Ecu Water Temp Line +gauge+ Starting Problems

[Dan_J]

hey guys,

so i stripped a bit of insulation off the ecu water temp wire just near the ECU, but did not cut the wire. now i wrapped a wire around it and sent it to the sensor terminal on the gauge, i wired up the gauge on the cigarette lighter at 12v's +/- and i even double checked it with the wrong terminal connected so i could make sure they were working on the right ones.

now the gauge works and reads the water temp, but when i leave it for a few hours i get a sort of temp reading draw/change to the ecu which in turn means that i cant start my car unless i disconnect the gauge sensor wire from the ecu water temp wire.

help would be great, not sure how i would take it to the auto elec when i have to leave it there for a few hours just for the problem to start.

much appreciated

EDIT: for a rb20det

Edited June 22, 2010 by Dan_J

[mad082]

to be honest i'm suprised the gauge reads accurately. generally they need to be paired with their correct sensor to give an accurate reading. i'm guessing this is why the car doesn't want to start. the ecu is seeing a totally different temp to what it actually is and is therefore adjusting the fuel amount it is injecting to start the car.

my advice is to leave the ecu wire alone and use the proper sensor for the gauge and mount it in one of the alloy things you can get for them. the last thing you want is the ecu to be seeing the wrong temp and altering the mixture and timing. this could lead to either a loss of power or potential damage.

[Dan_J]

ok well i see i guess thats it, altho they guage it self is reading right, it gets to 40c and after a few mins 60c when idling.

does anyone know what the thread size is on the hot/cold sensor for the guage on the cluster? . its 12m + as my tap/die set doesnt go any higher

[mad082]

the temp should be up around 80 to 90 degrees once it comes up to temp, so if the gauge isn't getting that high then that says it all.

not sure on thread size for the dash sensor

[Dan_J]

no that's just it idling in my driveway under no load

thread size shud be 12m x 1.25, i'll see how i go.

cheers for the info

[PUDZ 32R]

doesnt matter if you are idling in your driveway or giving it full boost down conrod straight. it should read between 80 to 90 degrees. sometimes it will go up a bit higher when idling at the lights on a hot day but thats what your fan is there for. if it is reading 60 i am not surprised in any way that the car wont start or run properly. the timing will be retarded to the shithouse as the computer thinks the car is cold so it retards the timing to attempt to get the engine up to running temp faster. also will be choking on all the extra fuel getting injected.

Run your guage from the proper sensor. that is why the RB20 has 2. a super accurate one for ECU and a cheaper 1 pin job for the guage.

[Dan_J]

no, i just started it for the 1st time in the cold morning. sounds about right to me. the gauge is not hooked up when i drive so no after drive readings.

also 60c is bloody hot for coolant temps to be in the morning since last start being the other morning.

close thread please

Edited June 22, 2010 by Dan_J

[mad082]

wait, so 60c was what it was when you first started it, or was 40c? either way it is causing the ecu to see false readings.

[Dan_J]

ok well i wont be using the ecu water temp line as a sensor for the gauge so that is sorted.

temp is like under 40c before i start, as was commenting on the other post above as 60c is not something that is not seen at all and is such a big deal ... as cold starts are 40 under and as stated i dont drive with the gauge connected so no warmed up normal temp.

[toneski]

heres a fun fact in you simply unplug water temp sender under the hood your car wont start