1997 GMC 4.3L Sonoma S15 SLS model X died

[mentat]

Hello and thanks to anyone reading this.
My truck just shut off one day and has not started since. When it shut off i was turning off a road and went up a slight incline so the truck did essentially hit a slight bump. Then it shut off.

I have tried a bunch of things ,
1- new plugs , rotor button and cap, wires.
2- checked spark on 2 wires and checked it at the coil.
3- fuel pressure checks out at 60 lbs
4- timing chain is fine and did not skip a tooth
5- took the EGR valve off and cleaned and lubed it
6- scanned the computer but my codes were cleared, I had my bat cable off during timing chain inspection.

Ok so looking for advice as to what this could be. Things i've wanted to check were

Cam Sensor , Crank Sensor , Map Sensor or is it Maf?, Injector pressure? or Injectors, Distributor shaft skipping a tooth, altenator, battery, are there other coils? Computer, thats about all I can think of.

All the above are just assumptions of mine about what is wrong based on reading on the net , im not a mechanic so im not sure if some things i've said make sense. And not sure how I can check the above listed sensors etc, without buying them and trying them. I borrowed a computer but didn't see anything to show those sensors. Maybe we were in the wrong area of the software?

Anyway if anyone can help me here that would be great

[MT-2500]

07 was a bad year for ign switches.

Does the security light stay on?

What is the mileage on it?
Was check engine light on or5 flashing before it quit?

You need to check for good hot blue spark to all plugs.
Fuel pressure should be 65 engine cranking.
If you have good spark and good fuel pressure check for injector pulse.

Another good test for fuel delivery is to give it a shot of carb cleaner while cranking engine.
If it fires up on carb cleaner you have a fuel delivery problem.
Fuel pressure or injector pulse.

Post back if it willor will not fire on carb cleaner and engine cranking fuel pressure.

[mentat]

Hello, thanks for the reply.

Actually yes the check engine light was on for a couple months before this happened, and I never did get it checked. Learning the hard way it seems.

The security light I can not find on my dash

The mileage is 176,000 Km

I will try your suggestions tommorow and post results , thanks

[MT-2500]

Yes that light was trying to tell you something.
Be a good idea to check for codes to.
post back any code no.

[mentat]

I borrowed a computer scanner and couldn't recover any codes from the computer. I did have the battery cable off for a few days. I guess that was mistake #2. History codes etc there was no data.

[MT-2500]

Do you have good hot blue spark to all plugs?
Are the spark plugs wet or dry on the ends?
Do you have proper fuel pressure?
Well it fire on a shot of carb cleaner?

[mentat]

- the new plugs are wet and black on the end
- tried the carb cleaner it didn't fire up.

Forgot to mention aswell , with the intake off I remembered. The engine will turn over , turn over , turn over then poof out the intake, the carb cleaner i sprayed in got shot out.

Still no spark test on all wires and still no fuel pressure test while cranking.

Maybe there is an Ignitor Input test? I read for a honda this is one of 3 ways to determine if its a ignition switch, the other ways being fuse checks.

[MT-2500]

Does it have good spark to all plugs when engine cranking?

What is cranking fuel pressure?

Is the dist rotor turning when crnking?

Does the coil put ot spark when cranking?

[mentat]

Spark was only tested on 1 and 4
Fuel pressure was 62ish just with the key ahead and not cranking.
The rotor does turn when cranking.
And the Ignition Coil does put out spark when cranking.

[mentat]

Ok all plugs were tested, and all seem to be giving a yellow spark , some seem to alternate back and forth yellow , white.

[MT-2500]

Originally Posted by mentat

Ok all plugs were tested, and all seem to be giving a yellow spark , some seem to alternate back and forth yellow , white.

You need to get the spark up to a blue hot snapping spark.
Is the spark out of the coil good and blue and hot?

If plugs was wet and black on the end pitch them and replace them with the right AC delco plugs.

Also check that fuel pressure real good.
You need 64 lbs cold cranking fuel pressure to squirt injectors.

The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.

[mentat]

I didn't get a good spark from the coil either. I will try again though to be sure. So to get it to spark its either ignition coil problem or before the coil, ignition switch ?

These plugs are new and have never seen a running engine. They got black and wet trying to start it.

I will get the Fuel pressure tester again and test what you have mentioned. In the mean time since i know the non cranking fuel pressure is over 60 , could i block off the return line to boost pressure and try to start it as a test?

Also in an earlier reply you mentioned using Carb Cleaner , to see if the engine would fire. I thought by doing this it would determine if there was a fuel delivery problem.?

Thanks for your suggestions.

[MT-2500]

Originally Posted by mentat

I didn't get a good spark from the coil either. I will try again though to be sure. So to get it to spark its either ignition coil problem or before the coil, ignition switch ?

These plugs are new and have never seen a running engine. They got black and wet trying to start it.

I will get the Fuel pressure tester again and test what you have mentioned. In the mean time since i know the non cranking fuel pressure is over 60 , could i block off the return line to boost pressure and try to start it as a test?

Also in an earlier reply you mentioned using Carb Cleaner , to see if the engine would fire. I thought by doing this it would determine if there was a fuel delivery problem.?

Thanks for your suggestions.

Have the coil tested.

If plugs are wet/black gas fouled pitch them in the trash can.
I have never had a black/gas fouled plug run right after it got black on the end.

Do not block off return line for a start test.
Just for the fuel pump pressure test.
On the fuel pressure get it up to specs as in last post.

Post back pressures from test as outlined.

[MT-2500]

Also on the coil spark test make sure your battery voltage is up good and check for proper voltage to coil and check the spark from coil tower not at the coil wire enf.
A bad coil wire can cause bad spark from coil.

[mentat]

Hello,

I replaced the Ignition Coil today. First flick it started!

It idles nicely though now there is a slight shake to the truck. Timing maybe? The truck is slow to rev up when you step on the gas and seems to be almost powerless trying to move it. Rough stumbling idle at low rpm when reving not idling, and seems to smoothen out at high rpm. Any ideas on this ?

Edit: the check engine light was on solid then after a couple minutes of running it went to blinking. It was like the the first 3 times i started it. Last time i started it i actually moved the truck to the other driveway and the check engine light was gone. Will check it again later.

Thanks for your help on this.