[T3] 71 Squareback MT/FI - Intermittent Engine Stopping

[Wisconsin Spryers]

From: Jim Adney <jadney at vwtype3.org>
To: type3 at vwtype3.org
Cc:
Bcc:
Date: Fri, 12 Jun 2020 15:48:58 -0500
Subject: Re: [T3] 71 Squareback MT/FI - Intermittent Engine Stopping

If you don't get 2 clicks, there's definitely a FI problem. Did you EVER
get 2
clicks? If not, you may have a wiring problem that is keeping your fuel pump
running any time the key is ON. If you're only getting 1 click, make sure
the
pump isn't running at all with the key ON.

> When the engine has successfully started, I've always gotten the 2 clicks
> from the fuel pump relay. I'd place my hand on the relay and could feel
> the 1st click when the relay was being energized when turning the key to
> the ON position and then the 2nd click about 1 second later when the
> ECU interrupted the ground connection at the 85 terminal resulting in
> the fuel pump stopping. I've never had an issue where the fuel pump
> keeps running any time the key is ON without starting the engine.
> During yesterday's episode, when turning the key ON there were
> no clicks from the fuel pump relay...only 1 click from the main power
> supply relay under the rear seat.

You say you held the primer switch DOWN. You should be pulling it toward
you, unless you have the switch installed backwards. Toward you should be
the momentary, spring-loaded, direction.

If you were actually doing the right thing (pulling against the spring)
then this
should have run the pump in spite of any other problem. In that case, it
seems likely that there is a problem with either the power or the ground for
the FI brain.

> Sorry for the confusion. When I wrote "held down the primer switch" it
> was in the momentary, spring-loaded direction - pulled toward me. And the
> fuel pump started running. However, the engine did not start when turning
> the key from ON to the START position while pulling the toggle toward me.

The brain gets its power via 2 wires that run rearwards from the main power
relay under the back seat. First, make SURE that the large red wire from the
battery + to the power relay is connected at both ends. Then make sure that
the 2 wires leading rearward out of the relay are both in good condition.

> The large red wire from the battery + to the main power relay is
> connected. The relay-side of the wire looks solid: no frays, terminal fits
> snug onto the relay. On the battery side, a spade connector crimped onto
> the wire could be in better shape. I might replace this one. When first
> checking this out I did notice the battery + terminal connecter was
slightly
> loose. I could jiggle the spade connector wire on the bolt, so I
tightened
> that down. The 2 grey wires crimped into a single female connector that
is
> attached to terminal 87 on the main power relay look to be in good
> condition: solid connection to the terminal, no fraying.

If that looks okay, go to the engine compartment and look at the far
forward,
left corner of that space and find 2 wires that come out of one harness and
connect to 2 white wires that go into the FI harness. Those are the 2 power
wires that feed the brain. They both need to be there and connected
properly.

> I found the 2 wires from the one harness in the engine compartment
> that connect to the power relay and their connections seem solid
> leading into the double cable connector with the continuation of the
> 2 wires feeding the ECU. The continuity from the main power relay to
> the double cable connector seems solid on both wires based on what
> I can see using my Ohm meter.
> Is the ground wire that goes from the fuel pump relay to the ECU
> accessible anywhere? In my wiring diagrams I see a single cable
> connector is noted between the fuel pump relay (terminal 85) and
> the ECU (pin 19), but couldn't see anything like the area where the
> harness leads up to the ECU.

If those look good, look to the left of the breather stand on the engine.
There
will be a 3-lug ground connector there with 3 connectors (6 wires) plugged
into it. Verify that they are all tight. One of them is the ground for the
brain.
There may also be another ground connection on the case that you should
check at the same time.

Let us know what you find.

> The 3-lug ground connector with the 3 connectors (6 wires) look solid:
> tight connections, no visible fraying or breaks, lug connector tight to
the case;

> Before reading this latest reply this morning, I started up the engine
while
> holding the fuel pump relay in my hand. I felt the 2 clicks as expected
when
> turning the key to the ON position. The engine ran for about 40 seconds
> then died. When trying to restart for the 1st time after it stopped, I
did not
> get any clicks from the fuel pump relay - only heard the 1 click from the
main
> power supply relay. I then checked the connections on the fuel pump
relay,
> specifically the plastic female connector with the two wires that plug
into
> the 85 terminal (grey wire)  & 86 terminal (blue-white wire). I then
tried to
> re-start the engine and I now felt the 2 clicks and the engine started.
> After going thru the additional checks you've suggested, I've
successfully
> started the car multiple times since. Last attempt I let it run for 10
minutes
> at idle without issue. Hummmm! Don't ya just love these intermittent
> problems!!

-- Richard Spryer
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.vwtype3.org/pipermail/type3-vwtype3.org/attachments/20200614/b1bba3dc/attachment.html>