Interesting DME T/S tip
09-12-2013, 10:48 AM
#1
Team Owner
Thread Starter
Interesting DME T/S tip
I was just cruising the forums and saw this .. thought a DME is a DME and might help some 911 guys too .. i dont know how to cross post so just copied and pasted .. Credit to the 944 forum if it is helpfull. ....
I suggest that everyone save this to your computer
"The following information refers to Clark's Garage document IGN-02 and the Porsche shop manual section on testing the DME and associated sensors. Porsche uses an oscilliscope to test everything. I don't have one, could not find one and I certainly wasn't buying one! So, lets use LEDS to test.
First, start by buying two LEDS. Radio Shack #'s 2760022 & 2760041
One lead on each LED is shorter that the other. That is the negative side, which is important. Mark that one black with magic marker on each. Now remove your fuel pump fuse and disconnect the 35-pin connector from the back of the DME. Using Clark's Garage document IGN-02, page 5 "DME plug connector" locate and mark pins 8,25,26,27.
8 & 27 are the Speed Sensor outputs; 8 is negative, 27 is positive. Insert your RED LED (2.6 volt) between the two. Remember your + & - !
25 & 26 are the Reference Sensor outputs; 26 is negative, 25 is positive. Insert your GREEN LED (2.1 volt) between the two. Remember your + & - !
Make sure the leads don't touch. Now crank the engine over as you would normally. If everything is kosher your green LED should be blinking and the red LED should be almost steady as the engine spins.
This worked like a charm for me, helping me to determine that the DME was bad and ultimately solving my problems. If I didn't explain well, please ask for clarification. I'm no teacher! Good luck sir!!! " - shiners780
"I have used this method and it works great."- joes
Sorry for no pictures joes is the one you did is for me when I was building my car in Alabama two years ago.
I suggest that everyone save this to your computer
"The following information refers to Clark's Garage document IGN-02 and the Porsche shop manual section on testing the DME and associated sensors. Porsche uses an oscilliscope to test everything. I don't have one, could not find one and I certainly wasn't buying one! So, lets use LEDS to test.
First, start by buying two LEDS. Radio Shack #'s 2760022 & 2760041
One lead on each LED is shorter that the other. That is the negative side, which is important. Mark that one black with magic marker on each. Now remove your fuel pump fuse and disconnect the 35-pin connector from the back of the DME. Using Clark's Garage document IGN-02, page 5 "DME plug connector" locate and mark pins 8,25,26,27.
8 & 27 are the Speed Sensor outputs; 8 is negative, 27 is positive. Insert your RED LED (2.6 volt) between the two. Remember your + & - !
25 & 26 are the Reference Sensor outputs; 26 is negative, 25 is positive. Insert your GREEN LED (2.1 volt) between the two. Remember your + & - !
Make sure the leads don't touch. Now crank the engine over as you would normally. If everything is kosher your green LED should be blinking and the red LED should be almost steady as the engine spins.
This worked like a charm for me, helping me to determine that the DME was bad and ultimately solving my problems. If I didn't explain well, please ask for clarification. I'm no teacher! Good luck sir!!! " - shiners780
"I have used this method and it works great."- joes
Sorry for no pictures joes is the one you did is for me when I was building my car in Alabama two years ago.
09-12-2013, 10:49 AM
#2
Team Owner
Thread Starter
I realize the pin outs may be different on a 911 DME but thought someone with a 3.2 might pick up the mantle of the 911 guys .. We seem to get a lot of no start threads where the sensors are suspect and though this might be helpfull.
09-12-2013, 02:57 PM
#3
"We seem to get a lot of no start threads where the sensors are suspect and though this might be helpfull."
Complete testing of the speed & ref sensors is very simple not requiring
additional devices other than the VOM (volt-ohm-meter) used to check
the resistance. All one needs to do to further check the sensors for a signal
is to set the VOM to volts A.C. with the scale less than 5 volts. The speed
signal (pins 8 & 27) should produce about 1.0 - 2.0 volts A.C. while cranking.
The ref sensor (pins 25 & 26) should produce about .100 volts A.C. while cranking.
It's as simple as that.
For more info check here under 'No Start': http://www.systemsc.com/diagnostic.htm
Complete testing of the speed & ref sensors is very simple not requiring
additional devices other than the VOM (volt-ohm-meter) used to check
the resistance. All one needs to do to further check the sensors for a signal
is to set the VOM to volts A.C. with the scale less than 5 volts. The speed
signal (pins 8 & 27) should produce about 1.0 - 2.0 volts A.C. while cranking.
The ref sensor (pins 25 & 26) should produce about .100 volts A.C. while cranking.
It's as simple as that.
For more info check here under 'No Start': http://www.systemsc.com/diagnostic.htm