My AAR shorted-out melting the ignition harness. There is infinite continuity between the pos. terminal and ground. Air passes freely through the valve despite heating the housing to 160 degrees F.

My research indicates used OEM valves cost about $90. Typically these don't come with a guarantee. "Rebuilt" or NOS units cost about $200. "Cold start valves" of a similar configuration, e.g., VW, 944, Datsun, Mercedes, etc. begin at $140. Moreover, the off-brands on E-bay are pictured to be identical to the Bosch unit, and that gives me pause.

Many members of this forum have friends with stashes of old parts to trade, I don't, and am relying on the market to source replacement parts. My car starts and runs without it andI don't want to spend $100, let alone $200 for this part; however, I recognize that the AAR vastly simplifies tuning and the general operation of the motor.

Should I:

1. Attempt disassembly and repair of my AAR, per Anders, et al?
2. Purchase a used OEM valve without a warranty?
3. Try a non-stock unit?
4. Go without AAR (how to tune?)
5. None of the above?

Maybe someone has an AAR for a 1.7 FI motor they would like to sell for less than $90? If so, please let me know that too. Or if that's bad forum etiquette, just tell me I should place a Wanted ad in the classified forum.

Do I detect a little confusion here? The AAR is NOT the cold start valve. It passes air, the CSV passes fuel. It's possible to use an L-jet or CIS AAR, which are a dime a dozen in boneyards, and work just fine. You'll have to make a bracket, but it's just not all that difficult to install one. Get some of the wire and the plug with it, too.

The Cap'n

Cap'n has given you some good tips, and I'll add to not try rebuilding your own unless you're fairly competent with that work, but if you can't find a functioning used one around (try GPR) - then the AARs are available rebuilt from Pelican IIRC (maybe GPR too) for more than $90, but it will be reliable & a R&R bolt-in match to what you have (i.e.: no need to make a bracket/etc.).

http://www.gprparts.com/shop/

Last time I looked Pelican, AA, PP/Automotion, etc. wanted a grand for a new "genuine" AAR for my 73 2L!!!!

PS - the cold start valve is actually more like a 5th injector (at the throttle body IIRC) which kicks in more gas when the motor is cold.

The AAR is bone-simple. Once you get into it (the "lip" of the housing is crimped around the "lid" that has the pipes coming out of it) you will see how simple it is.

It has a rotary valve, which is a shaft with a hole through it side to side. That is on a bi-metal spring that acts as the thermostat part of the valve. And down in the bottom is a coil of resistance wire that gets hot when current goes through it. That's all there is to it!

You can replace the resistance wire with ~13 ohms of resistor, but make sure you use resistor(s) rated at 1A or better. And check for clearance with the other parts in there. Solder them in; one end of the resistor (or of the chain of resistors if you need to use more than one) should be fastened to the housing, the other should go THROUGH the housing to have the power wire connected to it. Or run the wire (with insulation!!) through the housing to the end of the resistor. Just make sure the power wire doesn't touch the housing, or you'll get a dead short to ground again.

Make sure the shaft of the rotary valve actually rotates in place. Penetrating oil is your friend for that; you can also use a screwdriver in the end of the shaft in the slot that the spring slides into.

If you like, you can glue the top back onto the can with RTV. It's not necessary, but it can be a little easier than folding the lip of the can over the lid.

What's the worst that could happen--you could break the AAR so it doesn't work any more? You're already there! Just be careful that you don't short the hot wire to the cannister, which is the ground for the AAR.

--DD

I would post a WTB on this site. Mine was bad and I bought a tested, operational used one from a member on here for $60. I plan on repairing my old one following Dave Darlings instructions down the road.

I have 3 AAR valves..; If your interested PM as I was going to list for sale next week along with?

1 1.7/2.0 that has some gold cad plating still from beng in storage 25 years works perfect.

1 1.7/2.0 (nearly NOS?) taken off a Brand New 914 by Racer, Engineer whom stored it since then in a box with 1970's newspapper and complete FI..

1 New Bosh Replacment AAR( the one that looks modern and styled exactly as the 1.8 but different part. #,

that is the best that I have seen except for an NOS on Ebay Germany that sold for 375 EUROS with lots of action.

anyways PM me if your interested in any of them.. Joe

You can also call Rich at High Performance House in Redwood City,CA. I bet he has dozens of them in his 3 story 914 warehouse.

Thanks Cap'n. That is gold because I love junkyards. I'll start by IDi'ing CIS cars. If I'm not mistaken CIS = mechanical fuel injection? Carrera comes to mind, but there must be less exotic makes and models that used it.

BTW, no confusion on the "cold start valve" except maybe by NAPA and Autozone. I'd been browsing for AAR substitutes and those operations combine both the air bypass valve and what at least one of the Bosch d-jet manuals identified as the, "cold, cold start" injector into one category. I'm speaking from memory here, so maybe I am confused, but at any rate that is why I put "cold start valve" in quotations.

Now that Cap'n Krusty has expanded my horizon of substitutions I'm going on a junkyard tour on Monday.

I also appreciate the info on where to look for good used. That's what I needed for a fallback if I come up empty at the "Boneyard."

Dave's challenge to rebuild the existing one is also compelling. Replacing the coil with a resistor is brilliant. I think I have the right thing in a box of salvaged electronic components. Thanks very much for the step by step. Rainy day project and I'll make a report.

Your responses answered all my questions and each one contained relevant info. Astonishing. You have my sincere gratitude.
and soon,

the cheapest is to just hold your foot on the gas til it warms up some....

In the Porsche world, MFI refers to the very early injection system that uses a very very high-pressure pump with variable delivery to each intake individually. The pump in the 911 is run off of the left cam-shaft. Throttle position, RPM, and exhaust heat are the only inputs. MFI was used on the 69-73 911S, the 69-73 911E, and the 72-73 (except for "1973 1/2") 911T, plus many of the race cars.

Early BMWs also used a similar but not identical type of injection.

Both are based on a diesel fuel pump.

CIS is also known as K-jetronic injection by Bosch. It uses a lower-pressure pump, and the air coming into the intake is measured by a metal plate that gets lifted by the air pushing against it. The whole system is controlled by the fuel in some parts of the system changing pressure. The fuel pretty much doesn't stop squirting, hence the designation "continuous".

CIS was used in the 1973 1/2 911T, and all 911s from 74 through 83. Some of the Turbos used it later than that, and other European cars also used it.

--DD

From your info it seems that Porsche used three utterly different FI systems in 1973. Being a Porsche mechanic must be hard work!

I have wondered--what is K-jet? Completely different system from MFI. Fascinating Thanks for straightening me out.

I've been doing that for a couple of weeks now and I wonder if anyone adjusts their vacuum or A/R settings to account for no AAR?

With leaking injectors and an MPS that won't hold vacuum, I guess it doesn't really matter how I tune the engine so long as it will start and run. I'd still like to know what others have done.