Engine has 5-6 volt charge!
06-29-2010, 10:07 PM
#1
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Engine has 5-6 volt charge! yup can almost ground out a test light and connect it to the block and have it light up! not quite
gonna be fun but figure i would stop in here to see if u guys have any advice or have had this problem before before i go ripping the whole harness out of the car to find the short.
to start the block with everything hooked up (all sensors) and key on has 5.5-6 mvolts...disconnect the IAC sensor and im down to 4 mvolts disconnect the alternator plug and down to 2.3 mvolts cant seem to get below that
disconnected sensors with no change
O2s
MAF (Not on car, speed density tune)
coolant temp
IGN coils both sides
Cam posisition
MAP
TPS
IAT
ABS (Deleted)
AIR (Deleted)
EGR (Deleted)
Evap (Deleted)
If i pull the ENG CTRL fuse or turn off the ignition the engine block goes back to grounded charge of 0 mvolts (Makes connection with grounds on the body)
Battery is located in the rear as car grounded to the rear quarter panel (Spare tire location). It has FM turbo setup just got done putting 317 heads and ls9 cam in. moved cam sensor to the front cover. 2000 camaro z28
Car runs and drives fine for getting around town.
Fuel rail carries 10 mvolt charge with all the injectors hooked up and 2.0 with all disconnected
gonna be fun but figure i would stop in here to see if u guys have any advice or have had this problem before before i go ripping the whole harness out of the car to find the short.
to start the block with everything hooked up (all sensors) and key on has 5.5-6 mvolts...disconnect the IAC sensor and im down to 4 mvolts disconnect the alternator plug and down to 2.3 mvolts cant seem to get below that
disconnected sensors with no change
O2s
MAF (Not on car, speed density tune)
coolant temp
IGN coils both sides
Cam posisition
MAP
TPS
IAT
ABS (Deleted)
AIR (Deleted)
EGR (Deleted)
Evap (Deleted)
If i pull the ENG CTRL fuse or turn off the ignition the engine block goes back to grounded charge of 0 mvolts (Makes connection with grounds on the body)
Battery is located in the rear as car grounded to the rear quarter panel (Spare tire location). It has FM turbo setup just got done putting 317 heads and ls9 cam in. moved cam sensor to the front cover. 2000 camaro z28
Car runs and drives fine for getting around town.
Fuel rail carries 10 mvolt charge with all the injectors hooked up and 2.0 with all disconnected
Last edited by kellysmith; 06-30-2010 at 02:58 AM.
06-30-2010, 05:04 PM
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Got the engine harness out after finding battery voltage (10-12) on 2 of the grounds running to the back of the drivers side head. Circuits producing this are 839(Fuse output ign 1) and 639(Power lead from injector fuse 9) as i was able to stick the multimeter in the pink wires on connectors c100, c101 and establish a connection with the grounds on the back of the head (Volt meter went to 000.0)
With the harness out of the car nothing at all connected to it measured pink wires in C100 and 101 to the grounds again and no connection
With the harness out of the car reconnected the C101 and C100 connectors and measured the grounds looking for positive charge and nothing... connected only the PCM to the harness and one of the grounds started reading 4.7 volts...
BTW with engine harness out engines no longer carries a charge!
What do u guys think bad circuit/circuits in the PCM? Going to borrow another PCM when my buddy gets off work in 15min.
With the harness out of the car nothing at all connected to it measured pink wires in C100 and 101 to the grounds again and no connection
With the harness out of the car reconnected the C101 and C100 connectors and measured the grounds looking for positive charge and nothing... connected only the PCM to the harness and one of the grounds started reading 4.7 volts...
BTW with engine harness out engines no longer carries a charge!
What do u guys think bad circuit/circuits in the PCM? Going to borrow another PCM when my buddy gets off work in 15min.
Last edited by kellysmith; 06-30-2010 at 05:19 PM.
06-30-2010, 08:22 PM
#3
TECH Senior Member
Are you talking mV or V...?
On the VDC range/scale on your DMM...?
From engine block to which ground...?
If engine block connected to the battery negative terminal...?
DMM showing 0.000VDC is not necessarily a short unless the circuit is live (current flowing).
What symptoms are you seeing...?
On the VDC range/scale on your DMM...?
From engine block to which ground...?
If engine block connected to the battery negative terminal...?
DMM showing 0.000VDC is not necessarily a short unless the circuit is live (current flowing).
What symptoms are you seeing...?
Last edited by joecar; 06-30-2010 at 08:29 PM.
07-01-2010, 03:26 AM
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Are you talking mV or V...?
On the VDC range/scale on your DMM...?
From engine block to which ground...?
If engine block connected to the battery negative terminal...?
DMM showing 0.000VDC is not necessarily a short unless the circuit is live (current flowing).
What symptoms are you seeing...?
On the VDC range/scale on your DMM...?
From engine block to which ground...?
If engine block connected to the battery negative terminal...?
DMM showing 0.000VDC is not necessarily a short unless the circuit is live (current flowing).
What symptoms are you seeing...?
When i pull the grounds off the back of the head mainly the long one that bolts closest to the manifold/header its showing 5V with no sensors connected to the harness(Draped over the fender) DMM grounded to radiator support... Now connect all the sensors and it shows 10.31V i find it weird that the ground would show a (+) charge.
O2s not cycling is what lead me to this. I took a volt meter to the - and it read +V. Had all 3 grounds together with one bolt on the back of the head. Dont know if that could have caused it. When i had MAF installed had to hotwire it to get it to read and it was not getting power thru the factory harness.
Got PCM and engine harness out of a buddies totaled(Rear quarter panel into a tree) 2000 Z28 and ground is still showing + charge. Not exactly sure how to replace the harness that connects to the firewall on the drivers side to change that.
07-01-2010, 11:29 AM
#5
TECH Senior Member
5mV (millivolts) is just noise...
Voltage drop across a ground is significant if it is more than 0.1-0.2V (100-200mV) with current flowing (e.g. while cranking the starter).
If your block shows a significant voltage relative to chassis/battery ground, then your block is lacking the ground connections (the RHS of the block should have a cable going directly to the battery negative terminal).
Voltage drop across a ground is significant if it is more than 0.1-0.2V (100-200mV) with current flowing (e.g. while cranking the starter).
If your block shows a significant voltage relative to chassis/battery ground, then your block is lacking the ground connections (the RHS of the block should have a cable going directly to the battery negative terminal).
