Motronic Multimeter Readings

[JoshGti 8]

Okay so after completing my motronic 3.1 conversion (which seems to be the only thing i post about in this place) and making my new loom up i'm having overfueling issues

 

First port of call is to change the temperature sensor for the engine management but this seems to be fine when ive tested it off the car, ie resistance changes with temperature.

 

Ive rebuilt my mixture potentiometer with new parts after measuring the components so its good but my problem is the wires, they got pulled out and possibly confused, so i dont know if they are in the right order in the plug, the same applies for the throttle potentiometer.

 

So my request is this, can someone with a working 8v converted to motronic take readings of voltage and resistance between the wires with the ignition in the "on" position on the throttle potentiometer and the mixture potentiometer, between pins and for individual pins, so i can work out what voltages are supposed to be going to which pin on the throttle pot and the mixture pot. This will also give me a reading for the throttle initial position so i know that it is at least in the right starting position.

 

Please help as this is the only thing stopping me getting my 205 back to life after i ripped the jetronic out.

 

Josh

[welshpug 1,662]

managed to find this in Autodata (under 106 as it happens, sod all data for the zx or 405)

 

mixture pot;

 

pin 3 should have 5v +, reference signal - comes from ecu

 

voltage across 1+2 when connected should be between 0.5 and 1.2

 

 

throttle pot;

 

pin 1 should have 5v +, reference signal - comes from ecu

 

2+3 throttle closed - 0.6v, throttle open, 4v.

 

 

the 5v+ for both comes from pin 9 of the ecu.

 

 

I'd be interested in details of how you rebuilt the mixure pot, I did open a spare one up a while ago with my brother which a bit of a computer/electronics geek and found some parts on the RS site, but I never looked into it further, now he lives miles away

 

I'm sure my mixture pot doesn't work as turning the screw doesn't do much at all...

Edited June 8, 2011 by welshpug

[JoshGti 8]

cheers for the above speedy reply welshpug, i bought a manual that covers a 605 mp3.1 but thats a lambda model and doesnt cover the mixture pot!

 

I basically did similar to what you seemed to have done, luckily for me i have access to the electronics lab at uni so i just borrowed their soldering iron and some solder wick to remove the original components, then bought direct replacements, 300k resistor and a 5k trimmer pot. I had to use the numbers from the top of the original to find the correct replacement.

 

If you can spare a jiffy bag and a stamp i would happily replace the components in your spare FOC for you as i had to buy 5 potentiometers and 50 resistors so have spares, and it will only take 5 mins.

 

Josh

[pug_ham 244 3 Cars]

I think those of us that have converted to MP3.1 seem to have high co reading issues at MOT time, I know mine used to take a few attempts to get through.

 

When I took my loom out to swap the wiring for the lambda sensor instead of the mix pot I found a spare spade connector near the ecu plug (405 loom) which could be for the injection coding resistor I've seen on the 405 Haynes manual diagrams that might change the readings into the ecu from the mix pot which was joined into the mix pot earth pin & also a white wire spade from the ecu plug pin 24 iirc which is the input signal back from the mix pot.

 

From the limited time my car has been run since being back together the lambda is a far better fitment than the mix pot, my idle co had dropped to 0.23% for its MOT earlier this week.

 

g

[welshpug 1,662]

sounds like it may be worth me fitting a lambda then if the ecu is capable, improve its economy even more

[pug_ham 244 3 Cars]

sounds like it may be worth me fitting a lambda then if the ecu is capable, improve its economy even more

It's really easy to do, only a couple of wires to change ecu plug position, one to splice into the ecu earth pin 5 & a switched feed, I joined mine into the fuel pump feed.

 

You also need to run the lambda earth to a suitable engine or chassis earth point but that just needs a ring terminal & I used the o/s front panel earth point.

 

Graham.