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Old 11-12-2011, 02:24 PM   #1
Caveman1953
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Default 03 Saturn doesn't start periodically, but eventually does start

If I shoot ether in the air cleaner it starts right up. We have had this car since it was brand new and it has been well maintained. This problem just started last week.

The thing is is that this is my wife's car, so I don't know what she is doing when she tries to start it. I also don't know much about fuel injection. A carbureted engine has a primer in the carb that pumps gas into the engine when you pump the throttle. Does FI have the same thing? I'm thinking if she would pump the throttle, maybe this car would start every time.


This is an L300 with the 3L V6. 85K miles

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Old 11-12-2011, 02:45 PM   #2
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2003 L-Series 3.0L Sedan
Default Re: 03 Saturn doesn't start periodically, but eventually does start

Good old school starting techniques still works to help in troubleshooting.

With EFI systems, the equivalent carb primer/accelerator pump is done with electronics. The coolant sensor tells the ecm what the engine temperature is (cold) so the ecm responds automatically by lengthening each injector pulse, longer ON time for more fuel, to do the same enriching process. As engine temps change the ecm detects this to automatically adjust fuel pulses to match needs. It also increases/decreases idle rpm automatically to adjust for loads. Pumping the pedal is no longer needed with EFI systems. Knowing that starting fluid was needed suggests the ecm is having a problem so its a subsystem problem with either a sensor or a mechanical issue.

A less than ideal fuel mixture may be fuel related; either pressure is lower than ideal, due to pump/filter/regulator leaking problem or something else. A fuel pressure gauge helps here. Pressure should be between 39-43psi with ignition ON. Sometimes a fuel filter strangles pressure while a leak somewhere won't be known unless a pressure gauge is used to see pressure leak down after the pump turns off. If this isn't fuel related then it may be another part of the EFI system that can be difficult to understand - the mass air flow sensor.

The maf sensor must detect 100% of all air entering the intake manifold as it measures air volume to help the ecm determine the air/fuel ratio. Any vacuum leak between the maf sensor and intake manifold would skew this air flow measurement that also corrupts info sent to the ecm. Ensuring the maf sensor tubing is secure without any vacuum leaks as well as a spray cleaning of maf sensor cleaner on the maf sensor can help. CRC MAF Sensor cleaner.

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Old 11-13-2011, 01:01 AM   #3
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Default Re: 03 Saturn doesn't start periodically, but eventually does start

So if the ecm adjusts fuel pulses, would not opening the throttle do the same? This car never does this while I'm driving it. I'm thinking that maybe it's because I'm doing something different that she is.

Also, it did it while the car was warm the yesterday.

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Old 11-13-2011, 02:16 AM   #4
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Default Re: 03 Saturn doesn't start periodically, but eventually does start

Well, for one thing, you'd better ask your wife how she starts the car so you can share what no one knows about her starting preference.

This car uses drive-by-wire technology. No cable to operate the throttle plate, its all electronics. With ignition ON, the throttle pedal signal is fed directly to the ecm that moves the throttle plate via servo motor. The throttle has two position sensors to feed back to the ecm. The same for the pedal. If you know model radio controls, this is proportional control; move the pedal and the throttle servo motor moves the exact same amount using position sensors so the ecm knows where the pedal and throttle plate are. When you spray ether into the intake and before the maf sensor, this can have an unknown effect on the maf sensor that's between the air filter and throttle body. Use caution as you're a Beta tester for spraying a solvent that does affect the maf sensor. Any more spraying can have negative consequences right up to damaging it, with a costly replacement needed.

Opening/closing the throttle plate does not directly control injector pulse width. Throttle position is one of many sensors used to determine correct fuel mixtures. The maf sensor measures air flow volume and is another sensor the ecm needs to know what fuel amount to use, along with coolant temperature, the map sensor, O2 sensor, and air temperature. All sensors are used by the ecm to know the correct amount of fuel in proportion to air intake. Its all part of electronic fuel injection. Google EFI systems for some basic info.

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Old 11-25-2011, 09:56 PM   #5
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Default Re: 03 Saturn doesn't start periodically, but eventually does start

It seems to have been the crankshaft positioning sensor, what ever that is.

I can remember when cars used to be powered by internal combustion engines. There is nothing you can do to a 64 Chevy that I can't fix, but with the cars they are building today, I'm lost.

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Old 11-25-2011, 10:15 PM   #6
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Default Re: 03 Saturn doesn't start periodically, but eventually does start

B..bu..but you fixed it!?

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