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Crank Sensor circuit has me scratching my head...


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icyblack
New User

Feb 17, 2019, 8:21 PM

Post #1 of 8 (258 views)
  post locked   Crank Sensor circuit has me scratching my head...  

New back yard wrench turner here, looking for help.

]Bought a 2004 Kia Rio RX-V, 1.6L engine, 5 speed standard, 180,000 Kms for cheap, but it has an issue. I've owned Rio's for 17 years now, did alot of work on them but this one issue has me scratching my head. Long post, bear with me.

Car will (hard) start with Crankshaft Position Sensor unplugged, and it shouldn't - at least my other 04 Rio doesn't. Seems to idle fine with crank sensor unplugged, but stumbles when revving - it's like the car is in limp mode.

The weird part of it - if I remove the crank sensor from the trans housing - but keep it plugged in, it will start. Hard start. Start the car with the crank sensor unplugged - and plug the sensor in while running, car stays running - still in limp mode. Idles fine, stumbles when revving.

No other codes, just the P0335 when the Crank sensor is disconnected. Wish other codes would pop up.



I have verified timing, all good.

With Crank sensor plugged in, and cam sensor unplugged, no start.

Key on, compared with my other Rio, 12V/5V and ground are fine.

Another computer was installed, no difference.

Tried two other used crank sensors, no difference.

Looking down the hole for the crank sensor, spun the engine manually, all the teeth from the reluctor look good.



I'm at a loss. any ideas are appreciated.


(This post was edited by Hammer Time on Feb 17, 2019, 9:00 PM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 17, 2019, 9:01 PM

Post #2 of 8 (240 views)
  post locked   Re: Crank Sensor circuit has me scratching my head...  

OK first, red text is not necessary.

Second, I don't get what you are doing here. Why would you be unplugging any sensors?



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



icyblack
New User

Feb 17, 2019, 9:10 PM

Post #3 of 8 (235 views)
  post locked   Re: Crank Sensor circuit has me scratching my head...  

I see blue text... Sorry, I'm new here.

Bought the car with a no start condition, sorry, should have mentioned that. Unplugging the crank sensor is the only way to get it running.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 18, 2019, 6:09 AM

Post #4 of 8 (206 views)
  post locked   Re: Crank Sensor circuit has me scratching my head...  

You don't diagnose a problem by unplugging anything.


All "crank, no start" conditions are approached in the same way. Every engine requires certain functions to be able to run. Some of these functions rely on specific components to work and some components are part of more than one function so it is important to see the whole picture to be able to conclude anything about what may have failed. Also, these functions can ONLY be tested during the failure. Any other time and they will simply test good because the problem isn't present at the moment.
If you approach this in any other way, you are merely guessing and that only serves to replace unnecessary parts and wastes money.



Every engine requires spark, fuel and compression to run. That's what we have to look for.

These are the basics that need to be tested and will give us the info required to isolate a cause.

1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.


2) Test for injector pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injector with the key on.


3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.

4) If all of these things check good, then you would need to do a complete compression test.

Once you have determined which of these functions has dropped out,
you will know which system is having the problem.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Feb 18, 2019, 6:10 AM)


icyblack
New User

Feb 18, 2019, 9:22 AM

Post #5 of 8 (190 views)
  post locked   Re: Crank Sensor circuit has me scratching my head...  

Sorry, maybe I'm not making things clear.

The car runs with the sensor unplugged - purrs like a kitten at idle, just doesn't rev properly. To me, that's not a failure in any of the other systems. She has spark, fuel, air and proper timing.

If I pull the crank sensor out of the trans, leave it plugged in - the car starts, idles, but can't be revved. It's like a limp mode.
Unplug the sensor, keep the car running, plug the crank sensor back in and the car stays running - but can't be revved. No change.
Like I say, I have another Rio, same year, will not start with the crank sensor unplugged, so why will the other start?Key on comparison between the cars shows 12V, 5V and ground are good.

I've got 3 crank sensors, are they all bad? Don't know. Is the car killing sensors? Don't know. Going to see if I can test them today. I don't want to start swapping parts from my other car in case the car is somehow killing the sensor.

So is the crank sensor interfering with the other systems? Or is something else interfering with the crank sensor? That's what I need to find out.


(This post was edited by icyblack on Feb 18, 2019, 9:24 AM)


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 18, 2019, 10:06 AM

Post #6 of 8 (183 views)
  post locked   Re: Crank Sensor circuit has me scratching my head...  

OK, if you want to continue using you worthless methods, you really don't need us. We have a totally different way of approaching these issues.

I suggest you clear the codes and perform the testing suggested and stop unplugging things.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



(This post was edited by Hammer Time on Feb 18, 2019, 10:07 AM)


icyblack
New User

Feb 18, 2019, 10:30 AM

Post #7 of 8 (172 views)
  post locked   Re: Crank Sensor circuit has me scratching my head...  

The fact that the car starts and idles fine doesn't mean that the fuel, air and electrical are functioning? What is the sense of testing everything else when the car starts and runs? She's backfiring when trying to start with the sensor plugged in - generally means there's fuel and spark, just at the wrong time - but timing is correct and verified.

The first response you made is a copy and paste for typical troubleshooting for a non-start condition, I get it, been working on cars for over 20 years.
This car starts and runs, just doesn't run properly.


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 18, 2019, 10:37 AM

Post #8 of 8 (168 views)
  post locked   Re: Crank Sensor circuit has me scratching my head...  

That may have been a copy and paste set of tests but I assure you I created it many years ago and it has helped hundreds of people.

It has become very apparent to me that you think you know better so I am ending this thread right now so we can move on to people that actually will follow our free advice.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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