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Ambient temp sensor and glow plugs
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=87710		 Page 1 of 1
Author:  TerryZ91 [ Wed Jan 17, 2018 2:19 pm ]
Post subject:  Ambient temp sensor and glow plugs
I’m from Chicago with 05 Jeep Liberty crd and have done extensive rebuilding of my upper motor to make this jeep more reliable and daily driver. You can see everything I replaced so far here viewtopic.php?f=5&t=85506 jeep has been running great so far with only two exceptions.

1) Cold start issue: living in the Windy City, it can get cold in the single digit regularly and sometimes in negatives with the windchills. I have never plugged in the block heater. Sometimes when it’s in the teens it takes me 3-4 long cranks to get her going. And this is with me having Sasquatch intake heater on for 1.5-2 minutes and cycling glow plugs 3-4 times.
I’ve recently read that ambient temp sensor controls the glow plug time. So I hooked up the OBD scanner to see if I’m getting any reading on the ambient temp sensor. And nothing. It read 0. I checked to make sure I do in fact have the ambient temp sensor and it is connected properly. I didn’t dig much deeper since it’s still cold outside but I wanted to see if anyone was able to get a reading on their ambient temp sensor using any of the obd app? I don’t have the overhead information console, not sure if that matters.

2) MPG issue: I average anywhere from 21-23 mpg in the summer with mostly highway driving with 70mph speed. In winter it’s 16-18 mpg. I still have the viscous heater plugged in and the mechanical fan in. I know they increase fuel consumption. I also always put in diesel kleen power service white or silver bottle depending on the weather. GDE eco tune is already flashed. I saw 18.5g/s on my MAF. This is with new rockers about a year old with 10,000 miles. I always see people talking on this forum how they get 25-30mpg. I have never seen that. Wondering if there is something wrong with my crd? Two things I plan to do, not sure if they are causing this issue. Replace MAP sensor and boost solenoid. I been hearing buzzing noise from the passenger side and traced it to the boost solenoid. And the solenoid also feels hot to touch after driving for 20-30 minutes.

Thanks for your time! I have learned great amount from this forum to better take care of my CRD. Words can’t describe my gratitude towards you guys.

Terry
Author:  flash7210 [ Wed Jan 17, 2018 9:27 pm ]
Post subject:  Re: Ambient temp sensor and glow plugs
I don’t know of any OBD scan tool that can read the ambient temp sensor. Maybe the Chrysler star scan can. But I do know that if you disconnect the ambient temp sensor it will set a code.

What glow plugs are you using?
If you still have the 7v plugs you may want to consider putting in 5v plugs.
(edit: I see in your sig that you already have 5v plugs)

A lot of things effect MPG. And what people report isn’t always accurate.
My wife’s CRD has an EVIC and it says she gets 30 mpg. But hand calculated she’s only getting 25-26 mpg.

Edit: Things that most effect my MPGs are-
1. wind resistance (I have a roof basket)
2. aggressive off road tires
3. driving style
Author:  GordnadoCRD [ Thu Jan 18, 2018 3:36 pm ]
Post subject:  Re: Ambient temp sensor and glow plugs
Removing the front bumper will make nearly 5 mpg drop at highway speeds (4.833)
Removing the fender flare from one side makes exactly 3 mpg around here (45-55 mph) (straightening the fender after it got bashed in by a "soft cloth" car wash.)
These are with nearly stock tires, and no lift.
Author:  TerryZ91 [ Sun Jan 21, 2018 3:50 pm ]
Post subject:  Re: Ambient temp sensor and glow plugs
flash7210 wrote:
I don’t know of any OBD scan tool that can read the ambient temp sensor. Maybe the Chrysler star scan can. But I do know that if you disconnect the ambient temp sensor it will set a code.

What glow plugs are you using?
If you still have the 7v plugs you may want to consider putting in 5v plugs.
(edit: I see in your sig that you already have 5v plugs)

A lot of things effect MPG. And what people report isn’t always accurate.
My wife’s CRD has an EVIC and it says she gets 30 mpg. But hand calculated she’s only getting 25-26 mpg.

Edit: Things that most effect my MPGs are-
1. wind resistance (I have a roof basket)
2. aggressive off road tires
3. driving style


Yeah, I use the 5V Bosch plugs with 5v plug flash from GDE. I was thinking if the ambient temp sensor was bad, the glow plug "heat" time will be greatly effected. The liberty turns on fine when engine is warm or when it is warm outside (over 50F). And it struggles when its cold. I noticed that when I turn the key, I have about voltage drop of 0.6-0.8v, I figured this was for the glow plugs. The voltage drop is only there for 9-10 seconds regardless of temp outside. When I cold start it, even if it's 50F, it will still have 9-10 seconds and same when it's 8F.

As far as MPG, you're correct Flash. I recently took 300 miles trip and I used the torque app to calculate MPG and also hand calculated. The temp was 25F-40F, and it was combination of highway (70-75mph) and local driving. Torque app calculated average MPG to 29.4 while hand calculation from fill up at the pump came out to 24.6 mpg. There is a very big difference with hand and computer calculations (5 mpg). I guess it depends if people who claimed they average over 28-30mpg, are getting the data from hand calculation or just a number from EVIC.

Edit: I just read on another thread that coolant temp controls the glow plug "heat" time so it's not the ambient temp? :banghead:
Author:  flash7210 [ Sun Jan 21, 2018 4:20 pm ]
Post subject:  Re: Ambient temp sensor and glow plugs
I have heard that the coolant temp sensor is involved with glow plug operation.
You could do an experiment by unplugging the coolant temp sensor to see if that improves the cold weather starting.
Then plug the sensor back in once started.
Author:  Sir Sam [ Sun Jan 21, 2018 5:39 pm ]
Post subject:  Re: Ambient temp sensor and glow plugs
flash7210 wrote:
I have heard that the coolant temp sensor is involved with glow plug operation.
You could do an experiment by unplugging the coolant temp sensor to see if that improves the cold weather starting.
Then plug the sensor back in once started.


Yes, coolant temp is used for glow plug operation.
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