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 Daniel Wilson Your Own Question
Daniel Wilson
Daniel Wilson,
Category: Medium and Heavy Trucks
Satisfied Customers: 4397
Experience:  Owner at DJ Wilson
65405794
Type Your Medium and Heavy Trucks Question Here...
Daniel Wilson is online now
A new question is answered every 9 seconds

I have a 05 379 I am having problems with the engine not

Customer Question

I have a 05 379 I am having problems with the engine not picking up the throttle position acts like it wants to but just cant. (Sometimes) it acts like it's starving for fuel and starts fluttering and shaking . At the same time the air dryer will spit @ 100 lbs and will do a full purge @ 120. When this all goes on it puts considerable drag on the engine. It feels like it is fighting itself and recently the abs light comes on and goes off. Humidity and wet weather make symptoms worse as long as it stays in a stable environment it works well. I'm thinking fuse panel or something like that?
Submitted: 9 months ago.
Category: Medium and Heavy Trucks
Customer: replied 9 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Daniel Wilson replied 9 months ago.

Hi Tammy. My name is***** will be glad to help. What is the make , model and serial of the engine?

Expert:  Daniel Wilson replied 9 months ago.

For initial checks, check the fuel lines between the tank and pump for leaks or restrictions indicating a loss of fuel supply pressure and sucking in air. Install a sight glass or clear hose to check for bubbles indicating air in the system. Let me know what engine make and model so I can give you details on the engine checks whether it is Cat C15, Cummins ISX, Detroit...??? Let me know

Expert:  Daniel Wilson replied 9 months ago.

Hi, It appears there is some technical difficulty. Let me know if you can see my responses

Expert:  Daniel Wilson replied 9 months ago.

I can provide with some schematics and troubleshooting info to help once I get your engine information.

Customer: replied 9 months ago.
Bsx25790 did everything u suggested. All was ok.
Customer: replied 9 months ago.
C15
Expert:  Daniel Wilson replied 9 months ago.

What are the first three characters of the engine serial number?

Expert:  Daniel Wilson replied 9 months ago.

Is the check engine light coming on at all?

Expert:  Daniel Wilson replied 9 months ago.

Click here for your schematics.

Schematics

Expert:  Daniel Wilson replied 9 months ago.

Check your fuel pressure with a gauge. Should be 75-90 PSI consistent even under a load. If low your could have a faulty pressure regulator or transfer pump. The other cause is faulty injectors if high mileage. You can have an injector test done with Cat ET connected. Let me know

Customer: replied 9 months ago.
Have had 2 sets of injectors in. fuel pressure runs 92 running down the road and 89 at a 800 rpm. What is normal turbo boost? I'm only getting about 35. Injector tested ok, but it always runs fine in a stable environment.
Expert:  Daniel Wilson replied 9 months ago.

That is in range for boost. Are you getting any fault codes? Check engine light come on? Hard starting? you mention when the air compressor is pumping/cut in the symptoms are worse? Or are the symptoms only present when the air compressor is cut in? What is the complete engine model and serial number from the ID tag?

Customer: replied 9 months ago.
No codes, no lights. Not hard starts cat c15 bsx25790. Doesn't semester to matter if air compressor cuts in or not. Btw new.
Expert:  Daniel Wilson replied 9 months ago.

If the fuel system checks out ok and there is no codes then check your throttle position sensor for loss of signal and corrosion/poor connections in the harness, Check the ECM power connections between the battery box and ECM for corrosion or loose connections, Check the cam sensor and harness for loss of signal or erratic signal and it would be worth while to read live data with Cat ET connected to monitor what is happening with the sensors etc when this problem occurs. Also reflashing and updating the ECM software for test purposes might not be a bad idea or if you have access to a test ECM. Be sure to check all grounds which could cause a lot of odd things to happen. Let me know

Customer: replied 9 months ago.
Throttle sensor itself is new. Have had alot of wire issues under cab and between ecm and ignition. Ecm is new (2x) all wiring harnesses from ecm to engine as re new and the harness on cab side of ecm is new. Cam senior is new as well as ambiance air senior and temp sencor. What is a "cat et"? Would I be able to leave it in going down the road for an extended period of time? Grounds have all been checked and cleaned.
Expert:  Daniel Wilson replied 9 months ago.

Cat ET is the diagnostic software for Caterpillar programmed into a laptop that plugs into the diagnostic connector using a communication adapter between the truck and laptop. If you know a shop that has this or a scan tool that will read live data. The Cat ET setup is pricey. You can go on Ebay and buy a Launch brand reader and if you have time to wait buy it from a China seller to get it at half the money. I got one on my road truck and it works great.

Customer: replied 9 months ago.
It would have to be connected going down the road and be able to record data for long periods of time. Every time the shop hooks the computer to it everything checks out ok (stable environment) and I can't make it act up.
Customer: replied 9 months ago.
I've been fighting this for 2 years. I've been to 8 different shops. Everybody checks the same things as what you are discribing. But I think you might be on to something with the throttle harness. Seems like when it acts up I push the throttle down and there is nothing there. It will flutter and almost act like it's applying the breaks. It will drop the front end instead of picking it up.
Expert:  Daniel Wilson replied 9 months ago.

Thanks for the update. Check the engine brake circuit as well. It sounds like you might have the engine brake coming on or sticking when it should not be. Watch to see if this happens with the engine brake turned off.

Customer: replied 9 months ago.
Circuit was just replaced. Turn Jakes off sometimes it seems to get better other times doesn't make a difference. Could it be effecting the abs? Seems like it wants to pull to the left if it gets bad enough. Had this same problem with my kw with the n14 in it. It's possible I have more than 1 problem but when it runs good all the symptoms go away. I've noticed at its worse the air dryer does not purge
Customer: replied 9 months ago.
It will also steer hard and get a shake. But it gets better if I use lots of air (dump bags, slam on brakes, etc.) Last night it was 20 degrees and dry. It ran good. But was making a howling noise. Seems if the noise is than it doesn't feel like the brakes are applied.
Expert:  Daniel Wilson replied 9 months ago.

Thanks for the update. I think you have multiple things going on. For the engine, if the fuel system tests good and the injectors test good after being tested with Cat ET software plugged in and they pass then I recommend having the valves, injectors, and jakes adjusted and the jake housings inspected for leaks and possible sticking plungers, etc. With the valve covers off and engine idling you can test the jakes by pressing the center of the solenoid one at a time to see if they are sticking or working properly. As far as your vibration, Check your suspension and steering components, driveline components and input and output yokes for looseness, center bearing, engine and transmission mounts.

Related Medium and Heavy Trucks Questions