[Gmecm] MAP troubleshooting.

[Darryl M Gilbert]

Hello: On your MAP sensor itself where the plug plugs into it is marked
with the letters C B A, this is the numbers of the pins. Pin C should
have +5 volts on it (measured from ground). Pin A is the reference (or
ground, this ground goes to the ECM) Pin B is the output signal to the
ECM. You could use a voltmeter with very sharp probes and probe through
the wire insulation to make contact with the wire to verify this. If you
probe say from a good ground to pin B and apply vacuum to the MAP you
should see a change if you get enough vacuum applied. They can also be
tested with a small hand held vacuum pump. The MAP is very important in
having your TBI set up work properly. Something wrong with the MAP sensor
or MAP ckt will give you all sorts of fits.
Good luck
Darryl...

On Wed, 21 Sep 2005 13:32:53 +0200 Tali Orlov <tashutali at gmail.com>
writes:
HI all. 

I am now in the process of converting my Jeep CJ8 carbureted 258 to EFI. 
I bought at the junk-yard TBI system from GMC Safari truck, 1989 , 4.3 V6
.

I connected my laptop to the ECM with ALDL I/F , and I saw that the MAP
sensor was giving a constant value. 4.4 Volt.
I did not connected the MAP sensor vacuum port to the TBI yet because I
am waiting for the manifold adapter, but I gave vacuum to the sensor with
my mouth and also by connecting it with a hose to the bottom of the
carburetor, below the throttles. 

no response from the sensor. 

The junk yard owner gave me another Map sensor but the results are the
same. 

I also checked the signal voltage with a multimeter and I get a constant
4.4 volt.
There is 5 volt reference signal to the sensor. 

Do I do something wrong or I got two bad sensors? 

Thanks. 

Hanan. 
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