My kids impreza L 1999 runs great, but once in a while it will not start when its below freezing, in the morning before going to work. Today was the 1st time this season, and only 30 degrees. Last year it happen 3-4 times, and then seemed to go away. I did verify there is spark. Now the temp is up to approx 33-34. And it started. I'm starting to suspect water in tank or lines. What's the best solution? I hate adding additives but is there any that are good and really  work? (for water)

     If this no start occurs again, what other diagnostics should I do? I see some say verify fuel flow? Is this done by loosening fuel line at filter? or install a "T" with gauge? or is there a hidden port?

   Does this engine have a MAF, because I see where some say to pull plug to see if it starts. Where is it located?

    Should I try ether? if "yes" where is best place to induce it? I did try a bit right behind filter at big hose clamp, but when I cranked, the engine did not actually start but did crank easily and faster rpm. Shouldn't it start momentarily?

   Any help is appreciated. Thank you ahead of time.

 

 

any CEL codes? maybe scan after the no-start.

 

kinda seems like a fuel issue - perhaps the Engine Temp Sensor. (might be 2 temps sensors on your car, the 2 pin/wire unit would be the ETS. if you have a single sensor, it will have 3 wires) 

 

It is supposed to signal the ECU when temps are cold so the injectors can be opened more - like a choke on old carb systems. But, you said it runs well - does that include when it does start at cool temps?

 

ever smell fuel in the engine bay? some Imprezas have had fuels leaks at cold temps - just loose clamps usually. Never read of that causing a no-start though....

I Doubt, that it is fuel supply issue. Water in fuel would run poorly no matter the temp.  I'm leaning towards an electrical issue. If your car has a maf it will be located in line just upstream of the air filter box , large connector ,easily removed . They do go bad and cause a temp no start or a running stall ...  I have never tried disconnecting one with a no start ... I have made them stall by tapping on the maf ,but give it a try if it has one.   The coolant temp sensor is also a possibility.  The engine should have trouble codes  stored even if the check engine light is not on. By the way, If your check engine light is not on , it will be after you try disconnecting sensors.

Runs good when cold when it does start. It looks like there is a maf on intake tube. Where is the fuel relay located? I will check for ETS. (but wouldn't it run poorly cold if ETS suspect?)

If I do trigger CEL, can I reset it easily?

Dothe scanners that Autozone or Advance auto uses, work good enough to pull the codes? or is it proprietary codes that only Subaru dealers can see?

Take it to auto zone (or most parts houses) they will read your codes for free .. Easiest way without a code reader is too disconnect the battery. Problem with that, is any codes on there will be erased at the same time.  

2 codes came up, p0135 and p0705. the guy said something about bank 1 oxy sensor, and 2nd is tranny range sensor. Tranny seems to be working fine. Can the oxy sensor cause the nostart condition when cold?

P0135 is for the o2 sensor heater,not the sensor.No effect on startup.

 

Trouble may well be the transmission range selector.

Engine computer expects the range selector to be in P or N at startup,but it is not seeing that.
I would adjust or repair it before looking too hard elsewhere.

 

I would also use a scanner to confirm what temperature the computer sees at startup.

I thought the tranny range selector locked out power to starter? Engine still cranks but wont fire.

Range selector might contain more than one switch or the wire to the computer may be compimised.

This am approx 27degrees and started fine. I did make my kid fill up tank last night.

Update, still starting fine.