How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Cat Man Your Own Question
Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8336
Experience:  I am ASE Master Truck Certified.
Type Your Medium and Heavy Trucks Question Here...
Cat Man is online now
A new question is answered every 9 seconds

I have a 2002 Chevy 850 with a cat 3126 engine. It quit

Customer Question

I have a 2002 Chevy 850 with a cat 3126 engine. It quit running will not start even with starting fluid. Light on dash I looks like a gear. Any suggestions
Submitted: 4 months ago.
Category: Medium and Heavy Trucks
Customer: replied 4 months ago.
I have paid its been over 24hrs still no word
Expert:  Cat Man replied 4 months ago.
Thanks for asking your question. I will try and help you out.
Does a yellow check engine light come on when the key is turned to the on position? It should be shaped like an engine or say check engine.
Customer: replied 4 months ago.
Expert:  Cat Man replied 4 months ago.
Thanks for the information.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 25 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 on the back of the head or a weak fuel transfer pump. The pump is located on the back of the HEUI pump.Second is a low injection actuation pressure. This is the high pressure oil system that activates the injectors. The engine needs at least 870 psi to start. If it is low, you have either a failed Injection actuation pressure control valve in the HEUI pump, a weak HEUI pump, a high pressure oil leak at an injector, or a faulty Injection actuation pressure sensor. To test the sensor, just unplug it. If the engine starts, the sensor is bad. It has 3 wires and is located on top of the engine near the front and screwed into the head.Third is a failed engine speed timing sensor. Your engine has two. They are located on the driver’s side of the engine on the back of the engines front cover under the HEUI pump. The bottom sensor is the primary start sensor. If it has failed, the engine will be hard to start. The top one is the primary run sensor. They come as a pair.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.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.
Customer: replied 4 months ago.
It does have cruise. I have never gotten codes before
Expert:  Cat Man replied 4 months ago.
Use the following procedure to retrieve the flash codes from the check engine light:
Turn the ignition key switch to the On position/ Engine OFF.
Turn the cruise control ON/OFF switch to the OFF position.
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 key switch has been turned to the ON position.Let me know what two digit code you get and I can tell you what the problem is.
Customer: replied 4 months ago.
With key on it flashes if u push cruise or not
Expert:  Cat Man replied 4 months ago.
I see. Thanks for the information.
Unfortunately sometimes this procedure does not work on Chevys or GMC's. Not sure why.
If the light is flashing with just the key on. The engine has an a curve code. It would be best to have someone read the codes with a service tool. I am sorry.
Customer: replied 4 months ago.
Can't find speed timing sensors. Don't seem to be located there
Expert:  Cat Man replied 4 months ago.
They are behind the air compressor on the back of the front cover under the heui pump on the drivers side of the engine. They are hard to see.
Expert:  Cat Man replied 4 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.

Related Medium and Heavy Trucks Questions