Temp gauge not working, seems to be running rich

[ember1205]

'86 SE-i. Was able to ride it for the first time today, and I noticed that the temperature gauge doesn't show anything. I have done zero troubleshooting yet, but I'm wondering if there's a good place to start?

Also, is it possible that this is affecting how the bike runs and is causing it run rich?

[neoracer]

if the coolant temp switch is not working most likely you should have a fuel injection system warning light,there is a way to check that but requires to read the voltage off the sensor to be read

most likely you will need a copy of the sei supplement and the wiring diagram in order to test

[bs175dths]

Is the member whose son knows a boat load about the EFI still active?
I remember there were threads along these lines of questions and concerns.
Have you tried doing a search of SEi?

(the join of ANY EFI system........ troubleshooting)

good luck and keep us updated

[ember1205]

I've done quite a bit of additional reading about SE-i and LTD bikes in various places. From what I have found, the engine temp sending unit has exactly ONE job - feed the temperature display in the dash. The Pb sensors have an impact on fuel/air mix by driving a variable voltage to the ECU (which adjusts the mix), and the thermostat switch operates the cooling fan. They're all separate pieces.

I'm not even going to bother THINKING about measuring my MPG until after the oil/filter change and replacement of the air and fuel filters.

[neoracer]

i beg to differ,the air temp sensor and the coolant temp sensor are both tied into the left and right pbr's which are then connected to the ecu
last year i tracked down a bad coolant temperature connector after observing occasional changes in instant mpg readings on the travel computer,when the connector became loose the readings would drop from approx 40+ to 16 mpg,slowing down and stopping would return the mc from a rich condition and mc would run fine,culprit ended up being a missing clip on the coolant connector,previous po had no idea when and if this area had ever been accessed

[ember1205]

The wiring diagram shows NO intersection of the Green/Blue wire from temp sensor with any other wire. Additionally, the three wires off of each Pb sensor go only to the ECU, TPS, and ground.

Do you have more information about where the wire from the temp sensor is routed? I can't find it in the harnesses and wanted to try and avoid digging that deep into the motor just to trace it in order to start doing some basic resistance tests.

[neoracer]

sent you a copy of the cfi unit circuit from the 86 honda etm

[ember1205]

Thanks... Looked through it, found some different info from the wiring diagram I was working from, located a connector plug under the faux tank, ohm tested it and it seems that it is, in fact, connected to the sensor. So, the next thing I have to do is to get to the back of the LCD and see if there's continuity on that wire to that point.

Any tips on the easiest way to gain access to the back of the dash panel? All of the LCD bars work (as evidenced by the start-up self test of the dash itself), but grounding the pink wire does nothing to get the bars to light on the panel. I'm suspecting a break in the wiring or possibly a disconnected coupler somewhere, but I need to validate continuity or not first.

[neoracer]

the coolant temp sensor is also connected to the dash via C57
2nd file sent

[ember1205]

I know it's been a while, but I have had zero time until recently to poke at this more.

I was able to pull the shield off of the front of the motor and get to the sensor located immediately behind it. It works. I can hit it quick with a torch and watch the resistance drop and then slowly come back up as it cools off.

I've also been able to trace the wiring up to two pins in a red connector block to the left of the handlebars and validated that the resistance changes read there as well.

I reconnected the harness, turned the key on, and hit the sensor with the torch for a second. Nothing registered as far as temperature.

I know that the LCD 'bars' work because the gauge area works properly when showing the other setting (forget what it is). Does anyone have very details information on where else I need to look to find connectors? Or, am I relegated to continuing to follow the wires through the bike looking for a break?

And, can someone confirm that this specific sensor is, in fact, the one that drives the temp gauge in the cluster? On top of the motor, in front of the coolant tubes that run side-to-side. There is another one behind the tubes, but that's the "water sensor", and I think that one is used for the ECU to control the mix.

Thoughts?