Chevrolet Lumina:

3.1 lumina injectors not staying on

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# 1  11/2/2009 11:42 AM

blake1
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Registered: 11/2/2009
Posts: 4

3.1 lumina injectors not staying on

The car will start and run fine for about 30 min. then stall. It will not start till it has cooled down sufficiently. It still has fire on the plugs, and fuel pump still comes on. It will start using starting fluid, but dies immediately once fluid is taken away. Fuel filter, ecm, and ignition module has been changed with no positive results. Any ideals would help, Thanks

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# 2  11/2/2009 2:02 PM

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Re: 3.1 lumina injectors not staying on

Hi blake1:

Sounds like you've narrowed it down to a lack of fuel.

Next I would check for any trouble codes stored in the powertrain control module which may lead you to the cause of the problem.

You said the fuel pump is working. Does that mean you heard it buzzing in the fuel tank, or saw gas squirt out of the pressure valve? Either one is not always a confirmation of the fuel pump supplying enough fuel. You really need to hook up a fuel pressure gauge and test for pressure and volume available at the fuel rail (injectors). It could be a bad pump with very low pressure, or even a good pump and the fuel pressure regulator isn't holding back enough pressure.

After confirming trouble codes and adequate fuel pressure, I'd check for voltage and injector pulse signals at the injectors from the powertrain control module (when hot and not starting).


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# 3  11/3/2009 1:09 AM

blake1
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Registered: 11/2/2009
Posts: 4

Re: 3.1 lumina injectors not staying on

No your right, I don't have a pressure reading, just the noise of the pump and some pressure out of the valve. There are no codes stored in the memory or appear when the stall comes and nothing shows up while trying to start it back up. I'll check the injectors next. Thanks.

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# 4  11/3/2009 2:05 AM

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Re: 3.1 lumina injectors not staying on

Yeah, you're really paddling upstream without a pressure gauge.

You could have say 20 psi, while you need 45.


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# 5  11/18/2009 9:43 PM

blake1
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Registered: 11/2/2009
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Re: 3.1 lumina injectors not staying on

sorry took so long to make it back , but finally got a pressure gauge on the fuel line, and it showed no differences from when it was running and after it stalled and wouldn't restart. I don't know the precise value but it is at 40 on this gauge (before, during, and after). Any idea on whats next?

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# 6  11/19/2009 4:48 PM

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Re: 3.1 lumina injectors not staying on

OK. You didn't mention the model year, but I'm looking at the info for a 1998 Lumina/3.1L.

Fuel pressure should be 41-47psi with the key on, engine off. When you turn the ignition on the fuel pump runs for 2 seconds. You also want to see if the pressure drops quickly after that. That could mean pressure is bleeding back past the pump, the regulator or an injector(s) (but that should not prevent it from starting).

Fuel pressure good, strong spark, and still not starting sounds like the injectors are not receiving power (+), or a ground (-) pulse from the powertrain control module.

You can check that with a test light at the two terminals at each injector connector. Terminal "A" on each injector should have power from the 15 amp F/INJN fuse with the key on. Terminal "B" should be getting a pulsing ground while cranking.

Test light between "A" and "B" should be flashing while cranking, ground to "A" should always be on with the ignition on, and 12 volts to "B" should be flashing while cranking.

Find out which you're missing -- power or ground pulse. There could be a bad connection between the fuse and the injectors, or the PCM and the injectors, or a bad PCM. Good spark tells us that the PCM should be receiving the needed signals from the crank/cam sensor to pulse the injectors also.

If you have good pressure, spark and injector pulse, it could be restricted injectors or incorrect data from a sensor going to the PCM, or another odd-ball condition which requires a scanner and experience to test further.

Test, test, test...


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# 7  11/19/2009 9:27 PM

blake1
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Registered: 11/2/2009
Posts: 4

Re: 3.1 lumina injectors not staying on

There is a pulse on the injectors when cranking. We had a new pcm put on it, with no change.Ill  re-check the terminals again .(Sorry, this is a 92  3.1) Thanks ill get back to you on it.

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# 8  11/19/2009 10:43 PM

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Re: 3.1 lumina injectors not staying on

Strong spark, good pressure, and injector pulse tells me to scan the system for trouble codes and correct incoming sensor data. And, of course, we're eliminating a mechanical failure since it does run cold.

Another possibility is contaminated fuel and/or clogged injectors.

There's a special tool for testing the injectors. It pulses the injectors at a certain rate individually, while observing the drop in fuel pressure. Too little and/or too much of a variance between pressure drops from each injector indicates obstruction. I guess a primitive test without the tool would be removing the fuel rail (with everything attached) and visually inspecting the injector spray pattern while cranking. It should be cone-shaped and uniform.

The fuel may also be contaminated with water, sugar, or whatever. That's never a good thing. A quick check for that would be bleeding fuel out from the pressure gauge into a glass to see what it looks like.

Also, you're saying it won't start. Have you tried starting it with the throttle partially applied? A large vacuum leak or an EGR valve stuck open can cause a no-start and no-idle condition, but the engine will typically still fire with the throttle partially applied.

At this point -- without a scanner (and experience using it) and the injector tester -- it can get tough. But check for starting off-idle and fuel contamination first.


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