relay Board
There is one wire left, and it seems to come out of the same place as the trigger point connection. Anybody know what it shoudl connect to? Anybody that can tell me will have my ever lasting admiration.

Thanks,

[JeffBowlsby]

All 1.7, 1.8 and 2.0 FI wiring harnesses have ONLY white wires in them. (The 912E and 914/6 are different, they do have colored wires.)


From Brad Anders page on the TTS:

Function: Senses cold starting condition and provides additional fuel during starting to richen the mixture.
Normal Value(s): Bosch says the cold start valve coil resistance should be 4.2 ohms. Measurements I've taken on a NOS 0 280 170 015 valve I have are R = 4.24 ohms. Coil inductance was 4.51 mH.
Failure Modes Open control wire from the thermo/thermo-time switch: Prevents valve from operating. Poor cold start operation. Check by inspection.
Shorted control wire from thermo/thermo-time switch: Causes valve to stay open. Very rich mixture across all operating conditions. Check by inspection.
Open or shorted thermo/thermo-time switch: Prevents valve from operating (open) or causes valve to stay open (shorted). Poor cold start operation (open) or rich mixture (shorted). Check by removing the switch, placing it in your freezer for a full 10 minutes (see notes section below), and checking for continuity from the terminal to the case. If there is no continuity, the switch is open and bad. Allow the switch to warm up to room temperature (70 deg. F) and check for continuity. If there is continuity, the switch is shorted and bad. Note that if you have a 75-76 2.0L, you have a thermo-time switch which has an internal heater that limits the time the switch is active. This switch also has two leads instead of the single lead on the thermo switch. I don't have a pin-out on the thermo-time switch and don't know which terminal is the switch and which terminal is the heater lead (+12V).
Open or shorted thermo-time switch heater: The 75-76 2.0L thermo-time switch has a heater element which limits the time the switch is active. If this lead is open and the heater is inoperative, you could experience flooding or fouled plugs during repeated attempts to start the car. If the lead is shorted, you will likely blow a fuse (unknown which one) when you start the car, which may disable other systems. I don't have the pin-out for the thermo-time switch and don't know which terminal is the switch and which terminal is the heater lead (+12V).
Open power lead from the relay plate to the valve: Prevents valve from operating. Poor cold start operation. Check by inspection.
Valve Stuck Open: Very rich mixture across all operating conditions. See URL in the Injection Valve section above for a test method.
Valve Stuck Closed: Poor cold start operation. See URL in the Injection Valve section above for a test method.
Valve Leaking. Rich mixture across all operating conditions, poor fuel economy. See URL in the Injection Valve section above for a test method.
Mismatched thermo/thermo-time switch: Provides wrong temperature set point for operation, poor cold start performance. Check part number against the table above.

Notes: The cold start valve provides a fine mist of fuel in the intake manifold to richen the mixture during cold starts. For most of us living in the continental US, the valve doesn't turn on except in the coldest months of the year. The valve is controlled by the thermo- or thermo-time switch and operates independently of the ECU. The valve is active only when the key is in the "start" position and the temperature is below the set point of the thermo-time switch. Actual measurements of the switching temperature of a sample thermo switch (311 906 161 C) indicate a lower temperature than quoted by the FWM, somewhere closer to 0 deg. C / 32 deg. F.Jeff Bowlsby found a reference (VWTG) that has a table of actuating temperatures for the early and later thermo switches, but not the thermo-time switch (note there is an error in the units conversion of the entry in the VWTG for first sensor listed below that has been corrected here): 311 906 161 : -12 to -18 deg. C / 10 to 0 deg. F
311 906 161 A : 0 to -10 deg. C / 32 to 14 deg. F
311 906 161 B : -2 to -8 deg. C / 28 to 18 deg. F
311 906 161 C : -6 to -14 deg. C / 21 to 7 deg. F