LoveX1/9s
True Classic
Thanks Bob, That’s very kind. I think i may have isolated the break but I have to cut it back and see.
Complete Wiring Harness
- Thread starter LoveX1/9s
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LoveX1/9s
True Classic
Thanks Bob, that’s kind but I don’t think I’m up to it at this point. I may have found my open circuit on the harness. Stay tuned.
Steve Thomas
True Classic
Can be misleading if you measure this with no load.
LoveX1/9s
True Classic
So I need an education on how things tie together. It’s my understanding that the Thermo time switch when cold is closed. This completes the current to the cold start injector. When the coolant reaches a certain temperature, it’s open and so is the connection to the cold start injector. When cold, the car gets a little extra fuel. When hot it doesn’t. Is this correct so far? The circuit is fed by the starter which goes through the multi relay but the starter is also connected to the ignition switch. Is this correct?
What I’m seeing is no current down the Thermo switch connector even when someone is trying to start the car. I got the car to move by accident after the starter engaged. That was a surprise but it looks like it’s tied in on the electrical diagram. There’s a branch on the harness that’s shows open scorning to my scanner, is this normal or there really a break there? I’m just sending a current through it.
I hope I find the issue when I cut the harness open but am I just spinning my wheels? Could there be a break somewhere to the starter? I got the car to jump so I’m co fused as to how that could have happened if there is really a break from the Thermo time switch connector and the starter.
The rookie thanks you in advance.
What I’m seeing is no current down the Thermo switch connector even when someone is trying to start the car. I got the car to move by accident after the starter engaged. That was a surprise but it looks like it’s tied in on the electrical diagram. There’s a branch on the harness that’s shows open scorning to my scanner, is this normal or there really a break there? I’m just sending a current through it.
I hope I find the issue when I cut the harness open but am I just spinning my wheels? Could there be a break somewhere to the starter? I got the car to jump so I’m co fused as to how that could have happened if there is really a break from the Thermo time switch connector and the starter.
The rookie thanks you in advance.
ng_randolph
Bjorn H
Mostly correct. The thermo-time switch is heated both by the engine coolant and by an internal heating element. The warmer it is the less time the thermo-time switch will remain closed. As you noted, the TTS / cold start injector are powered from the same source as the trigger wire to the starter, so this system is only active while cranking the starter.
After several starting attempts, the TTS will get warm (due to the internal heating element), so you will see a very short on-time or no on-time at all.
The TTS is a three terminal device, with body ground being the third terminal. The two terminals of the connector are not interchangeable; make sure the wiring is correct.
It is not unheard of for the TTS to fail. The original electromechanical one is no longer made, but Bosch Classic makes an electronic replacement, part number F026T03100
ng_randolph
Bjorn H
Maybe you could describe the problems you are having. Does the car not start? Does the starter not run? Does it stall after starting etc.
LoveX1/9s
True Classic
The car no longer starts. When I spliced in the connector I thought I kept the right wire with the right side of the harness. If I swap the wires, could it do any harm? It’s getting current now down to a branch in the harness. I don’t know why but sometimes the starter kicks in and the car jumps when the connector gets current from the ETC 3000 power probe.
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LoveX1/9s
True Classic
Thanks for the help. Both wires on the connector are white. Is there a way to tell if it’s backwards? Could I screw things up if I swap them.
ng_randolph
Bjorn H
If the wires to the TTS are reversed, the TTS will short battery voltage to ground whenever the TTS on and the ignition switch is in the start position. See pinout of the TTS below:
When you say it does not start, what exactly does it do? Does the starter not run? Does the starter run, but the engine never catches? I assume you mean the former. In this thread you showed what appears to be a hard start relay installed by a previous owner. You should concentrate your search around this relay and trace out the wires.
Terminals 85 and 86 on the relay connect to the relay coil (look for terminal numbers embossed at the bottom of the relay, or search for "Bosch relay pinout"). One of these terminals (preferably #85) needs to be connected to ground. The other (preferably #86) needs to be connected to the "start" wire from the ignition switch. This wire will have battery voltage when the ignition switch is in the "start" position, no voltage otherwise. In stock form, this will actually be two wires (one RED and one RED/BLK) terminated into a single female 1/4" connector with a white plastic housing hanging out in the engine compartment in the starter neighborhood. Do not separate the RED and RED/BLK wires; they will both go to the same terminal on the relay
The relay switch contacts are brought out on terminals 30 and 87. One of these (preferably #30) should be connected to unswitched battery voltage. Typically this is taken from the stud on the starter that has two fat wires going to it. The other, preferably #87, should be connected to the trigger port on the starter. Your relay may also have a terminal numbered 87a; nothing should be connected here.
Make sure the transmission is in neutral when you play around with this; we don't want your next post to be about physical damage or bodily harm...
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LoveX1/9s
True Classic
So after messing with a connection to the engine harness, I managed to lose ground to body and ground to engine. The Thermo time switch is still reading zero and the connector to the cold start valve is reading zero now. Moving the harness around didn’t make my car happy. Nothing is disconnected. I did find a thin section of wire in the tts line and spliced in good wire but it’s a no go.
LoveX1/9s
True Classic
Hi Bjorn,
That’s for the detailed answer. The car is acting like it’s getting zero fuel on start so it doesn’t catch.
I got it to run great for 2 days with a ton of hot, warm and cold starts and then a hot start didn’t work. I managed to break off the left side of the connector on the tts while poking around and took the other side off when I brought it to the parts shop to see if their part would work. I drove the car home about 20 miles after splicing it in. I Tried starting it in the drive way as soon as I got home and it worked and the next morning I got nothing. After resting it for an hour or 2, the first try sounded like for a split second it wanted to try but then all I got was the sound of just the engine turning. It’s been that way since but after I spliced into the harness more for the tts I lost the ground to engine and ground to body. The attempt to start does nothing more than the basic I’m not getting any fuel - so nothing. In addition, the cold start injector which was getting 8.5 volts is getting zero. The tts connector has gotten zero all along instead of 12 volts. I
Basically have no clue at this point and will retrace the above. I don’t think the wires on the hard start were mixed.
I guess my question is if the wires to the tts were swapped, did I ruin the part and if I try to swap then and they are correct, will I ruin the part. The tts is impossible to find.
My guess is that the car started because of it cooled down, it would start. Perhaps it was above 35C but cooled down enough so the cold start process didn’t kick in. That’s why the car got me home but wouldn’t start the next day.
Should I swap the wires on the tts and see what happens or could that make matters worse?
Hi Bjorn,
Thanks for the detailed answer. The car is acting like it’s getting zero fuel on start so it doesn’t catch.
I got it to run great for 2 days after replacing the thermostat, fuel pressure regulator, the spark plugs spark plug wires, rotor, distributor cap and coolant temperature sensor- with a ton of hot, warm and cold starts and then a hot start didn’t work.
I managed to break off the left side of the connector on the tts while poking around and took the other side off to bring it to the parts shop to see if their connector would work.
I drove the car home about 20 miles after splicing it in. I Tried starting it in the drive way as soon as I got home and it worked and the next morning I got nothing but it tried to start for a split second. Now, it just won’t try at all. It’s clearly getting no fuel On cold start.
After getting ride of the exposed wires in the harness where the connector was spliced in for the tts, I lost the ground to engine and ground to body - most likely I wiggled things around too much.
In addition, the cold start injector which was getting 8.5 volts is getting zero now. The tts connector has gotten zero all along instead of the 12 volts I expect.
Basically have no clue at this point and will retrace what you noted. I don’t think the wires on the hard start were mixed but given that both wires of the tts are white, they could have been but I tried to keep the wires on the same side as they sat. Can I test each wire with a multi meter to see which is the G side?
I guess my questions are, if the wires to the tts were swapped, did I ruin the part and should I try to swap the wires as they are now? I’m showing an open circuit using my
ECT 3000 the way things are now. So does that mean I did swap the wires which caused 0 volts to go through the connector?
I’m getting zero voltage to the connector so if I swap the splice should I get 12 volts to the connector? And if the wires are crossed will I ruin the TTS?
What started all this was the car would not start when warm - even if I drove it for 2 blocks and tried to start it. After resting it, it would start. Sometimes, depressing the gas to the floor would do the trick.
Now, it just doesn’t catch at all when cold.
LoveX1/9s
True Classic
ng_randolph
Bjorn H
If the wires to the TTS are reversed, damage is likely. Don't change things around just to test. It is quite easy to find out if the TTS is correctly wired: Unplug the trigger wire from the starter. Unplug the electrical connection from the cold start valve. Unplug the electrical connection from the TTS. Have an assistant hold the the ignition switch at "start". Check for voltage on the connector for the TTS, and refer to the photo in this post. The wire normally going to the "G" / Heating Element pin of the TTS should now have battery voltage. The wire normally going to the "W" / Switch should be floating.
I disconnect one of the wires to the coil ballast resistor when I leave the ignition on for any amount of time during testing. This to not unnecessarily heat up the coil / ballast resistor / ICU. Just remember to reconnect it when you want to start the car.
The cold start valve / TTS is there to provide additional fuel during a cold start. The regular fuel injectors still provide fuel as they normally would. The car will still start if the TTS / Cold start injectors are not functioning, but not as easily. When the TTS failed on my '85, the car would still start in 50°F weather, but it took more cranking.
Your ETC 3000 is quite a useful tool, but keep in mind that the results need to be interpreted. If it reports a "short", there probably is a short, but not necessarily. Same thing with "open"; the tool can easily be fooled.
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LoveX1/9s
True Classic
So my car started today - just because. Probably for the opposite reason that it didn’t start. Just because. I saw this in the fuse box though. Not stock. It was part of the fuse box at one time but my mechanic took it out for some reason. Probably because it toasted on him once. Have a call into Midwest bayless to figure out if it’s problematic which it must be because it’s spliced together and no longer is wired to the fuse box.
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ng_randolph
Bjorn H
kmead
Old enough to know better
I am with Bjorn, I would take that connection apart to see what is under there. Going to a bolted connection through properly crimped eyelets would be desirable.
I would have a look under the fuse box to see if there are any other questionable connectors or connections and then fasten it down to the carrier.
OK so now you have something which can be chased and found with no power to the pump. First verify the fuel pump fuse is good. There are two fuses on the late box related to the fuel injection, G and W which are the top right and bottom right fuses when looking at the box.
Failing that it is time to check along the wiring diagram at the connections and verifying power is where it needs to be. The path of power to the fuel pump is somewhat circuitous. Power starts at the ignition switch on one leg and a continuous power supply to the double relay on the other.
The fuel pump gets its power through the double relay, this is actuated differently depending on the mode of either starting or running. When starting, power to excite the double relay comes from the starter solenoid. So the wire which is crimped to the wire at the starter solenoid needs to have power back to the double relay when the starter is running. The double relay is in the spare tire well and the wire from the solenoid to the double relay, the wire from the starter is red with a black tracer and goes to terminal 86a on the double relay. This power to excite the double relay continues until the starter is shut off.
Once the AFM is registering airflow, a switch in the AFM closes and power from the other side of the double relay now powers the fuel pump. The double relay closes and supplies power based on power coming from the ignition coil to the relay’s coil at 86c.
LoveX1/9s
True Classic
Thanks guys. This is very helpful. I'm going to try an get the junction that was hanging off the left side of the fuel box at one point. Not sure, if that box was wired elsewhere or if the 3 wires (I believe I have the brown wire mod) just tied together at the junction.
By the way, I suspect this can’t be good... Not sure how these were suppose to connect to the junction given someone removed the box and came up with this fix. I suspuct the box was removed becuse it got fried while one of two mechanics was working on it.
By the way, I suspect this can’t be good... Not sure how these were suppose to connect to the junction given someone removed the box and came up with this fix. I suspuct the box was removed becuse it got fried while one of two mechanics was working on it.
Attachments
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kmead
Old enough to know better
The junction used to be nutted to the threaded stud you can see on the bracket for the relays.
So what likely happened in the past is that the plastic housing for the junction of those three wires was melted due to some corrosion on one of the wires. The corrosion created resistance and resulted in heat which melted the plastic (particularly of the brown wire) and may have damaged the crimped on connectors.
The person who had the car at the time didn’t own good crimpers or didn’t have the correct connectors to crimp and didn’t want to buy another OE Fiat part with the worry it would also melt at some time in the future. So they ended up taking off the crimped connectors and soldering them together.
In general most people, in the automotive/aeronautics fields, frown on soldered connections due to the possibility of the flux for soldering damaging the wires and causing them to fail due to the acid. Additionally soldered joints can suffer from failure due to being a rigid connection and vibration causing failure due to being flexed back and forth. Both are valid concerns.
In this case the connection looks good, the joint isn’t seeing rhythmic motion relative to the three wires so I would let this one lie at least for now. It doesn’t look like the source of your problem.
It would have been nice if the person who did this had used a nice heat shrink material to enclose and reinforce the connection.
I would tape it up well and secure the wires using a wire tie so they don’t get jostled repeatedly as you work in the box. In the future you might consider going to a different connection strategy but that is down the road…