1999 Tahoe w/~160k Cranks but won't start (some shudder)

[gof]

Ok, I came back from a week long vacation for the holidays and my Tahoe decided it's time for it's own vacation. I'm in the Chicago area so it's currently in the 35-45F range of temps. It was raining a bunch when I returned. Tahoe parked outside.

Symptoms: It has a new battery so no issues cranking, but no indication of ignition. When I stop cranking (typically less than 5-6 seconds) there are sometimes a residual shudder or two indicating a late ignition event. Very week and nothing I would classify as even close to trying to start.

Testing: I've checked the OBD port which confirms RPM during cranking, but no other logged events shown (using Torque lite). Full tank of gas. I tried a bit of starter fluid thinking perhaps a clogged fuel line, but no change. I pulled the wire from the coil to distributor and inspected. All looked ok but I sprayed with electronics cleaner, blew out, and let dry before reinstalling as well as in incoming wire harness. Engine compartment all looks dry (and it's now been 3 days since rain). I tested for spark by testing coil wire to near ground and doing a couple of short (< 3 second) starts. Visible spark to ground but I can't really gauge how strong it was. It seemed consistent.

So now I'm at a bit of a loss. Could be the coil, could be the distributor (I didn't remove it yet, thought I'd check here before going too deep).

Any suggestions or insight would be welcome. Obviously with age I'm not looking to sink a lot back into it (despite the miles, it's becoming a rust bucket).

 

[drakon543]

moisture under the cap can be common and once it's in there it can cause all kinds of problems. you wont pop a code for that unless it actually starts. if it did start it would run poorly. remove the distributor cap and look for moisture or a green splatter. also you can check resistance between the spark pick up and the spark plug wire connector. check between the other probes too. moisture will cause the spark to jump around inside the cap and possibly burn a carbon path between the other cylinder paths. also possible to have had it arc down the cap and strike the cam sensor. your timing will either be nonexistent at that point or so far off it again wont run. ive also seen moisture buildup burn off the cap rotor pickup.

 

[east302]

Since it didn’t start at all with starter fluid, a fuel issue may be able to be ruled out. A pressure check still probably wouldn’t hurt, you need 60-66 psi at the test port with ignition on/engine off. You can hear the fuel pump run for a few seconds with ignition on, correct?

I’d grab a spark tester (the type that you can see the spark across the gap) and compare spark at all eight cylinders. You may just have a bad cap (replace with a Delco if you do) such that one or two just aren’t firing correctly.

 

[OR VietVet]

What they said and a good looking spark will be blue/light blue and weak will look orange.

 

[Mark Evan]

Have you plugged a obdII into it ?

 

[TheEngineer]

As Drakon said, moisture under your distributor cap.

I keep a torx driver and spare cap/rotor set in my 2001 Silverado, 190K miles.
About every 8000 miles I get the crank, no start, and everytime it is moisture has made it's way into the cap and corroded the points and rotor to the point of weakening the spark.

Replace your distributor cap and rotor, they come as a set for under $30.
If you are in a bind, you can get by with just taking the distributor cap off and lightly sanding the points and putting it back together.

IIRC distributor cap torx screws T15 or T20

Hope this helps.

 

[Floep]

You have not mentioned distributor ROTOR! They sometimes blow through the center to ground, no start

 

[gof]

Thanks for the input. I pulled the distributor cap and rotor. Both needed replacement (to put it mildly). See the comparisons between old and new. The cap was corroded (this picture was after wire brush) but it was even missing the center graphite post. As a result, the rotor terminal had been worn completely through. I have no idea how the thing was even running (spark was obviously jumping from center post to nearby rotor terminal remains).

 

[drakon543]

yup the coil is before the distributor and thats what builds the energy to jump the gap in the spark plug. spark energy jumps the first gap thats not actually supposed to be there losing spark energy. jumps the second gap which is supposed to be extremely minor but probably not in that case. by the time it makes it to the spark plug you have very little spark. i have a thread somewhere of my own distributor failings. i replaced the original distributor in mine when i bought it and ive replaced it another 4 times after that. some on my own stubbornness and on just part fails.