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Discussion Starter · #1 ·
Why would the temp sensor malfunction prevents the engine to run?

TIA,

Carlos.
 

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depends on your settings, but if the temp sensor fails it usually fails open circuit, which basically tells the ECU that the car must be located somewhere in siberia and injects an amount of fuel accordingly. If the temps are warm then the engine will be flooded with so much fuel that it won't start.

When my temp sensor failed the car still ran, but it wasn't pretty. rough idle, lots of stumbling/soot out the tailpipe, etc.
 

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well, i had the same problem but luckily i just had the wires twisted together as a test before I hard wired them in. what happens is the computer reads that it's really cold (i don't remember the #'s), like well below freezing, and it tries to compensate by enrichening the mixture, because the wires were shorted and giving an erred reading.
 

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Yes, basically with the temp sensor disconnected it tells the ECU that its like 30 below F. Typical programming woudl dictate 1.5 times more fuel at this temp then at the normal coolant temp, thus you're injecting likely 40% too much fuel, and thus very rich.

Of course, if in all the fields you had 1.0, this would mean that the base pulsewidth calculation would be multiplied by 1, and thus no change, and the car would probably hard start and run lean, etc.

With the new switchable maps feature, on a race application I like to make one of the maps a "limp home" mode, in other words a map that will allow the car to run with the least amount of sensor inputs. This means putting 1's in all the temp sensor correction fields, as well as turning off closed loop programming, tuning w/o TPS inputs, etc. Then if one of the sensors fails in the middle of a race, you flip a switch, move over to this other map adn have a good running car, not as good as with all the sensors working, but much better than w/one of the sensors reading an incorrect value.
 

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Discussion Starter · #5 ·
Thanks for the explanations.

The reason I asked this question is that the temperature showing at the Panel screen is on the opposite scale, i.e., it shows 105C (engine cold, air temp 5C). I traced the wiring and couldn't find the problem, so I suspect the sender went South.
The gauge sensor (top one) is showing the correct temperature, so there is water on the flange that has both sensors.

1. Would it be possible that the ECU is thinking that the temperature is too hot and leaning the fuel to a starving condition? or worse?

2. Can I steal the signal from the top sensor (used by my panel's gauge)?

3. I can also use a resistor in place of the sensor and simulate a temperature? Which temperature woudl you guys suggest?

TIA,

Carlos
 

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Carlos, as you likely know, the ECU will only assign fuel and ignition values according to the programming. Thus, the ECU will only react to temp. as you've programmed it, ie-the values in the cell.

It sounds like you've got an issue with your temp sender, try another, the sender for the gauge won't work for engine managment purposes, its just a gauge sender. You want to be sure to use the White Bosch sensor, stock on the CISE cars, with 14mm threads. If the you've programmed the ECU for warm running properly, with a 1 in those fields, and the engine is bone cold, then its likely to be running too lean and may not start if its a fuel related problem.
 

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Discussion Starter · #7 ·
I ordered a new Temp sensor. The one I had in the car seems not working properly.

Anyway, I tried some options:

1. Jumped the temp sender conector (temp all the way to neg)
2. Let it opened (temp all the way to max)
3. Jumped the temp sender conector with a resistor (temp to 85C)

In all three instances the engine didn't produced combustion.

4. Keeping #3, I switched the cold temp to 90C forcing a simulated cold start.
5. Keeping #3 and 4, I switched the scaler from 14 to 24!
6. Keeping #3,4 and 5, I increased the priming number to 25.

Still no combustion.

So, I added lots of carb cleaner through the TB.

Quick combustion.

I took spark plug from cyl #1 out and it didn't smell fuel as I expected and from a brand new condition, now is all dry and black like carbon.

It seems that I'm having fuel issues.

Bouncing ideas:

1. My fuel got old and gunky, and now the injectors don't spray or spray very little. This would explain why the engine worked and now it doesn't (clogged injectors) with them still clicking.

2. Do you have a suggestion on how could I test the injectors? (like the CIS bottle system).

3. Any method to clean injectors at home?

4. Should I replace the fuel or is there an additive to "de-gunk" it?

Thanks,

Carlos.
 

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ok, to test the injectors, what i did was take a strip of either steel or aluminum about an inch wide, and drilled holes in it big enought for the small end if the injectors to sit in it (drill all five hole) and then just used a clamp or some wire or something to make sure the rail doesn't come off when you get pressure in the rail. then yea can lay the whole deal on top of the valve cover and let em fire away.

as to the degunking, i haven't a clue. you must have had that thing sitting for a long long time!! my dad has cars siting around for extende periods of time and they don't get gunky fuel, so, um, heh, i'm at a loss there.

and i don't think there is a way to clean injectors at home. unless you could soak them in a carbon cleaning solution.
 

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Yes, Derek has the right idea wrt testing injectors, but I'm not sure what you mean by "gunked up". It sounds like your injectors are not firing, it should start with a fuel values of 0 and 12. Do you hear your injectors priming when you cylcle the power? How about when you manually turn the distributor, you should hear each injector clicking everytime a window passes the hall sender.

What injectors are you using again?
 

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Discussion Starter · #10 ·
I'm going to test it all again, but they were priming and clicking with the "manual" distributor.

The injectors are 28# from GM cars, just like these ones: http://www.racetronix.com/Racetronix-De ... 1462R.html

I said they could be gunked up since my fuel might be a bit old.

At the same time the coloration of the plugs(carbon like dry) would suggest a very rich mixture, but what bothers me is the absence of fuel smell.

Hopefully, I'll have more time this weekend to go through all the test combinations and come up with something.

Thanks to you all for the ongoing help,

Carlos.
 

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Carlos, again, feel free to keep my # handy and give me a call, if I'm available I'll be happy to talk.

I doubt your injectors are aversely affected by the fuel, especially if you had the car running a couple weeks ago, but if your injectors are clogged that could definitely cause trouble.
 
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