SOLVED! Another crank but no start

[krighton]

Hey all, first post here. I've been lurking this and other forums for a while.

My 06 Trailblazer (4.2) started having a no start condition a few days ago, after getting the truck back from the stealer. Long story short, I took it to dealer to for a soft brake pedal issue that I thought would be air in the system (very dirty fluid, wife's description). They told me it was the master cylinder - replaced it for an astronomical price (I could have done it myself for 5x less) - and didn't even fix the problem. My own debugging after getting it back and realizing they didn't fix anything, pointed to ABS problem at low speeds and possible dirty speed sensors. After cleaning them and test driving, the braking issue was resolved. However, the same day the truck began having starting issues.

Never had a no-start issue before and I really felt like "somehow" it was related to either work the dealer did, or the minimalistic work I did when I got it back to clean speed sensors. Note that cleaning of those sensors included me removing the ABS fuse to test drive (to determine issue was indeed ABS related). I put replaced the fuse afterwards of course.

The truck cranks fine, and has started a few times over the last few days. Usually if it does manage to start, it dies almost immediately. A couple times it seemed like I could keep it running by pressing gas pedal. Saturday it actually started all day. Made the mistake of driving it to the grocery store, where it did not start after coming out. It's gotten less and less likely to fire up now though (basically hasn't started since).

Here is what I've determined so far:

• No smell of fuel or sign of fuel leaking anywhere
• Fuel pump relay and fuse seem fine. I am going to get in there with a multimeter tomorrow to check voltages.
• I "think" the fuel pump sounds normal... my hearing isn't the greatest. Tonight when it was quiet, I tried bypassing the fuel pump relay and could definitely hear the pump kick in and run continuously. It actually started once when I did this - not sure if it was related to the bypass (since I had pressure without the bypass), or if I just got lucky. It did still die shortly after starting, then failed to start again.
• Has fuel pressure: tested it at about 55 psi with key on, with relay in
• I was getting NO codes until today. Now I'm getting a single code: P0230. I'm not sure if this is related to pulling the relay, my battery starting to deplete from all the cranking, or something else. Tested battery voltage and seemed slightly low but still in good range. Will charge it tomorrow.
• Has gas - reads quarter tank, but I added another 8 litres to make sure
• I tried spraying carb cleaner into intake and starting, but it would still not start

Some additional info:

• About a month ago, it had a rough idle. At that time I replaced all 6 spark plugs (ACDelco), cleaned throttle body, changed air filter, oil and filter change. After this, truck was running great. No check engine lights or codes prior to or since this.
• I believe the ignition switch and fuel filter are both original.
• Ordered a spark tester (don't really want to try and do it the manual way) and will test that this week when it arrives.
• I do hear the throttle body click and I notice it's opening a bit and closing when the key is turned "on" and then again on "off". I don't recall hearing that before, but maybe I just wasn't paying attention - is that normal? I didn't try cranking it with the cover off to see if the TB opens during crank - should I do that?
• This started happening the same day I pulled the ABS fuse (test drove it, then replaced it). I half wonder if perhaps the act of pulling that fuse, removing or replacing the fuse cover, etc - caused something to jostle loose or break in the fuse box. I consider this only due to how closely the no-start coincided to me messing with that fuse.

Initially I wanted to blame the dealer, since they basically milked me, did not fix my original issue and then my truck stopped running for the first time ever. But, I don't see how their work could have caused this, unless they nicked a wire or themselves damaged fuse box (master cylinder IS directly behind that stuff).

I know this sort of problem could be almost anything, but I'd love to hear some others' ideas?

Thanks

 

[gmcman]

Have someone turn the key to ON and place your finger on the fuel pump relay # 41, see if it clicks when energizing then clicks again when it shuts down.

Any chance the PCM harnesses were removed? I wonder if reseating them may help. Before you do that, I would assume it would be wise to disconnect the battery NEG first.

The code points to a voltage issue in the fuel pump circuit.

Also, check the brake booster to ensure there's not a huge vacuum leak.

 

[Mooseman]

We do have an existing thread you could read through and try the recommended tests and fixes.

Cranks but won't start

The P0230 was likely from pulling the relay.

Ignition switch is a cheap and easy swap to try off the bat since it is a high failure rate part.

If it doesn't start with carb cleaner or starting fluid, I would concentrate on the ignition.

 

[krighton]

I did see something interesting, which is the big wiring harness that is right next to the fuse box (and beside the master cylinder) was "floating". It has a clip that attaches onto a plastic piece (by sliding in) to the side of the fuse box, but it was not actually attached. I can't recall if it was like that before, but perhaps that points towards them touching that. I can try to disconnect/reconnect it. Didn't notice any damage to any wires anywhere (yet).

Regarding changing out the ignition switch, I suppose easy and cheap enough to try. Should I go with the ACDelco switch ($40 CAD)? The Dorman is $26 CAD.

I also tested the fuel pump relay slots in the fuse box this morning and this is what I found:

Key off:
- relay power to battery ground reads same as battery voltage (> 14v)
- relay ground to battery positive reads same as battery voltage
- switched/pcm controlled power reads zero (as expected)
- jumping power to fuel pump out does start fuel pump

Key on:
- relay power to battery ground reads same as battery voltage (~13.4v)
- relay ground to battery positive reads same as battery voltage
- switched/pcm controlled power reads ~ 12v *(lower than battery voltage - is this expected?)

The above readings are after charging my battery for a few hours. Prior to charging, I was getting the following readings:
- battery: ~ 12v
- switched/pcm controlled relay power reading < 11v

Is that normal to have a lower voltage on the PCM side of the relay?

 

[TollKeeper]

ACDelco only for the ignition switch.

 

[JayArr]

Check, double check and triple check all the connections on the left side of the engine, the dealership may have removed the ECU to make room for the master cylinder replacement and something may not be connected tight enough. There's a ton of wiring harness here and it's all sort of intertwined. Also, check the two grounding points on the side of the engine down below towards the starter, the act of moving the harness around may have loosened one of the ground straps and that can drive you nuts.

 

[mrrsm]

Welcome to GMT Nation...

Check the Ground Bonding Wire at the G-107 location on the Engine Block. There are Three Potential "Power Drains" sharing G-107 as a Common Ground and so they can affect one another by G-107 being either loose or corroded as per these Diagrams:

(1) Left Side Turn Signal
(2) Left Side Head Lamp Assembly
(3) Fuel Pump Relay


Checking any other Bonding Straps by Removing, Cleaning them Down to Bare Metal and Re-Attaching them with some Dielectric Grease would NOT hurt either.

 

[krighton]

Thanks all, the troubleshooting continues.

A couple more things I tried / looked at:
- Spark test shows spark (so I have fuel and I have spark). I only checked one plug/coil quickly last night. Spark from tester looked pretty dull, but that could just be the shitty quality tester I have (never used it before).
- Looked for possible vacuum leaks. Don't hear anything while cranking and I don't see anything. If there is one, I can't imagine it being big enough to stop car from starting. I tried clamping brake booster hose to rule a big leak out there.
- Checked many of the electrical connections (just visually) on driver's side of engine bay. Nothing too suspicious looking, aside from the harness that was unclipped from side of fuse box that I mentioned, as well as one ECM harness looked like the retaining clip was not completely locked down. I reseated those and a couple other connections.
- I get a minimal RPM reading while cranking (< 200)

While disconnecting the battery to reseat harnesses, codes were erased. I ended up with the following codes prior to that:
- P0230 (as mentioned): assuming maybe related to starting without fuel pump relay in
- The follow two pending faults: P0135 and P0141. Wonder if those were from cranking with the intake cover/hose off?

I still need to check some of the grounds mentioned above. New ignition switch will be here Friday and will try that when I have it, but I'm not holding out hope.

 

[krighton]

I figured I would run a couple more tests while I wait for the ignition switch to come.

Tested compression (dry) for all 6 cylinders. Reading of 190 psi across the board.

Also tested spark again for several of the plugs/boots, as I wasn't happy with the single quick test I did the other night.

Once again, I am not sure what to make of these tests. I have two different spark test tools, both showing same results. The spark I see is very faint and does not seem to be very consistent. Uploaded a couple vids of a couple of the tests. Is this normal, or do I have a problem here?

EDIT: Also worth noting, the plugs (which are a month old) were slightly wet, with a smell of fuel. Maybe that's just all the cranking I have been doing without the engine firing up?

Thanks

 

[krighton]

Update: Installed new ignition switch tonight and, low and behold, started!

Holding my breath that this wasn't just a fluke. I did take a bunch of stuff apart the last couple days and re-connected everything this morning - all the plugs, coils, battery, intake. Though, it still did not start this morning after putting it all back together (before installing the new switch).

I'll fire it up a few more times tomorrow in the driveway before attempting to take it for a spin. See if a couple speed bumps put me back where I started, or if it was the ignition switch all along! Crazy how that damn switch could cause pretty much every system in the truck to "appear" to be fine, but truck just wouldn't start, with a good crank.

Anyway, thanks for the tip on that, hopefully that was it.

 

[TJBaker57]

A few weeks ago I partially disassembled a new ignition switch thinking it might help in diagnostics. An interesting assembly.

The gear we see seems to have ramps on the sides of it and there are what I will call lifters that ride on these ramps and raise or lower a contact, opening or closing a single circuit. I discovered two discrete switch circuits, terminals D, E, F, G and then A, B, C. The order of connections was something of a surprise.

Terminal F closes to terminal E, powering up certain circuitry of the PCM and BCM almost immediately upon rotating the key even the slightest amount. My key can actually be removed at this point leaving the closed circuit intact! These 2 close even before the accessory position is reached. I suspect this is done intentionally to get these two modules up and talking in the serial bus before accessory power is applied?

Next, as the accessory position is reached terminal B connects to terminal A sending power to another BCM pin, the outside moisture sensor, windshield wiper motor and for the 5.3 engine the TCM. There may be more, I'm not certain I have finished going through the wiring diagram yet.

Turning past the Accessory position terminal G is added to the F terminal bus along with terminal E powering up the HVAC, an EBCM terminal and another BCM terminal. I dislike how the fuse listings tell you that a fuse sends power to the BCM but not what that power is ultimately supplied to beyond the BCM. There are other things also powered by terminal G like the suspension compressor.

When the key arrives in the RUN position terminal C is added to the terminal B bus along with terminal A. Terminal B sends power to another BCM terminal, some airbag stuff, the cooling fan relay 45, A/C relay 44, more PCM terminals C3-17 and C1-19, Evap solenoids, fuel injectors, ign coils and so on.

Now turning to START terminal G is disconnected from terminal F power and terminal D is connected in its place. Also on the other power circuit terminal A is disconnected from the terminal B power while in the START position.

Looking at the switch it's hard to say where the failures occur. Dirty arced contacts perhaps? Do the terminal strips overheat from current draw and lose some of the spring needed to make contact when the lifters retract? Inspection of failed switches might help determine this.

I've been working on a spreadsheet to detail these power paths.

 

[budwich]

If it is anything like the brake switch, the contact pit from arcing and eventually do not allow current flow thru the burnish contact. There might be some sort of "anti-corrosion" coating on the contacts to prevent this that gets worn out over time... maybe. On the brake switch, I tried light sanding / cleaning which only helped for a few days before a "no contact" happened again (loss of brake lights and cruise control activation).

 

[TJBaker57]

If it is anything like the brake switch, the contact pit from arcing and eventually do not allow current flow thru the burnish contact. There might be some sort of "anti-corrosion" coating on the contacts to prevent this that gets worn out over time... maybe. On the brake switch, I tried light sanding / cleaning which only helped for a few days before a "no contact" happened again (loss of brake lights and cruise control activation).

That's a good comparison right there, I have also had that pitting on the stop lamp circuit of the brake switch.

 

[Mooseman]

Apparently ACDelco improved the ignition switch with better contacts to prevent the pitting. IIRC, it can be identified with the grey cover.

 

[TJBaker57]

Apparently ACDelco improved the ignition switch with better contacts to prevent the pitting. IIRC, it can be identified with the grey cover.

I should check the new spare I have for that! It was bought in 2011 when I first got the truck. Turned out to not be the issue so I removed it immediately and put it back in the box and threw it in the glovebox where it has remained ever since!

 

[TJBaker57]

Was grabbing some modules at a couple of boneyards and saw an ignition switch hanging by the harness. Popped it open real quick for a look-see. Yep! There's that contact degradation. Evident on both circuits..