NEED HELP R&R RnP now cranks but won't start

TBdriver01

Member
2006, 4.2, 165k, 2wd
Cranks fine, no start.

Confirmed spark at the plugs,
Fuel keeps flooding the cylinders.
New cam sensor, inspected the connector and wiring.
VVT solenoid looks ok, screens intact.
Cleaned throttlebody- actuates fine,
CEL on, but no DTCs pulled on my scanner (it's a very basic scanner)
All fuses under the hood are good.
Relays also look good.

So the back story is, before the holidays, I replaced the rack n pinion and the PS pump. Last time it ran was when I noticed the ps fluid leak.
No powertrain issues in the year I've owned it.

I feel it may be related to ambient temp. Our weather dropped to below freezing this past week.

Also, maybe something with the timing. I sprayed starting fluid into the throttle w the fp relay off. I got nothing.

Really need to get it up and going again... :helpme:
 

djthumper

Administrator
Check and clean your Throttle body and do a PCM reset. If you are flooding the issue is likely the throttle body remaining too far open when it shouldn't be.
 

budwich

Well-Known Member
you may have "confirmed a spark" but not necessarily a "timed spark". Further, do a compression check if possible to see if you have basic mechanical sanity.

IF you think it is temperature related, get a hair dyer and point it at key areas... connectors at the pcm, pcm, connectors at the cam sensor, etc. See if it has any impact.
 

MRRSM

Lifetime VIP Supporter
If you did not knock the wiring loose from the (CKP) (Crankshaft Position Sensor) when you were thrashing out the Rack and Pinion Repair... and the Fuel Pump and Starter are working well enough that the Engine keeps Flooding from a No Spark Condition (Security No Start Circuit invoked?) After checking your PCM Connections... then your Next Step is to view this Excellent 4 Page "How To Check the COP (Coil On Plug) Ignition" path for Proper Spark at the Proper Time" series of instructions, noting the section on "How the COP Works":

http://troubleshootmyvehicle.com/gm/3.5L/how-to-test-the-cop-ignition-coils-1
 
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TBdriver01

TBdriver01

Member
Check and clean your Throttle body and do a PCM reset. If you are flooding the issue is likely the throttle body remaining too far open when it shouldn't be.
I cleaned it a few days ago.
I had my copilot press on the gas pedal and observed the valve move with it.
Also I see the valve flutter when the key is turned to on and off.
When cranking, it stays at its 'rest' position. Not sure if it supposed to do that.
 

budwich

Well-Known Member
look around the areas that you "played in" for any ground straps / wiring that might have broken / fell off.

as suggested check the crankshaft sensor AND also check the cam shaft sensor, ensure that it has 12V coming to it.
 
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TBdriver01

TBdriver01

Member
you may have "confirmed a spark" but not necessarily a "timed spark". Further, do a compression check if possible to see if you have basic mechanical sanity.

IF you think it is temperature related, get a hair dyer and point it at key areas... connectors at the pcm, pcm, connectors at the cam sensor, etc. See if it has any impact.
My compresion test kit has gone missing, so I'll have to rent one.

As far as temps, I will end up pulling it into the garage if not fixed soon. Should warm things up a bit.

Its due for an oil change. Could old really cold oil prevent the VVT solenoid from performing correctly? Im very unfamiliar w that system.
 

Paul Bell

Silver Supporter
On these LS engines, if either the crank or cam sensor is not picking up, there will be no spark. As you stated there is spark, they are functioning.

If the engine is flooded, press the gas pedal to the floor then begin cranking while holding the pedal on the floor. This puts the PCM into the "clear flood mode". It cuts the fuel at the injectors. It may take a few seconds to clear. When it does, it will begin to start, then let up on the pedal.
 
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TBdriver01

TBdriver01

Member
If you did not knock the wiring loose from the (CKP) (Crankshaft Position Sensor) when you were thrashing out the Rack and Pinion Repair... and the Fuel Pump and Starter are working well enough that the Engine keeps Flooding from a No Spark Condition (Security No Start Circuit invoked?) After checking your PCM Connections... then your Next Step is to view this Excellent 4 Page "How To Check the COP (Coil On Plug) Ignition" path for Proper Spark at the Proper Time" series of instructions, noting the section on "How the COP Works":

http://troubleshootmyvehicle.com/gm/3.5L/how-to-test-the-cop-ignition-coils-1
Its not a 4wd so once the subframe came off the RnP was easy. Really not much electrical to bang up. I will closely inspect the crank sensor thou.

I checked spark w a sparkplug test light w plug intalled, also w plug out and grounding it so I could observe its spark. Both ok.

Besides a visual, how else can i ck PCM connections?

Thats a really good guide, unfortunately it doesn't test for timing.
Wish I could just shoot this w a timing gun and know instantly! Lol
 
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TBdriver01

TBdriver01

Member
On these LS engines, if either the crank or cam sensor is not picking up, there will be no spark. As you stated there is spark, they are functioning.

If the engine is flooded, press the gas pedal to the floor then begin cranking while holding the pedal on the floor. This puts the PCM into the "clear flood mode". It cuts the fuel at the injectors. It may take a few seconds to clear. When it does, it will begin to start, then let up on the pedal.
Thanks for confirming about the sensors.

I have tried this WOT and cranking but í get nothing.
I've had these plugs out many times and have blowguned the cylinders to evaporate any fuel.

Starting fluid should fire it up some wouldn't it? ..nope.

I can't get any cylinders firing, or even misfiring. A couple times I did get a backfire from the exhaust thou.
:explode:
 

budwich

Well-Known Member
On these LS engines, if either the crank or cam sensor is not picking up, there will be no spark. As you stated there is spark, they are functioning.

....... .
From my readings, I don't think this is true. The engine if running, will continue to run in "limp mode". It is possible that the system is now in some form of "limp" and you are likely not going to be able to start until you get it out of this mode.
 

Reprise

Lifetime VIP Supporter
Getting the code associated with that CEL should help a lot with identifying next steps.

I know you mentioned that your reader can't decipher it - do you have access to a better scanner?
 
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TBdriver01

TBdriver01

Member
From my readings, I don't think this is true. The engine if running, will continue to run in "limp mode". It is possible that the system is now in some form of "limp" and you are likely not going to be able to start until you get it out of this mode.
I still have a constant CEL but my cheap-o code reader can't see what's behind it. I 'erase' codes but the light persists.
 
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TBdriver01

TBdriver01

Member
Getting the code associated with that CEL should help a lot with identifying next steps.

I know you mentioned that your reader can't decipher it - do you have access to a better scanner?
I need to procure one asap.
Are there any affordable ones that can read all things TB/Voy?
 

budwich

Well-Known Member
well... I wouldn't jump so quickly to the "get a reader"... although it may help. Since you played with the cam sensor, as suggested, check to see that you are getting 12v there as a first check.... your comment "connector looked good" likely means your "eyes" aren't seeing the electricity very good... :smile: My guess would be that sensor is not operating in compliance with design.... :smile:
 
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Mooseman

Moderator
A Bluetooth adapter with Torque on Android will work.

Until the engine starts, the CEL will stay on but if there is an actual issue, you should be able to pull the codes.

Check and smell the oil. If it smells of gas, change it. This used to be an issue every time my old Corsica would not start in damp weather and flood. Pull all the plugs and check their condition. Leave them out for a while to dry the cylinders out.
 

Reprise

Lifetime VIP Supporter
Well, 'affordable' is a relative concept, I suppose...LOL... and I don't have one that can read 'all things' with the platform...for that, you'll need something like a GM Tech 2 or one of the similar low-level protocol readers from Snap-On, etc (which are hella expensive, as most things Snap-On are)

I picked up a cheap Actron at one of the chain stores 2-3 years ago for another vehicle I had. It 'did the job'. $20-$30 (and up)

For about the same entry point, you can get Torque Pro on your smartphone, along with a OBD dongle that you'll need to connect Torque with. You can get the adapters on eBay (they're called 'ELM327', IIRC - and their quality varies WIDELY - stay away from the very cheapest ones, or you'll be buying another, most likely).

To go up to the next level, you're probably looking at something like one of the Harbor Freight scanners - they have about 5-6 at different price points. I have one and it comes in handy - although it's supposed to read ABS controllers, and wouldn't do that on two different vehicles. But it's very useful. $50-$75 and up.

After that, the next jump is $200-$300, and you'd be looking at one of the Chinese Tech 2 clones. You can find info on them in this forum, but you'll be waiting a while to get one (unless someone near you has one (or a real Tech 2))

And then if you have more $ than time, and want the best tool you can get, then you're looking at a 'real' Tech 2, or something like a Snap-On 'Verus' or 'Solus'. You can get the Tech 2 for $500-600 if you look really hard / get lucky. The Snap-On readers are $800-$8000 - but if you're in this segment, you're a professional mech yourself.

Finally - whichever scan tool you get, try and make sure it can read Controller Area Network (CAN) protocol - our trucks use this (along with OBDII).

If you're in Chicago metro, Harbor Freight probably hits the sweet spot for price / performance. Sears sells similar ones, but a year from now, I think HF will still be in business. Sears? Who knows? And then there are the chain parts stores, as I mention above. If the vehicle were driveable, some parts stores will read the codes for you for free.
 

MRRSM

Lifetime VIP Supporter
Just a few more thoughts...

You mentioned "Cleaning the Throttle Body" but did not clarify whether you completely removed it to "The Bench" to do so... if the TB Electrical Harness was disconnected... spray out the male side with an Electrical Contact Cleaner...and plug that baby right back in quite snug. Then... disconnect the Battery for 30 minutes while you R&R the Plugs to dry them out ...one more time can't hurt either.

As for the issue of "Timing" the engine... among all of the inter-related sensors concerning what happens to allow the vehicle to "Limp Home" ... of "The Big Three" CPAS, CPS and CKP... the major "timing" comes from the Notched Reluctor on the Crankshaft causing the CKP Sensor to signal the PCM about where all the rotating assembly components are situated at any given moment... and the PCM makes a decision based on those inputs as to "Which Spark Plug Gets Fired...When" ...so there is no way of doing any "external adjustments" as no physical equipment exists to do so. If any one of these goes sideways... the other two are supposed to compensate...with reduced power and performance...but enough to keep the engine running...supposedly.

I know mentioning this approach is probably sacrilegious... But... Here Goes:

If you cannot get your hands on a decent Scanner that can identify and log a set of Data and list the "P-000" Codes and want to spend a few bucks and take a chance this might work... changing the CKP Sensor makes "sense".... I say this because your method of checking the Spark with a LIGHT may not be sufficient to prove that it can connect to the PCM...other than hooking up the COP to a Positive and Negative Power source for a complete circuit... but THAT is insufficient to test the CKP circuit between the Crankshaft Sensor, The COP and the PCM.

You probably already know how to do this part... but for others who do not...

Its about a 10 Minute Job as long as the Right Sensor is being replaced here (the damned Knock Sensor is practically sitting in the CKP's Lap). It takes a 10 MM Socket and Ratchet to get the old one out and the new one in... if you think its worth doing... and if it Fires Up and Runs...albeit a bit raggedy... eventually, the PCM will figure things out and ... If this works... I think you'll have to get a CASE RE-LEARN done by Shop toting a Tech-2. Here are some images of the sensor location and appearance when the wiring is still attached... and some images without connectors:
 

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shovenose

Well-Known Member
on these trucks doesn't a passlock issue cause a crank/nostart?
 

Mooseman

Moderator
on these trucks doesn't a passlock issue cause a crank/nostart?
No, it would do a no crank/no start, same as when doing a security relearn.
 

MRRSM

Lifetime VIP Supporter
Okay... But you haven't mentioned whether or not the Engine will Start and Run... Yet. If it still does not fire up... I was thinking about how much of the "Starter Fluid" you might have sprayed down inside of each cylinder with the idea that having enough of that stuff in there would certainly loosen any Heavy Carbon Deposits... enough to the extent that if the stuff dropped down on top of the pistons...it can get wedged up in between the business end of the Spark Plugs... and short them out or obscure the Spark Path from the Combustion Chamber. That sensor looks gnarly... but might still be working... remember... in the absence of actually reading the Codes with a decent Scanner....this was my "Hail Mary" Pass at the problem.
 
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TBdriver01

TBdriver01

Member
Okay... But you haven't mentioned whether or not the Engine will Start and Run... Yet. If it still does not fire up...
That sensor looks gnarly... but might still be working... remember... in the absence of actually reading the Codes with a decent Scanner....this was my "Hail Mary" Pass at the problem.
Promise im not teasing.
I made a ck list to execute from all the feed back.
Here goes:
New STP oil filtre
New high milage engine oil. 7Q
Pull and clean spark plugs .043 gap
Blowgun all the cylinders dry
(snake a rubber hose past the plug holes)
Clean the CPAS as per Voymom's How-to thread
(ohms out at 7.1Ω, don't know the actual spec)
New CKP sensor
-see pic above
-.69kΩ , í think is within specs
-12V to it
Engine grounds..
-braided conn @valve cover: .002Ω
-block to batt neg cable: .001Ω
-other grounds on lower drv side of block: no diagram so didn't ohm out. Looked fine.
New Cam sensor (same as previous post)
Reset computer again.
(touch pos/neg 5 min.)
Trickle charge batt: 12.65V
New 'better' scanner:
C0455
C0244
Both are ABS system faults so not sure if they could affect my issue.
Rented FP testor: 57-60psi
(the gauge showed so fluctuation, stayed within these numbers)

Obviously, issue persists:
Cranks like a champ, but engine seems not to catch at all. I get an exhaust backfire when I stop cranking.

Gonna take possession of an engine compression testor just to rule that out...
 

MRRSM

Lifetime VIP Supporter
Nicely Done... ;>)

The only other things that come to mind without some "Code Help" are:

Intake Manifold Fasteners that are loose enough to be "turned with your fingers" 89 " lbs Here.
Severely Burned Exhaust Valves (Your Compression Test will reveal this)
Broken Rings at the Piston Tops
Burned-Fractured Piston Heads
Broken Valve Springs and Valve Train FUBARed (Over -Revved Engine...?)
Extremely Bad Rings (Your Oil Drops Wet vs. Dry Cylinder Compression Test will show this...)
and Last but not least... A Dead PCM...
 

djthumper

Administrator
I think a tech2 would be of great help at this point. It sounds like something isn't right in the PCM or another module. I could be wrong but it just seems like the PCM may be the issue if you have done all of this.
 
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TBdriver01

TBdriver01

Member
I hope you didn't try gapping the acdelco plugs that's a no go since you will ruin the iridium plugs.
Not at all.
I installed non-Delcos couple months before i found you all at GMTnation. It really ran just fine.
So im assuming if they fired before they will fire again.
 
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TBdriver01

TBdriver01

Member
I hope you didn't try gapping the acdelco plugs that's a no go since you will ruin the iridium plugs.
Not at all.
Nicely Done... ;>)

The only other things that come to mind without some "Code Help" are:

Intake Manifold Fasteners that are loose enough to be "turned with your fingers" 89 " lbs Here.
Severely Burned Exhaust Valves (Your Compression Test will reveal this)
Broken Rings at the Piston Tops
Burned-Fractured Piston Heads
Broken Valve Springs and Valve Train FUBARed (Over -Revved Engine...?)
Extremely Bad Rings (Your Oil Drops Wet vs. Dry Cylinder Compression Test will show this...)
and Last but not least... A Dead PCM...
May lead up to the PCM's timing, but in reference to compression, I always had good mpgs. Avg 18c/h. Which í think is good for these vehicles.
I use to drive a 04 ext 4wd v8 envoy, horrible 12mpg max. It had that rough idle problem. Got sold on...
 
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TBdriver01

TBdriver01

Member
I think a tech2 would be of great help at this point. It sounds like something isn't right in the PCM or another module. I could be wrong but it just seems like the PCM may be the issue if you have done all of this.
Old Saint Nick has come and gone so a tech2 is only a wish.
I stopped at my neighborhood shop and most he has is a higher end snap on. Upon conversing, the techs only asked me to tow it in. I live amongst the corn fields so a borrowed scan tool is hard to come by.

BUT.
Im walking out of the parts store w a compression test as í type.
And the new scan tool does provide some live data.
I'll ck back in soon...
 
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TBdriver01

TBdriver01

Member
Sorry wasn't able to post this up sooner. Had some family matters to tend to.

So compression test results:
Dry
1 - 150
2 - 165
3 - 165
4 - 150
5 - 150
6 - 150

I didn't do a wet test because í really didn't want to pour oil inside the cylinder chamber on a no-start motor. BUT I can only assume the psi would bump up closer to the 215psi spec. I just wanted to prove psi were uniform and that the valves didnt fail somehow.

Live data, Key ON:0107172101-1.jpg 0107172101a-1.jpg 0107172102-1.jpg

And while cranking:

Screenshot_2017-01-07-21-10-25-1.png Screenshot_2017-01-07-21-11-38-1.png Screenshot_2017-01-07-21-12-18-1.png


Is compression enough to fire right up or considered low?

What's a normal TPS throttle angle before cranking?

From where is the Ignition Advance reading taken?

Thoughts?
 

budwich

Well-Known Member
I don't believe your "dry readings" are bad / low but maybe. iirc, a 10% spread might be worrisome (should be less). "Normal" suggests 215psi.

Since spraying starter fluid doesn't get you much, my guess is still with "wrong spark / no spark" at the right time.

Further to your tests, I would do a couple of other things to see if the system is responding correctly and / or what the response actually is. First, since you indicate no Cel codes, cause one by unplugging the cam position sensor... crank, what happens? Similarly, the crank sensor, same thing. This hopefully will tell what is happening to the system "monitoring processes" in terms of their integrity.

Lastly, I didn't see in your "long list" of stuff that you have done... have you cleaned / checked the connection at the pcm?


One more thing... :smile:
I have never looked at "cranking data" versus "normal run data"... but I think that the 100% engine load is suspicious

double that one more thing .... :smile: :smile:
as suggested, disconnect the crankshaft sensor.... what happens?
 
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MRRSM

Lifetime VIP Supporter
Without knowing exactly where it is that you live in the State of Illinois... Your Mean FASL Elevation is right at 600 Feet... which does play a small part in the process of lowering compression a bit, due to lower ambient PSI. The other issue that needs to be considered is that at the approximate time you were doing these tests... the Ambient Inlet Air Temperature was only (7) Degrees Above Freezing.... (37 Degrees F)

And so with the Cold Contraction of the Rings and Pistons versus that of the 1.5MM Thick Cast Iron Cylinder walls, this could also play as a factor in lowering your compression. Trust me... with Two or Three Drops of 3&1 Oil dripped into each cylinder and when turning the Engine over BY HAND-WITH NO SPARK PLUGS INSTALLED... Your chances of Hydro-Locking the motor and damaging it are almost nil. Performing a Wet Test will always give more definitive results about proving information either that individual cylinders have Badly Worn Rings...or in the case of an overall improvement in the compression balance and levels in all (6) Cylinders... give you a better idea of what the Compression will be when the engine is warmed up and with the cylinders being well lubricated from below.

Right now... your Top Compression Rings are probably also carbon-ed up enough to be stuck tightly inside of their grooves... and so using a VERY TINY AMOUNT of Foaming Spray GM TEC down inside each cylinder and left for an hour or so would loosen them up and likewise improve compression. But again... you can avoid any problems of engine damage... by simply Hand Turning the motor over very slowly as mentioned above as the best way to ease any collected fluid out of each cylinder BEFORE Re-Installing the Plugs. GM TEC does acts as a light lubricant as well.

The Key Premise here is that you should be turning the engine over slowly enough that if the engine started to lock up...you would know it...because you would feel it and be able to react soon enough to abort turning the Crankshaft ... and then pull out all of the plugs again and Aerate each cylinder. As always... you cannot go wrong by Acting with an Abundance of Caution during each and every step.

The following link should hold out some comfort that based upon your latest Compression Test Results ... the engine was providing enough compression;l albeit Bone Dry... with No Oil and No Fuel to help seal the rings and allow for a decent "Spark and Burn".

http://www.gregsengine.com/cylinder-compression-testing.html

More and more... The PCM is looking fairly suspect here... or perhaps the Relay and Fuse Block Connections have a Broken Wire hidden underneath?
 
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