MoTeC Global Forum

Hello

I have installed a GM flex fuel sensor (Part nr 12570260) on a rally car, but I have problems getting the M400 too read it.

The sensor is wired looking into the sensor, from left to right, 1: Ground, 2: +12 V, 3: Signal. The signal is connected to 5 v with a 1000-ohm resistor.

The signal is wired too dig in 3 and dig in 4. Dig in 3 is set up with speed, Hz and dig in 4 is set up with msecs measuring.

The input signal is 0 and the raw input values are 0.

Does any one have an idea what can be wrong?

Hello Arve,

There is already a pull-up to 5V on the Digital inputs on our products so you do not need to wire this in externally, depending on the internal circuitry in the sensor you may find that it cannot switch both digital inputs, if it does not work I'd recommend trying with the sensor wired to one digital input.

hmm Dig 3 and Dig 4....

are you getting ANY reading at all from a raw value perspective?

How did you plumb the sensor?

btw

according to this

12v+ requires a 10k pull up not 1k

http://www.megamanual.com/flexfuel.htm

Hello

I have wired as above described, but the sensor is hooked up on the non-pressure side. Can that be a problem?
Is it the same witch way the gas go trough the sensor?

I have set up Dig in 3 with speed, Hz (alcohol), and dig in 4 is set up with msecs measuring (temp).
I dont get any raw signal, it is 0

I will try a 10k resistor to 5v!

Regards

Arve Flaat

Arve

I re-editted my post to show the pull up resistor.

10k on 12v + not 1k

It should not be a problem as long as the fuel goes through it on return. Now personally I would put it in line on the suction side of the fuel pump that way the car sees and adjusts before it gets to the fuel rail.

Arve I saw your edit...

doing some quick math

12v/10000 ohms = .0012 amps
5v/1000 ohms = .005 amps for an increase of .004 amps.
5v/2000 ohms = .0025 for a dif of .0013 amps
5v/3000 ohms = .0016 amps
5v/4000 ohms = .00125 ohms increase of .00005 amps.

If using 5v as the power supply, increase the ohms to 4k.

as for the wiring... feeding two Dig In with one sensor output.....are you sure that is ok to do? speaking froma digital domain, doing that usually cuts the already miniscule signal level in half, sometimes it can not read that low a level......

Avre

one final thing,

you DID setup the input channel under the Adjust > Sensor Setup > Input Setup > User Tab > User X = Dig3 and user Y = Dig4? right?

Save you from doing that daisy chaining that you did.

Also make sure that you turn on the Efficency Z and load Z and add the appropiate user table to each.

Hello

When I disconnected the pull up resistor the Flex fuel sensor functioned.
Using dig 3 for alcohol measuring and dig 4 for fuel temp measuring was no problem.

Thanks for helping me.

Regards
Arve Flaat