How did you mount your ecm?

[joegreen]

Hello, I have a 78 chevy k20 converted to tbi and the ecm currently resides in the glovebox. If you have an older body style truck such as mine or any vehicle where it was not tbi to begin with where and how did you mount your ecm. I am thinking i might mount mine behind the glove box and above the ductwork for the heat. I will probably have to rig up a mounting system and screw it to the firewall. Now when the ecm is mounted the case of the ecm has to be isolated from the body of the vehicle aka not grounded correct? If you guys have any pics of where you mounted yours feel free to post the up. Thanks

[steveo]

Now when the ecm is mounted the case of the ecm has to be isolated from the body of the vehicle aka not grounded correct?

in general, any electrical component that's encased in a metal chassis is safe to contact ground while operating, otherwise it'd have service warnings all over it, or would be designed with a plastic chassis. it definitely doesn't have to be isolated.

[lionelhutz]

I try to use the holder they came in from GM. Make a bracket to mount it onto the vehicle somewhere.

I'd have to disagree with you Steve. From GM they are always mounted in a plastic holder. Technically, it could be safe to touch ground with it but I wouldn't mount it grounded to the body. GM isolates them for a reason - the most obvious is to keep the PCM ground = engine ground and eliminate the possibility the PCM and wiring harness will attempt to ground the body.

[steveo]

good point for keeping the reference ground on the engine

[RobertISaar]

i'll have to look at it again, but I'm almost certain my 85 IROC PCM has a metal bracket attached to it?

the other PCMs I have around here.... I think they all went into a plastic carrier.

[sturgillbd]

When this snow finally clears up, I'll take a picture of an ecm that a buddy has that had the case grounded. It came out of a rock buggy that the engine ground had become loose. When they tried to start the buggy, it burned the harness on the ecm grounds. The battery ground went straight to the frame. They had a jumper from another part of the frame to the engine which became loose. Burned the ground pins off in the connector on the ecm and burned the ground wires from ecm to the engine.

[brian617]

Look for an 87 TBI truck or 87-91 Blazer and Suburban for the OEM bracket mounted under the right side of dash behind the glovebox.

[joegreen]

Look for an 87 TBI truck or 87-91 Blazer and Suburban for the OEM bracket mounted under the right side of dash behind the glovebox.

from what i saw they mounted the ecm below the air duct. My harness is too short or me to mount it there plus i don't want it so much in the passenger foot well. I will have to make some kind of plastic device to hold it off of the firewall so its not grounded. Too bad i dont have a 3d printer.

[JeepsAndGuns]

I have heard many times on here not to ground the metal case of a ecm. But I have mine mounted with some metal "L" brackets screwed directly to the firewall under the dash. I have had zero issue mounting it that way.

[joegreen]

I am going to keep it safe and not have the ecm grounded. Even if i have to wrap the ecm in something and then use metal straps.

[RobertISaar]

after finding the IROC ECM, I must have been thinking about the MAF burnoff box.... that has a metal bracket attaching it to the ECM and the ECM has a plastic tray it attaches to.

[lionelhutz]

When this snow finally clears up, I'll take a picture of an ecm that a buddy has that had the case grounded. It came out of a rock buggy that the engine ground had become loose. When they tried to start the buggy, it burned the harness on the ecm grounds. The battery ground went straight to the frame. They had a jumper from another part of the frame to the engine which became loose. Burned the ground pins off in the connector on the ecm and burned the ground wires from ecm to the engine.

I had a Firebird that lost the engine ground and the engine was at 12V while the body was still at 0V. The same thing would have happened if that PCM had been grounded to the body.