Re: fuel mixture guage

[Brad Sheridan <brads@mindspring.com>]

At 04:17 AM 8/17/98 -0500, you wrote:
>hello again
>
>someome a few months back mentioned that they had a fuel mixture 
>guage that they bought from summit.  i bought one of these before 
>waterfest and installed it.  It seemed to mess up my fuel mixture.  
>whenever it was hooked up my idle would stumble.  Also the guage 
>would always read lean even when i cranked it so rich that my eyes 
>were watering.
>The guage had a +12volt wire a ground wire and a wire that went to 
>the O2 sensor.  I had them hooked up right.  what I am guessing 
>happened is that the guage and my jetronic box were splitting the 
>voltage coming from my O2 sensor causing the guage to read lean and 
>my car to run shitty.    If any one has their guage working properly 
>can you drop me a line on how you did it.  

Thats basically how it should be done. Is the Summit gauge supposed to be
able to read the same sensor you use for the FI system? It should, even I
can make one that does that. All it requires is a high input impedance. It
sounds like you may have other problems though. Here's something you can
try to troubleshoot. Does the Summit gauge seem to work ok if its connected
to the O2 sensor, but the stock FI system is not connected? If so, add a 1
MOhm resistor in series with the wire from the Summit gauge to the O2
sensor. Plug the O2 sensor back into the stock computer. Does it all work
now? Be aware that if you make electrical mods, don't do them to the Summit
gauge they may not take it back. Check the signal for a short circuit to
both the ground wire, and the 12V wire. If either are shorted, send it
back, telling them it is defective, and ask them for a replacement O2
sensor also, because its not good to short the O2 sensor output to 12V.
If none of this works, and they won't take it back, let me know. I can
probably fix it.

Brad

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