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Very strange cold start valve issue


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Hi guys,

Having a really strange cold start valve issue here.

My cold start valve is not firing when connected to the harness even though it is getting the ECU signal to do so.   I connected the thermotime switch's bullet connectors together to simulate an "on" signal from the ECU which got power to both sides of the CSV's injector plug during cranking (with those connectors unplugged, the csv's plug only receives power on one side according to my test-light).  However, the csv is not firing when connected to the harness (I pulled the csv out of the intake manifold and put its end into a cup to collect the gas and got nothing).

I left the nozzle in the cup and used some alligator clip wires to connect both "teeth" of the csv's connector directly to the battery and it spit out gas so the valve doesn't seem broken.  The csv is only about a year old and I re-did all my injector connectors so neither of those parts are vintage.

 

Any ideas?

-chase

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I don't think it will work that way. 

The therotime principle works so:

Power comes from wire nr. 47 when engine is cranking. From 47 it goes to the thermotime via wire nr 45.

The power to the thermotime powers a coil around a bi-metal strip. That in turn will heat up and open the ground circuit.  The thermotime provides the ground via wire nr 46 for the csv through its internal contact switch.

The contact switch is there to stop you flooding the engine while repeatably cranking for long periods.

Bridging those two thermotime connector wires is a diagnostic test to see if you get battery voltage at terminal 21 on the ecu plug.

To test the csv you need to identify the power pin for wire nr 45 in the thermotime connector. Disconnect the thermotime and make a connector wire to the other terminal wire nr 46 in the connector and run it to ground. This will bypass the thermotime and give you a ground for the csv. Then crank the engine. It should work, being all the other components are working. If it works your thermotime is defect.

Hope that makes sense. The wiring diagram makes the thermotime function a little blury. I think I got it right.

 

Screenshot_20201206-104619.jpg

Screenshot_20201206-104726.jpg

Edited by EuroDat
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2 hours ago, TomoHawk said:

Right, the ECU does not controll the Aux air valve.  It's connected to the thermotime switch and coolant system.

Sorry if that was confusing, I'm talking about the cold start injector, not the aux air valve.

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6 hours ago, EuroDat said:

I don't think it will work that way. 

The therotime principle works so:

Power comes from wire nr. 47 when engine is cranking. From 47 it goes to the thermotime via wire nr 45.

The power to the thermotime powers a coil around a bi-metal strip. That in turn will heat up and open the ground circuit.  The thermotime provides the ground via wire nr 46 for the csv through its internal contact switch.

The contact switch is there to stop you flooding the engine while repeatably cranking for long periods.

Bridging those two thermotime connector wires is a diagnostic test to see if you get battery voltage at terminal 21 on the ecu plug.

To test the csv you need to identify the power pin for wire nr 45 in the thermotime connector. Disconnect the thermotime and make a connector wire to the other terminal wire nr 46 in the connector and run it to ground. This will bypass the thermotime and give you a ground for the csv. Then crank the engine. It should work, being all the other components are working. If it works your thermotime is defect.

Hope that makes sense. The wiring diagram makes the thermotime function a little blury. I think I got it right.

 

Screenshot_20201206-104619.jpg

Screenshot_20201206-104726.jpg

Gotcha, so just so I understand here's what I should do:

- use my test light to determine which of the two bullet connectors has power to it during cranking, and ignore it

- run an alligator clip from the other terminal to the negative post on the battery

- crank the engine and see if it works

EDIT: I just checked and both connectors that go to the thermotime switch have power during cranking is that right?

EDIT_2: Got it, thanks so much for the explanation!

 

right?

Edited by chaseincats
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OH-  Sorry mate.

I had my car in a shop to have the "datsun expert" check for vacuum leaks, and the first thing the guy told me when I went back was  that the ECU w3as not original (It was) and the "idle air motor" was missing.  The L28 does not have an idle air motor, whatever that is, nor would it be connected to the ECU.

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3 minutes ago, TomoHawk said:

OH-  Sorry mate.

I had my car in a shop to have the "datsun expert" check for vacuum leaks, and the first thing the guy told me when I went back was  that the ECU w3as not original (It was) and the "idle air motor" was missing.  The L28 does not have an idle air motor, whatever that is, nor would it be connected to the ECU.

I'm pretty sure he's talking about the aux air regulator.  For the record you don't need an expert to look for vacuum leaks you just need a $7 harbor freight hand transfer pump and a cigarette haha.

Edited by chaseincats
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3 hours ago, chaseincats said:

Gotcha, so just so I understand here's what I should do:

- use my test light to determine which of the two bullet connectors has power to it during cranking, and ignore it

- run an alligator clip from the other terminal to the negative post on the battery

- crank the engine and see if it works

EDIT: I just checked and both connectors that go to the thermotime switch have power during cranking is that right?

EDIT_2: Got it, thanks so much for the explanation!

 

right?

Yes you will get power out both bullet connectors. What's happening when you crank and test with the test light is the positive is also passing through the coil in the csv. If you disconnect the csv connector you should only get power from one bullet connector.

The other bullet connector will be the ground circuit for the csv and the (-) signal to terminal 21 in the ecu which tells the ecu the csv is active.

Edited by EuroDat
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42 minutes ago, chaseincats said:

My end goal is to wire this so that the cold start injector fires each time I start the car, regardless of the temp.

Is that even doable?

It is doable.

The cold start function only runs while engine is cranking. If you  ground thenegitive bullet connector the csv will always activate while cranking.

May I ask why you want to do this?

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49 minutes ago, EuroDat said:

It is doable.

The cold start function only runs while engine is cranking. If you  ground thenegitive bullet connector the csv will always activate while cranking.

May I ask why you want to do this?

Awesome, so with it setup to manually ground like this it won't continually run after the engine is running I'm assuming.

Doing it just so the engine starts faster.

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2 hours ago, chaseincats said:

I'm pretty sure he's talking about the aux air regulator. 

I'd expect an 'expert' to know the difference, especially since kept mention 'idle air motor' and he also called the ECU a 'computer.' 

Edited by TomoHawk
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Just now, TomoHawk said:

I'd expect an 'expert' to know the difference, especially since he also called the ECU a 'computer.' 

I'd get the car back in the garage if I were you lol.  You can find vacuum leaks in 10 minutes with cigarettes.

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  • 1 month later...
On 12/6/2020 at 12:14 PM, chaseincats said:

Awesome, so with it setup to manually ground like this it won't continually run after the engine is running I'm assuming.

Doing it just so the engine starts faster.

WELL here's a top tip for anyone reading this high on hubris like 'ol chaseincats - do not do this unless you enjoy being stranded lol (ask me how I know).

Basically, the engine will refuse to start after it has gotten up to operating temperature when wired like this and not had sufficient time to fully cool off.  This acts as a pseudo choke and it more-or-less floods the engine when starting if warm thus not allowing the car to start.  It makes perfect sense when you think about it - I just didn't know the CSV pumps THAT MUCH gas into the intake manifold to create a flooded condition.

Live and learn I guess.

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Personally, I'm happy that there is still enthusiasm for these cars.  Most people I know have ditched their S30 for a Nissan or infinity, or some other new model, because you just putin newq parts if something fails.

 

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