D-Jet Aux Air Valve repair is easy

[sean_V8_914]

I read on Brad Anders
http://members.rennlist.com/pbanders/
http://members.rennlist.com/pbanders/aar.jpg
web site that the Aux Air Valve was no longer available but easy to repair. He is correct. It took me about an hour to do the job. I used a screw driver and a hammer to pry open the pinch seam. Once I got it open I saw that the rotary valve was frozen from rust, dirt and carbon build up. The bottom contains a wire heater element and a ceramic piece . I cleaned it out gently, being careful not to break the heater wire and put it off to the side . The top assembly has the hose connestions and the bi-metal spring that turns the valve when it gets hot. One screw holds the bi-metal spring, I removed this. I sprayed the valve shaft, body and inner cavities with a combo of carb spray and WD-40. Let it sit a while, plugged the holes, shook it up. once I got the inside nice and clean, I put a few drops of 30wt oil in there and worked the shaft until it turned freely. I used some JB weld on the top right angle hose connection to seal it since the pinch seam was leaking air. When I re assembled the top to the bottom, I also used some hi temp silicone to seal the heater chamber. Now it work and the car idles correctly after warm up
thanks Brad!

[sean_V8_914]

[sean_V8_914]

valve pics

[Howard H]

Sean:

Thanks for posting the photos. I always wondered what the insides of that thing looked like.

One thing I don't understand though is how/why you sealed the heater chamber. Doesn't that slow down the heating of the bi-metal spring?

Howard

[415pb]

Sean, I did this same thing three weeks ago. My idle after warm up was around 2500. I took apart the aux air valve and cleaned it. I found the valve to be rusted open. I cleaned and lubed it, now when my 914 is cold the idle hunts from 0 rpm to 1000 rpm. When it's warm, my idle is right around 900. Do you think the small screw holding the circular spring is an adjustment?

Rod


_____________________________
1974 914 2.0 D-Jet

[Va914]

IIRC the Bi-metal spring is heated by the signal from the ECU. I don't think the engine temp heats bi-metal spring in the AAR.
Sealing the AAR prevents air leaks after the AAR closes.

Pease correct me if I am wrong.

Cheers
Kerry

[Dave at Pelican Parts]

The spring is heated by the coil in the bottom of the can. The coil is powered by the same circuit that powers the fuel pump--which is triggered by the ECU.

I recall that there is actually no air path from the can to the upper part, the valve, so making the can seal airtight is a bit of overkill. I remember that the valve itself was reasonably airtight, at least in terms of air leaking into or from the can.

Still, I RTV'd the seam when I did this repair to the AAR I was using...

--DD

[sean_V8_914]

heat chamber is isolated from the air switching valve top assembly. The bi metal spring is heated by the engine heat. I know because I tested it. the factory manual states that even if the heater element fails, the engine temp should close the Aux Air valve and my test confirmed that to be true. I sealed the heat element chamber to limit the air volume exchange thus slowing the corrosion of teh heat element. The heater is powered by 12 VDC from relay board via fuel pump relay's positive
Rod: the screw is an adjustment. I recomend putting it back to hwere it was unless you are going to cycle the valve to test it prior to re-sealing it . I think idle hunting is indicative of lean idle adjust on top pot on teh ECU. check Brads site under component failure analysis
http://members.rennlist.com/pbanders/DJetParts.htm

[415pb]

Thanks Sean, I'll give it a try......

[batman392]

I'm pretty sure the auxiliary air valve/regulator (1972 914 1.7) needs rebuilt, but before I tear it apart, I was wondering if anybody can tell me when the ecu sends the power to the valve. I tried checking for voltage with the key on Run, but got nothing. Any help would be greatly appreciated!

[Dave at Pelican Parts]

The AAR is powered by the fuel pump wire. So any time the pump is running, the AAR should be powered. With D-jet, that means you should see +12V for about 1.5 seconds when the key goes from "off" to "on", and then again when the starter is cranking, and again while the engine is turning over more than ~150 RPM.

If the fuel pump circuitry is not stock, the AAR may be powered while the key is on, or never powered, or maybe something else--depends on how things were wired.

--DD

[Highland]

How did you get the lip of the AAR body pried open? Is there a recommended tool?

[beatnavy]

IIRC, when I fixed mine in similar fashion, I used a very small flat tip screwdriver and gently tapped around the edges to bend the lip up.

[Dave at Pelican Parts]

I used a not-small flat tip screwdriver, and non-gentle tapping. The can is kind of thick and the lip doesn't really like to un-bend.

--DD

[beatnavy]

My memory may not be great. Maybe I DID smack the crap out of it

[Highland]

Does anyone have a source for a replacement/recommended AAR heater resistor?

[Dave at Pelican Parts]

You want about 13 ohms of 1-watt "bathtub" resistors. Make sure you get ones that can handle 1 watt; they'll be kind of big.

--DD

[zteles]

So, my AAR had a broken wire and I fixed it by removing a bit of it, but now it just takes to long to heat up.

SO, I'm planning on doing it again...

They recomended niquel-chrome wire 80/20, 0,8mm thick, but, locking at the specs in Ohm/m, I see that if I were to get to the 13 Ohm, that would be a whole lot of wire! To much!

Could this wire work?

Thank you!

[Dave at Pelican Parts]

Basically, anything you do that will give you around 13 ohms resistance should work. As long as it will hold up to over 1 amp of current!

The stock resistance wire is coiled to fit more in the space. Perhaps that could work? Wrap the wire around a thicker wire, then slide that thicker wire out so you have a coil?

Or just look up ceramic resistors and get one or two that add up to 13 ohms.

--DD

[zteles]

Thank you Dave!

Studying the subject and will follow up