NEED HELP Cranks but don't start

#1
I have a 2002 trailblazer 4.2 engine. I was driving to work and the truck just shuts off.i tried restarting it and it wouldn't start.i push the car off the road. Tried spraying starter fluid but that don't work. It cranks but don't start. What could be wrong?
 

MRRSM

Gold Supporter
#2
With a 16 Year Old TB... if it has never given you a lick of trouble, the First Thing to Suspect is that your Ignition Switch has gone T*TS UP... Try inserting the Ignition Key and jiggling it around a little...Don't Go Crazy doing this... and then see if the Engine will Start. If it does... then the Ignition Switch is the probable culprit and GMTN has scads of Threads on How to R&R The Switch.

Please provide more details about anything you have recently worked on, fixed, changed, altered or added and lets see if those issues factor in. This story never gets any more complicated than a problem or combination thereof involving These Three Things:

Fuel
Spark
Air (Compression)

But... In a complex, PCM controlled vehicle like your '02 TB with the LL8 Engine... without having a Simple Blue Tooth or Basic OBD2 Code Reader... then you are flying blind here... So investigate these and list any codes that you discover by first purchasing an inexpensive one from Autozone and plugging it into the OBD2 Port under your Driver's Side Dashboard Kick Panel (knee height) and see what it says.
 
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#3
I put in a ignition switch it still does the same thing. I had a guy check it out with a code reader he said that no codes are coming up.i did the spark plug test and im getting sparks
 

MRRSM

Gold Supporter
#4
Okay... Fuel Pressure and Availability is next.... But... are you sure that you have not accidentally run out of gasoline or has the fuel perhaps been siphoned and stolen overnight? When you open the Hood on the SUV... can you smell any Fuel? When you turn the Ignition Key.... Can you hear any "Clicking" with Hood Up from the Fuel Pump Relays and whirring sound from under the Driver's Side under-frame? Do you have a Fuel Pressure Gauge (Harbor Freight sells a decent inexpensive one as a kit) that you should attach to the Fuel Pressure Guage Port located under and behind the Driver side to Passenger under-carriage, right next to the Fuel Filter and then prop it up so you can crank the engine over and see if you are getting any fuel pressure on the Gauge? Say... something on the order of 45-55 PSI? These would be the next things to look at.
 

MRRSM

Gold Supporter
#6
Please Be Aware that since you cannot start the vehicle with the Fuel Pump Relay pulled out to run down any residual Fuel Pressure in the lines... that when you attach the Fuel Pressure Gauge Schrader Valve Connector... The gasoline can Spray Right into your Face and Eyes... Use Care when performing this Test ...and Don't Smoke or have anyone holding anything with an Open Flame Nearby... lest you have a Fire under some very inconvenient and dangerous circumstances. Please use some Rubber Gloves with their bottom ends folded up at the cuff with some paper towels tucked inside like a sleeve to catch any fuel draining out and of course wear Eye Protection as well.
 

budwich

Well-Known Member
#7
:-( how many miles does this nice vehicle have on it? If you sprayed in starter fluid and it didn't even "bung on bit", then it is unlikely to be a fueling issue.... but you should check pressures since you are heading that way anyway. Pull a plug and see what it tells you... color, dampness, etc.
How did you "spark test"? Sparking has to be at the right time otherwise it is won't help the engine. If you got it, at least one cylinder compression test might help you know if there is some sort of mechanical issue.
 

djthumper

Administrator
#8
Considering your location and the resent weather... Check the contacts on the PCM, you want to make sure that something didn't get in there and forced you to lose contact. What recent maintenance did you do?
 
#9
#10
:-( how many miles does this nice vehicle have on it? If you sprayed in starter fluid and it didn't even "bung on bit", then it is unlikely to be a fueling issue.... but you should check pressures since you are heading that way anyway. Pull a plug and see what it tells you... color, dampness, etc.
How did you "spark test"? Sparking has to be at the right time otherwise it is won't help the engine. If you got it, at least one cylinder compression test might help you know if there is some sort of mechanical issue.
:-( how many miles does this nice vehicle have on it? If you sprayed in starter fluid and it didn't even "bung on bit", then it is unlikely to be a fueling issue.... but you should check pressures since you are heading that way anyway. Pull a plug and see what it tells you... color, dampness, etc.
How did you "spark test"? Sparking has to be at the right time otherwise it is won't help the engine. If you got it, at least one cylinder compression test might help you know if there is some sort of mechanical issue.
My truck have 167,000 miles.i did the spark test by taking, out a coil pack and putting a spare spark plug inside the coil pack

Considering your location and the resent weather... Check the contacts on the PCM, you want to make sure that something didn't get in there and forced you to lose contact. What recent maintenance did you do?
The only recent maintenance i did was a oil change and front struts.

[Mod edit: Posts merged. Please use the multi-quote function instead of posting successively.]
 

MRRSM

Gold Supporter
#12
If all of your Spark Plugs appear "Fried Chicken Brown" and your Fuel Pressure Test proves out Okay... Revisit the possibility that:

(1) Your Ignition Switch might be an After- Market Brand notorious for failing right off of the shelf (Non AC-Delco or HQ Brand)
(2) When you installed the New Ignition Switch... it went in ... Just One Tooth Off... and the PASSLOCK feature has engaged.
 
#13
If all of your Spark Plugs appear "Fried Chicken Brown" and your Fuel Pressure Test proves out Okay... Revisit the possibility that:

(1) Your Ignition Switch might be an After- Market Brand notorious for failing right off of the shelf (Non AC-Delco or HQ Brand)
(2) When you installed the New Ignition Switch... it went in ... Just One Tooth Off... and the PASSLOCK feature has engaged.
I bought a new ignition switch cause i thought that was the problem of the no start, but it wasn't so i returned it
 

MRRSM

Gold Supporter
#14
Okay Mike... When and if you make any progress ...or encounter any setbacks... Please keep us updated. Even though you cannot see us ...here in the GMTN background... many will be with you all the way until things get sorted out...
 
#15
Okay Mike... When and if you make any progress ...or encounter any setbacks... Please keep us updated. Even though you cannot see us ...here in the GMTN background... many will be with you all the way until things get sorted out...
Im 100% lost, i use scan tool it says no codes. Battery terminals are clean , and battery is less then a year old.the spark plugs have spark , spray starter fluid it still don't start. I tried a brand new ignition switch, still doesn't start.I switched fuses around with the pump relay , still no start.what could else there be to check for this crank no start?
 

MRRSM

Gold Supporter
#16
Mike.. go back to @Mooseman ‘s suggested links to read... Get a sharp pencil and a pad and note any helpful suggestions you find in each of those threads. I know this will seem a very tedious task... but it is very likely that somewhere in a few of those links you will find the answers. Even though your vehicle has 165k Miles... unless you have mistreated this Engine... that is not very many miles. Nonetheless... your next thing to check is Compression... both Dry and Wet... You can check out YouTube for the How To instructions if you are unfamiliar with the Tester and Procedures. One last thing... It is no sin when a Man does not have experience with fixing mechanical things. Just know that all of us... even those with a considerable exposure and experience with automotive repairs... we too need help from each other from time to time. So do not feel reluctant to explain whether or not you are able to tackle things if they become more complicated than the ordinary...There is nothing simple or easy about diagnosing mechanical failures... but the answers to many questions lay in a field that has already been plowed for you if you seek them out and read them.
 

budwich

Well-Known Member
#17
you still didn't answer the question... what color / condition are your spark plugs... they will tell you what is happening in the cylinder.
 
#18
Just because there are no codes doesn't mean there isn't a problem. Lots of instances of this happening.

A compression test is a good idea at this point because if you have fuel (ether), air and spark, it should fire, or it's really badly flooded. Check for bad fuel smell on the oil dipstick. I've seen cars that wouldn't start because of so much fuel in the oil.
 
#19
Just because there are no codes doesn't mean there isn't a problem. Lots of instances of this happening.

A compression test is a good idea at this point because if you have fuel (ether), air and spark, it should fire, or it's really badly flooded. Check for bad fuel smell on the oil dipstick. I've seen cars that wouldn't start because of so much fuel in the oil.
I didn't smell any fuel on the oil dip stick
 

budwich

Well-Known Member
#21
ok... so the plug were "burnt" ... does that mean they were "black", "brown", "white" ... color is important... "burnt" no so much. Further, were they wet / gas smelly? If they were dry, that doesn't sound good.... especially if you have been trying to start for a bit with both gas and starter fluid. You likely need a compression test to help with this problem.
 
#22
ok... so the plug were "burnt" ... does that mean they were "black", "brown", "white" ... color is important... "burnt" no so much. Further, were they wet / gas smelly? If they were dry, that doesn't sound good.... especially if you have been trying to start for a bit with both gas and starter fluid. You likely need a compression test to help with this problem.
The center & side electrodes were black and some of the spark plug threads had oil on them
 
#24
Mike.. go back to @Mooseman ‘s suggested links to read... Get a sharp pencil and a pad and note any helpful suggestions you find in each of those threads. I know this will seem a very tedious task... but it is very likely that somewhere in a few of those links you will find the answers. Even though your vehicle has 165k Miles... unless you have mistreated this Engine... that is not very many miles. Nonetheless... your next thing to check is Compression... both Dry and Wet... You can check out YouTube for the How To instructions if you are unfamiliar with the Tester and Procedures. One last thing... It is no sin when a Man does not have experience with fixing mechanical things. Just know that all of us... even those with a considerable exposure and experience with automotive repairs... we too need help from each other from time to time. So do not feel reluctant to explain whether or not you are able to tackle things if they become more complicated than the ordinary...There is nothing simple or easy about diagnosing mechanical failures... but the answers to many questions lay in a field that has already been plowed for you if you seek them out and read them.
Even if the truck won't start with starter fluid , is there a chance it still could be the fuel pump ?
 

budwich

Well-Known Member
#25
OK... oil on the thread just likely means you have intake gasket issues.... this is likely your source for "rich" as then unmetered air is getting in resulting in the system pushing fuel to compensate. BUT that isn't likely you issue for not starting. Further, IF there was a significant "rich running", the plugs would be wet from a non-start / crank effort... which you don't indicate. Further, although you don't say it, new plugs didn't solve your problem. :-( This likely means you are not looking / changing the right area. Try starting fluid again with the new plugs?

I would again suggest some form of compression test.
 
#26
OK... oil on the thread just likely means you have intake gasket issues.... this is likely your source for "rich" as then unmetered air is getting in resulting in the system pushing fuel to compensate. BUT that isn't likely you issue for not starting. Further, IF there was a significant "rich running", the plugs would be wet from a non-start / crank effort... which you don't indicate. Further, although you don't say it, new plugs didn't solve your problem. :-( This likely means you are not looking / changing the right area. Try starting fluid again with the new plugs?

I would again suggest some form of compression test.
I sprayed starter fluid in the throttle body , i seen a video on YouTube of somebody spraying starter fluid in the main vacuum hose which is by the brake fluid reservoir. I didn't try it thought, i want to know what you think about trying that?
 

budwich

Well-Known Member
#27
either way is basically ok... although the spraying thru the brake vacuum may be an issue as you may in terms of "vacuum break" (ie. you need to ensure a relatively good connection of the hose / sprayer... it would matter for long term if it is leaky (causing stumble as a vacuum leak) but for testing, the vehicle should still "bunge" a bit as it tries to start.... which you don't appear to be getting... basically just a plain crank with NO fire... :-(
IF your compression is not good, no amount of fueling will help

Further, I am assume you have a helper... one person spraying while another cranks... right?
 
#28
either way is basically ok... although the spraying thru the brake vacuum may be an issue as you may in terms of "vacuum break" (ie. you need to ensure a relatively good connection of the hose / sprayer... it would matter for long term if it is leaky (causing stumble as a vacuum leak) but for testing, the vehicle should still "bunge" a bit as it tries to start.... which you don't appear to be getting... basically just a plain crank with NO fire... :-(
IF your compression is not good, no amount of fueling will help

Further, I am assume you have a helper... one person spraying while another cranks... right?
I spray while m
either way is basically ok... although the spraying thru the brake vacuum may be an issue as you may in terms of "vacuum break" (ie. you need to ensure a relatively good connection of the hose / sprayer... it would matter for long term if it is leaky (causing stumble as a vacuum leak) but for testing, the vehicle should still "bunge" a bit as it tries to start.... which you don't appear to be getting... basically just a plain crank with NO fire... :-(
IF your compression is not good, no amount of fueling will help

Further, I am assume you have a helper... one person spraying while another cranks... right?
Yes i had somebody try start it while i spray
 
#29
Oil on the threads of a spark plug just means a valve cover leak at the plug well. Not a big issue unless the plug is swimming in oil.
 
#30
either way is basically ok... although the spraying thru the brake vacuum may be an issue as you may in terms of "vacuum break" (ie. you need to ensure a relatively good connection of the hose / sprayer... it would matter for long term if it is leaky (causing stumble as a vacuum leak) but for testing, the vehicle should still "bunge" a bit as it tries to start.... which you don't appear to be getting... basically just a plain crank with NO fire... :-(
IF your compression is not good, no amount of fueling will help

Further, I am assume you have a helper... one person spraying while another cranks... right?
Should i try changing the crankshaft sensor , before i get it towed away for a compression test
 

budwich

Well-Known Member
#31
you could try that. you can also do a "kind of check" compression by trying to turn the crank by hand using a socket wrench on the crank pulley (with the belt removed). If it turns "freely" without a significant feel of resistance, then you have issues.

I am concerned that one... you say your plugs aren't wet... they should be if there is cranking and no fire.
and two... you have some form of spark so that IF things were ok in general, starting fluid should get you some form of reaction.

Lastly, do you have any anti theft indication / system happening?
 
#32
Should i try changing the crankshaft sensor , before i get it towed away for a compression test

I wouldn't do that as that would require a CASE relearn by the dealer ($$$). If not getting a code for it, leave it alone.
 

MRRSM

Gold Supporter
#34
It is a shame that the early model Trailblazer and Envoys did not sport a Fuel Pressure Schrader Valve Port, right off of the Fuel Rail where it could be more easily accessed for Testing Fuel Pressure… and while we’re on that subject, @budwich mentioned earlier about the "curious dryness" of the Spark Plugs… so perhaps the Fuel Pressure Regulator has gone sideways and is not allowing the fuel to pass through the fuel rail.

I think @Locksmith might have "The Key" to answering this problem ...because in these GM Ignition Designs... The PASSLOCK mechanism is nested within The TUMBLER and if IT has gone T*TS UP... Replacing the Key and Tumbler as a Set from a GM Dealership might just solve this problem. This Video is for Demonstration purposes only of How the Key Tumbler works... You won't have to go through the use of an Air Tool to get yours R&Rd:


And beyond the PASSLOCK problem if doing that repair does not get the SUV running again... it may wind being a Bad PCM. While this video shows the value of having a Tech2 and a Lighted Probe to Diagnose a No Crank- No Start condition… and even though this problem is not exactly like yours… The VOP (Video Original Poster) proved that the replacement Swap-In PCM was “ScrabNoid” in midstream during updating because of the sketchy wire signaling at the Ignition Switch involving the Pink Wire. So the original PCM needed to be put back in as “VIN”ed to that TB... and it would be necessary to Replace The Ignition Switch FIRST prior to re-programming the PCM to operate properly again. Unfortunately, this is the kind of Diagnosis that does NOT lend itself to 'Pure Mechanical Intuition' in order to get fixed and few other Scanners can perform such repairs such as this one:

 
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#35
you could try that. you can also do a "kind of check" compression by trying to turn the crank by hand using a socket wrench on the crank pulley (with the belt removed). If it turns "freely" without a significant feel of resistance, then you have issues.

I am concerned that one... you say your plugs aren't wet... they should be if there is cranking and no fire.
and two... you have some form of spark so that IF things were ok in general, starting fluid should get you some form of reaction.

Lastly, do you have any anti theft indication / system happening?
The ac delco 41-103 spark plugs come gapped @ .043 , can they go in the trailblazer with that gap or they need to be adjusted?
 

Shaw520

Well-Known Member
#38
P0300 is a random misfire,...if you let it go a bit longer it may indicate which cylinder the misfire is occurring, IE; P0305 would be cylinder #5
 
#39
Thanks for the help guys , the crank no start problem was a fuel pump. When the car started it had a rough idle , code p0300 came up. I just bought 3 new ignition coils and that fixed the problem.now tomorrow im do oil change & change oil pressure sensor