Colorado won't start at times - Chevy Colorado & GMC Canyon

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Old 11-08-2010, 11:50 PM   #1 (permalink)
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Default 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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Old 11-09-2010, 02:15 AM   #2 (permalink)
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Default 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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Old 11-09-2010, 08:43 AM   #3 (permalink)
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Default 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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Old 11-09-2010, 08:45 AM   #4 (permalink)
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Default 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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Old 11-09-2010, 04:47 PM   #5 (permalink)
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Default 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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Old 11-09-2010, 05:38 PM   #6 (permalink)
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Default Re: Colorado won't start at times

How to disable passlock.


viewtopic.php?f=8&t=84432&p=1095530#p1095530
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Old 11-09-2010, 05:42 PM   #7 (permalink)
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Default 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.
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Old 11-10-2010, 02:26 AM   #8 (permalink)
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Default 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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Old 11-10-2010, 08:50 AM   #9 (permalink)
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Default 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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Old 11-10-2010, 12:20 PM   #10 (permalink)
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Default 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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