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Andy, Technician
Category: Heavy Equipment
Satisfied Customers: 1658
Experience:  310s and 310t technician licenses, 17 yrs experience, International Diamond Certified Tech 7 yrs
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have GMC C7500 with a 3126 Cat engine, wont start even on ether

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have GMC C7500 with a 3126 Cat engine, wont start even on ether

Hi there! My name is XXXXX XXXXX I think I can help you resolve your problem!

I don't know a whole bunch about Cat but if we stick to the basics we may be able to resolve the issue.

If it is not trying to fire at all on any cylinder, then it sounds like you may not have power to the ecm to energize the injectors to spray fuel into cylinders . Does your engine lamp come on when you first turn the ignition on (should only come on for a second as a bulb test , then go out)? This should indicate that the ecm is powering up or not. Most trucks have smaller wires leaving the batteries that feed directly to the ecm . These wires will likely have an inline fuse right in the battery box. I would start by checking the inline fuse holder for a blown or melted fuse due to bad connections there. If your ecm is not powering up , you could crank forever and nothing will ever happen because ecm is not powered up to fire injector coils.


I would follow those wires right up to ecm to make sure they are secure and not rubbed out anywhere . Look for corroded or loose connections . Good luck!


Edited by Andy3221 on 5/4/2010 at 2:34 PM EST
Andy and 2 other Heavy Equipment Specialists are ready to help you
Customer: replied 7 years ago.
I will check these wires, there is no fuse in the battery box and I have search for all fuses that I can find. Thank you and I will get back to you
Is your engine lamp coming on momentarily when you turn key on ? This tells you that ecm is powering up