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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8346
Experience:  I am ASE Master Truck Certified.
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I have a lite ck engine light with key on so power to ecm

Customer Question

Good afternoon sir I have a lite ck engine light with key on so power to ecm how can I manual ck for power out also If I have power out how can I ck power to timing sensor its been replaced 4 months ago don't think it bad
Submitted: 2 months ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 2 months ago.
Thanks for asking your question. I will try and help you out.
The ECM does not send power out to the timing sensor. It's a magnetic pick up that generates its own frequency.Since the yellow check engine light comes on, this indicates the engine ECM is receiving power and functioning. There are several things that can cause a crank no start on this engine.The first is a low or no fuel pressure condition. The engine needs at least 35 psi to start. If it is low, the injectors will not get filled and it will not start. If the engine has a hand priming pump, and it gets stiff when operating it, the engine has enough pressure to start. If there is no hand priming pump, I would connect a psi gauge and measure the pressure. If the pressure is low, I would change the fuel filters first if you haven’t already. If it is still low, I would suspect a failed fuel pressure regulator in the secondary fuel filter housing, a weak fuel transfer pump, or restricted fuel inlet line. The pump is located on the front of the engine.Second is a failed engine speed timing sensor. Some engine have one, some have two. It depends on your engine serial number. If the engine speed timing sensor has failed, the ECM gets an RPM/TDC signal and will not send AC to the injectors.Next is low battery voltage to the ECM while cranking. The ECM must have at least 7.5 volts DC to operate. I have seen weak batteries or a poor connection cause low voltage. You could have a poor connection at the batteries or starter.Next is a faulty engine ECM. The ECM has an injector driver module inside. This is what powers the injectors. If it fails, the ECM will log injector codes for all the injectors.Lastly are worn injectors. Over time the injectors can wear if they have a lot of hours on them. To verify, I like to check AC to the injectors while cranking. You should have between 20-40 AC while cranking. If you do, and you have good fuel pressure, the injectors are worn. If you do not have 20-40 AC while cranking, you have either a failed engine speed timing signal, low power to the ECM while cranking, ot a failed ECM.Most often when these things are happening there will be diagnostic codes in the ECM. If your engine has cruise control switches, you can pull the codes. If you have never done this, let me know. I can get you the procedure.Please reply back if you need more help or have more questions. I am happy to assist.
Expert:  Cat Man replied 2 months ago.
Hey. I just wanted to see how things were going. Please let me know if you need more help. I am happy to assist. If my information was helpful, please leave a good or higher rating so that I receive credit. Thanks.

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