Cold start valve bypass?

[dutchgeordie]

Hi all,

I have a problem with the cold start valve or the thermo switch that controls it. When the engine is hot it will not start again while there is a strong smell of petrol in the air. I found out that when that happens if I just unplug the cold start valve connector the engine starts fine, I just plug the connector back in and I'm on my way.

The fault lies in the valve or the thermo switch but either way they are hard to get and expensive so I thought I'd just run some wiring to the dashboard and put a switch there that lets me interrupt the wiring to the connector on the valve.

At first I thought interrupting the LBlue-Red wire only should do the trick but that didn't work. So I ran a second wire and got a different switch and now I'm interrupting the LBlue-Red and the LBlue-White wire coming from the thermo switch but it still won't start when hot until I unplug the connector completely.

I don't understand how this can still be happening. Where am I going wrong?

Here's the wiring diagram for the cold start valve: http://www.dropbox.com/s/6ipoxqoanpy6fs ... g.jpg?dl=0

Any help is greatly appreciated.

Rolf

[micbrody]

Lots of things happen during ignition.
How sure are you that the problem is with the CSI/TTS?
When you get car started when hot, is it always in this order:
1) attempt start; does not start
2) unplug CSI
3) restart successful

Or do you proactively skip step 1 when you know car won't start? The reason I ask is there are two other systems that might cloud your hypothesis:
AAV
Thermo sender at T-coolant

Before getting into details:
Did you see if CSI/TTS is actually bad? Sounds like you feel it is continuosly open. To check:
Remove CSI and have it point into glass see-through jar ; cover up hole from CSI mount with tape ; and crank engine .
If stuck open , it will continuosly squirt gas during entire ignition sequence and when car running . If engine temp cold (60-80 deg), it should just squirt a few seconds at most

[dutchgeordie]

it is always in the order you mention:
- try to start, no such luck
- unplug csi
- start successful almost immediately

I have not done any further diagnostics yet; will do what you suggest at the weekend

But that won't explain why my switch doesn't have the same effect as pulling the plug. I really can't get my head around that.

[micbrody]

I am making a guess that the CSI/ TTS is working. The reason that disconnecting CSI and car starting has nothing to do with CSI directly; more likely the time it takes to disconnect has changed the residual fuel/air mixture to a condition that favors a startup that does not require extra fuel from CSI.
The reason for non-start is either too lean or too rich mixture. When car warm, the T-piece temp probe will tell ECU to send less fuel at startup(making it a more functionally lean fuel startup); however, if car warm , the AAF will allow less bypass air into plenum(making it functionally more fuel rich).Lots of variables.........
Another possibility is an air leak that worsens when car hot (maybe more expansion of crack in air plenum, hose, etc.....
I think first step is CSI testing

[dutchgeordie]

Thanks for helping me to get the problem sorted.

But I think your guess is wrong. I have ran the car for a couple of weeks with the CSI continually disconnected. The cold start always took a while but it did eventually start. And I had no problems whatsoever starting it when hot!

If I do the CSI test and it shows that it is basically continuously open can I then conclude that the thermo switch is faulty (taking into account my observations when disconnecting the CSI)?

[RRoller123]

Yes, that would be the right conclusion, because if it (CSI) were operating correctly but continually leaking after the 6-8 seconds spray cycle, I think you would probably have a rich and stumble operating condition, with a strong exhaust smell. It sounds like it is on all the time and flooding when a warm start is attempted. OR possibly it runs for the proper few seconds, stops, but then TTS is not reacting correctly to the warm start condition and is running the 6-8 second spray cycle again. If the engine runs well immediately after you warm start it, after disconnecting the CSI, then this is a likelihood too. Maybe the wrong wires were switched due to there being common wire colors used throughout the wiring loom.

[RRoller123]

Thinking about this a little more.... what happens if you shut it off and immediately try to restart it when warm (like within 10-15 seconds). What I am thinking is whether it is leaking (slowly or rapidly) or spraying when it shouldn't. If it is leaking slowly, a restart should be no real issue if done quickly, but after sitting for a time would be a problem.

But that being said, if it were leaking, there would be no change when you pull the connector, as there is always pressure on the Injector. So maybe it is likely that it is just spraying a start cycle when warm and shouldn't be.

Looking forward to seeing the results of your testing the CSI in the jar as suggested, it will help expand the knowledge base on this topic quite a bit, as this is a common issue that seems to come up all the time!

[spider2081]

I could not open the wire diagram you are using. I am not a dropbox subscriber.
My diagram shows all white wires for the cold start valve and the thermal switch.
The thermal switch and cold start valve both receive voltage in the start position of the ignition only. If you crank the engine for for more than approximately 10 seconds the thermal switch should time out and the cold start valve should turn off.
The thermal switch supplies the ground to the cold start valve to open the valve and let fuel in. As I mentioned the Cold start valve only has voltage on it in the "start" position of the ignition switch.
If you have someone turn the key to the "start" position and you measure the voltage on the cold start valve connector you should have voltage on one pin only. (cold Start valve disconnected from harness)
The pin with out power is the one you need to interrupt to simulate the thermal switch operation.
The cold start thermal switch should be closed at temperatures below 35 degrees C. (adding fuel)
I have seen cars with the wrong connector plugged into the thermal switch and the cold start valve. The thermal switch usually has a brown connector and the cold start valve usually has a blue connector.

Hope this helps.

[dutchgeordie]

I've changed the location of the diagram so you don't need a dropbox account (I hadn't realised you needed one).
I think/hope this works: https://1drv.ms/i/s!ArH0fTCQFXR8oySQQliarfj-tP0n

[dutchgeordie]

Thanks you all. I will give an update after I've had a change to rummage around with it at the weekend.

[spider2081]

I've changed the location of the diagram so you don't need a dropbox account (I hadn't realised you needed one).
I think/hope this works: https://1drv.ms/i/s!ArH0fTCQFXR8oySQQliarfj-tP0n

That wire diagram is incomplete. Here is a link to a Fiat publication with the wire diagram for the Fuel Injection system on page 20. Also explains circuit operation

https://www.mirafiori.com/forum/viewtop ... 49&t=96323

Hope this helps.

[micbrody]

My guess was based on you telling me that you always attempt to start car with CSI connected; and then disconnect when attempting again.

Since you did have it disconnected for a many initial starts, I would agree that it is more likely the CSI/TTS spraying longer or stuck open than it needs to be.
Still a possibility of the other issues; but best first thing to do is just to observe CSI function

[dutchgeordie]

Hi All,

I finally got round to testing as you suggested.

On both cold and warm/hot start the cold start injector opens when starting the car and as long as the key is in the start position it stays open.

This suggests to me that the thermo switch is faulty.

I'll see if I can get a hold on a new one and if not or too expensive I'll install a switch on the wire coming from the thermo switch.

Thanks for the help and pointers in the right direction.

[micbrody]

that's good news that you found problem.

It could either be mechanically stuck open CSI or electrically stuck "on" TTS. Don't remember: Does problem happen when CSI unplugged?

[dutchgeordie]

that's good news that you found problem.

It could either be mechanically stuck open CSI or electrically stuck "on" TTS. Don't remember: Does problem happen when CSI unplugged?

The warm start is fine if I disconnect the CSI so it's not mechanical.