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Cat Man
Cat Man, Cat Engine Expert
Category: Medium and Heavy Trucks
Satisfied Customers: 8418
Experience:  I am ASE Master Truck Certified.
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I am having a timing problem with a c15, 6nx50341 6nz It's

Customer Question

I am having a timing problem with a c15
JA: What is the complete model and serial number of your machine?
Customer: 6nx50341 6nz It's in a peterbilt
JA: Are you fixing this yourself? What have you tried so far?
Customer: I unframed it and can't get the timing right it smokes white really bad and backfires wondering if I put cam gear on 180 off
JA: Anything else you want the equipment mechanic to know before I connect you?
Customer: I moved the gear a tooth and it helped a little but didn't fix it. Needing to go 1.4 degrees retarded
Submitted: 1 month ago.
Category: Medium and Heavy Trucks
Expert:  Cat Man replied 1 month ago.
Thanks for asking your question. I will try and help you out.
If it were 180 degrees off. The engine would not run. I'm sure it's not 180 off.
Did you put a bolt in the flywheel and then line up the cam gear timing mark to 12 o'clock on the cover mark?
Customer: replied 1 month ago.
I did
Expert:  Cat Man replied 1 month ago.
Thanks for the information.
Then it sounds like the timing is correct.
You most likely have another problem.
Was the engine running good before rebuild? Have you verified you were given the correct parts?
Customer: replied 1 month ago.
No it blew the rings out of a few holes. Had lots of blow by. But found the rings to be a problem.
Expert:  Cat Man replied 1 month ago.
Thanks for the information.
Are there any codes? Has the fuel pressure been checked?
Customer: replied 1 month ago.
How critical is the timingcan you be off a tooth and it run fine? Fuel pressure is at 100psi
Expert:  Cat Man replied 1 month ago.
A tooth off will not cause the engine to do that. Not critical.
Is the pressure 100 at idle ?
Customer: replied 1 month ago.
that at a idle? What the max pressure I can run? 150? I'd like it at 130 at 900 rpm. Or will it not run there?
Expert:  Cat Man replied 1 month ago.
Thanks for the information.
You should have around 75 at idle and up to 95 at high idle. No more is needed.
If you have 100 at idle. You may have a return line restriction. This can cause your problem. Return line restriction causes the fuel to get hot and aeriate the fuel. This will cause your problem. I would make sure there is no return line restriction.
Customer: replied 1 month ago.
OK. I reversed the flow also. Ran 1/2 in to rear of head then where the steel line end ran 3/8 to filter base
Expert:  Cat Man replied 1 month ago.
I see. That may be causing your problem. I would run it back the way it was.
Customer: replied 1 month ago.
I can try that. But I know a guy who does it all the time.
Expert:  Cat Man replied 1 month ago.
I see. May I ask why? That's a new one on me.
Customer: replied 1 month ago.
Get more fuel to injectors to many times there's not enough to return some. Were going for a little higher horsepower than stock
Expert:  Cat Man replied 1 month ago.
I see.
You may also want to verify they gave you the correct parts. I've seen the wrong camshaft cause a problem just like yours.
Customer: replied 1 month ago.
It's a stock cam. Same one I had.
Expert:  Cat Man replied 1 month ago.
I see.Next I would check for air in the fuel. Possibly getting past an injector. Or a JAKE brake sticking.
Customer: replied 1 month ago.
OK I did put new I injectors in I lubed the orings and pushed them all the way down by hand then bolted them down.
Expert:  Cat Man replied 1 month ago.
Yeah it's rare. But you may have gotten a defective head and the injector is not seating good.
Customer: replied 1 month ago.
Can cat et tell you the story?
Expert:  Cat Man replied 1 month ago.
having ET connected to the engine will help diagnose

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