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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3362
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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My 2004 Peterbilt 379 caterpillar c15 is having starting

Customer Question

My 2004 Peterbilt 379 caterpillar c15 is having starting issues. No power issues when running, but starting it has a problem. When turning the key, sometimes just a click happens with no turn of the starter happens once every 30 times a start is attempted.
The normal reaction is that the starter is turning and trying to start motor but it wont turn on, if I try to turn it on 5 times maybe once it will turn on. We replaced the starter relay because it went out by starting to click really fast and then just stopped
making any noises and starter would not turn. We replaced the starter even though no real problems were occurring with it. However when the starter was replaced the motor was turning on every time for about an hour and then it went back to normal. Normal as
in turning on a couple times out of ten tries. Replaced both filters and the union for hoses from tanks to the filters that was leaking diesel. Took truck to shop, once I got to the shop the truck was turning on correctly about 20 times straight so I took
it back home about 30 miles. Then waited two hours and it started have the starting issues again. What do you advise?
Submitted: 2 years ago.
Category: Medium and Heavy Trucks
Expert:  Jeremy replied 2 years ago.

My name is ***** ***** I will assist you.

Have you tried changing the solenoid in the battery box to see if it resolves the issue you are having? Most of the Peterbilts have a solenoid mounted in the battery box.

When you say the truck won't start, does the starter rotate and it won;t fire or the starter kicks and won't rotate or the starter isn't even rotating when this issue happens?

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Customer: replied 2 years ago.
Have not tried changing the solenoid in the battery box, I think I have seen it with a good sized fuse covered with a protector on top of batteries. When I try to turn it on the starter rotates and tries to turn on but most of the time it doesnt turn on. Its not a slow turn its a normal good turn by the starter.
Expert:  Jeremy replied 2 years ago.

So you are getting starter rotation, just not getting a engine run. I believe I am understanding you correctly?

Do you have a check engine light?

Do you have fuel in the filter and fuel getting to the engine?

Customer: replied 2 years ago.
iam getting starter rotation and it will turn on like normal every now and then. But for the most part the starter just keeps turning, eventually after another 5 or 10 tries it will turn on. It will turn on with starting fluid pretty quickly though. I replaced both filters as well. Did get the pid 385 fmi code and replaced both sensors. Problem still exists, I feel like its getting air from somewhere but cant find the spot.
Expert:  Jeremy replied 2 years ago.

Sounds like you are describing a fuel problem.

Does this happen with fuel tanks being full, at a certain level, it doesn't matter if full or near empty? I ask because Peterbilt tends to have problems with the pick up tubes inside the tanks cracking and they suck air there. I want to rule that out.

Next is to go under the truck on the frame between the 2 tanks and see if where the fuel line comes off the tank to that valve there, see if that valve is leaking. It has o-rings inside where the lines attach and I've had the o-rings go bad over time and cause leaks.

Next is if you have that little heater warmer on the driver frame with the little filter, bypass it and see if the problem persists. I've had the heaters suck in air and cause a lot of problems on these engines.

Last is on the rear of the head is the fuel return. That is the regulator. It goes bad often on these engines and it will cause the fuel to not pressurize in the injectors properly and cause EXACTLY what you are describing. It is a little harder to get to and that is why I list it last so we can rule out error, even though it is the most common problem I;ve had with these engines doing what you described. The regulator will stick and you will get hard or long starts, then suddenly no issue and then a issue again until you crank a few times. It is highly common on these engines to do that.

Expert:  Jeremy replied 2 years ago.

I'm mistaken on the regulato location for this engine.

It is located underneath the secondary fuel filter housing. It's near the back side and is near the fuel return line. It looks like a plug and it is about 1 inch in size.

Most likely it is the culprit because when the engine is off, it leaks down the system fuel and is causing the issue you are having. I would actually change it first and then check for air leak issues. I got this confuse with the non ACERT engine, which has it on the back of the engine.

Customer: replied 2 years ago.
Ok I will check tommorrow on those possibilities and fill you in. I havent check those so might be one of those.
Customer: replied 2 years ago.
Secondary fuel filter is which one? Outside frame or one attached to motor?
Expert:  Jeremy replied 2 years ago.

The one attached to the motor.

Customer: replied 2 years ago.
Ok will check
Expert:  Jeremy replied 2 years ago.

Let me know, thanks.

I have a onsite service repair at 0700 and another at 1000 setup for me tomorrow. I'm eastern time. I will try to check in between those times. Thanks.

Expert:  Jeremy replied 2 years ago.

I'll be on after the second one for I will be getting off after the second one. Shop is closing for a repair tomorrow at noon and the weekend. We're getting the floors striped so I'll be online (hopefully) from about 130pm on. Thanks.

Customer: replied 2 years ago.
Ok yea iam central time I should be going through the potential fixes on the truck all day and will let you know.
Expert:  Jeremy replied 2 years ago.

Ok, thanks.

Customer: replied 2 years ago.
I changed some engine harnesses and will change another one tommorrow. Found alot of worn and broken harness wires up to injector area. Will keep you updated. Changed leaking hoses and check pickup tube no cracks and also had tank filled up to be safe. Still same problem
Expert:  Jeremy replied 2 years ago.

Just checking to see how things are going.

Customer: replied 2 years ago.
First mechanic gave up and brought it back to us now taking it to another because we cant figure it out