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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old November 11th, 2007, 14:35   #1
claytski
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Default Fuel Shut off solenoid issue(n109)

just rebuilt a ahu. motor was toast, bought it like that, rebuilt it, and now its running. I couldn't get it running. I cranked it over with no fire. I hooked up the vag com and the only thing I pulled up was the fuel shut off solenoid, open or short to ground(n109). I checked the 109 relay and it seems to work. the glow plugs seem to be hooked up to this relay and without it, they don't work. with it, the glow plug light comes on, and stays on. The fuel shut off solenoid however does not. I took a positive wire from the battery and grounded out the solenoid. it will fire up if I do this. I have read that the needle lift valve wiring may have something to do with this? I had the original #3 injector worked on and I got a different one back. mine was so bad that frank worked me into a different one with a different plug. I have it jerry rigged to work with my harness. I have a blue wire and a grey wire from the harness. on the plug, there is positive and negative labeled. I have negative hooked up to the grey, and positive up to the blue. does that sound right? I pulled the 109 relay out and I tested it. it works fine it seems. any help on this would be great. now the time for the breakin.
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Old November 12th, 2007, 07:36   #2
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The fuel shut-off solenoid is electro-mechanical, not "electronic" per se. That is, the fuel shut off solenoid is a separate, stand-alone item that is either active (on, allowing fuel), or not. The #3 injector lift sensor is far more 'electronic' in that it is sending changing values back to the ECU where the ECU logic uses the data to control amounts of fueling, and even at that, the #3 lift sensor is a back-up to the main fuel metering system.
The fuel shut-off solenoid should be powered (on, allowing fuel) anytime the ignition is switched to the ON position, even if the engine isn't cranking or running on its own. These are times when there is zero lift to be sensed by the #3 lift sensor.
Summary: I think the two are completely separate issues.
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Old November 15th, 2007, 12:48   #3
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ok, I just replaced the 109 relay with a new one. no change. any thoughts?
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Old November 16th, 2007, 08:24   #4
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Quote:
Originally Posted by claytski
I took a positive wire from the battery and grounded out the solenoid. it will fire up if I do this. .
This makes me think you have a short in the wire leading to the N109. Trace the wire.
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Old November 16th, 2007, 12:02   #5
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Or trace the wire from the solenoid, I had mine break under the protective plastic covering for the harness. One butt-splice later and I was up and running.
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Old November 22nd, 2007, 17:36   #6
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I had to splice in the harness. then, I went to the big connector with the 16 pins in it and tested. on the harness side I get .62 volts. I know the relay is good on it cause its new and it didn't change from one relay to the other. I would consider the fuse is blown but if the fuse was blown, it wouldn't put out voltage at all. anyone have any ideas?
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Old November 23rd, 2007, 14:22   #7
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any ideas? its definatly wiring related.
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Old November 23rd, 2007, 14:54   #8
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Sounds like you need to ohm out the individual wires to the fuel shutoff relay to their power source. Since you spliced the harness, I'd check for a crossed wire or a splice crimped to the insulation rather than the wire. Also check the fuse for input and output voltage. Since the engine was removed, make sure all the grounds were reinstalled. A missing or bad ground can cause these kinds of problems. Good luck.
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Old November 25th, 2007, 13:15   #9
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I only reconnected the wire that was cut. no other wires so the wire isn't crossed and the wire has continuity from the solenoid to the large multi connector.
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Old November 25th, 2007, 13:16   #10
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is there anyone out there that can help me trace out the fuel shut off solenoid circuit? I know relay 109 is good and new, and at the solenoid I get 0.67v. traced it back to the large multi connector. the wire is good from the connector to the solenoid. on the harness end of the connector, I still get 0.67v. From there it goes into the main engine harness and goes threw the firewall. anyone have any expirience with this?

also, pulled all the grounds off, cleaned them and put the dielectric grease to it.
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Old November 26th, 2007, 06:40   #11
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This is exactly why you should buy a Bentley manual for your car...

Pin #53 on the ECM connector sends voltage directly to the N109 solenoid through two connectors, the 24 pin round one at the cylinder head and the 3 pin one down by the oil filter/ IP area, in a properly functioning circuit you should put one lead of your multimeter ( reading resistance ) on pin 53 of the ecm and the other on the disconnected end of the wire on the N109 and see .3 ohms +- ( .5 or so ohms ), if not, you've got a problem with the wiring, if you do, look elsewhere like inside the ECM for bad solder or a burned area.

Nothing on this circuit goes through the firewall into the car, this particular part of the harness goes up and across the back of the engine compartment over to the AC switches by the interior HVAC air filter, goes through a sheetmetal divider and then up onto the wiper "shelf" where the ECM is mounted.
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Old November 26th, 2007, 06:56   #12
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...and relay 109 isn't directly connected to N109...
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Old November 26th, 2007, 06:58   #13
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Quote:
Originally Posted by DPM
...and relay 109 isn't directly connected to N109...
It's indirectly connected, Relay 109 powers the ECM, the ECM powers the N109 shut off valve...
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Old November 26th, 2007, 14:41   #14
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yes, but it's pointless trying to do a continuity check from one to the other.
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Old November 29th, 2007, 15:23   #15
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ok, I have the bently. I buy bently's for everything I own. I am not the greatest at reading and diagnosis on wiring. I did ohm it and there is nothing. so I guess the wire is toast.
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