1998 Silhouette No Start Condition - Odd Symptoms...

[Mark R.]

1998 Oldsmobile Silhouette - We have owned it since brand new.
Kids are grown. All seats are out. Used mainly for hauling and moving.

Running great, then died unexpectedly at a stoplight, and will not restart.

Strong battery cranks well. Engine sputters and tries, but won't start.

Died pretty suddenly. Checked for DTC codes, and there are NONE set.

No blown fuses found in either location (side of dash and under hood).

Excellent fuel pressure (300+ kPa). Builds fast at key on and checks well.

Strong spark signal present on all six cylinders while cranking.

It just seems like the injectors are not being commanded to fire...

Any ideas what to check next..? Thanks very much in advance!

.

[shorod]

Which engine does your Silhouette have? Do you have a noid light set, or access to an oscilloscope to check for injector pulse width? Have you tried spraying some starting fluid or throttle body cleaner in to the intake to see if that will get the engine to start, supporting the lack of injector pulse?

-Rod

[Mark R.]

Hi Rod, Thanks for the reply.

It has the 3400 V6 engine (3.4 Liter).

I do not have a noid light or an oscilloscope.

I did try spraying starting fluid into the intake.
The engine started and ran for a few seconds.

So I'm pretty sure it's the injectors not firing.
I just don't know why... Thanks again!

.

[Mark R.]

-> Could a failed Camshaft Sensor or a failed Crankshaft Sensor keep the engine from starting?

In one of my search results, I read that with either failure the car should still start, but will run poorly.

Both sensors have dedicated DTC codes that should set when they fail, and I had no codes set.

Just wondering if I can rule out these two sensors...

.

[aleekat]

Usually if those sensors are bad, you won't get spark. Since it will start with starting fluid you have a fuel delivery problem

[Mark R.]

Yes. And as I mentioned, there is very good fuel pressure present.

So the question is: What would keep the fuel injectors from firing?

What signal or input is needed to fire them, that might be missing..?

.

[maxwedge]

Crank sensor, wiring to it, ign module another possibility, see if you have cranking rpm read on a scanner. Bad injector can pull down voltage from the remaining injectors, not an easy diagnosis. Disconnect the maf, see what happens.

[Mark R.]

I had already tried cranking with the MAF sensor disconnected and that gives no change.

I do see an RPM reading on my scan tool. It bounces around 180-200 RPM while cranking.

When cranking, I get what appear to be valid readings for TPS, RPM, MAF, MAP, ECT, and IAT.

What can I check next...?

.

[maxwedge]

See if you have voltage to the injectors, key on.

[Mark R.]

OK. I will have to check that tomorrow.

I'm not sure how accessible they are. The fuel rail is buried underneath the intake manifold on that engine.

So am I looking for full time voltage with the key on, or just a momentary voltage pulse, or..?

.

[shorod]

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

[Tech II]

It could be his Theft/Security system if the injectors are not firing.....fuel pressure is ok, and he does have spark.....

Does your owner's manual state PassLock, or PassKey I, II, or III?

You don't have to remove the plenum to check for voltage to the injectors, check at the injector connector outside the plenum....terminal D, pink wire, should be hot with key in run position....

[shorod]

^^^ Good point.

-Rod

[Mark R.]

The owner's manual is very vague about the security system, with no mention of which type (Passlock, Passkey, etc.).

It simply refers to it as the "theft deterrent alarm system" option, which we do have on this vehicle.

There is NO security indicator light or symbol anywhere on the instrument cluster gauges.

There is only a red LED that sits up on the center top of the dash, and blinks slowly when it is armed.

The manual does state: "The system will also cut off the fuel supply, preventing the vehicle from being driven."

That is literally the only line that even mentions this. There are no other explanations or details...

In the past, when we've set the alarm off, the horn pulses and the lights flash. None of that is happening now.

Both of the keys we have are original from the factory - the ones that came with the vehicle when brand new.

I did go and get the other key to see if it made any difference, but it yields the exact same symptoms...

.

[aleekat]

Pretty sure you have a PK3. If original key it should be stamped on the key. But with no security illuminated at all then I'm not sure what that means.