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Cat Man
Cat Man, Caterpillar Engine Expert
Category: Heavy Equipment
Satisfied Customers: 8956
Experience:  23 Years Caterpillar Engine experience.
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c12 cat no start no codes in ecm getting fuel no blown fus

Customer Question

c12 cat no start no codes in ecm getting fuel no blown fuses
Submitted: 6 years ago.
Category: Heavy Equipment
Expert:  Cat Man replied 6 years ago.
Hi. Thanks for using JA! I will try and help you out.

Could you get me your engine seriel number please?

Also, when you cranks the engine does the engine smoke at all or sound like it is trying to fire?

And lastly, does the check engine light come on when you turn the key to the on position, then go off?
Customer: replied 6 years ago.
the check engine light does come on and goes out,

Engine # MBL17569

sometime it tries to start.
Expert:  Cat Man replied 6 years ago.
Thanks for the information.

Since you have no codes and sometimes the engine acts like it is trying to start, I would first suspect a low fuel pressure problem. Your engine needs at least 30 psi to start and should have 75 to 90 psi when running.

There is a fitting on the secondary fuel filter housing that you can use to check the preesure. If it is low I would change the fuek filters first. If the pressure is still low, I would next suspect you have a faulty fuel pressure regulator. I have seen this before. It is located in the secondary filter housing as well.

Please let me know if you have more questions or need more help.
Customer: replied 6 years ago.
i have installed new filters try to get gadget to check fuel pressure. U say there is a regulator on secondary housing.
Expert:  Cat Man replied 6 years ago.
Yes, it is located on the bottom of the housing near the return line. It's about an inch size looking plug.
Customer: replied 6 years ago.
we have 70 psi at engine turn over
Expert:  Cat Man replied 6 years ago.

Thanks for the information.


That is plenty of fuel pressure to crank.


Does your engine have a hand primer pump?


Could you tell me how it started?


Did the engine just shut off one day while driving?


Or did it just not start one day?

Customer: replied 6 years ago.
check this out when i first checked fuel pressure it was at 10 at start so i screwed compucheck fitting out to make sure of no block in fitting screw back in check fuel pressure again truck started ran about 10 minutes shut down no start now.fuel pressure is at 70 now.

it does have hand primer pump when i pull pump out it will suck gauge
down past 0

when truck came in it was going down road and would jerk every so it would drop fuel pressure.just for a split second thou.

then just no start now
Expert:  Cat Man replied 6 years ago.
Thanks for the information.

That sounds like you may have a faulty hand primer. I would suggest moving the quick connect to the front of the housing beside of the fuel line that runs up to the head. That is the best place to check the pressure. Cat puts the fitting on the back of the housing just to fill the engine with fuel. If you have a problem with the hand primer, it will not show up on the psi gauge if you are checking it on the back. I have seen 70 psi on the back of the housing but with a plugged hand primer, I only had 15 psi after the housing.

You can swap and leave the fittings. They are the same size.
Customer: replied 6 years ago.
So update installed new hand primer pump truck started and run fine for 10 minutes and shut down still no codes.
Expert:  Cat Man replied 6 years ago.

Thanks for the information.


The only thing left is a faulty transfer pump. It sounds like after you prime up the fuel system, you have enough fuel to start and run then the fuel pressure drops off again.


After it shuts down, have you operated the hand priming pump and found it to NOT be stiff?


Or was it stiff after operating it?

Customer: replied 6 years ago.
no it is stiff and hard to push in and pump up.Thanks for your patience
Expert:  Cat Man replied 6 years ago.

Thanks for the information.


If it is stiff after shutdown, then I would think you do not have a fuel pressure problem. I would suspect something else.


Lets try and pull the fault codes from the engine ECM. I have seen the ECM be the problem when the injector driver module inside of the ECM fails. When this happens, you will have fault codes in the ECM for all 6 injectors. If you have never done this before, here is how to pull the codes. All codes are 2 digits.



Use the following procedure to retrieve the flash codes if the engine is equipped with a diagnostic lamp:


  • 1. Turn the ignition keyswitch to the On position/ Engine OFF.
  • 2. Turn the cruise control ON/OFF switch to the OFF position.
  • 3. Move the SET/RESUME switch to either position. Hold that position until the yellow lamp begins to flash.

The yellow lamp will flash in order to indicate a two digit flash code and the SET/RESUME switch may be released. The sequence of flashes represents the system diagnostic message. Count the first sequence of flashes in order to determine the first digit of the flash code. After a two second pause, the second sequence of flashes will identify the second digit of the flash code.

Any additional flash codes will follow after a pause. These codes will be displayed in the same manner. Flash Code 55 indicates that No Detected Faults have occurred since the ignition keyswitch has been turned to the ON position.




Let me know what codes you get (if any) and I can tell you what they mean.

Customer: replied 6 years ago.
we have a pro linkm iq.
Expert:  Cat Man replied 6 years ago.
Oh I see. I'm sorry. So there are no active or logged codes?
Customer: replied 6 years ago.
there is none. but i can also tell you that when the truck shuts down the truck will not let you acsess the ecm till you cycle the key on and off. when the truck shuts down the check engine light will come on.
Expert:  Cat Man replied 6 years ago.
Thanks for the information.

It sounds like since you have no codes and good fuel pressure, your engine ECM is loosing power or defective.

Here is what I would do. When the engine will not crank, I would remove the rear 70 pin truck connector from the ECM and check for power and ground. You should have power on pins 52, 53, and 70. 65 and 67 are the grounds. If you have power and ground, I would suspect a faulty ECM.

Let me know what you find.