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kpfoten
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Joined: May 24, 2010
Posts: 31
Location: Escanaba, MI
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 Posted: Mon Aug 03, 2015 1:21 pm Post subject: Is fuel pump supposed to run briefly when key on? |
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Dumb question, I know....
82 vanagon 2.0. Doesn't sound like the fuel pump turns on when key on. I'm not sure if it supposed to. It definitely runs at startup but I know that many times ignition-on will pressurize system first- |
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AndyBees
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Joined: January 31, 2008
Posts: 2332
Location: Southeast Kentucky
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| Posted: Mon Aug 03, 2015 1:38 pm Post subject: |
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Yep! It supposed to run a few seconds, then shut-down if the ignition is not turned to Start. <<< EDIT: This is incorrect, see posts below.
When I purchased my '83 Air-cool in 1985, the previous owner had opened up the air flow box and did a mod or two. So, when I got it, the pump ran continuously with the ignition ON. I learned later (about three years), reading in the Bentley, that the pump is supposed to shut-down if the engine isn't started. ....... I'd suspect for safety purposes.
And, BTW, I've been carrying a new air flow meter since 1986 and never needed it. I purchased it for the trip to Alaska in the summer of '86.
_________________
'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.
Last edited by AndyBees on Mon Aug 03, 2015 2:35 pm; edited 1 time in total |
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kpfoten
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Joined: May 24, 2010
Posts: 31
Location: Escanaba, MI
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| Posted: Mon Aug 03, 2015 1:47 pm Post subject: |
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That's great to know--thanks!
Now, if it doesn't run briefly when the ignition turned on, does anyone know where the defect lies? Mine doesn't--is it the double relay? |
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Randy in Maine
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Joined: August 03, 2003
Posts: 34890
Location: The Beach
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| Posted: Mon Aug 03, 2015 1:53 pm Post subject: |
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The pump should only run when the key is in the "start" position. It should not come on until you hit start.
After the engine starts, the double relay will allow it to run as long as the little flap inside the AFM unit is allowing air in.
The pump will vibrate when it is pumping. It should also be cool to the touch as it pumps. You can test it with a volt ohm meter to see if it is really getting 12 volts.
Here is how you troubleshoot the double relay....
http://www.itinerant-air-cooled.com/viewtopic.php?...e200bee45b |
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AndyBees
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Joined: January 31, 2008
Posts: 2332
Location: Southeast Kentucky
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| Posted: Mon Aug 03, 2015 1:56 pm Post subject: |
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| kpfoten wrote: |
That's great to know--thanks!
Now, if it doesn't run briefly when the ignition turned on, does anyone know where the defect lies? Mine doesn't--is it the double relay? |
I believe the air flow box and ECU are the two items in charge of the pump. There's no sensor that provides fuel rail pressure info to the ECU.
I'd start with the air flow box. Seems there is a contact (spring loaded) that provides the bridge for the circuit!
It's been a long time since I studied those schematics...
_________________
'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003. |
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AndyBees
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Joined: January 31, 2008
Posts: 2332
Location: Southeast Kentucky
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| Posted: Mon Aug 03, 2015 2:00 pm Post subject: |
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Randy from Maine, may be correct........
As I stated in my last post, it's been a while since I studied the schematics and worked on the Air Cool. Although, I still own my '83, I don't drive it much at all ........
EDIT: Yeah, (without all the details) instructions in the Bentley to test injectors is to operate starter. So, just turning ON the ignition will not cause/make the fuel pump operate (unless modified as I pointed out previously).
_________________
'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003.
Last edited by AndyBees on Mon Aug 03, 2015 2:16 pm; edited 1 time in total |
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kpfoten
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Joined: May 24, 2010
Posts: 31
Location: Escanaba, MI
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| Posted: Mon Aug 03, 2015 2:03 pm Post subject: |
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| Ok so only when started engaged then- |
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AndyBees
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Joined: January 31, 2008
Posts: 2332
Location: Southeast Kentucky
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| Posted: Mon Aug 03, 2015 2:34 pm Post subject: |
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| kpfoten wrote: |
| Ok so only when started engaged then- |
Okay, I just had to look in the Bentley Schematics at the AFC fuel injection system (as on the Air-cooled engine, 2.0).
During the Start Position, the 50 circuit in the ignition switch provides power to the Fuel Pump Relay. The activated FPR provides power to the fuel pump via a 30 circuit (always hot). As long as the starter is engaged by the ignition switch, the fuel pump will operate.
Once the engine starts (ignition switch back to ON position), the air movement through the air meter box closes a switch that provides power to the Fuel Pump Relay, thus keeps the fuel pump in operation as long as air is moving through the box.
_________________
'84 Vanagon Tin-top, ALH TDI. 1989 Tin-top
1983 Air-cool, 225k miles, 180k miles mine. Seven trips to Alaska from 1986 thru 2003. |
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VWCOOL
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Joined: June 02, 2006
Posts: 1821
Location: Down under
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| Posted: Mon Aug 03, 2015 4:33 pm Post subject: |
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| Hi, does the Vanagon uses a Bosch L-Jet system? |
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Wildthings
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Joined: March 13, 2005
Posts: 50352
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| Posted: Mon Aug 03, 2015 7:44 pm Post subject: |
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| VWCOOL wrote: |
| Hi, does the Vanagon uses a Bosch L-Jet system? |
Don't know for sure where they drew the line for the L-jet name, but yes the aircooled Vanagon is very similar to the FI on the L-jet fueled bay window buses.
FWIW the engine doesn't need to start for the points in the AFM to close, with the starter engaged once the engine begins to turn over and draw air the flap in the AFM will move and the points will close whether the engine has started or not. |
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VWCOOL
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Joined: June 02, 2006
Posts: 1821
Location: Down under
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| Posted: Tue Aug 04, 2015 1:28 am Post subject: |
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OK, here's a clue: There is a wire from the starter circuit to the EFI harness on my EFI Bug; it's under the back seat
My assumption is it runs the fuel pump when the engine is being cranked, priming the fuel system, before there is airflow to close the fuel pump contacts in the air flow meter
HTH |
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