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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8958
Experience:  I am ASE Master Truck Certified.
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I have a 98 Peterbilt 379 with a 2WS E model cat motor. Yesterday

Customer Question

I have a 98 Peterbilt 379 with a 2WS E model cat motor. Yesterday the engine started up and ran fine. This morning tried to start it up and it hit once, but failed to start. After that it will crank but not start. No fault codes present. Thought is was low on fuel so put 10 galloons in each tank. Took line off that comes out of transfer pump and goes into hand pump manifold. Had fuel pressure there. Loosened filter, primed system, tightened filter. Still just cranks. On ether is sounds like it is just about ready to fire, then runs out like no fuel.
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 2 years ago.
Hi. Thanks for asking your question! I will try and help you out.
Does the yellow check engine light come on when the key is turned to the on position?
Also, does the engine have a hand primer pump? If so, does it get stiff when operated?
Customer: replied 2 years ago.
yes the check engine light comes on then goes off after a few seconds. yes it does have a hand pump and it does get stiff when pumped.
Expert:  Cat Man replied 2 years ago.
Thanks for the information.
If the hand primer gets stiff. Then the engine has enough fuel pressure.
When you say there's no codes, how did you check for them? Do you have a service tool? Or did you use the cruise control swotches?
Customer: replied 2 years ago.
No codes using the cruise control method
Expert:  Cat Man replied 2 years ago.
Did it flash a 55?
Customer: replied 2 years ago.
No it hasn't flashed at all
Customer: replied 2 years ago.
Just so you know, the truck came with a 6 TS motor and this 70 pin was installed using a Mawk industries adapter .
Customer: replied 2 years ago.
It never flashed at all.
Expert:  Cat Man replied 2 years ago.
Thanks for the information.
If the yellow check engine light does not come on when the key is turned to the on position and the engine will not start, there are only 2 things that can cause this.
The first and most common is the engine ECM is not getting the correct power and ground to function. The ECM should have power on pins 52, 53, and 70 of the rear most ECM connector. This is the truck side harness connector. 70 is the key switch wire. The grounds are on pins 65 and 67. You can remove the connector and check for power on these pins. If you do not have power on these pins, you most likely have a blown fuse in the electrical system. I would check all fuses first.
If you do have correct power and ground to the ECM, you most likely have a failed ECM. I have seen this many times over the years. To confirm the ECM is bad, you would need to install a known good ECM on the engine or you can take the ECM to the dealer to be tested. Unfortunately the ECM cannot be repaired. Replacement is the only option. I am sorry. I wish I had better news.
Please reply back if you need more help or have more questions. I am happy to assist.
Customer: replied 2 years ago.
Just to verify, the yellow check engine light comes on when the key is switched to the on position, then it goes out after a few seconds... When I try to retrieve engine codes using the cruise control the yellow check engine light never flashed.
Expert:  Cat Man replied 2 years ago.
I see. Thanks for the information.
Sometimes the procedure does not work. Not sure why. It definetely sounds like an ECM problem.
Did you have the key on, cruise off, then hold down the set and resume?
Customer: replied 2 years ago.
I have power to pin 70, but not on pin 52 or 53. Looking now for blown fuses but have yet to find any
Expert:  Cat Man replied 2 years ago.
Thanks for the information.
Yeah no power on pins 52 and 53 are most likely the problem. Thise are the unswitched power. Should be a fuse somewhere for these.
Please reply back if you need more help or have more questions. I am happy to assist.
Customer: replied 2 years ago.
Where might I be looking??? I checked all the fuses in the fuse block. Found none burnt. Checked 1 breaker that is marked ignition and had power coming in and out. Where else should I be looking?
Expert:  Cat Man replied 2 years ago.
Some trucks have a fuse in the battery box. I would look there.
Expert:  Cat Man replied 2 years 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!