what stops fuel injectors from firing?

[generalorde...@gmail.com]

Obviously faulty fuel pump, horribly clogged injectors, clogged fuel filter. Bad crankshaft position sensor. The usual. Vehicle is a 1992 3.1 mpfi Chevrolet Lumina. Died one day as I shifted from park to drive. Runs with starter fluid, and funky gas vapor contraption my friend hooked up to the intake for a short time (2 seconds, it's very funky). No smell or indication of gas when cranking.

My understanding is these injectors receive a pulse, but not constant power, that opens them. I ohmed the 2 injectors that could be, 12 ohms. I ohmed as much as I could and it checks out (trust me, I'll explain if I have to), therefore the injectors themselves do not seem to be the problem.

Computer has no stored codes. Nothing has ever been done to this car. But I payed some idiot to replace the ignition module about 4 years ago. Whenever it rains and the car sits for 4+ hours, it won't start until I put a spot lamp or heat gun on my wires/coil packs for usually a few minutes. There is spark and that should rule out the module. But I was told by one source that the ignition
module is what supplies pulses to the injectors at the very beginning of a start.

Could a sensor be responsible for all this? Fuses and relays seem good. Is there some input the computer isn't getting that prevents it from firing injectors, and doesn't store a code?

Just curious if it was possible to switch key to ON and either supply a constant voltage or pullse to the injector/s to see if the injectors will open?

[generalorde...@gmail.com]

Forgot. A few months ago I was having acceleration problems accelerating above 50 say. It remained a higher speed problem for most of that time. Became progressively worse really not long before it croaked.

Changed the fuel filter, 40.5 psi at the Shrader valve.

[T0m $herman]

On 11/3/2013 8:08 PM, generalorde...@gmail.com wrote:
> Obviously faulty fuel pump, horribly clogged injectors, clogged fuel filter. Bad crankshaft position sensor. The usual. Vehicle is a 1992 3.1 mpfi Chevrolet Lumina.

A 21-year old Lumina? This is the tool you need:
<http://www.overbuilt.com/assets/images/uploads/crusher-opening-header.jpg>.

--
T0m $herm@n

[Paul in Houston TX]

Injectors are usually fired directly by the ECU.
Even if your cam sensor is bad the injectors should go into
default multiport firing, assuming the crank sensor is good.
Buy an injector noid light or make one out of a #194 bulb
and test one or more.
Check for bad ground on the ECU.
Injectors often have a fuse in the panel under the hood.
If so, then ohm it with the fuse out of the car.

[Steve W.]

3.1 - VERY common problem with the 3.1 is shorted injectors. They fail
internally and the ECM shuts down to protect itself.

Dan has a good video set about it and how to test.

http://www.youtube.com/watch?v=KF9viLxwJNc
http://www.youtube.com/watch?v=3gTLY6vsxMg

for a much better price on the parts
http://www.lindertech.com/reconinj.htm

--
Steve W.

[Scott Dorsey]

<generalorde...@gmail.com> wrote:
>
>Could a sensor be responsible for all this? Fuses and relays seem good. Is =
>there some input the computer isn't getting that prevents it from firing in=

>jectors, and doesn't store a code?

Plugs are firing but the fuel injectors aren't squirting? That is an
interesting one. All that should be needed for most EFI systems is the
TDC sensor, which should tell the computer when to fire and the plugs and
when to squirt.

If that sensor fails, neither the ignition nor the fuel should work.

So my inclination would be to first check the pressure at the fuel rail,
before anything else. If that is good, get someone with a proper scanner
who can look at the inputs and outputs of the computer and determine if
the computer is turning the injectors on or not. Then I'd get a "noid light"
and put it in place of the injector and see if the injector is getting the
command from the ECU.

Start at the beginning, work down the line.

>Just curious if it was possible to switch key to ON and either supply a con=
>stant voltage or pullse to the injector/s to see if the injectors will open=
>?

Yes, but it's easier to go the other direction with the noid light and see
if the injector is getting a command in the first place. Still, I would
make sure you have pressure before anything else.

I'm likely to think you won't have any pressure at the rail when you measure
it, because your pump or regulator is bad or because the computer isn't
turning the pump on. But you won't know until you measure it.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[SRN]

"Steve W." <csr...@NOTyahoo.com> wrote in message
news:l57jum$98l$1...@dont-email.me...

> > Dan has a good video set about it and how to test.
>
> http://www.youtube.com/watch?v=KF9viLxwJNc
> http://www.youtube.com/watch?v=3gTLY6vsxMg
>
> for a much better price on the parts
> http://www.lindertech.com/reconinj.htm
>
> --
> Steve W.

Those Youtube videos on shorted GM injectors ARE excellent.



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http://www.avast.com

[generalorde...@gmail.com]

scannerdanner's videos are instructive for sure. But in the one entitled "No Start Diagnostics (1992 Chevy Lumina)" he uses a lot of equipment to show what could be determined with a simple resistance test. With one injector removed from the circuit (unplug the connector on either side of the plenum), you have 2 parallel banks of injectors, 1 with 2 parallel connected injectors, the other with 3 parallel injectors. My injectors (the ones I could measure directly) were about 12 ohms. Assuming the rest are about that, measuring resistance across the pins of the pulled connector I get 2.6 ohms (ideally 2.4). I have to assume there are no shorts here.

What I think I'm going to try is manually "pulse" the bank or the 1 lone injector as I crank to see if it even tries to start. anyone think this is a bad idea?

[generalorde...@gmail.com]

my pressure at the Shrader valve is 40.5 psi.A bulb or noid light will tell me if the computer/sensors are ok. But if for instance there's corrosion of the fuel rail itself due to ethanol it won't tell me that (and yes I need to stick a bulb in one receptacle to test for pulses, haven't gotten around to it). As Magilla from the School of ExceptionallyTalented Gorillas has pointed out, this car is 21 years old. The fuel rail is aluminum, and can rot out due to the additive.

[Geoff Welsh]

generalorde...@gmail.com wrote:
> scannerdanner's videos are instructive for sure. But in the one
> entitled "No Start Diagnostics (1992 Chevy Lumina)" he uses a lot of
> equipment to show what could be determined with a simple resistance
> test.

ummmmm, no. That's the entire point of the video. The injectors break
down under load, and by the time you pull the intake manifold off to
test them with an ohmeter, they would test fine, which would do you no
good at all, because they are not fine.

GW

[generalorde...@gmail.com]

I have not removed the plenum. What do you think those connectors are for? To simply allow you to measure the resistance of those 2 injectors? Stare at the wiring diagram for a few minutes and tell me what pulling either connector accomplishes. Well what happens is you're isolating or eliminating that injector from the circuit. But you have the diagram, you know what the rest of the circuit consists of. Pull both and you remove 1 injector from each bank. But you still know what the rest of the circuit consists of.

2 banks of 3 resistors (assuming 12 ohms each) would equal 2 ohms. do the equations. 2 banks of 2 and 3 would be 6 ohms and 4 ohms in parallel - you get 2.4 ohms. 2 banks of 2 injectors in each, 3.0 ohms. Ideally, assuming all of them measure about 12 ohms each.

[generalorde...@gmail.com]

ok, I reread your post. Well I guess if that's the case, that they can check out but break down when a pulse is applied, then a simulated pulse would indicate that. There's pure crank right now. No sign of the engine trying to turn over. If simulating the engine by pulsing them results in no activity, then the problem lies solely in the area of the injectors themselves. But I honestly can't see how you can measure the resistance and it checks out, but when you apply the pulse, the who thing shorts out. It would be nice if someone could explain that.

[T0m $herman]

On 11/5/2013 7:25 PM, generalorde...@gmail.com wrote:
> my pressure at the Shrader valve is 40.5 psi.A bulb or noid light will tell me if the computer/sensors are ok. But if for instance there's corrosion of the fuel rail itself due to ethanol it won't tell me that (and yes I need to stick a bulb in one receptacle to test for pulses, haven't gotten around to it). As Magilla from the School of ExceptionallyTalented Gorillas has pointed out, this car is 21 years old. The fuel rail is aluminum, and can rot out due to the additive.
>

I drove a 1992 Lumina rental car in 1993, and was not at all impressed.
Unlike certain alcoholic beverages, cars do not improve with age.

--
T0m $herm@n

[Nate Nagel]

Some however look better with the perspective of age. The Lumina is
arguably better than most of its derivatives. And either makes one
nostalgic for a late 60's Chevelle.

nate

--
replace "roosters" with "cox" to reply.
http://members.cox.net/njnagel

[money2noise]

On Tuesday, November 5, 2013 7:18:02 PM UTC-7, generalorde...@gmail.com wrote:
> ok, I reread your post. Well I guess if that's the case, that they can check out but break down when a pulse is applied, then a simulated pulse would indicate that. There's pure crank right now. No sign of the engine trying to turn over. If simulating the engine by pulsing them results in no activity, then the problem lies solely in the area of the injectors themselves. But I honestly can't see how you can measure the resistance and it checks out, but when you apply the pulse, the who thing shorts out. It would be nice if someone could explain that.

Looking at the wiring diagram, it looks to me like they are all grounded by a single driver to the ECU. If one injector shorts out, I believe all will stop firing. Also found this to confirm!

http://www.justanswer.com/chevy/1e681-1992-lumina-no-start-fuel-pressure-40-45psi-good-spark-noid.html

[T0m $herman]

But compared to a Honda Accord from the same year, would any rational
[1] reason make a person choose the Lumina instead?

[1] Without such things as cult-like following, anti-Japanese bias, etc,
the US motor vehicle industry would have disappeared in the 1970's.

--
T0m $herm@n