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Emissions, Electronics, Schematics

Matt S.

NAXJA Forum User
Location
Fresno, CA
Some of you are aware that I took on the task to build a custom dash in my Jeep. I started it last september and it sat for 5 months while I stepped away from it. Now I am back at it and hoping to have the dash finished in a couple weekends.

I bought the Autometer Phantom gauges to use. They look like this.
atm-5698.jpg



To my knowledge, a full dash replacement has never been done. So alot of this is difficult to figure out. Plus I dont have a FSM :gag: This is where some of you might have some knowledge on a few questions I have come up with. This is on a 88' 4.0 with an auto just for reference.

1) Does the Jeep computer system use the stock gauge cluster in SERIES? For exaple: The Tachometer is the OUTPUT signal of the engines RPMs. Does the Input signal go to the computer FIRST, then relayed to the gauge?Or is the signal sent THROUGH the gauge then to the computer?

I am trying to figure out if by removing the gauge cluster am I distrupting the computers operation.

If the gauge is meerly a reading of what the computer is seeing then I will splice into the system with the new aftermarket gauges. Now, if the gauges are an integrial part of the computer circuit, I am going to have to trick the computer by fighting with resistors to mask the loss of the gauges.

Everyone with me so far?

2) The OH SO IMPORTANT check engine light! My goal in this whoooooole thing is cleanliness. I would like to use idiot lights for things like the headlamps, check engine light, turn signals, etc. FarmerMatt brought an EXELENT question. Will an idiot light work as a check engine light? Or is a light that literally says "Check Engine" required? I personally would have never thought about that, but most deffinatly a good thing to think about!

3) Does anyone have access to a online FSM?

I know I will have more questions that you all may beable to help answer, so thanks now, and thank you later!

Matt

And a teaser pic!
buggy0021ck.jpg
 
The various gages are run by outputs - replacing/removing them won't cause you any trouble, and you can play with the signals all you want.

There is NO Check Engine/MIL light on the XJ until MY1991, so that's a non-issue. If you are somewhere where smog control is an issue, you would have to reproduct the MIL light in (close to) original form and function, but that's not a problem for us RENIX guys.

If you're not going to use the old gage cluster/housing, could I have it? I was getting ready to ask for a few for a similar project (I'd like to do mine with aircraft gages, just because I like them and I can wedge more information into the same space, I think.) Let me know.

If you PM or email me with your addy I may be able to get you electronic FSM and info onto a CD (have to have my wife burn it for me at work - my computer's being goofy...) I'm pretty sure I have 1988FSM as .pdf, and I can include OEMR parts cataloging and RENIX manual as well (and it looks like you have the AW4 - I should be able to toss that on there as well.)

CONDITION - you share information! Like I said, I'm working on something along the same lines, and I never did like having to reinvent the wheel if I could avoid it...

5-90
[email protected]
 
I can tell you that I have run my 90 without the dash being plugged. It changed nothing in the way the jeep worked.

I'll be curious to see your dash when it is done. I was just thinking about tearing out my dash the other day. I have a VDO electronic speedo installed in mine, and it is problematic. I don't know that it's the speedo's fault, it acts like it's getting some really noisy power, so it's probably the install.

Fred
 
And AFAIK, the check engine light on an 88 is activated by a timer gizmo to remind people to change their O2 sensor, it's not an output from the fuel injection computer.

Fred
 
5-90 said:
The various gages are run by outputs - replacing/removing them won't cause you any trouble, and you can play with the signals all you want.

My new gauges came with the required sneding units. Like the oil pressure one. Would it be best to simply tap into the existing harness? Or completly remove that wiring and rebuild the harness? I am trying to thin the stock harness as much as possible. So digging into it is not a problem by any means for me.

If I remove the factory sending units, will it effect the computer operation and or the MIL?

Matt
 
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