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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8724
Experience:  I am ASE Master Truck Certified.
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I have 1999 bus with a cat diesel engine. It will idle fine

Customer Question

I have 1999 Thomas bus with a cat diesel engine. It will idle fine & then when I drive down the road after a bit it seems to just shut off like I switched the key.
JA: Sometimes things that you think will be really complicated end up being easy to fix. The heavy equipment mechanic I'm going to connect you with knows all the tricks and shortcuts.
Customer: what should the oil psi be in this type of engine at idle & under a load?
JA: Anything else you want the equipment mechanic to know before I connect you?
Customer: what should the oil psi be at idle & under a load
Submitted: 6 months ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 6 months ago.
Thanks for asking your question. I will try and help you out.
Does a red or yellow check engine light come on before it shuts down?
Will it start right back up after a shutdown?
Customer: replied 6 months ago.
No lights come on. It will start up right away.
Expert:  Cat Man replied 6 months ago.
Thanks for the information.
If something like low oil pressure or high coolant temp or low coolant level was shutting it down, the red engine light would be coming on.
Also if it was running out of fuel or had low fuel pressure, it would be hard to restart.
Since yours has no lights and will restart. I must suspect the engine ecm is losing DC voltage intermittently. Or the ecm is faulty.
The ecm needs power on pins 52 53 and 70. 70 is the key switch wire. The only way to verify is when it shuts down you can remove the oem connectors and check power on these pins. If you have power. You may have a faulty ecm.Please reply back if you need more help or have more questions. I am happy to assist.
Expert:  Cat Man replied 6 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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