# Help, Frequency valve intermitently stops buzzing on 81 rabbit convertible



## fredsed (Dec 12, 2004)

Shouldn't the frequency valve buzz all the time when engine is running hot or cold or when fuel pump is on? Mine does not buzz all the time and also appears to be causing hot or cold start issues when not buzzing with fuel pump relay jumpered, If I disconect the sinle wire o2 sensor or jumper out the coolant temp switch it will buzz full rich and improves my starting issues hot or cold above 40F. Then I unjumper the coolant switch or plug back in the o2 sensor and it will buzz for a while in what I assume is in o2 sensor controlled mode. Yesterday I replaced the O2 sensor and I thought it may have helped but the FV still intermittently quits buzzing until I disconect the o2 sensor or jumper the coolant switch. Lamda relay is realativly new. popped cover of contacts close and look clean. Is it normal that the frequency valve does not buzz under hot o2 sensor controlled mode or what could be the problem. any advise is appreciated.


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## ABA Scirocco (May 30, 2001)

*Re: Help, Frequency valve intermitently stops buzzing on 81 rabbit convertible (fredsed)*

The frequency valve should be buzzing any time the fuel pump is running. A while back I had a problem with the FV operating intermittantly. In my case, to was a bad ground connection to the ecu, in my car the ECU is grounded to the engine at the cold start valve, that connection was bad. 
My problem seemed to be a much more random then yours so it's probably not the same thing however a faulty ground is still an area worth looking at, electronics can do some really STRANGE things when the ground is faulty. The easiest way to check check that is to find the brown wire at the ECU, splice into it and with the engine running measure the voltage between that and the negative terminal of the battery it should be zero at all times, if not the ground is faulty, run a wire from your splice to the directly to the negative of the battery, if that cures yours problem then make a good permanent ground connection from that brown wire to somewhere on the engine block.
As a general note, I'm on my 5th VW A1, the newest an 86 Scirocco, I've put over 1,000,000 total combined Kms on them and based on my experiences with them the #1 cause of any electrical, electronic problem on a VW, BY FAR, is faulty grounds.
Anyways, good luck.


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## fredsed (Dec 12, 2004)

Thanks for the suggestion ABA Scirrocco. Your suggestion sure makes sense. I will check for continuity between the Brown and white on the ECU (I asume the component under the glove box?) and the negative battey post when I catch the frequncy valve not buzzing as it should. The only ground I see on my car is from the negative battery terminal to chasis to transmission and a broken braid between the chasis and hood but I think the car should run without any hood at all. In your experience do you recomend auxilary grounds and if so from where to where or just cleanup the existing ground between negative post chasis and transmission? Thanks


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## ABA Scirocco (May 30, 2001)

*Re: (fredsed)*

I'm not sure where the ecu would be in your car, in mine it's under the hood in the rain tray near the left fender. As for auxiliary grounds, I usually run an extra ground wire from the battery to the engine block and one from the alternator to the same point on the block.


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## kamzcab86 (Feb 14, 2002)

*Re: (fredsed)*


_Quote, originally posted by *fredsed* »_I will check for continuity between the Brown and white on the ECU (I asume the component under the glove box?) 

The K-Jetronic, Lambda control box is under the dash on the passenger side, mounted with one of the kneebar bolts.
You might also want to check the fuel injection power supply relay (aka Lambda relay); not positive on the early Cabs, but it should be in _position_ #3 on the relay panel.


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