Colorado won't start at times - Chevy Colorado & GMC Canyon
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post #1 of 36 (permalink) Old 11-09-2010, 12:50 AM Thread Starter
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Colorado won't start at times

My 2005 5 cyl crew cab colorado is having a problem not starting. Hot battery, plenty of gas, it just grinds over but no start. Wait 20 -30 minutes and it starts fine. Been to dealer twice and it's not throwing codes that would lead to a fix. Anyone else having this case of trouble?

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post #2 of 36 (permalink) Old 11-09-2010, 03:15 AM
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Re: Colorado won't start at times

I suspect a fuel pressure / fuel filter / fuel pump / fuel pressure regulator problem. Throw a fuel pressure tester on it and see if it comes up to pressure immediately when you turn the key on. The pump only runs of 3 to 5 seconds and shuts down. If it is not up to pressure by then the truck will not start no matter how long you crank. Turning the key off for 5 to 10 seconds resets the timer and the next time you turn it on the pump runs again for 3 to 5 seconds or continuously if the engine starts.

I have not worked on a Colorado with this problem so I do not know the pressure numbers. I have worked on many other GM vehicles with this type of problem.

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post #3 of 36 (permalink) Old 11-09-2010, 09:43 AM
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Re: Colorado won't start at times

I have had this problem a bunch.
I suspect the security system, but can't prove it, and the dealer can not find anything.

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post #4 of 36 (permalink) Old 11-09-2010, 09:45 AM
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Re: Colorado won't start at times

Does the red security light come one on the dash when this happens? I'd say itís a passlock II issue, if just waiting fixes the problem. The fuel system doesnít just "heal" itself unless something electronic is restricting it from working. When the passlock system reads your key wrong, it locks out the injectors. It will allow the car to crank, but it will not supply any gas to the cylinder. Waiting 15-20 min would correct this issue and allow you to start. Next time you have this issue see if the red lock over car symbol is on, if so this is a passlock issue.



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post #5 of 36 (permalink) Old 11-09-2010, 05:47 PM
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Re: Colorado won't start at times

Here is the issue with the fuel system and "healing itself". The system on other GM vehicles pumps up to 55 to 60 PSI and then the regulator opens and returns excess fuel (and pressure) to the tank. The system maintains the pressure based on the regulator returning the fuel. When you shut down the vehicle, the pressure in the system is maintained by a combination of the regulator and a check valve in the fuel pump located in the tank. The next time you go to start the vehicle you already have the system up to pressure and the vehicle starts immediately. You do not have to wait for the pump to pressurize the system again.

Now introduce a slight leak in the check valve or regulator. Overnight the pressure bleeds off and when it comes time to start again there is a delay getting the pressure back up. Add to that the 3 second or so time out on the fuel pump when the engine is not running and you have a situation where the engine will not start. Cycling the key off and on a few times allows the pump to run through several 3 second run cycles and to build the static pressure back up.

This is a very common failure on GM vehicles. The failure usually is the check valve in the in-tank fuel pump. It occasionally is the fuel pressure regulator in the engine. I have an adapter that blocks the return to the tank line. I install the adapter to block the return and run the pressure up. Then watch the gauge. If the pressure bleeds off quickly or overnight then the problem is the check valve in the fuel pump. If the pressure stays up (with the return blocked) then it is the regulator bypass valve leaking. Nothing is healing itself. The check valve is not used when the pump is running and there is enough volume (and pressure) to overcome a slightly leaking regulator when the pump is running.

Put a fuel pressure gauge on the port located on the intake manifold and check it out for yourself. You can see if it is your problem or not.

I did not want to explain this whole thing in my first post to keep it shorter, but since someone challenged me I hope I have explained it thoroughly enough now.

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post #6 of 36 (permalink) Old 11-09-2010, 06:38 PM
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Re: Colorado won't start at times

How to disable passlock.


viewtopic.php?f=8&t=84432&p=1095530#p1095530



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post #7 of 36 (permalink) Old 11-09-2010, 06:42 PM
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Re: Colorado won't start at times

Quote:
Originally Posted by n9cv
Here is the issue with the fuel system and "healing itself". The system on other GM vehicles pumps up to 55 to 60 PSI and then the regulator opens and returns excess fuel (and pressure) to the tank. The system maintains the pressure based on the regulator returning the fuel. When you shut down the vehicle, the pressure in the system is maintained by a combination of the regulator and a check valve in the fuel pump located in the tank. The next time you go to start the vehicle you already have the system up to pressure and the vehicle starts immediately. You do not have to wait for the pump to pressurize the system again.

Now introduce a slight leak in the check valve or regulator. Overnight the pressure bleeds off and when it comes time to start again there is a delay getting the pressure back up. Add to that the 3 second or so time out on the fuel pump when the engine is not running and you have a situation where the engine will not start. Cycling the key off and on a few times allows the pump to run through several 3 second run cycles and to build the static pressure back up.

This is a very common failure on GM vehicles. The failure usually is the check valve in the in-tank fuel pump. It occasionally is the fuel pressure regulator in the engine. I have an adapter that blocks the return to the tank line. I install the adapter to block the return and run the pressure up. Then watch the gauge. If the pressure bleeds off quickly or overnight then the problem is the check valve in the fuel pump. If the pressure stays up (with the return blocked) then it is the regulator bypass valve leaking. Nothing is healing itself. The check valve is not used when the pump is running and there is enough volume (and pressure) to overcome a slightly leaking regulator when the pump is running.

Put a fuel pressure gauge on the port located on the intake manifold and check it out for yourself. You can see if it is your problem or not.

I did not want to explain this whole thing in my first post to keep it shorter, but since someone challenged me I hope I have explained it thoroughly enough now.

I didn't challenge your "knowledge" in the understanding of a simple return style fuel system, i challenged your trouble shooting based on his complaints. Trouble shooting quickly is how we tech, make our money.

What you attempted to explain is something that would NOT be an intermittent problem, it would be something that happened every day, or anytime there was a long delay between running, and starting.



2006 Metallic Blue Colorado 7Z1: 3" SM keys, 2" rear shackels, 15% tinted windows, Kenwood KDC-X494 HU, Infinity Kappa 6.1 perfect all around. Infinity 475a amp, remote start/alarm.
2007 cobalt SS/SC: sold
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post #8 of 36 (permalink) Old 11-10-2010, 03:26 AM
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Re: Colorado won't start at times

Actually I have one right now that has been doing this for over two years. It does not happen every day. It has a bad check valve in the pump that sometimes seats and other times does not. Since it is mine, I am too lazy to drop the tank and change it. When it happens I simply cycle the key again and it starts and runs. THis was his same description of the problem he was having.

I caught the problem by putting a pressure tester on it and checking it every morning. Sure enough I caught it one morning with the pressure very low and it refused to start on the first try. It only made it to 40 PSI on the first try before the fuel pump timed out. Cycling the ignition off and on brought the pressure on the second try up to normal operating range of around 60 PSI. I have a replacement pump for it but I will not install it until the pump quits completely. That vehicle has about 24,000 miles on it since I first started seeing the failure.

I do not know if this is his problem but I have seen it multiple times on multiple GM vehicles. I have never see it on a Colorado. If he would throw a pressure tester on it over night and see if he has the problem in the morning he could confirm or eliminate this as a possible problem.

Note: I have never seen any error codes logged from this problem. If is also difficult for a dealer or other shop to diagnose this problem as there are no codes and it never fails when the vehicle is in the shop. To find it you have to attach the gauge and read it when it fails to start.

I was first put on to the solution to this problem by two long time GM dealership mechanics with 43 years experience between them. The problem they face in the dealership is they next never can trap this failure in the shop. It is an expensive "guess" repair as the GM pump assembly is over $500, plus labor. I have not checked the retail price on a Colorado pump but it is probably in the same price range. You can get them elsewhere for about 1/2 of the price.

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post #9 of 36 (permalink) Old 11-10-2010, 09:50 AM
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Re: Colorado won't start at times

Quote:
Originally Posted by n9cv
Actually I have one right now that has been doing this for over two years. It does not happen every day. It has a bad check valve in the pump that sometimes seats and other times does not. Since it is mine, I am too lazy to drop the tank and change it. When it happens I simply cycle the key again and it starts and runs. THis was his same description of the problem he was having.

I caught the problem by putting a pressure tester on it and checking it every morning. Sure enough I caught it one morning with the pressure very low and it refused to start on the first try. It only made it to 40 PSI on the first try before the fuel pump timed out. Cycling the ignition off and on brought the pressure on the second try up to normal operating range of around 60 PSI. I have a replacement pump for it but I will not install it until the pump quits completely. That vehicle has about 24,000 miles on it since I first started seeing the failure.

I do not know if this is his problem but I have seen it multiple times on multiple GM vehicles. I have never see it on a Colorado. If he would throw a pressure tester on it over night and see if he has the problem in the morning he could confirm or eliminate this as a possible problem.

Note: I have never seen any error codes logged from this problem. If is also difficult for a dealer or other shop to diagnose this problem as there are no codes and it never fails when the vehicle is in the shop. To find it you have to attach the gauge and read it when it fails to start.

I was first put on to the solution to this problem by two long time GM dealership mechanics with 43 years experience between them. The problem they face in the dealership is they next never can trap this failure in the shop. It is an expensive "guess" repair as the GM pump assembly is over $500, plus labor. I have not checked the retail price on a Colorado pump but it is probably in the same price range. You can get them elsewhere for about 1/2 of the price.



In the end, with the known facts itís pretty ignorant for the both of us to assume we know the problem. There are ways of testing and figuring out whether itís a faulty security problem, or whether itís a fuel system problem. Iíve done 4 years of training/schooling, and 4 years in the field. Iíve dealt with 14 instructors, and mentors over the years. Any respectable tech will give you their best guess over the internet, and be able to tell you for certain if they were able to test the vehicle, which we obviously canít do. My suggestion to you is just to watch some of the main indicators we both have said, that should narrow it down for you. Hope we have helped you in some way or another.

What lead me to believe that it was a security issue was the fact that him waiting for the same amount of time it takes the passlock II system to rest, allowed him to start.



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2007 cobalt SS/SC: sold
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post #10 of 36 (permalink) Old 11-10-2010, 01:20 PM
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Re: Colorado won't start at times

I've had a problem starting my 2006 twice in the last 3 weeks. Once first thing in the morning, and yesterday when I left work to go home, the truck had been sitting for about 4 hours since lunch. I can here the fuel pump run for a few seconds but the truck just cranks. The first time the tank was near empty and backed into my driveway. The second time it was sitting on flat ground with a half tank.

Both times it just started right up after about 15 minutes which sounds like a passcode problem as discussed.

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post #11 of 36 (permalink) Old 11-10-2010, 03:45 PM
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Re: Colorado won't start at times

Quote:
Originally Posted by noximus
Quote:
Originally Posted by n9cv
Actually I have one right now that has been doing this for over two years. It does not happen every day. It has a bad check valve in the pump that sometimes seats and other times does not. Since it is mine, I am too lazy to drop the tank and change it. When it happens I simply cycle the key again and it starts and runs. THis was his same description of the problem he was having.

I caught the problem by putting a pressure tester on it and checking it every morning. Sure enough I caught it one morning with the pressure very low and it refused to start on the first try. It only made it to 40 PSI on the first try before the fuel pump timed out. Cycling the ignition off and on brought the pressure on the second try up to normal operating range of around 60 PSI. I have a replacement pump for it but I will not install it until the pump quits completely. That vehicle has about 24,000 miles on it since I first started seeing the failure.

I do not know if this is his problem but I have seen it multiple times on multiple GM vehicles. I have never see it on a Colorado. If he would throw a pressure tester on it over night and see if he has the problem in the morning he could confirm or eliminate this as a possible problem.

Note: I have never seen any error codes logged from this problem. If is also difficult for a dealer or other shop to diagnose this problem as there are no codes and it never fails when the vehicle is in the shop. To find it you have to attach the gauge and read it when it fails to start.

I was first put on to the solution to this problem by two long time GM dealership mechanics with 43 years experience between them. The problem they face in the dealership is they next never can trap this failure in the shop. It is an expensive "guess" repair as the GM pump assembly is over $500, plus labor. I have not checked the retail price on a Colorado pump but it is probably in the same price range. You can get them elsewhere for about 1/2 of the price.



In the end, with the known facts itís pretty ignorant for the both of us to assume we know the problem. There are ways of testing and figuring out whether itís a faulty security problem, or whether itís a fuel system problem. Iíve done 4 years of training/schooling, and 4 years in the field. Iíve dealt with 14 instructors, and mentors over the years. Any respectable tech will give you their best guess over the internet, and be able to tell you for certain if they were able to test the vehicle, which we obviously canít do. My suggestion to you is just to watch some of the main indicators we both have said, that should narrow it down for you. Hope we have helped you in some way or another.

What lead me to believe that it was a security issue was the fact that him waiting for the same amount of time it takes the passlock II system to rest, allowed him to start.

Agreed.
Any diagnosis over the Internet is a"guess" at best. Without actually having the vehicle in front of you, the tech is at a great disadvantage.

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post #12 of 36 (permalink) Old 11-12-2010, 01:31 PM Thread Starter
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Re: Colorado won't start at times

My dealer finally figured out what was causing the no start problem and my face is a bit red. The key on the key ring I usually use to start the truck has a digital tire gauge on it along with a Mobil speed pass that I have not used in years. When I take my truck in to the dealer I leave a spare key with them, that I have for that purpose, with nothing else attached to it, that way I wonít lose anything. This last trip to the dealer my wife took the truck in and left them the key with the speed pass.

It seems that when you start the truck and the speed pass is hanging down it will start as normal. But at times the speed pass ends up on top of the key. I guess itís dying and giving off a bogus signal to the key which the truck reads as an improper key and the pass-lock feature locks the key out and wonít let the truck start. Itís unlikely any of you have a speed pass on your key ring but this is a tough case of trouble to diagnose if you do. Also if you have the intermittent no start trouble try a different key.

I also had a banging noise when the left rear door was slammed shut. It seems there is a bracket in there that holds the door mechanism that runs the window, door workings and who knows what else. It was mostly broken loose but everything was still working. My service advisor said this happens and if I had let it go until the bracket broke completely loose they would have to pull the back seat out from the rear passenger side and work the door skin open to open the door so they could take the workings apart. A new bracket would have to be installed. $200.00 was the price he quoted for bracket and labor. They are able to reattach the bracket if itís only partly loose by drilling and what-not. $98.00 for the job. I bet itís something a guy could do himself. Iím handicapped now and canít do most work on my cars any longer or I would have got into that door myself just to see what was going on.

Bottom line: "It was a security issue".

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post #13 of 36 (permalink) Old 11-12-2010, 01:36 PM
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Re: Colorado won't start at times

well i'm glad you got it all figured out man!



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post #14 of 36 (permalink) Old 11-12-2010, 01:41 PM Thread Starter
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Re: Colorado won't start at times

You called it.

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post #15 of 36 (permalink) Old 11-13-2010, 07:39 AM
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Re: Colorado won't start at times

????

I guess I do not understand how the passlock "feature" works and why the mobil speed pass affected it.

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post #16 of 36 (permalink) Old 11-13-2010, 09:40 AM Thread Starter
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Re: Colorado won't start at times

I understand the speed pass is a low level transmitter at times. Passlock reads your key among other things and if the key is bogus it won't let the truck start. You can't get a new key cut and expect it to work. You have to get a key cut at the dealer and then programed to the truck. Great way to sell keys. My mobile speed pass has been on that keyring ever since I got the truck, it just started effecting things the last few months. I won't know for sure that I have a fix until the truck starts fine for the next month or so. Wish me luck.

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post #17 of 36 (permalink) Old 11-14-2010, 03:31 AM
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Re: Colorado won't start at times

Now I'm really confused. I also have a 2005 and I do not have the chip in the key you are describing Mine keys are just plain old keys. I have personally cut 3 new keys at my friiends key shop and can guarantee that I do not have the chips. GM must have made the change to that style key later in the model year or at least after mine was made.


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post #18 of 36 (permalink) Old 11-15-2010, 11:38 AM
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Re: Colorado won't start at times

The way the PASSLOCK works is there is no special ignition key (Easily copied at a hardware store). The security is built into the ignition lock cylinder and housing in which through a magnetic field cause the vehicle's computer to sense the rotation of the ignition lock in order for the engine to start.
If there is a problem where the rotation can't be sensed or some other problem, the engine will crank, but will not start. This system does not interrupt the starter and only the injector pulse of the fuel.

I'm guessing in some way that pass threw off what the computer sees as a valid start. Definitely a weird one!



2006 Metallic Blue Colorado 7Z1: 3" SM keys, 2" rear shackels, 15% tinted windows, Kenwood KDC-X494 HU, Infinity Kappa 6.1 perfect all around. Infinity 475a amp, remote start/alarm.
2007 cobalt SS/SC: sold
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post #19 of 36 (permalink) Old 11-15-2010, 10:09 PM
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Re: Colorado won't start at times

AH HA. NOW I understand.

Thanks.

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post #20 of 36 (permalink) Old 12-09-2013, 06:28 PM
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I've had the same problem a few times over the past year. Initially was told it was probably a faulty fuel pump. After waiting until the temperature dropped well below zero and having it happen a couple more times I took it to the shop and had the pump&filter replaced and flushed the fuel system. When I got it back home I also changed out the plugs. Was running fine. Stopped at the grocery store, came out after about 15min and same problem. Turned over with no start. I'm guessing its most likely the pass lock but will probably throw in a pressure regulator first (since it's only a couple screws and $70 part). Have to do some more research on how to fix the passlock problem if it still happens. Can go weeks without any problem and then out of the blue it'll pop up again. Walk away from the truck and come back later and it starts again...gotta be the passlock right???
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