1971 Type 3 Fastback and ECU compatibility

[Fasty1973]

Hello all,
I have recently purchased a 1971 FI Manual Fastback and have been going through the motions with figuring out why it is running the way it is.
I have noticed that the ECU I am running is a Black Sticker with codes VW 311 602 021 E and Bosh 0 280 000 028.
I know the car is a 1971 and probably around mid 1971 but hard to tell.
Having numerous issues with idle and power and intermittent idle power loss so thought I would start at the "brains"of it.
Would love some help as I am at my whits end!
I will post photos shortly as well but thought I would get started with the above.

[Fasty1973]

Some photos of the car.

[Tram]

Does your throttle valve switch have 4 or 5 prongs in the plug.
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Немає виправдання для війни! Я з Україною.

[Fasty1973]

Hi Tram,
I will have to check when I get home and get back to you.

[Fasty1973]

[KTPhil]

4-prong and '71 are consistent, but they need a "D" ECU. While some components interchange and will run (or can be modified to run), it is generally best to match up parts as a set as in this table:

[Tram]

[Fasty1973]

Thanks gents. I am going to take out the MPS this weekend as I have photos of it but cant read the number.
It seems to run OK sometimes and then other times feels like it is only firing on 2 injectors.
I have a second engine that I had built with carbs about 10 years ago that only has around 3000 kms on it but I want to persist with this one.

I do feel like I have to go through all the hoses and clamps as Tram has suggested to other forum members first and eliminate as many issues as possible.

[72squareguy]

I have a couple "C" ecu's if he'll need one.
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72 F.I Squareback
70 Beetle Daily Driver

[Fasty1973]

One thing I have noticed over the years in Australia is that vehicles are not always registered according to VW model years. Mine is registered as a 1971 and I have the original paperwork from when it was purchased. it has the VIn and engine number and also the date of delivery here in Australia.
Delivery was October 1971 however the VIN and Engine match vehicles made up to August 1971.
72squareguy, once we get to the bottom of it I might get in contact with you.
Cheers

[Fasty1973]

My previous auto 1971 TLE was a 1971 but the old cases VIN matched a 1972 built period. It was also written down as a TL not the TLE.
In any case, I want to get this baby purring so willing to out the hard yards in!

[Fasty1973]

Finally had some time to go over the engine and found the following with some odd missing parts.

ECU 311906021E with Black Sticker as I have mentioned before.
MPS - 311905051D
Thermo Switch - 311906161C
Temp Sensor 1 - 0280130006
Temp Sensor 2 - Couldn't get to it.
Throttle Valve Switch - 311906111C

There is no Cold Start Valve (probably due to the fact the car was originally from the subtropics in Australia) being in Sydney I can't see that being an issue as it rarely gets to 5 Dec C in the middle of winter here??)

When removing the Air Filter to check the Thermo Switch I noticed the Pressure Switch had been removed as well?

I still need to check the fuel line from front to back to check all is OK but would the pressure switch missing be causing the car to run so rich?

[KTPhil]

Starting in '70 there was no pressure switch; that "full load" function was built into the MPS, and later into the TPS. So it wasn't removed. it was never there.

Agreed, you don't need the cold start injector or thermo switch.

ECU: '72/'73
MPS: Still don't know what a D is for, but if it has a black plastic cap (or a place for it), it's probably ok with the '72/'73 setup
TVS: This is for a '70/'71. You need a different TVS. Full throttle enrichment was handled by the TVS for '72/'73, and the earlier unit lacks the fifth connector which signals this.

What distributor do you have? I's important that the whole "team" play well together.

[Fasty1973]

It seems as thought I have a bit of a cocktail of parts.

I have used the guide that Tram provided, and what I have in various manuals, and there are slight variations to what is able to be used and what is outright incompatible.

Looks like the TVS is original and the ECU was replaced with a later version and possibly the MPS as well?

I have not taken out the distributor as yet. Where is the part number written on it? Maybe I can get to it without removing?

It seems that whoever has worked on this car in the past may have had some knowledge of FI in these cars as it almost adds up.

[Typ3nut]

MPS 311 906 051 D
"D" Unit info was gathered from here : https://oldtimer.tips/en/d-jetronic/55-mapsensor

311 906 051 D used on Type 3 Models 1.6 ...
Bosch Part Number:
0 280 100 101 from Aug 71 - July 72
0 280 100 016 & 017 from Feb 70 - July 73

[Fasty1973]

Will have to check whether it was a 311905051 or 311906051D.
Was half asleep when posting!

[Brunoafonso]

Hello there, i Just found your post.

I have the 311906111C Part if you need it.

Have a nice day

[raygreenwood]

[Fasty1973]

So, is it a case of changing to the correct ECU to match the Engine or find an MPS that may work with the ECU???
My car according to the VIN was built in the 12/1970 - 08-1971 period.
I know I have a lot to test in terms of the fuel line, connections and the like, but with the car starting up quite well, running slightly high in revs for the first 5 minutes or so (and is not to bad to drive apart form the revving and running rich), when it gets to operating temp and the revs drop right off, it is almost impossible to get any power. (very frustrating) From what I have read, and there are probably a few things that it could be, my MPS may be cactus.
I have seen the test that Dr D Jet does to test pressure retention and may have to do the same I gather to further isolate the issue.
With Christmas coming up, and some spare time, I need to methodically go over it from front to back and tick off what works and what doesn't.
Thanks again all, till next time...

[Fasty1973]

Ok, so thanks to some other members, I have sourced the correct ECU, MPS and picked up some NOS Trigger Points and the like.
I changed over the ECU and MPS for the new ones, fired her up and she started and idled for a while, not perfectly, I must say, then as the engine appeared to get to operating temp, it would slowly lose revs and stall. each time i restarted it would idle for about 2-3 seconds, and then stall.
totally different to the issues I was having with the old ECU and MPS but hopefully, easier to solve. I have some the NOS Trigger points to replace if need be as well.
Thoughts???