[T3] Question 73 T-3 FI /auto trans.Grounds on engine.

Mon Oct 30 11:41:04 PDT 2017

 I only cleaned the grounds because both the brass ground trees over the 
years had road dust mixed with whatever oil mist was on them and  inside the 
male spades . Also the brass trees had quite a bit of tarnish on them.

 I just wanted good grounds and know over time the tarnish will return . As 
long as they are clean now and tight the tarnish will not be where the 
spades contact..

 This is a Calif late 73 T-3 so it has ALL the extra wiring mainly addeed to 
fit the EGR system. On this system as you know since you own one also added 
a ground to the body of the pressure sensor and ECU case and one to the EGR 
relay.

 I removed the EGR valve long ago since had some filter that was never 
changed which turned the valve into garbage from exhaust heat and also rust. 
Then capped off the port on the right heater box flange with a steel plate 
and small metal exhaust gasket where it entered the tin right front corner. 
I also removed the EGR relay which was mounted near the pressure sensor .

 Point of all this is all that remains is the wiring . The EGR valve had one 
double red lead that is feed off the fuel pump relay which also feeds the 
electric AAR . I cannot locate the single plastic cover where 2 wires become 
1 . I know it's not inside the main harness cover yet there is still power 
on those leads key on. That same red lead also in one male small spade at 
the EGR valve connector is a double wire feeding back to the EGR relay plug. 
. Then there is wire #14 on the ECU along with the air temp sensor mounted 
on the ECU case . That wire ends at the relay connector it's not doing 
anything. Then there are the 2 wires on the relay plug that begin at the TVS 
#14 & #17 that are in series at the EGR relay then to the ECU . I don't 
think I need wire #14 all it seems to do is send a signal from the TVS at 
some point in it's movement to the EGR relay to open the EGR valve. I have 
no clue what affect #14 has in the ECU yet it does still receive a signal 
from the TVS.

 All of this is on page 19 Bentley fuel system.section.

 Back to the 73 Calif system . There is one ground tree on the case center 
line and another on the case vent tower , the stud at the front left .

 The ground harness on the right of the IAD had one wire enter a single 
plastic connector then it exits as 2 leads both crimped into one male spade 
that runs across to the ground tree on the case centerline. I do not know 
what ground wire this is or why VW would use one ground wire then exit the 
plastic single connector with 2 wires that both are crimped into one male 
spade and run it about 11" and ground it at the case center line ground 
tree. The Bentley does not show this at all.
. It does show 25 as a ground tree and it shows 26 for all injectors yet 
states 26 is on the cyl cover plate.

 On the actual engine there are two grounds into one male spade on both the 
case tree and the vent tower tree. I think these are the injector grounds 1 
& 2 and 3 & 4 . There are a few numbers on these grounds nothing I could 
read due to the condition of the ground leads once they exit the harness 
cover.

 I did tighten all the other FI connectors then decided to do the grounds. I 
did check from the ECU plug to each componant yet those grounds do not go to 
the ECU plug they go from each componant to their respective ground point on 
the engine case other than #11   does not provide injector grounds as 
bentley suggests yet #11 is a ground and does appear to go to 26 . # 12 is 
the trigger point ground yet looking at the bentley #11 appears to be the 
main ECU ground .

 I'm just trying to figure out the actual grounding and the Bentley is not 
helping.

 The only ECU that uses #14 is the E unit Calif model 72 and 73 and #14 is 
the EGR signal yet # 14 & #17 off the TVS also play some part in this and I 
can find no info how they work . I can assume since I have the EGR relay out 
and the valve all that's left is # 14 from the TVS . Then I read the TVS Doc 
you sent me and tried to tie the two together. " Full Load Enrichment 
Contact Testing: Connect your VOM between the 3rd & 5th pins (12/47 & 2/14.) 
The resistance should go from high to low at some point close to full 
throttle."  There is #14 & #2. Does this mean on full load only # 14 perhaps 
triggers the EGR relay to fully open due to the low resistance at that 
point?

 I may be over thinking this because I never had issues with the EGR relay 
removed yet I have to wonder just what # 14 on the ECU does since it is part 
of the EGR system and full load.

----- Original Message ----- 
From: "Jim Adney" <jadney at vwtype3.org>
To: <type3 at vwtype3.org>
Sent: Monday, October 30, 2017 6:57 AM
Subject: Re: [T3] Question 73 T-3 FI /auto trans.Grounds on engine.

> On 29 Oct 2017 at 17:03, William J wrote:
>
>> I cleaned all the grounds on the two brass trees. I did the trees and the 
>> male spade ends.
>
> I've never found this to be helpful. It's always tempting to think that 
> clean is
> good, but the only thing that really matters is that the connectors are 
> tight. If
> they are tight they will make good contact. If they are loose the 
> connection
> will be intermittent, so tightening them will be important. When you clean
> them, most of what you clean has no role in making a good connection.
>
>>  The Bentley page 19 fuel injection section is just no where close ,
>> it tells you the injector grounds are on the top cover plates.
>
> I'm guessing that you have a Calif car with EGR. That adds a LOT of extra
> wiring to the system. The Bentley didn't cover all of that. I have one of 
> those,
> too, and, yes, it's a lot more complicated system.
>
>>  Is there a better wiring schematic out there ?
>
> Yes, the Bosch literature covers all the FI versions. There must have been
> VW literature that did, too. I don't think the dealer E manuals covered 
> this,
> but I'll bet it was in the K manual.
>
>>  Why would they do it this way?
>
> Bentley had to stop somewhere. This is one place where they made that
> decision. It was just a matter of economics.
>
> -- 
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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