[T3] Fuel Pump Relay - 69 Fastback

[William Jahn]

Last thought , if you find there is an issue with the power relay I think
Jim may have some good used ones or just a 30 amp Bosch relay wired the
same way will work , they all work the same way. It's just the amperage
that differs.

On Fri, Jul 9, 2021 at 8:52 PM William Jahn <willjahn975 at gmail.com> wrote:

> From what you said I doubt if the pump relay is the issue. I bet you find
> that red /black wire at the battery is either loose or corroded or the
> eyelet on the end of that wire is not making good contact to that wire. If
> it's not there check the spade connector on the power relay. It has to be a
> good connection at both ends. If it is that red/black I would still make
> sure the power relay spade connectors are all sound and fit snug . I went
> through mine a while back and found the brown ground screw was fine yet the
> spade connector only had one rolled edge . It worked I was just checking
> and happened to find it. So I checked them all . it's even possible the
> power relay contacts have high resistance yet they don't have that much
> current to burn them. Mine is the original on my 73 I decided to just check
> for voltage drop and found there was some so I removed the relay cover and
> cleaned the contacts. This is my only car and the last thing I want is to
> be sitting somewhere stranded.
>
> On Fri, Jul 9, 2021 at 8:34 PM William Jahn <willjahn975 at gmail.com> wrote:
>
>> On the positive battery post there is one red/black wire that runs across
>> from the battery pos to 30/51 on the power relay . That wire is fastened to
>> the pos battery clamp  bolt by an eyelet then the battery clamp nut . This
>> wire is the only power to the power relay . Check that to make certain it
>> has a good connection to the battery . If there is a voltage loss there you
>> will not get 12 volts at the pump relay . All it takes is it being loose or
>> corroded . It runs all the way from the battery to the power relay. That
>> may explain why it works then doesn't. That is the contact part of the
>> relay that sends power to 85 on the pump relay. If it's loose or corroded
>> all it takes is to try to start the car and you get an arc which might be
>> just enough for it to make enough contact to run the pump . I would check
>> that before going any further. If there is going to be a bad connection
>> either it's loose and you know how battery cables get corroded . It's
>> simple to check and rule it out . It runs near the top inside of the wall
>> held by small tabs . You will be able to see it easy.
>>
>> On Fri, Jul 9, 2021 at 8:01 PM Tim Schiller <schillertim at comcast.net>
>> wrote:
>>
>>> Replaced fuse with 8 amp just in case it was bad. Bentley manual shows
>>> most fuses are 8 amp except 9 & 11 are 16 amp. Appears several mine are 16
>>> when they should be 8. Separate issue.
>>>
>>> I hear the 2 clicks, both the fuel pump relay a main power relay when
>>> key is turned on.
>>>
>>> I tested pump again with a direct power source and it buzzes. Car
>>> actually started a ran for a while after immediately hooking relay back up.
>>> However, when I turned it off it would not start again. When car was
>>> started, the 87 pin was reading 12V
>>>
>>> Back to testing the fuel pump relay. The voltage to pin 87 is not
>>> consistent. Turning key I sometimes get a zero reading, sometimes a 5-6V
>>> reading and sometimes a 2-3 V reading. I tested when the pump wire was not
>>> attached trying to eliminate the ground wire to the pump as a possible
>>> issue. Not really sure how anyone can follow that brown wire between relay
>>> and pump.
>>>
>>> I found some help to turn key so I could hold on to pump. There is a
>>> little bit of a buzz when the key is turned on, but didn’t seem that
>>> strong. It feels like it is priming or buzzing for 1-2 seconds when the key
>>> is then turned off. Seems just opposite of what it should be doing
>>>
>>> Currently trying to find something on Samba forum for a similar problem.
>>> I really struggle with the search function on Samba
>>>
>>>
>>> Sent from my iPhone
>>>
>>> > On Jul 9, 2021, at 12:39 PM, Jim Adney <jadney at vwtype3.org> wrote:
>>> >
>>> > On 9 Jul 2021 at 10:48, Tim Schiller wrote:
>>> >
>>> >> I will follow the ground and check the fuse
>>> >>
>>> >> I did hook a reliable 12V to the red wire going to pump. Pump buzzes
>>> loud
>>> >> and clear.
>>> >>
>>> >> I had purchased 2 relays and swapped just in case one was bad, but
>>> same
>>> >> results
>>> >
>>> > One other quick check you can easily do if the car is in a quiet
>>> place, is to
>>> > listen when you turn the key ON. You should hear a relay click when
>>> the key
>>> > goes ON and a second relay click about 1 second later.
>>> >
>>> > If you have questions about whether this is happening correctly, look
>>> under
>>> > the back seat, on the  driver's side. Mounted on the top rail, there
>>> will be 2
>>> > relays, each mounted with a single screw. One of them has a ground
>>> wire
>>> > under that screw head. Make SURE that screw is tight. That's the
>>> ground for
>>> > the main power relay coil.
>>> >
>>> > --
>>> > *******************************
>>> > Jim Adney, jadney at vwtype3.org
>>> > Madison, Wisconsin, USA
>>> > *******************************
>>> >
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>>
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