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Discussion Starter · #1 · (Edited)
Hi, my name is Aaron I have been reading old threads for the last few hours but still have some questions...

the car is a 2000 2.0 turbo. well maintained (i thought, what's up with this 'sludge' thing?)

starting last winter there have been intermittent hard starts when the car and air are cold (<40) it actually did not start at all one morning last spring on a very cold friday morning, had it towed and monday morning after sitting in the garage over the weekend it fired right up for the tech. they couldn't find anything but they are bmw / merc /porsche specialists.

So i always thought it was the fuel pump being slow to prime, but after reading the many cold start post on this site i decided to check the intake air temp sensor. my question is, How far off does the resistance have to be to cause problems? I had a reading of 1.9 kohms at about 60F. according to the numbers i found here that is too low, but is that enough to cause problems?


also is there anything else i should be checking?
how / where do i check the static fuel pressure? i assume there is a check valve somewhere to prevent leak back, right?


i thought i was going to have to have the car towed again today after work, it took forever to finally start, and the dang exhaust flex pipe broke on the 21st. not happy with the little swede lately. :cry:

Edit, also, i put the sensor in an ice water bath, so pretty close to 32f, adn got a reading of 4.6k ohms (should be ~6k ohms)
 

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Welcome to Saab Central.

The sensor is not linear, so the reading at 32F could be correct. In any case, this might make the engine run poorly, but it would not keep it from starting. (that table is for the NG900 btw, and I can't say 100% it applies to the 9-3 exactly).

Testing the fuel pressure reliably is not that easy, because you have to separate the fuel line, insert an adapter, and plug the gauge into the adapter. Frankly, it does not sound like the fuel pump, either.

edit: there is a valve at the fuel tank which keeps the fuel lines pressurized for a while, but not overnight, I think.
 

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Discussion Starter · #3 · (Edited)
yeah, i really don't know what to do at this point. my GF is the primary drier of it so i was not around today when when didn't think it was going to start.

as for the 32f temp sensor reading, i don't know exactly how the line should be but an exponential line fit nicely.

nevermind, i am only allowed to upload 18kb photos :lol:

but when graphed, 32F should be about 6k ohms
 

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Discussion Starter · #4 ·
OH, i almost forgot, when i took the temp sensor out, it was loose in the intake tube. could that little be causing my troubles?
 

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There is the coolant temperature sensor to consider, this partially replaces the old cold start injector or a choke, but is much more precise. It is located on the intake manifold

Its resistance values :
20 degrees C....2.3 to 2.7K ohm
60 degrees.......565 to 670 ohm
90 degrees.......200 to 240 ohm
 

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Discussion Starter · #6 ·
earthworm said:
There is the coolant temperature sensor to consider, this partially replaces the old cold start injector or a choke, but is much more precise. It is located on the intake manifold

Its resistance values :
20 degrees C....2.3 to 2.7K ohm
60 degrees.......565 to 670 ohm
90 degrees.......200 to 240 ohm
the sensor i checked was on the the intake tube between the ic and the tb. is this what you are talking about?
 

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AaronB said:
OH, i almost forgot, when i took the air temp sensor out, it was loose in the intake tube. could that little be causing my troubles?
This is what I call an incorrect condition - a loose fit causes an air leak which probably causes problems..

The coolant temperature sensor is located on the inlet manifold, between number 3 and 4 , IIRC.
 

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Discussion Starter · #8 ·
earthworm said:
This is what I call an incorrect condition - a loose fit causes an air leak which probably causes problems..

The coolant temperature sensor is located on the inlet manifold, between number 3 and 4 , IIRC.
tightening the loose sensor had no effect (put a little ptfe tape on the threads before i noticed there was a small gasket stuck to the pipe, oh well, now it is double sealed), apparently it still started hard this morning (gf was using it).

i will check the coolant sensor tonight. would any issue with this sensor show up on the temp gauge on the dash? or is there a diffrerent sensor for that.
 

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AaronB said:
i will check the coolant sensor tonight. would any issue with this sensor show up on the temp gauge on the dash? or is there a diffrerent sensor for that.
There are two different engine temp sensors.

The one at the intake manifold is connected to the Trionic engine control module, and used in running the engine. The one on the side of the engine, above the transmission is connected to the ICE module, and used for the gauge on the instrument panel, and to turn on the electric radiator fan. Two completely separate systems and sensors.
 

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Hard to start ?

The cranking time should be 2 to 4 seconds; and at a fast clip.

All items in this "circuit" must be good.
battery ?
plugs ?
compression?
DIC ?
vacuum hoses?
CPS ?
fuel pump ?

sensors ? But these primarily affect the driveability, performance, mileage.

I am thinking that the coolant temperature is the only one that tells the ECU that it is cold; so more fuel is necessary. But if this one malfunctions, either starting will be difficult, or fuel economy will take quite a hit.:nono;
What I need is a good book on this, explaining the functions and interactions and exactly how to test.
 
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