[T3] ECU question .

Fri Jul 8 21:52:16 PDT 2016

 All I really have or have ever seen as far as part numbers go is a list 
Russ Wolfe posted on Samba and all it has are VW part numbers listed and it 
goes to Aug 72 but nothing for late 73 and mine is late mid Nov 73 .

 Since it had only VW numbers and the main differences were the ECU and MPS 
and TVS I never paid any attention to the Bosch numbers . I don't recall if 
the ECU in my car has a Bosch number , I know  it has  VW number and may 
have both I simply went by his chart and many others did as well , few seem 
to have 73's let alone Calif built as in my case. I read many times on Samba 
Aug 72 were the last built.

 My 73 case was an X the 72 is a U . I have no idea if the 73 X that came in 
this car was ever rebuilt or replaced , everything was there and in it's 
place not one part missing even had the redish sort of fiber cover over the 
voltage reg and two relays , still has. When I tried to remove the heads off 
the 73 the cylinder were stuck so tight I had to tap and rock them off. The 
72 came apart easy I rebuilt that case and have used it since 98 . Both had 
the stepped heads and dished pistons. I assume the U case is late 72 from 
that or Calif  sold.

 Assume is all I can do . All I do know is in 97 here they changed the smog 
law and 73 is exempt even with the 2 different MAP's the read always came 
out the same no matter what I did it was always a bit rich then the EGR was 
inop and this was the old sniffer in the exhaust then after I rebuilt the 72 
case they did the dino and it just made it .

 I've never driven another one to compare yet as mine was when I got it in 
85 it ran real well even if the MAP was the proper VW # and the wrong Bosch 
. I worked on cars long enough to know when any tiny thing has changed .

 As far as what Bosch # is correct for my 73 . I did get the proper Bosch 
number MPS has no VW # so who knows. It runs better than it did with the one 
I had on there yet before it ran great so who knows what changed since 2006 
ran fine then .

 I didn't rack up many miles since 2006 . I did notice the left rear side 
panel had the fiber board cracked when I first removed it to remove and 
paint the fenders so someone was in there at some point . I really have no 
idea what was done it seemed to sit a while I do recall . The odometer 
didn't work I have no idea how many miles were on it ,it had 88k and a bit .

 It seems to run well enough just has that idle deal but it's better now 
with the new MPS . I doubt it has more than 40 k on it since I rebuilt the 
engine in 98 does have more years on the wiring and who knows what else. 
.all I changed was the HTC and MPS and the fuel lines and other things to 
maintain it.
----- Original Message ----- 
From: "Jim Adney" <jadney at VWType3.org>
To: <type3 at vwtype3.org>
Sent: Friday, July 08, 2016 8:33 PM
Subject: Re: [T3] ECU question .

> On 8 Jul 2016 at 14:58, William J wrote:
>
>> this other ECU does have the EGR thermo switch on it and the bracket .
>> Wouldn't this make it a 73 or 72 late ECU?
>
> Yes, it could be either. Some '72s came with EGR; I used to have one.
> Those were all the X prefix engines.
>
>> I don't understand why late units can replace early but not the other
>> way around.
>
> There's a certain amount of speculation in this, but here's my
> thinking:
>
> If late ones were not a replacement for early ones, they would have
> given them a different part suffix. So the new E parts must be
> suitable replacements for all cars that came with E parts. So late
> can replace early.
>
> That's the easy part.
>
> There were 3 changes going from '72 to '73: distributor, pressure
> sensor, and brain. VW clearly viewed these as a new "set" of parts
> that would work well together and meet the '73 EPA emissions
> standards. If the earlier E part would work just as well in the later
> cars, there would have been no reason to make any changes in it, but
> we know that it was changed, since it got a different Bosch part #.
>
> To me, this means that VW felt that the early parts were not suitable
> for use in the later cars. BUT, what we don't know was how many of
> the early parts were still in VW dealership and distributor parts
> inventory when the design changed. If VW recalled all those early
> parts and replaced them with later parts, that makes their intensions
> clear. But if they let the old parts mingle with the new ones it
> means that they didn't think it was important enough to make a
> difference.
>
> Note that it's also possible that the later parts were introduced
> into the VW parts distribution system sometime within the '72 model
> year, so that all the early inventory could be gone by the time the
> '73 cars came out. This would have been perfectly legal and would
> have assured that dealer repaired '73s and '72s would continue to
> meet their EPA requirements. If VW was smart, that's what they would
> have done, because they clearly knew what the '73s were going to come
> with long before those cars hit the showroom.
>
> It's may also be important to note that in the Bosch parts
> literature, where the VW part numbers were not used, they continued
> to call out different Bosch parts for '72 and '73 at least for the
> next 20 years, which is as late as my Bosch catalogs go.
>
> Finally, the Bosch test booklet, which has the instructions for
> testing the FI using the Bosch D-jet tester, has listings for
> different brains what can be substituted for each other. This lists
> the B as a suitable replacement for the A and the D as a suitable
> replacement for the C (if the temp switch is replaced), but there are
> no substitutions listed for either E brain.
>
> In general, I come down on the side of prefering to see factory
> compatable parts used together. Certainly there are other
> combinations that you can get away with, but there's no way to know
> what the consequences might be.
>
> -- 
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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