ECM Ground
04-30-2013, 07:35 PM
#1
ECM Ground Guys just put a 6.0 in a 1969 chevy truck for a friend and when we went to start it up we had nothing the fuel pump would not come on are anything i was looking at the ECM and as i moved it and it grounded to the glove box and the pump camre on and we had power so i made a jump wire to ground the ECM but i dont think it needs to be grounded i know my Nova with the LS1 dose not have a ground wire so whats the deal.
I have all the wires in the motor harness grounded to the back of the head like they should be and i have a ground strap to the block like it should be and the battery grounded to the block do i need one to the cab to make the ECM Ground?
With out the Ground wire touching the ECM we have nothing but as soon as we touch the wire the pump comes on and we have power and the truck will start and run but its runing real Rich.
I have all the wires in the motor harness grounded to the back of the head like they should be and i have a ground strap to the block like it should be and the battery grounded to the block do i need one to the cab to make the ECM Ground?
With out the Ground wire touching the ECM we have nothing but as soon as we touch the wire the pump comes on and we have power and the truck will start and run but its runing real Rich.
05-01-2013, 12:57 AM
#3
You didn't say what the harness and PCM came from. But I know my F-Body PCM (a 411) has grounds connected via the harness on Pin #1 and #40 of both Red and Blue Connectors. You should check the pin and wires to make sure they are good.
There should be no need to ground the PCM's body directly to the Frame, body or the Battery.
Check the grounds and make sure the Battery is grounded well and/or add some more grounds. My Battery ground has wires to the Body, Frame and Engine. I also have extra grounds from the Engine to the Body and Frame.
BC
There should be no need to ground the PCM's body directly to the Frame, body or the Battery.
Check the grounds and make sure the Battery is grounded well and/or add some more grounds. My Battery ground has wires to the Body, Frame and Engine. I also have extra grounds from the Engine to the Body and Frame.
BC
05-01-2013, 11:20 AM
#4
You didn't say what the harness and PCM came from. But I know my F-Body PCM (a 411) has grounds connected via the harness on Pin #1 and #40 of both Red and Blue Connectors. You should check the pin and wires to make sure they are good.
There should be no need to ground the PCM's body directly to the Frame, body or the Battery.
Check the grounds and make sure the Battery is grounded well and/or add some more grounds. My Battery ground has wires to the Body, Frame and Engine. I also have extra grounds from the Engine to the Body and Frame.
BC
There should be no need to ground the PCM's body directly to the Frame, body or the Battery.
Check the grounds and make sure the Battery is grounded well and/or add some more grounds. My Battery ground has wires to the Body, Frame and Engine. I also have extra grounds from the Engine to the Body and Frame.
BC
and a connection to the battery ground ensures a proper ground...
From what I can recall... the PCM has a Ground wire that ties directly to the Back of the passenger side head on an Fbody
and a big ground that ties from the block to the battery
the fbody PCM also ties to the Chassis, which is tied to ground on the battery as well(ground strap from engine to chassis typically, so chassis grounds thru engine to battery.)
the reason Aftermarket ECM's tell you to make sure you have a good ground to the block and to the battery is so everything works properly...
no ground = no workie
good/proper grounds are Rule # 1
Last edited by soundengineer; 05-01-2013 at 11:29 AM.
05-01-2013, 11:38 AM
#5
actually, a good connection to the Block is required for proper spark firing...
and a connection to the battery ground ensures a proper ground...
From what I can recall... the PCM has a Ground wire that ties directly to the Back of the passenger side head on an Fbody
and a big ground that ties from the block to the battery
the fbody PCM also ties to the Chassis, which is tied to ground on the battery as well(ground strap from engine to chassis typically, so chassis grounds thru engine to battery.)
the reason Aftermarket ECM's tell you to make sure you have a good ground to the block and to the battery is so everything works properly...
no ground = no workie
good/proper grounds are Rule # 1
and a connection to the battery ground ensures a proper ground...
From what I can recall... the PCM has a Ground wire that ties directly to the Back of the passenger side head on an Fbody
and a big ground that ties from the block to the battery
the fbody PCM also ties to the Chassis, which is tied to ground on the battery as well(ground strap from engine to chassis typically, so chassis grounds thru engine to battery.)
the reason Aftermarket ECM's tell you to make sure you have a good ground to the block and to the battery is so everything works properly...
no ground = no workie
good/proper grounds are Rule # 1
I have on of my car/engine, an extra ground from the back of the head to the firewall.. on the PCM harness that has a ground near it.. I ground it to the same screw on the firewall for that one coming from the head. I have a lot of grounding loops (so called).
Bottom line as you stated is Rule #1 = Good grounds.. But grounding the case of the PCM will not do any good. If you notice, most of the PCM are mounted to plastic and no direct contact to of the case to the chassis or frame of what is being used to mount the PCM.
BC
05-01-2013, 11:54 AM
#7
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I had to ground the body of my PCM too. I have a GMPP harness kit and it didn't mention you had to ground the body of the PCM, but it wouldn't start til I did.
Just my experience.
Just my experience.
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05-01-2013, 12:47 PM
#8
What ecu unit are you guys working with that needs a chassis ground ? I have an e38 and I don't believe its required for that particular unit , this will be valuable info for anyone in the future .
05-02-2013, 07:59 PM
#10
Thanks for the help guys i found a ground that was not making connection ran a gound from the battery over to it and with the ground unhooked from the ECM the fuel pump came on and it all started working like it should with out he ground hooked to the ECM.
