Does the ecu have to be mounted to function?

[noid]

I am attempting to install a used ecu into my 2g gst. I plugged the harnesses into the ecu with out mounting it to see if it was a working ecu. The car would not start. It turns over and sputters alittle ,but does not run. So basically I just want to know Does the ECU have to be mounted to work correctly? I plan on mounting it tomorrow ,but i do not want to get my hopes up for nothing. Thank you for any help.

 

[snowborder714]

Nope, just plug it in.

 

[GooeyGus]

I drove mine around for like a year with the ECU on the floor.... worked like a champ

 

[tkelly27]

I'm not planning on ever putting mine back. Everyone that comes in my car gets the "don't put your feet on that box or that box" talk though.

 

[ilco187]

I drove mine around for like a year with the ECU on the floor.... worked like a champ

me also, i hooked up my afc and just never stuffed it back in.

 

[92dsm1]

My ecu is also just laying on the floor. I was taking it out to much checking the wiring for the SAFC the PO put in the car.

 

[Morphius]

Nope, just plug it in.

Are you sure that is 100% true. Doesn't the ecu case need to be grounded?

Reason I say this. My 90, back in the day, blew the ECU. Leaky caps. I was short of time and pulled it, simply plugging in another in it's place. I didn't ground it. Left it hanging out there on the pass side. Car cranked but wouldn't start. I knew the ECU was good, because I had just pulled it out of a running parts car. Long story short. Decided that maybe it needed grounded and so I threw it up under the dash and put one bolt in to ground the case. It then started.

Maybe it was a total fluke. I'm not a EE.

 

[08talon08]

I think the ECU case has to be grounded...my car would start but would stay running...i put it back in the stock location...bolted it in...and it started and purred like a kitten

 

[chadnum1]

Ive always tested ecus without mounting them.

 

[Morphius]

Also note, I speak from a 1g perspective. Differences between 1g-2g electrical and specifically grounding? There are both 1g and 2g users commenting here. (ie the result I had with my 1g may be different with a 2g??)

 

[-TunedDSM-]

My 2g never had a problem with it just plugged in, if I had my 1g running I would go try it.

 

[08talon08]

yes it does it pulls grouds through the frame weres its mounted if not it atempts to ground via other sources wicth will burn up the ECU making the car run poorly

 

[turbosax2]

From Dave on the dsmlink forums:

It's entirely possible that the case vibrating against ground could generate electrical noise that the ECU sees. Also, some 1G ECUs have caps leakage that has flowed up under the heat sink and has created a short between a connector pin and the case of the ECU. When the ECU is bolted in place, this shorts that signal to ground. If this is an ECU I worked on, hopefully that is not the case, but I've seen a few ECUs develop such a short a year or two after service because the leakage had gotten inside a part that looked just fine from the outside. You might check operation with the ECU properly grounded to the chassis of the car.

Dave

Possible explanation why some of your ecu's won't work unless they're properly mounted/grounded. Also, the wires could be stretched or not making good contact with the ecu not mounted.

 

[Leonthefaded]

This thread is old but it doesnt answer the question, especially my specific one. I have a black box ECU from a 2g TSI in my 98 GSX, it was swapped with a non eprom GST ECU which was properly mounted, I dont have the mounting hardware to mount the black box ecu in the same place the GST ecu was. Reason I havent attempted getting the mounts for the black box ECU is because the ECU will not "fit" where the old GST ECU was. How should I go about mounting this black box ecu so that i can avoid damaging it, or leaving it on the floor being an eyesore? I am currently in the process of designing a bracket for it to fit under a single din radio in the radio pocket in our 2g cars.

 

[josh1095]

you may want to be careful how close you place it to the radio. they put out a good amount of heat. and i can tell you heat is always the enemy when it comes to electronics. putting it under neath would be much better but just make sure it doesnt get roasted!

 

[Leonthefaded]

Well natrually that is where it would have togo. In place of or in the little bin that comes with the singl din kits to fit in double din spaces

 

[cliffkemp]

I just rebuilt my engine and put link in it. It is sitting in a covey hole and is not mounted and the car runs fine. I have a 92 laser. I am not sure about the 90s but, the 91 thru 94 should run fine. Unless I just got lucky or it was grounded another way, it runs fine. I do have a 90 talon too but, it has a greddy and have never pulled the cpu so, I cannot say on it. As far as I have read, there is a ground wire that is part of the harness wiring. It sounds more like a loose wire or a broken wire. Sometimes the fine strands fray and cause a very weak connection and that will play havock with anything it goes to.

 

[jmelocik]

As posted previously by turbosax2, If there are other issues, the ECU MAY do strange things.

From Dave on the dsmlink forums:

Quote:
It's entirely possible that the case vibrating against ground could generate electrical noise that the ECU sees. Also, some 1G ECUs have caps leakage that has flowed up under the heat sink and has created a short between a connector pin and the case of the ECU. When the ECU is bolted in place, this shorts that signal to ground. If this is an ECU I worked on, hopefully that is not the case, but I've seen a few ECUs develop such a short a year or two after service because the leakage had gotten inside a part that looked just fine from the outside. You might check operation with the ECU properly grounded to the chassis of the car.

Dave

 

[Mr PopUps]

Ok, has anyone who replied to this ever taken the engine harness out of a car? Take it from me, ive dissembled more than i care to count. On a 1G bolting it in wont make any difference as around 12 or so inches from the plugs is a mass of ALL the black wires that bolt to the car.

 

[Leonthefaded]

Hey just an fyi. I figured out how to slide my ecu in behind the dash! No need anymore to make a custom mount. Its sitting nice a snug!