[T3] Fuel Pump Relay - 69 Fastback

Tim Schiller schillertim at comcast.net
Sat Jul 10 15:51:20 PDT 2021 

Voltage at battery 11.84, voltage at power relay 11.84

Turn key on and voltage at power relay drops to 11.67 Is this enough of a drop to make a difference?

Voltage at fuel pump relay (87 pin to fuel pump)when cranking engine is 9 to 9.8

Sent from my iPhone

> On Jul 10, 2021, at 3:02 PM, William Jahn <willjahn975 at gmail.com> wrote:
> 
> To know if that red wire is good, do a voltage drop test on it. Find a good
> ground use the battery neg voltmeter black then turn the key on touch the
> pos battery post then do the same with the voltmeter on the relay where the
> red wire is connected both should read the same , if not the wire is not
> good. I don't know if the wire is red /black that what the bentley shows ,
> I don't recall on my 73 it seems to be red, at least the part you can see.
> I doubt someone changed the wire and ran it through the sleeve. The
> important part is the power relay should show battery voltage even if it's
> low . The battery cranks the engine over it should be enough to work the
> relay. If the battery is old or has a dry cell then that can present
> issues. Most batteries have a date code on them. There is another wire from
> the starter to the ECU that powers the relay while cranking yet if your
> voltage is too low just key on that may not be an issue, It runs from the
> starter to a connector near the left of the engine it's above the engine
> tin . I just don't   see it on a 69. Try to find out why you don't see
> battery voltage on the power relay first, don't trust visuals, do a voltage
> drop test. Or if you have a wire you can bypass it. It needs to be at least
> the same gauge larger is ok.
> 
> The only other thing is the ign switch , it may have an issue because it
> not only engages the starter it also powers that system once you release it
> . That would also  cause things to work and not work. You may at times hit
> a good spot when it does run.
> 
>> On Sat, Jul 10, 2021 at 2:35 PM Tim Schiller <schillertim at comcast.net>
>> wrote:
>> 
>> The red/black wire (all red on my car) appears to be in very good shape.
>> Since it is all red running through a black outer casing, I’m assuming it
>> was replaced. I’m the 3rd owner of my car. The original couple purchased at
>> Riviera Motors in Portland and after 32 years sold it to their mechanic who
>> had it for another 15 years when I purchased. It doesn’t surprise me that
>> it may have been replaced.
>> 
>> I still removed, cleaned at battery and cleaned & checked all connectors
>> at main power relay. Car still no start. Since I have a couple new relays I
>> replaced power relay just to rule out. That did not fix either. I did not
>> cut the outer casing/sleeve to confirm the entire wire is good.
>> 
>> Since the electronics on the car are so sensitive, I wondering if the
>> problem could be the battery. The car cranks over without problem, but I
>> checked the resting voltage and I get a reading of 11.87. My understanding
>> is it should be 12.6 or higher. My boat battery is closer to 14.
>> 
>> Before I buy a new battery, is this a possibility?  I will put on charger
>> to see if I can get it higher, if only to test this theory.
>> 
>> 
>> 
>> Sent from my iPhone
>> 
>>>> On Jul 9, 2021, at 9:14 PM, William Jahn <willjahn975 at gmail.com> wrote:
>>> 
>>> No problem . If you find you need a relay this one would work just fine.
>>> 
>> https://www.autozone.com/electrical-and-lighting/relay-and-resistors/p/novita-40-amp-spdt-accessory-replay/849395_0_0
>> .
>>> 
>>> 
>>> Wouldn't hurt to have a spare and it has all you need and can be mounted
>>> easy. Still I feel it's that one wire.
>>> 
>>>> On Fri, Jul 9, 2021 at 9:07 PM Tim Schiller <schillertim at comcast.net>
>> wrote:
>>>> 
>>>> It’s hard not to run out right now and check all those, but will early
>>>> tomorrow morning. Thx for some direction
>>>> 
>>>> Sent from my iPhone
>>>> 
>>>>>> On Jul 9, 2021, at 8:58 PM, William Jahn <willjahn975 at gmail.com>
>> wrote:
>>>>> 
>>>>> 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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