coolant temp sensor
Thread Starter
Instructor
Joined: Dec 2014
Posts: 144
Likes: 9
coolant temp sensor
Has anyone ever had an issue with the coolant temp sensor causing no start problem? I found a flow chart in the manual for hard start/no start issues and the first check is on the CTS. Been fighting issue for a while, have a new sensor for 91 on the way. We'll see what happens.
Racer
Joined: May 2015
Posts: 265
Likes: 21
From: Grand Rapids MI
A faulty coolant temp sensor can cause both lean and rich mixtures. The ECU seeing a temp reading higher than actual will cause a lean condition, and vice versa. If too extreme, this can indeed cause a no-start condition.
Usually, if the sensor fails it will be a loss of ground, and the computer will see a temp of -40, causing it to dump a lot of fuel on startup. Following the "clear flood" procedure generally allows the engine to start and run, so if it starts and dies you may have other problems complicating matters.
However, if the ECU is seeing a temp considerably higher than actual, there is a short to power in the sensor; this will result in a lean mixture and "clear flood" will of course have no effect, preventing startup.
If you have a couple bucks and a laptop I recommend getting a cable (eBay) and computer program (free, several options) capable of showing you what the sensors are saying to the ECU. Having that information at your fingertips will be invaluable in your future diagnoses.
Usually, if the sensor fails it will be a loss of ground, and the computer will see a temp of -40, causing it to dump a lot of fuel on startup. Following the "clear flood" procedure generally allows the engine to start and run, so if it starts and dies you may have other problems complicating matters.
However, if the ECU is seeing a temp considerably higher than actual, there is a short to power in the sensor; this will result in a lean mixture and "clear flood" will of course have no effect, preventing startup.
If you have a couple bucks and a laptop I recommend getting a cable (eBay) and computer program (free, several options) capable of showing you what the sensors are saying to the ECU. Having that information at your fingertips will be invaluable in your future diagnoses.
Last edited by 84Z51J; Jun 18, 2015 at 03:30 PM.
Thread Starter
Instructor
Joined: Dec 2014
Posts: 144
Likes: 9
A faulty coolant temp sensor can cause both lean and rich mixtures. The ECU seeing a temp reading higher than actual will cause a lean condition, and vice versa. If too extreme, this can indeed cause a no-start condition.
Usually, if the sensor fails it will be a loss of ground, and the computer will see a temp of -40, causing it to dump a lot of fuel on startup. Following the "clear flood" procedure generally allows the engine to start and run, so if it starts and dies you may have other problems complicating matters.
However, if the ECU is seeing a temp considerably higher than actual, there is a short to power in the sensor; this will result in a lean mixture and "clear flood" will of course have no effect, preventing startup.
If you have a couple bucks and a laptop I recommend getting a cable (eBay) and computer program (free, several options) capable of showing you what the sensors are saying to the ECU. Having that information at your fingertips will be invaluable in your future diagnoses.
Usually, if the sensor fails it will be a loss of ground, and the computer will see a temp of -40, causing it to dump a lot of fuel on startup. Following the "clear flood" procedure generally allows the engine to start and run, so if it starts and dies you may have other problems complicating matters.
However, if the ECU is seeing a temp considerably higher than actual, there is a short to power in the sensor; this will result in a lean mixture and "clear flood" will of course have no effect, preventing startup.
If you have a couple bucks and a laptop I recommend getting a cable (eBay) and computer program (free, several options) capable of showing you what the sensors are saying to the ECU. Having that information at your fingertips will be invaluable in your future diagnoses.
Thanks
Racer
Joined: May 2015
Posts: 265
Likes: 21
From: Grand Rapids MI
What you're looking for is an ALDL (assembly line data link) cable that has a USB connection. Some have a serial port and will only work if you have a laptop that also has a serial port.
As for the program, I know WinALDL is one, and I believe TunerPro has a free option. I know there are several more out there; just have to find one that will work at the correct baud rate (rate at which the ECU processes information). I could be wrong so do your research, but I believe yours would be 8192 baud.
As for the program, I know WinALDL is one, and I believe TunerPro has a free option. I know there are several more out there; just have to find one that will work at the correct baud rate (rate at which the ECU processes information). I could be wrong so do your research, but I believe yours would be 8192 baud.
