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Old 06-30-2017, 01:25 PM   #16
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

You need to have this vehicle scanned for "B" codes...unfortunately, only high end scanners can do this....the BCM turns on the theft/security light....
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Old 06-30-2017, 03:49 PM   #17
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

With key on, we have 12.5 Volts at the pink wire in terminal D of the injector harness connector.

Had to remove the front struts and rotate the engine forward just to get access to that connector...

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Old 06-30-2017, 05:18 PM   #18
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

OK, a bit of a new development here (possibly a setback).

While I was out today, I picked up a can of starting fluid to confirm what my son had told me.

He and his buddy had tried a few things, before paying $120 to send it home on a flatbed.

They had said that they were able to get it to fire using a can of carb cleaner.

I'm not sure if something has now changed, BUT, I can NOT get it to start using starting fluid.

And that really surprises me, because it appears to be getting a good spark signal. And I doused it pretty good.

My apologies for any confusion this adds to the situation. All other parameters are as previously described.

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Old 06-30-2017, 05:32 PM   #19
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

I've been using a Timing Light with an inductive pickup to check for spark on each of the cylinders.

I get a nice bright pulsing light from each of the plug wires when the engine is cranking.

Is this a reliable enough method to conclude I have good spark..?

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Old 06-30-2017, 05:40 PM   #20
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Also, I checked the vehicle alarm system and everything appears to be functioning like it always has.

I set it off intentionally (horn pulses and lights flash), and then turned it off with the key like normal.

The red LED blinks slow when it's armed, faster when unlock the door, and goes dark once the key is inserted in the ignition.

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Old 06-30-2017, 06:39 PM   #21
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

To review, this happened suddenly, no early symptoms, how many miles? Sound like it has good compression?
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Old 06-30-2017, 08:16 PM   #22
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Yes. It happened quite suddenly with no previous indication or symptoms.

Just coasting up to a stop light and it stalled and hasn't started since.

Mileage is ~170k. New head gaskets were installed around ~120k.

I believe compression is generally good. Have not measured it recently.

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Old 06-30-2017, 08:39 PM   #23
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Can you get a noid lite on one of the injectors? Confirm pulse? I know this can be tough. Also, may have jumped time, compression test the front cylinders to confirm its still in time. See if there is raw fuel on the plugs when doing the compression test, if none the injectors are not pulsing, you probably have determined this already.
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Old 07-01-2017, 12:23 AM   #24
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Tomorrow I will pull the front spark plugs and check their condition and the compression.

And I will see if I can locate a noid light, although I don't see how I could possibly get it installed.

I can't even see any of the injectors, let alone get my fingers onto any of them.

From my experience, if the injectors were firing during all these attempted starts, I would smell fuel by now.

I have cranked this engine so many times, that I've had to keep a battery charger on it most of the time.

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Old 07-01-2017, 10:48 AM   #25
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Quote:
Originally Posted by shorod View Post
Unfortunately I no longer have access to the GM service manuals to confirm, and most of my experience is with Fords. From what I've seen on Fords, and suspect GM is similar, the injectors receive constant voltage with the key in the Run position (probably battery voltage, but could be 5V) and the ground is switched via driver transistors in the PCM. So you should expect to have constant power and switched ground.

-Rod
Your supposition is correct - The B+ is constant and grounds are sequentially switched by the PCM, if all required conditions are satisfied.
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Old 07-01-2017, 12:49 PM   #26
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Quote:
Originally Posted by Blue Bowtie View Post
The B+ is constant and grounds are sequentially switched by the PCM, if all required conditions are satisfied.
And as previously discovered, there is good voltage at the injector input connector.

So the question is: What would cause the PCM to loose the ability to ground the signal?

What input (sensor, signal, etc.) that the PCM requires, might currently be missing?

The sudden way the car died makes me think electrical, rather than anything mechanical...

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Old 07-01-2017, 02:51 PM   #27
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

The PCM needs to see crankshaft reference pulses from the ignition system. On the 3.4L V-6 that's usually a function of the 24x CKP. Since you are (were?) getting spark, that's already a "given." The system also requires a signal from the CMP to properly sequence/phase the injector pulses. If that is missing the injectors may not fire. On the older 3.8L Buick V-6 the system would eventually batch-fire the injectors in the absence of the CMP signal after protracted cranking. I'm not sure the 3.1/3.4L PCM setup does that, however, and thus may NEED a cam signal from the CMP. Of course, all of this has to route to the PCM.

Another item which will prevent injector pulses is the security system. If the "SECURITY" warning is flashing or on, it likely will not start even if it cranks.

A third item is the wire harness itself, including wires and connectors.

Most of that has already been covered here, too.

As for other, less likely causes in this instance, one item which is required for the injectors to operate is sufficient fuel pressure. The mere presence of pressure is not enough. It must be above 25-27 PSI to open the pintles and flow properly. Since you've already measured that at around 43 PSIG it should be more than sufficient.

Max is correct that a slipped timing chain could be indicated, but unless the chain is broken and the cam is not turning, there would be injector pulses, albeit out of sequence. The resultant fuel should either show up on the spark plugs and/or cause backfire in the intake or afterfire in the exhaust. Pulling a couple of easily accessible plugs might be revealing.

Instead of dismantling the intake, you might try back-probing the C102 connector to check the injector signals:

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File Type: jpg 1998SilhouetteInjectorHarnessConnector.jpg (96.1 KB, 16 views)
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Old 07-01-2017, 06:00 PM   #28
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Well, finally enough of a break in the rain to go out and remove the front spark plugs.

The good news is that there's a strong spark on all three plugs with the engine cranking.

The bad news is there is very little compression on all three cylinders...!!!

During multiple readings on each, the values were inconsistent, and never got over 50 psi.

This seems like some very major bad news...

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Old 07-01-2017, 07:05 PM   #29
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

It will still run on low compression. I've seen some lower than that driving into the shop as smoothly as can be. It's not optimal, but it might not be the worst thing. It also might indicate slipped timing, but there should still be fuel. If you can remove the front rocker cover without a major effort you might see if the valves are moving.

The fact that you have spark means the CKP is reporting to the PCM. You're halfway there.
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Old 07-01-2017, 07:45 PM   #30
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Re: 1998 Silhouette No Start Condition - Odd Symptoms...

Now that I'm cranking with the front three plugs out, I'm actually smelling more fuel.

So the injectors may indeed be firing. I also hear an occasional light backfire pop out the exhaust.

When I remove the oil filler neck, I can clearly see both of the valve springs for the middle cylinder.

And no matter how long we crank the engine, those two valve springs never move.

I think there's a significant mechanical disconnect (like maybe the camshaft isn't turning)..?

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