Replacing AAR, aka "cold start valve", discouraging options Options

[Prospectfarms]

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. (IMG:style_emoticons/default/blink.gif)

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. (IMG:style_emoticons/default/huh.gif)

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. (IMG:style_emoticons/default/idea.gif)

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? (IMG:style_emoticons/default/pray.gif) If so, please let me know that too. Or if that's bad forum etiquette,(IMG:style_emoticons/default/chair.gif) just tell me I should place a Wanted ad in the classified forum.

[Cap'n Krusty]

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

[Prospectfarms]

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

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.

[Dave_Darling]

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?

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

[Prospectfarms]

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.