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: 8617
Experience:  I am ASE Master Truck Certified.
30708357
Type Your Medium and Heavy Trucks Question Here...
Cat Man is online now
A new question is answered every 9 seconds

Why does my catapiller A7 (350hp with a turbo)eng hesitate

Customer Question

why does my catapiller A7 (350hp with a turbo)eng hesitate when accellerating from a stop. K&N air filter (air draw gage is almost at bottom of green band), fuel filter changed two years (about 10K) ago. Along with oil and filter. recently noticed while pulling a max (little more) trailer load - 10K max was 11.5K. Trip Atlanta to El Paso, TX and noticed problem first in MS. Temp stayed around 190-198 digital and analog. Idles fine and once above 1700 RPM runs fine and through remaining gears. Held cruise at 1550-1650 (60-65 MPH) due to load. No smoke noted from exhaust.
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 year ago.

Thanks for asking your question. I will try and help you out.

Has the fuel pressure been checked on the engine while driving?

Has the engine always done this? Or did it start recently?

Customer: replied 1 year ago.
Fuel pressure hasn't been checked. It just started to have this problem.
Expert:  Cat Man replied 1 year ago.

Thanks for the information. There are two things I have seen cause this.

I would check the fuel pressure first. Your engine should maintain a fuel pressure between 65 and 85 psi. There is a plug beside of the secondary fuel filter that is used to check the pressure. If it is low, I would first try the fuel filters if you haven’t already. If it is still low, you may have a failed fuel pressure regulator, which is located on the back of the cylinder head. I have replaced a ton of these for low fuel pressure. It is kinda a known problem. You could also have a weak fuel transfer pump or restricted hand primer pump, if your engine has one.

If the fuel pressure is in specs. I must next suspect the injectors. Over time the can wear and begin to cause this problem.

Please reply back if you need more help or have more questions. I am happy to assist.

Customer: replied 1 year ago.
Understand the checks to look at. One item I didn't pass on is: while at idle place in nuetral and when pressing the accelerator it will bogg down. But if you keep pumping (slowly) and let the rpm's raise the problem will be greatly reduced to disappear. Takes less than two minutes. Then the unit/engine has no problem.
Expert:  Cat Man replied 1 year ago.

I see. Thanks for the information. I would definetely check the fuel pressure. Since there is no engine light coming on, it sounds like a fuel pressure issue.

Expert:  Cat Man replied 1 year 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.

Customer: replied 1 year ago.
I'm going to test the system this weekend and l will let you know the results.
Expert:  Cat Man replied 1 year ago.

Ok sounds good. Let me know how you make out.

Expert:  Cat Man replied 1 year 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