2002 Trailblazer Cranks but won't start


Ju1nito
12-22-2008, 06:42 PM
I have a 2002 trailblazer that will start fine in the morning and after it sits for an hour or two, but once i start it and run it for over ten minutes and i shut it off when i try to re-start it, it will crank but won't start. the dealer cleaned the throttle body and injectors, check the fuel pump for presure and it was fine,and they got no error codes?????? I've read that in can be the ignition switch?? any ideas??

Thanks

Juan

maxwedge
12-22-2008, 07:53 PM
Usually the ign switch has other symptoms, when this happens you must check for spark ( not easy) and/or fuel pressure.

h2oskier5
12-22-2008, 11:23 PM
On my 06 trail blazer, the ignition switch went out.. It is a know problem with the TB's... My would not crank.. It's not bad to replace, maybe 30 minutes.. Also if you can get it without the long harness, it's under 20 bucks.. That's what I did...

When you turn the ignition on before cranking, can you hear the fuel pump? Also to check for spark, pull one wire off and insert a old used plug to check.. Be sure to ground the plug or you'll become the ground..

maxwedge
12-23-2008, 09:15 AM
Keep in mind there is no " wire" to pull off, this is coil on plug ign. you will need to access the plugs, then pull the coil off, make sure it is grounded then put a spark tester jumper onto the plug and coil and crank the engine, not a quick process as I mentioned.

Ju1nito
12-23-2008, 12:26 PM
If their's no spark would this happen this way(intermittent)? I don't understand why it only happens after i run it for a couple of miles but it works fine when it sits over night or for an hour, I'm puzzled????

maxwedge
12-23-2008, 04:45 PM
No way to predict why these things happen this way, all the proper diagnostics must be performed.

Ju1nito
01-09-2009, 10:38 AM
Cleaned the throttle body but no change,but i can get it started if i press the gas pedal all the way down while cranking it, but it will rev high for a few seconds when it starts?????

h2oskier5
01-09-2009, 11:16 AM
Boy that sounds like a weak fuel pump but not sure.. Although the dealer checked the pressure..

On my sons blazer it wouldn't start also.. When he turn the key on and off 2 or 3 times without cranking it, then it would start.. What that does is cycle the electric fuel pump and insures the right fuel pressure if you have a weak pump. The pump is on a timer when you just turn the key to run, you shuld be able to hear the pump run, then shut off..Then I changed the pump and ran great..

Give it a try.. :smooch:

maxwedge
01-09-2009, 11:45 AM
Again, a scan and some diagnostics are in order, there is no quick answer or shortcut here. Possible throttle control motor or tps issue.

josh9816
01-10-2009, 03:13 PM
I have the EXACT problem that u do Juan. also my ECT senor goes on and off but i think thats just a bad conenction. let me know if you find out what it is. DOES ANYONE KNOW?

josh9816
01-10-2009, 03:15 PM
O and i replaced my ignition switch and it did not help at all.

Ju1nito
01-13-2009, 05:44 PM
Boy that sounds like a weak fuel pump but not sure.. Although the dealer checked the pressure..

On my sons blazer it wouldn't start also.. When he turn the key on and off 2 or 3 times without cranking it, then it would start.. What that does is cycle the electric fuel pump and insures the right fuel pressure if you have a weak pump. The pump is on a timer when you just turn the key to run, you shuld be able to hear the pump run, then shut off..Then I changed the pump and ran great..

Give it a try.. :smooch:


I tried it and didn't work, im going to have it scanned this week and see if i get any error codes.

Ju1nito
02-12-2009, 02:07 PM
I posted another thread about my temp. gauge that stays at 100 and jumps to 210 then back to 100 and stays there, but when the gauge decides to work properly the problems does not exist, can this be linked to the temperature gauge????? puzzled!!!!! and still have no codes.

cdc692003
03-04-2009, 02:38 PM
You have a dash cluster that is going bad, I have replaced at least 50 in the past year alone. If one gauge goes out more are sure to follow. Use it as long as you can,
most rebuilds run at least $ 300.

GM POS
07-31-2011, 06:01 AM
Sorry for the long post but I think it is beneficial to share the entire story so you can see if my issue is the same as yours and hopefully what fixed mine will fix yours.

I HAD...key word HAD, a 2005 Trailblazer EXT 4.2L that had this problem. It started off as an intermittent issue where it would crank but would not start and then when it did it ran rough until I gave it some gas. It would then run fine until the next time I would try to start it...sometimes. Like I said, intermittent issue.

One night my wife was driving it and it just quit on her while she was going down the road. She called me and I had her try turning the key on to see if the fuel pump was starting up (that little "whir" sound you hear when you first turn on the key is the fuel pump pressurizing the system). No sound...boom...problem found, all I have to do is replace the fuel pump (as if that is an easy job!!). All it would do is crank but would not even try to start.

Next day I drop the tank, pull out the pump, put 12 volts on on it and....wait for it...wait for it...the pump works perfectly fine. Well...I checked the relay---good---checked voltage at the plug for the pump---5 Volts (should be 12v)---checked wiring from the underhood fuse block (where the fuel pump relay and pcm B fuse is) for continuity to the plug---everything was fine. So why 5 volts---must have a bad connection somewhere but since everything appears fine from the fuse block on it must be in the fuse block to the computer.

As I was messing with the fuel pump relay I noticed that it seemed a little loose compared to the other relays in the block. Keep in mind, at this point I am 6-7 hours in of troubleshooting and I have established I am getting 12 volts to the fuse block but only 5 volts out to the fuel pump. I thought maybe the clips that the relay press into might be messed up (but how though---it can't be that----can it?---wait it gets better). So as I am trying to establish whether the clips that the fuel pump relay are somehow bad or if there is a bad connection to the relay, at one point I try to crank the engine to see if it would start and I get...nothing---no cranking, no starter relay clicks, no fuel pump relay clicks. Wow, great---7 hours and now I am worse off than when I started!!

After some time of messing with the fuel pump relay(moving it around while my son tried to start the engine to see if it was a bad connection issue) I decide it is going no where so I begin to look at the PCM B fuse (20 amp) which is right next to it and, as a way of looking at it, works with the fuel pump relay. The fuse was fine but I decided to try pressing down on it and moving it around as my son tried to start the engine. Fuel pump kicked on and it started up and ran just fine....holy crap!!! REALLLY!!

So, now 8-9 hours in I have established the issue lies in the PCM B fuse and it appears there is an issue with the clips that the blades of the fuse press in to. Unfortunately no matter how I moved or pressed it though I had to keep pressing down on the fuse to get it to work. I even tried adding some shims to the fuse blades and it worked for a minute but then stopped working.

The next day I decide I need to remove the fuse block to inspect the clips for the fuse (which is loads of fun---good luck!) Come to find out, in GM's infinite wisdom they design the fuse block in such a way that you can't just take the block apart to inspect the clips. I decide to work around the issue by knocking in the flared ends of the wiring harness' bolt sleeves---there's 4 of them(trust me you'll see what I am talking about if you try this) and gain access to the clips at all cost (figure if I screw it up too much then I would just have to go get a junkyard one anyways so what do I have to lose---local dealer said it would be "about $300 for that"). I get the block apart, figure out which clips are for the PCM B fuse, and for good measure the ones for the fuel pump relay, and press them back together so when I push the relay and fuse back in they will be making better contact.

With much anticipation, hope, and doubt I reassemble everything and......it worked perfectly! And it continued to work for as long as I needed it to because the next day we went and traded this GM POS in for a new Ford Edge. I have been a GM guy all my adult life...but no more. This issue was just one in a long line of stupid issues I have had with it. Hope this helps...it is my contribution to the forum community since this is where I come to whenever I have a problem.

Oh, and also if you are having trouble with your blower motor for the heat/AC(lose the 5 setting first or it quits working altogether) don't just assume it is the blower motor resistor going bad and replace it. GM has a crappy design on the connect from the blower motor resistor to the blower motor. It is a loose connection which makes it heat up to the point where it melts the connector around the pin(s) (presumably for the "5" setting since that is the one I was having trouble with). They sell replacement connector harnesses (which tells you they know there's a problem and just aren't willing to fix it by a recall) or you can shim the connector and pin with a small piece of aluminum (which is what I did) to fix it.

Last thing, if your rear Heat/AC blower stops working, the wires going into the fuse by the motor (you have to remove the plastic interior panel in the right rear where the blower motor is located) have a bad connection too. If you push them in to get the blower motor working and then use cable ties to keep some pressure (pushing them into the fuse connector) that will fix that issue. These are just one of many issues and all on a vehicle that is only 6 years old. I could go on but I probably lost most people in the 2nd or 3rd paragraph.

maxwedge
07-31-2011, 08:38 AM
Sorry for the long post but I think it is beneficial to share the entire story so you can see if my issue is the same as yours and hopefully what fixed mine will fix yours.

I HAD...key word HAD, a 2005 Trailblazer EXT 4.2L that had this problem. It started off as an intermittent issue where it would crank but would not start and then when it did it ran rough until I gave it some gas. It would then run fine until the next time I would try to start it...sometimes. Like I said, intermittent issue.

One night my wife was driving it and it just quit on her while she was going down the road. She called me and I had her try turning the key on to see if the fuel pump was starting up (that little "whir" sound you hear when you first turn on the key is the fuel pump pressurizing the system). No sound...boom...problem found, all I have to do is replace the fuel pump (as if that is an easy job!!). All it would do is crank but would not even try to start.

Next day I drop the tank, pull out the pump, put 12 volts on on it and....wait for it...wait for it...the pump works perfectly fine. Well...I checked the relay---good---checked voltage at the plug for the pump---5 Volts (should be 12v)---checked wiring from the underhood fuse block (where the fuel pump relay and pcm B fuse is) for continuity to the plug---everything was fine. So why 5 volts---must have a bad connection somewhere but since everything appears fine from the fuse block on it must be in the fuse block to the computer.

As I was messing with the fuel pump relay I noticed that it seemed a little loose compared to the other relays in the block. Keep in mind, at this point I am 6-7 hours in of troubleshooting and I have established I am getting 12 volts to the fuse block but only 5 volts out to the fuel pump. I thought maybe the clips that the relay press into might be messed up (but how though---it can't be that----can it?---wait it gets better). So as I am trying to establish whether the clips that the fuel pump relay are somehow bad or if there is a bad connection to the relay, at one point I try to crank the engine to see if it would start and I get...nothing---no cranking, no starter relay clicks, no fuel pump relay clicks. Wow, great---7 hours and now I am worse off than when I started!!

After some time of messing with the fuel pump relay(moving it around while my son tried to start the engine to see if it was a bad connection issue) I decide it is going no where so I begin to look at the PCM B fuse (20 amp) which is right next to it and, as a way of looking at it, works with the fuel pump relay. The fuse was fine but I decided to try pressing down on it and moving it around as my son tried to start the engine. Fuel pump kicked on and it started up and ran just fine....holy crap!!! REALLLY!!

So, now 8-9 hours in I have established the issue lies in the PCM B fuse and it appears there is an issue with the clips that the blades of the fuse press in to. Unfortunately no matter how I moved or pressed it though I had to keep pressing down on the fuse to get it to work. I even tried adding some shims to the fuse blades and it worked for a minute but then stopped working.

The next day I decide I need to remove the fuse block to inspect the clips for the fuse (which is loads of fun---good luck!) Come to find out, in GM's infinite wisdom they design the fuse block in such a way that you can't just take the block apart to inspect the clips. I decide to work around the issue by knocking in the flared ends of the wiring harness' bolt sleeves---there's 4 of them(trust me you'll see what I am talking about if you try this) and gain access to the clips at all cost (figure if I screw it up too much then I would just have to go get a junkyard one anyways so what do I have to lose---local dealer said it would be "about $300 for that"). I get the block apart, figure out which clips are for the PCM B fuse, and for good measure the ones for the fuel pump relay, and press them back together so when I push the relay and fuse back in they will be making better contact.

With much anticipation, hope, and doubt I reassemble everything and......it worked perfectly! And it continued to work for as long as I needed it to because the next day we went and traded this GM POS in for a new Ford Edge. I have been a GM guy all my adult life...but no more. This issue was just one in a long line of stupid issues I have had with it. Hope this helps...it is my contribution to the forum community since this is where I come to whenever I have a problem.

Oh, and also if you are having trouble with your blower motor for the heat/AC(lose the 5 setting first or it quits working altogether) don't just assume it is the blower motor resistor going bad and replace it. GM has a crappy design on the connect from the blower motor resistor to the blower motor. It is a loose connection which makes it heat up to the point where it melts the connector around the pin(s) (presumably for the "5" setting since that is the one I was having trouble with). They sell replacement connector harnesses (which tells you they know there's a problem and just aren't willing to fix it by a recall) or you can shim the connector and pin with a small piece of aluminum (which is what I did) to fix it.

Last thing, if your rear Heat/AC blower stops working, the wires going into the fuse by the motor (you have to remove the plastic interior panel in the right rear where the blower motor is located) have a bad connection too. If you push them in to get the blower motor working and then use cable ties to keep some pressure (pushing them into the fuse connector) that will fix that issue. These are just one of many issues and all on a vehicle that is only 6 years old. I could go on but I probably lost most people in the 2nd or 3rd paragraph.

Great story, but about 2.5 years late, as you will note on the last dated post.

GM POS
07-31-2011, 10:30 AM
I understand the thread is old but it also describes the problem I was having and if someone searches for something like "Trailblazer wont start" it will be in this thread. There is a method to my madness my friend....it was not intended to solve this particular members issue but to just put the info out there in a place it is more likely to be found. Given the nature of the problem I am sure my GM POS is not the only one with this issue....thanks...and have a nice day!!!

kjjosker
08-21-2011, 03:47 PM
Thank God that you did post that, My wife has a 2007 Trailblazer that wouldn't start so I did a google search and I found your post. It turned out to be the same cause- i wiggled the PCM b fuse and the damned thing started!!! I don't know if i would have ever figured that one out without your help. Thanks!!
...and BTW, I've already had to change the blower motor resistor last year and noticed that the connector was melted also. I have also been a lifelong GM fan, but no longer after dealing with this thing.

TrailRunner
11-29-2011, 05:08 AM
Thank you GM POS for the useful post. I am currently fighting this problem myself with an 03 I6. I am trying to help a friend with a rod knock. A junk yard motor later he should be on his way. Nope. It did not start. It ran when I pulled it into the shop. The engine started after I lowered the fuel tank to gain access. I figured I jarred the pump to make it work, and I had power at the orange with a black strip. A $300 fuel pump did not solve the problem which led me to look at the wiring. Later I discovered that it had power but not 12V because I just used a test light. There is no break in the orange and black all the way to the PCMB connector.
My problem is that I cannot figure out why they wired it like they did. Shouldnít the PCM provide a signal to a relay which will turn on the fuel pump, this way high amperage current does not have to flow through the PCMB. Does the PCMB (Which I believe stands for power train control module blue) relay and 20 amp fuel pump fuse provide power to the entire PCMB Portion (a third of the computer)? The Chilton manual shows that power is provided to it by two violet wires. Then power leaves the PCMB and goes directly to the fuel pump. This Orange with a black strip is correct. But the wire that leaves the relay is Grey not violet(?) in position F3. The Power coming in is an Orange wire position A7. And the signal wire is a small diameter violet wire in position B6. The ground for the relay is actually two small diameter black wires that are in position F2. I donít know where the wires go to because I only opened the loom a little way so I donít mess up the integrity of the factory wiring.
The signal for the relay works intermittently and is weak. But when I provide power directly to the relay (Small purple B6) it does nothing. When I provide power to the load Grey F3 it does nothing. It has no power and is not grounded. I applied the power while I had a friend turn on the key simulating what the signal do.
What pin Locations are the two Violet wires providing power to(there are more than two)? What does that have to do with the Grey wire? Is the Key signal not reaching one of the PCMs?
I need to find a better wire diagram and an explanation of the design of this system.

maxwedge
11-29-2011, 07:46 PM
Welcome to AF, yes you need a GM manual of factory diagram here, try autozone.com, repair guides, or a subscription to Alldata.

Schurkey
11-30-2011, 04:22 PM
With much anticipation, hope, and doubt I reassemble everything and......it worked perfectly!
Appreciate the post. My TrialBlazer currently works great...but that can change at any time.

the next day we went and traded this GM POS in for a new Ford Edge.
And yet, the phrase "out of the frying pan...into the fire" comes to mind.

GM POS
12-01-2011, 07:16 AM
Like I said it was hard to switch...been a GM guy all my life but figured a Ford couldn't be any worse than what I was already dealing with...one too many problems with my cars and my friends and family were having problems as well...quality has apparently taken a back seat at Government Motors...I am hoping that since Ford was the only American car company that didn't need a bailout this means they are doing something right....with emphasis on "hoping"...And I sure as heck ain't ready to drink the kool aid and go get a foreign jobby.....

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