RENIX sensor/ecu ground question.

[xcm]

As a little backstory, i am re-wiring a 1990 4.0 renix from scratch.

I am seeking opinions on the matter of renix sensor grounding... some ground out to wherevers clever, ie the oil dipstick ground cluster. Some have specific grounds at the ecu, and thats obviously like that for a reason, but others make it a point to go back to the common sensor ground, D4, i beleive (dont have my notes in front of me).

Would it hurt anything to run these to a common ground i am installing in the firewall? This ground is a bolt thru the firewall near the oil dipstick ground, and is connected to the motor with a thick lead. I will connect it on the inside to a lead to the battery, as well as the ecu/dash ground's.

Is 1 grounding point desireable? or?

Thanks.

 

[5-90]

Often, "scattered grounding" is the results of beancounters wanting to cut the amount of wire used.

As long as the ground plane proper is solid, there's no reason you couldn't run with a single-point ground for the sensors and suchlike that I can think of.

However, the guy you'd really want to ask about this is old_man - he's an EET, I'm not. (I'm just a guy with a load of practical experience - he's got experience AND education!)

 

[tugalo]

The D4 you mention is on the diagnostic connector. It is wired to the ground at the dipstick.
All the sensors ground thru one wire that goes to this ground., break that wire and you lose several sensors at once, depending on where the break happens to be. In my opinion, a separate ground for each sensor makes troubleshooting considerably easier......works like a champ on my MJ.

 

[tjmotter]

Well, I'm a EET as well so to chime in, if the ground plane across the car is good, you can tap into it anywhere and it will provide a consistent pathway back to the ground post on the battery. The problem is that it is not always good (as we have all seen with the Renix systems). Corrosion, paint, oil, undercoating and loose connections (including other factors) can create electrical isolation that will cause incorrect readings back to the computer. The same thing can happen to things like windshield wiper motors but it becomes obvious pretty quickly that the motor isn't working. The problem with the onboard computer is that without a logic analyzer and a lot of patience, most people would be hard pressed to figure out if it is getting good signals or not.

When in doubt, wiring everything back to a common ground is a good practice. If I were to attempt a rewire of the whole car, one of my first steps would be to map out the ground path for the sensors to ensure consistency and ease of troubleshooting.

Again, if it were me, I would buy myself a terminal strip like this:

http://www.grainger.com/Grainger/Te...ci_sku=6YH65&gclid=CPSCtqv82awCFeFdTAodwztvqA

couple all the connectors together with a bunch of these:

http://www.zorotools.com/g/00034078...kw={keyword}&gclid=CKm9nrz82awCFSxrtgodmBAtqg

and then tie my computer ground, all of my sensor grounds and a good chassis ground all into this strip. I wouldn't worry about the other circuits (lights, radio etc..) since they will be easier to figure out if they fail.

HTH
Todd

 

[Ecomike]

Hello Houston!! What part?

 

[tjmotter]

Hello Houston!! What part?

North West (near the old Compaq campus). You?

 

[Ecomike]

North West (near the old Compaq campus). You?

I work, commute out towards 290 and beltway 8 a few days a week. Live in SE Houston, Hobby, Pasadena area. Bio-Chemical Engineer from, U of H....who has a football team this year,:yelclap: LOL!

 

[old_man]

The biggest issue is keeping the large current devices (starter, fan motor, horn,headlights) from using the same ground path as the small signal sensors (cps/tps/ping sensor).

 

[Ecomike]

The biggest issue is keeping the large current devices (starter, fan motor, horn,headlights) from using the same ground path as the small signal sensors (cps/tps/ping sensor).

OMG!!! It is going to RAIN!!!

I actually agree with you, LOL!:cheers:

 

[tjmotter]

I work, commute out towards 290 and beltway 8 a few days a week. Live in SE Houston, Hobby, Pasadena area. Bio-Chemical Engineer from, U of H....who has a football team this year,:yelclap: LOL!

LOL! I'm a UT grad but it has been a little hard to get excited about college football the past couple of years. Having said that, the win against A&M was nice to see ;-)

Houston is definitely on the map for College football this year and the Texans ain't doin too bad either...

 

[tjmotter]

The biggest issue is keeping the large current devices (starter, fan motor, horn,headlights) from using the same ground path as the small signal sensors (cps/tps/ping sensor).

Well technically speaking they all end up on the same ground path in the end ;-) but I fully agree with your point that you REALLY don't want to be tying high current devices through the same wire as your sensors (at least until you get to the 4 gauge off the battery). I built a replica of a 1965 Shelby Cobra and while it is an "old school" carb'd engine there are still a lot of computerized elements (instruments, ignition box...) so I had to be very careful to make sure that the high current stuff had a nice clean path (+ and -) that was as independent as possible from the "sensitive" stuff.....

 

[Ecomike]

LOL, in the end we are all dead!

That is why I ran new grounds from my Renix sensors all the way to the negative post on mine.

Well technically speaking they all end up on the same ground path in the end ;-) but I fully agree with your point that you REALLY don't want to be tying high current devices through the same wire as your sensors (at least until you get to the 4 gauge off the battery). I built a replica of a 1965 Shelby Cobra and while it is an "old school" carb'd engine there are still a lot of computerized elements (instruments, ignition box...) so I had to be very careful to make sure that the high current stuff had a nice clean path (+ and -) that was as independent as possible from the "sensitive" stuff.....

 

[xcm]

Thank you all for posting.