Date: Sun, 17 Oct 1999 10:49:31 -0700
Reply-To: David Marshall <vanagon@VOLKSWAGEN.ORG>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Marshall <vanagon@VOLKSWAGEN.ORG>
Subject: Re: Eurospec problems
In-Reply-To: <38074590.B511CD1E@rambus.com>
Content-Type: text/plain; charset="us-ascii"
Volkswagen never made the schematic for the Digifant ECU available to the
public or to their dealers.
Pin 86 (on the fuel pump relay) does get pulled low by Digifant II ECU's
pin 3. What you are watching the built in safety feature of all VWs. In
the event of an accident, the last thing you want is your fuel pump running
to spray fuel all over everything! On CIS based VWs the fuel pump relay
had a pin #1 (or 31A) that went to the coil. This wanted to see 12V pulses
(or lack of 12V pulses) that indicated that the coil was firing the spark
plugs. If there were no 12V pulse for more than 2 seconds the relay would
shut off. On some models this also acted as a rev limiter, if there were
more than X 12V pulses per time second the relay would turn off.
If you want to eliminate the Digifant ECU from controlling the fuel pump,
get a 1984 to 1989 Cabriolet / Scirocco Pump Relay instead. This has:
30 12V Constant (to battery, usually RED)
87 output (to fuel pump, usually WHITE on a Vanagon)
15 12V Switched (usually a BLACK wire)
31 Ground (attach to body)
1 (31A) Coil #1 (attach to coil pin #1, usually RED/BLACK, sometimes GREEN)
This is what I use for all my engine conversions with great sucess. I even
do this with CIS-E systems that usually control the fuel pump in the same
manner as the Digifant II ECUs do.
Another thing that could be your problem and some of my customers have
experienced problems with this is the CIS-E and Digifant II usually require
a check valve between the fuel pump and the fuel tank. This prevents the
fuel from rushing back into the fuel tank and depressurizing the system. A
warm start depends on a certain amount of residual pressure in the fuel
lines. If you don't have it, you usually have to crank it for up to 5
seconds before something happens.
Hope this information helps, good luck!
>David,
>Eurospec wired the relays a little differently. Pin 85
>is switched 12v but not off the coil pin 15. Pin 86 goes
>to the computer. Pin 86 gets pulled low to turn the relay
>on but goes high (> 6volts) after the pump has primed to shut
>it off. This only happens when you switch the ignition on, not
>while the engine is running. When the engine is running, pin 86
>is low. I think with my hot start problem, the computer is not
>pulling pin 86 of the fuel pump relay down low.
> Does anybody have a schematic for a '91 jetta ecu? or is this
>a ridiculous question?
>
>Grant
At 08:17 AM 15/10/1999 -0700, Grant Holst wrote:
>David Marshall wrote:
>>
>> As per the Digifant wiring diagram that I emailed the list, the Digifant
>> computer ground pin number 85 on the fuel pump relay. Pin 86 goes directly
>> to "15" which is "12V with key on" a simple way to tell if this is working
>> or not is disconnect the terminal 86 wire on the relay and run a test lead
>> from 86 on the relay to 15 on the ignition coil. This assumes that your
>> coil is getting 12V when the key is on...
>>
>> At 01:31 PM 14/10/1999 -0700, Grant Holst wrote:
>> >Does anyone know what energizes the coil in the
>> >fuel pump relay? I think one side comes from the positive
>> >side of the igntion coil and the other end goes to the ecu.
>> >
>> >Grant
>>
>> -- David Marshall - - Quesnel, BC, Canada --
-- David Marshall - - Quesnel, BC, Canada --
-- 78 VW Rabbit, 80 VW Caddy, 84 VW Westie, 85 VW Cabriolet --
-- 87 Audi 5000 Quattro, 88 2.0L VW Syncro Double Cab --
-- David's Volkswagen Home Page http://www.volkswagen.org --
-- Fast Forward Autobahn Sport Tuning http://www.fastforward.ca --
-- david@volkswagen.org (pmail) or vanagon@volkswagen.org (list) --
