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My '07 Hummer H3 suddenly won't start. It cranks, but will

Customer Question
Hi, my '07 Hummer H3...
Hi, my '07 Hummer H3 suddenly won't start. It cranks, but will not start fully. I've tried the Learn method and that hasn't worked either. I did notice last week that it was idling a bit rough when I came to stops or red lights...I cAn hear the fuel pump hum when I turn the ignition on...I'm at a loss here. We tried jumping it, that didn't work. Any suggestions?
Submitted: 1 year ago.Category: GM
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Answered in 1 minute by:
11/29/2016
GM Mechanic: Amedee, GMC Technician replied 1 year ago
Amedee
Amedee, GMC Technician
Category: GM
Satisfied Customers: 27,076
Experience: ASE certified tech with advanced level specialist. Wisconsin certified emissions state inspector
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Hello and welcome!

My name isCustomerand I can assist you with your question.

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GM Mechanic: Amedee, GMC Technician replied 1 year ago

I have a lot of suggestions and things to try.

However, I would recommend that you diagnose the problem by checking for spark and fuel. Would you like me to elaborate on this?

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GM Mechanic: Amedee, GMC Technician replied 1 year ago

Or is there a security light on or flashing on the cluster?

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Customer reply replied 1 year ago
The security light is not flashing at all..it comes on when I turn the ignition on but disappears within seconds
Customer reply replied 1 year ago
Please elaborate on checking for spark and fuel
GM Mechanic: Amedee, GMC Technician replied 1 year ago

Ok, then the problem is not related to the security system.

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Customer reply replied 1 year ago
Any other possible suggestions?
GM Mechanic: Amedee, GMC Technician replied 1 year ago

You will have to pinpoint what the engine is missing.

1. Spark

2. Fuel

3. Compression

All three of these are tested when the engine is being cranked over. There are two way of checking for fuel. Fuel pressure and fuel trigger. Both are very important and must be present for the car to start. Fuel pressure is self explanatory. You just hook up the gage and see what the reading is. Injector pulse is check with a noid light. The injector gets unplugged and the noid light gets plugged in to the injector clip. With the engine cranking over, this light must blink. This is the signal to the injectors from the computer. You can have all the fuel pressure in the world, but it wont matter if the injector is not pulsing gas into the cylinder like it should! All three tests play a very important part in diagnosing a no start condition. Be extremely careful when doing these tests. A simpler test would be to see if it runs on starting fluid. If it does, then you know you have spark and compression and you simply have a fuel delivery problem.

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Customer reply replied 1 year ago
This is where my problem lies. I'm going to need to have it towed to have it diagnosed as I don't have the tools to diagnose it myself... :/
GM Mechanic: Amedee, GMC Technician replied 1 year ago

Sounds good.

I am glad I can help!

It has been a pleasure working with you. Please dont forget to honor your good faith deposit by rating my answer as "5 STAR SERVICE" for assisting you today.

Keep in mind, we can still continue this conversation at no further cost to you even after you rate my answer. Just reply back to me using this page and I will get it and get back to you ASAP!

Also, if you are a member or if you have a subscription to the site, you still need to rate my answer in order for me to get credit for assisting you with your question.

Please let me know if you have any further questions.

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Customer reply replied 1 year ago
Thank you
GM Mechanic: Amedee, GMC Technician replied 1 year ago

Your welcome.

You should see the rating system towards the top of the page.

Have a great night!

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GM Mechanic: Amedee, GMC Technician replied 1 year ago

Hello! It'sCustomerfrom just answer.

I am just checking in to see if you need any further assistance?

Let me know!

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