Wiring question

[Squidders]

Hi fellow Fiatisti,

I have a question regarding the wiring diagrams for a 1980 FI spider. Tracing the wiring diagram shows that position 4 on the ECU (light blue/ white wire) goes to the Dual Relay, which leaves the Dual Relay via number 86 and then goes to Cold Start Valve/ Injector and then the Thermo Time Switch.

Shouldn't it go to the Dual relay to the Thermo Time Switch and then that the Cold Start Valve/ Injector to fire (on a cold engine)?

Thanks in advance.

[kmead]

The thermo time switch and the cold start injector share the same power supply wire. Both have power applied continuously whenever the ignition switch is in the ‘on’ and start positions.

The thermo time switch has two modes of operation:
The first is as a thermal switch, if it is too warm as in base engine temperature, the switch opens
The second is as a heated switch which opens once it has been heated sufficiently by the internal heater

The cold start injector has a second wire that leads to the other side of the thermal time switch, the flow of power from the injector leads through the injector to the switch side of the thermo time switch. The switch on that side leads to ground which when the switch is closed, allows the injector to open and inject fuel into the intake plenum.

So when the temperature is high enough or is the unit is heated enough, the switch opens and there is no longer a path to ground for the cold start injector so it either stops firing or it never gets the chance to fire as the switch is open and there is no path to ground.

I hope that is clear.

[Squidders]

Thanks Karl, It explains it in detail. Will go back and revisit the wiring.

[spider2081]

Both have power applied continuously whenever the ignition switch is in the ‘on’ and start positions.

I believe the cold start valve and thermal time switch are powered when the ignition switch is in the "start" position only. Power from the "start" position of the ignition switch enters the Dual relay and exits the dual to power them. This is a hard contact and not dependent on the relays operation but simply that the wires be connected to the relay to complete the circuit.

I suggest the use of Fiat Publication titled "Spider 2000 Electrical Diagnostic Manual 1980-1981" for all Spider electrical issues. Even if the Spider is a different production year this manual will help ones understanding of circuit operations, parts locations and their operation. This manual is available of Mirafiori. com for members in their library section. It is also available in NJfiats.org in their resource section.

[Squidders]

Thanks for the resource tip. It is very detailed!

[alaindelval]

Hello Spider2081 and all other thermo time switch fans!. Could you try to help me? Spider2081 mentioned that cold start valve and thermal time switch are powered when the ignition switch is in the "start" position only, and that there is a hard contact and not dependent on the relays operation and I agree with that (even if I don't understand how the cold sart valve when very cold will receive 12V for 8 seconds when ignition switch will be on start only for 1 or 2 seconds - I you know how, I'm intersted to know).
But my main question mark is this : I have two dual relays and on both of them the hard contact between 86a and 86 is broken. So my question is, could this hard contact has been broken by a leaking thermo time switch, creating a short circuit? And, to avoid to buy a new dual relay, my idea was to connect directly wire conneted to pin 86a to wire connected to pin 86. Is this a good idea or not? Thank you!

[RRoller123]

I think the TTS and the CSI work through the ECU. Both have direct connections to the ECU through the harness.

[spider2081]

even if I don't understand how the cold start valve when very cold will receive 12V for 8 seconds when ignition switch will be on start only for 1 or 2 seconds

I think the circuit operates this way if the outside air temp is cold enough the thermal time switch contacts close. When closed these contacts supply a ground to one side of the cold start valve's coil. If the ignition switch is in the "start" position the cold start valve will then have 12v to one side of its coil and ground on the other. This opens the Cold start valve and it adds fuel to the engines intake manifold. If the engine fails to start after 8-10 seconds the thermal switch opens removing the ground to the cold start valve. this stops the additional fuel from being supplied and possible engine flooding from excess fuel.
If the engine starts in less that 8-10 seconds the ignition switch is no longer in the "start" position so there is no 12v power supplied to the cold start valve cpil. This turns the valve off eliminating the extra fuel. The ground to the cold start valve could still be supplied by the thermal timer but the cold start valve is not letting fuel out because it's coil has no 12v power.

to avoid to buy a new dual relay, my idea was to connect directly wire conneted to pin 86a to wire connected to pin 86.

I believe terminals 86 and 86a of the dual relay should be connected together by a printed circuit connection. The printed circuit board is multi layered so this connection is not easily seen. Sometimes shining a light through the board one can make it out visually. It is a very thin connection so if there was/is a short to ground on the wires connecting to pin 86 land, it would quickly burn open. I might solder terminal 86a to 86 with a 5 amp fuse. This way if there is a short in the wiring you don't cause more damage. just the fuse would blow

[RRoller123]

I believe that the TTS is only temperature dependent, not time dependent, and when the coolant is warm, tells the ECU not to fire the CSI. I think the ECU controls the ~8 seconds, which I have tested with a noid light, and 8 seconds is about right. There isn't enough room inside that bolt in TTS sensor on the bottom of the intake manifold to do much other than a temperature sense. Certainly it doesn't do any decision making with the temp data, just sends it to the ECU, and it is possibly just binary, although I haven't verified that, purely a guess.

[spider2081]

I think the ECU controls the ~8 seconds

page 23 Spider 2000 Electrical Diagnostic Manual 1980-81

(Path 3 powers the COLD START VALVE through the THERMO TIME SWITCH (when starting with the coolant temperature below 95°F). The switch remains closed and the COLD START VALVE operates, until: 1) the coolant temperature goes above 90°F; or 2) the current flow through the heater in the switch generates enough heat to open the switch.)

I think the 8-10 second time, is how long it takes the thermal time switches heater to get the bi metallic switch contacts to open. The "start" position of the ignition switch provides +12 volts to the cold start valve and the thermal time switch provides the ground for the cold start valve,
Looking at the wire diagram for the fuel injection system I don't see an output connection from the ECU to the cold start valve. Pin 4 of the ECU is 12v "start" input telling the ECU the engine is in the "start" mode.

[alaindelval]

Thank you all for your replies. I agree with spider2081, the TTS will provide ground to CSV during 0 to 8 seconds through a bi-metal blade inside the TTS heated by the 12v connection (or the coolant temperature).
I have dismounted my faulty double relay and a very thin connection on the printed circuit between 86 and 86a is broken. As I live in Belgium with rather mild winter (more and more with the global warming), I will not use anymore the CSV and TTS, and crank a few seconds more if ever needed.
Everytime I learn about my fiat 124, everytime I'm amazed by the complexity, the ingenuity of the engineers who have created all this and by the fact that 40-50 years later, it'still working!

[RRoller123]

Bingo, that is it.

[bdinardo]

I am trying to diagnose a rough idle and coughing upon pushing the accelerator problem and so I'm checking vacuum and electrical connections. (1980 FI motor) I noticed a deteriorated connector to the cold start valve/injector on the intake. There were 3 white wires for that connector despite one of them being cut right at the base of the connector head. I would have only expected 2 wires given it's a 2 prong connector.
1. Are the 3 white wires actually correct?
2. If yes to 1. then should the third wire go to the top or bottom prong?
3. If no to 1. I suppose it's just an incorrect pigtail.

Thanks.

[spider2081]

I suggest you join Mirafiori.com go to the library and read or download the manual: " Spider 2000 Electrical Diagnostic Manual 1980-81"
The FI wire diagrams are complete as is the circuit description.
Both the CSI and the thermal time switch are powered through the dual relay terminal 86. Their parallel junction is at the cold start valve.
So yes one of the CSI pins has 2 wires on it and the other has only one. The wire are white and have numbers stamped into their last few inches. Wires 45 & 47 go to one pin and wire number 46 goes to the other pin. The pin location is not important in the CSI connector but having the correct wire numbers connected in parallel is very important for the CSI to work properly.

[bdinardo]

I suggest you join Mirafiori.com go to the library and read or download the manual: " Spider 2000 Electrical Diagnostic Manual 1980-81"
The FI wire diagrams are complete as is the circuit description.
Both the CSI and the thermal time switch are powered through the dual relay terminal 86. Their parallel junction is at the cold start valve.
So yes one of the CSI pins has 2 wires on it and the other has only one. The wire are white and have numbers stamped into their last few inches. Wires 45 & 47 go to one pin and wire number 46 goes to the other pin. The pin location is not important in the CSI connector but having the correct wire numbers connected in parallel is very important for the CSI to work properly.

Perfect thanks. Yes the diagnostic manual confirmed your assessment of 45 and 47 going together and 46 by itself. I've fixed this connector but unfortunately my rough idle and stumbling upon pushing the throttle problem is still there. I've checked my vacuum leaks and all appears to be fine so continuing to diagnose.