Wiring harness diagram for aircooled VW type 4 engine

[MadMax78]

Hi,

Recently I started a topic about converting an aircooled VW type 4 L-jetronic engine to MS. Unfortunately this topic was lost when there was a database problem and the backups had to be restored. Anyway, I did get some answers and I decided to push on with this project.

I want to use as many components from the original L-jet system, so I also want to integrate the original double relay (Main relay + Fuel pump relay). Besides the relay I will use all the existing sensors and I plan on adding a Bosch TPS (part 0 280 122 001) and a LC-1 lambda sensor. I plan on using the IAT which is integrated in the AFM and the fuel pump contact switch in the AFM as well. For coolant temperature I'm using the stock cylinder head temp sensor (CHT). I made a little draft drawing of how I think the system should be wired, see attached image. Please let me know if you find anything wrong with it. I'll then correct it and when it's good to go I'll make a nice photoshop image of this.

[Matt Cramer]

Is the TPS an on/off design? If so, you won't be able to use it. Just wanted to check as a lot of Bosch systems didn't use a potentiometer type TPS.

[MadMax78]

According to the Bosch website it is a potentiometic angular position sensor with linear characteristic curve, so that should do the trick. My engine is installed in my 78 VW type 2 bus, these busses did not have a TPS installed from the factory. However, some older busses did have throttle bodies with D-shafts and a mounting base for the TPS. So I'll swap in one of those throttle bodies and mount this new sensor on it.

[LeslieTroyer]

don't know much about L-Jet -- but IIRC the older busses used D-Jet which definetly has a switch type TPS -- which is not compatiable with MS.

LEs

[msoultan]

don't know much about L-Jet -- but IIRC the older busses used D-Jet which definetly has a switch type TPS -- which is not compatiable with MS.

That is correct, but the throttle body is compatible... well, with the correct TPS sensor

The nice thing is that bosch looks like a good bolt-on replacement. I used a Vishay-Spectrol TPS sensor and I had to make an adapter plate so it would bolt on to the bottom of my throttle body. It would be really nifty if I could get that bosch sensor and have it bolt right on...

[Matt Cramer]

Ok, that sounds like a good plan. I was just thinking of the stock TPS, which could have been a problem.

[msoultan]

Ok, that sounds like a good plan. I was just thinking of the stock TPS, which could have been a problem.

Yeah.. I got one of those in a ziploc in the garage. I wonder if the bosch TPS and that throttle switch use the same connector - wouldn't that be handy!