Cold start valve wire power voltage

[mtopxsecret6]

Hi everyone,

Ive done a search, though I cant find exactly what  I'm asking here. The cold start valve(under the TB on the rb20det), what voltage does it see at the plug? Is it 12v? And when does it see a voltage? Cold engine, ignition on(engine not running), should I be seeing a voltage at the plug for the valve?

Im not getting a voltage under this scenario, if I'm  suppose to, any ideas on where to look to fault find this? I've finally had enough of the horrible cold starts and rough warm idle problems and I'm finally doing something about it.

Thanks everyone!

[blind_elk]

Air Regulator (cold start valve) is powered by the fuel pump relay.

[mtopxsecret6]

Ok, so this means it should have a constant 12v signal with ignition on? The fuel pump fires up and runs, so its getting a signal to run.

Ive pulled the cold start valve apart, its dead clean inside, I've hit it with 12v and nothing happens. I can move the pcb with my hand forward and back against the spring, though I'm not sure what normal operation is meant to be with a 12v signal.

Thanks

[Dose Pipe Sutututu]

It's super slow acting valve, not something that reacts fast like your idle control valve or similar.

They often die on RB20DETs and you see hacks where people just block the air feed to it to prevent super high idle.

[mtopxsecret6]

I dont get super high idle, I get super hard cold starts, and hunting and super low idle when warm. 

[mtopxsecret6]

Does anyone know which is positive and negative on the plug?

Thanks

[GTSBoy]

The circuit for this is clearly shown in the R32 GTR manual.

[blind_elk]

11 minutes ago, mtopxsecret6 said:

Does anyone know which is positive and negative on the plug?

Thanks

test which terminal has continuity to earth = -ve

 

Easiest to test if you remove it.

Look through where the hoses fit. There should be a shutter, and it should be roughly half open at ambient temp. Then apply battery voltage across the terminals - the shutter should fully close (takes several minutes).

Check resistance across the terminals - 70 - 80ohms at 20C

[mtopxsecret6]

20 minutes ago, blind_elk said:

test which terminal has continuity to earth = -ve

 

Easiest to test if you remove it.

Look through where the hoses fit. There should be a shutter, and it should be roughly half open at ambient temp. Then apply battery voltage across the terminals - the shutter should fully close (takes several minutes).

Check resistance across the terminals - 70 - 80ohms at 20C

Why didn't i think of this! Haha

Ive tested the ohms, its 75 as stated on the plug. The opening isnt quite half way, its more a quarter. And ive had it sitting on the test bench and it has moved. To a closed position. Is there a process to open the valve a bit more to get it to half way? Ive attached a photo of mine at the cold position, you can just make out its on the quarter open position. So for some reason I have no power at the plug through the loom.

[blind_elk]

Well, it appears that it is pretty much working correctly.

Upon reflection, the symptoms you describe - poor cold start, poor hot idle - don't seem to mesh. I would start looking at dirty injectors. Try a big chunk of injector cleaner in your next tank of fuel.

Have you confirmed that the fuel pressure is ok? Base ignition timing? Water temp sender?

Edited July 15, 2020 by blind_elk

[mtopxsecret6]

I'm m not getting power to either of the solenoids, so I'm confident this is the issue.

Both leads on the cold start valve is earthing out. And with a cold engine, I have no power at the AAC valve plug, I did momentarily have some yesterday. 

I had the injectors cleaned, fuel is at 50psi, not sure how to test ignition timing.

I'm going to swap ecus and see if that has anything to do with it.

[GTSBoy]

19 minutes ago, mtopxsecret6 said:

I'm going to swap ecus and see if that has anything to do with it.

Don't do this. If there is a fault in the wiring that has damaged the relevant circuit in the ECU, then swaptronics is a good way to kill another ECU.**

Instead, why not look into the health of the loom? Point to point check the wiring with a multi-meter. Use the wiring diagrams in the manual to show you what you should be looking for and where.

 

** Granted, the power for this valve does not come directly out of the ECU, so the risk to your spare ECU in this circumstance is not high. I'm just making a point that you need to think about what you're doing, instead of risking spare parts. Swaptronics is bad practice.

[mtopxsecret6]

14 minutes ago, GTSBoy said:

Don't do this. If there is a fault in the wiring that has damaged the relevant circuit in the ECU, then swaptronics is a good way to kill another ECU.**

Instead, why not look into the health of the loom? Point to point check the wiring with a multi-meter. Use the wiring diagrams in the manual to show you what you should be looking for and where.

 

** Granted, the power for this valve does not come directly out of the ECU, so the risk to your spare ECU in this circumstance is not high. I'm just making a point that you need to think about what you're doing, instead of risking spare parts. Swaptronics is bad practice.

Where do I find this wiring manual? Is it a file on the website?

[GTSBoy]

It is freely downloadable from any of a gazillion links that you will find if you google it. You want the R32 GTR service manual. It has RB20 stuff in it too, because it covers GTS4.

[blind_elk]

2 hours ago, mtopxsecret6 said:

I'm m not getting power to either of the solenoids, so I'm confident this is the issue.

Both leads on the cold start valve is earthing out. And with a cold engine, I have no power at the AAC valve plug, I did momentarily have some yesterday. 

I had the injectors cleaned, fuel is at 50psi, not sure how to test ignition timing.

I'm going to swap ecus and see if that has anything to do with it.

Air Reg / AAC problems have to be unrelated.

AAC is powered by the ECU relay, and the ECU switches to earth thru pin 4.

Edited July 15, 2020 by blind_elk

[mtopxsecret6]

12 minutes ago, blind_elk said:

Air Reg / AAC problems have to be unrelated.

AAC is powered by the ECU relay, and the ECU switches to earth thru pins 4 and 60.

I'm waiting for a new AAC valve, the cold start is working on the test bench. And it turns out when you crank the motor thats when the fuel pump relay kicks in, and you get power to those two plugs.. Durr..

So, the solenoid on the AAC is cactus, so that explains why that wont work, and I believe the cold start may have been just jammed etc. I pulled it apart, hit it with electrical cleaner, and I'm m currently cycling it on the test bench atm, and it seems to be operating.

When I get the new AAC valve, I can continue this adventure, and give progress updates.

Thanks for the help/brainstorming so far everyone!

[GTSBoy]

Cold start is AAC.

Idle control is IACV.

[mtopxsecret6]

Isnt cold start under the throttle body, and the AAC is warm idle control on the end of the plenum, with the idle control screw on the rb20det?

[GTSBoy]

No. AAC means Auxiliary Air Control. It is just that. Auxiliary, as in extra.

IACV is Idle Air Control Valve. Is the actual idle air stepper motor controlled by the ECU.

[mtopxsecret6]

Ok, we are referring to the same thing items then.