 Fuel Evaporative Control System-AKA Charcoal Canister, More information than anyone wants to know |
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Model Specific Information
914/4: 70 71 72 73 74 75 76 914/6: 70 71 72
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| JeffBowlsby |
 Jun 29 2010, 01:13 PM
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#1
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914 Wiring Harnesses  Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None 
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So how does this system work? Review these first two graphics from the factory repair manual to find out.
(PS I wonder why the forced induction guys dont't use the air from the fan housing to spin their turbos? (IMG:style_emoticons/default/confused24.gif)) Attached image(s)  
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| JeffBowlsby |
Jun 29 2010, 01:28 PM
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#2
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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Then as a test, whats wrong with the charcoal conister installation on these diagrams? The first one is in the factory repair and Service and Training Manuals.
When you are done with this I have more... Attached thumbnail(s) 
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| JeffBowlsby |
Jun 29 2010, 01:29 PM
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#3
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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| SirAndy |
Jun 29 2010, 02:22 PM
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#4
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Resident German Group: Admin Posts: 41,606 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Jeff Bowlsby @ Jun 29 2010, 12:28 PM)  whats wrong with the charcoal conister installation on these diagrams? They both show the air from the fan shroud go into the wrong end on the canister ... The pressure side on the canister is on the side with the two nipples. Fresh air and vapors come in from the same side. The vapor/air mix is then expelled on the drivers side of the canister and routed to the engine air-filter housing ... What do i win? (IMG:style_emoticons/default/biggrin.gif) Andy |
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| JeffBowlsby |
Jun 29 2010, 02:39 PM
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#5
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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Jahvol Mein Freund (IMG:style_emoticons/default/biggrin.gif)
Win? HA! This is a documentary... But wait there is more. The later plastic case charcoal canisters can be opened up and the activated charcoal can be replaced (check Google for suppliers). This should be done...every 50K miles according to the repair manual. Attached thumbnail(s)  Attached image(s)  
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| Pat Garvey |
Jun 29 2010, 06:52 PM
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#6
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Do I or don't I...........? Group: Members Posts: 5,899 Joined: 24-March 06 From: SE PA, near Philly Member No.: 5,765 Region Association: North East States |
Jeff, you know you had to open a "can 'o worms" here.
What about the older cars? I was told by the local PD (dealer) in about '75/76 that the canister was self healing, in that it would clear itself & rejuvinate itself over time - like I believed that! Charcoal has limited capabilities of absorbing hydrocarbons. Yes, it works fine for a few yeas of normal driving, but then it becomes, in the case of these pellets. over absorbed.. I suppose after that some " parked time" the pellets could clear of hydrocarbons, but would then absorb ambient moisture. Bad? Not certain, but I think so. And, when that moisture is released to the chamber & tank, corroson might occur. Now, I seem to remember that there was a maintenance bulletin that recommended changing the canister on the early cars at around 50K. By that time (one my 914) they were unavailable. So, given that my 914 is 37 years old, and isn't required to have emission testing in PA, would I be better off bypassing the canister? Is it of any value at this point? Pat |
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| JeffBowlsby |
Jun 29 2010, 10:30 PM
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#7
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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Well Pat...
You can see the factory manual recomendaiton above indicating replacement at 50K intervals. Thats all I know. I dunno nuthin' 'bout the mineralogical properties of the activated charcoal, bet Google knows. I believe its primarily an emissions thing...filtering raw hydrocarbons from the air (the fuel tank is not pressurized, its open to the atmosphere). If people smell gas in their cabins, it must be a faulty hose, loaded-up charcoal canister or some other flaw in the system. OR, you could find an NOS charcoal canister correct for your model year...OR you could locate a later-issue <gasp> plastic canister and change out the charcoal as in the above picture. Next chance I get I will post photos of the different styles of canister and their different locations... How many different canister styles were their? How many different mounting locations? (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/smile.gif) |
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| JeffBowlsby |
Jun 30 2010, 10:03 AM
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#8
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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How many different canister styles were their? How many different mounting locations?
A 1970 model Attached image(s) 
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| JeffBowlsby |
Jun 30 2010, 10:04 AM
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#9
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4712908458
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| JeffBowlsby |
Jun 30 2010, 10:05 AM
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#10
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4722907659
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| JeffBowlsby |
Jun 30 2010, 10:05 AM
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#11
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4732903509
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| JeffBowlsby |
Jun 30 2010, 10:06 AM
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#12
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4732914926
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| JeffBowlsby |
Jun 30 2010, 10:06 AM
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#13
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4732926371
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| JeffBowlsby |
Jun 30 2010, 10:07 AM
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#14
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4742905929
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| JeffBowlsby |
Jun 30 2010, 10:07 AM
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#15
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4742915964
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| JeffBowlsby |
Jun 30 2010, 10:09 AM
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#16
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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From the 1975 Service and Training Manual
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| JeffBowlsby |
Jun 30 2010, 10:09 AM
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#17
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4752903075
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| JeffBowlsby |
Jun 30 2010, 10:10 AM
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#18
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914 Wiring Harnesses Group: Members Posts: 8,477 Joined: 7-January 03 From: San Ramon CA Member No.: 104 Region Association: None
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VIN 4762901268
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| SirAndy |
Jun 30 2010, 10:37 AM
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#19
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Resident German Group: Admin Posts: 41,606 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(Pat Garvey @ Jun 29 2010, 05:52 PM) I suppose after that some " parked time" the pellets could clear of hydrocarbons, but would then absorb ambient moisture. When i removed mine ('70 914-4), i opened it up to have a look inside. It was empty! (IMG:style_emoticons/default/huh.gif) I guess after 30+ years, all the charcoal inside had turned to dust and was happily burned by my engine ... (IMG:style_emoticons/default/popcorn[1].gif) Andy |
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| Peter Zimmermann |
Aug 23 2011, 04:11 PM
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#20
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Newbie Group: Members Posts: 11 Joined: 15-August 10 From: Bakersfield, CA Member No.: 12,055 Region Association: None |
QUOTE(SirAndy @ Jun 30 2010, 08:37 AM) QUOTE(Pat Garvey @ Jun 29 2010, 05:52 PM) I suppose after that some " parked time" the pellets could clear of hydrocarbons, but would then absorb ambient moisture. When i removed mine ('70 914-4), i opened it up to have a look inside. It was empty! (IMG:style_emoticons/default/huh.gif) I guess after 30+ years, all the charcoal inside had turned to dust and was happily burned by my engine ... (IMG:style_emoticons/default/popcorn[1].gif) Andy FWIW; this is the only suitable place I could find on my '74 1.8 (VIN 7173). There were no holes in the left side body to bring the lines forward from the shroud/air cleaner, and the car did have the 5mm plastic line in the tunnel. Result? No fuel smell at all in the car or garage. Attached thumbnail(s) 
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