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Junior Member
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Discussion Starter #1
A freind of mine has a truck with this motor in his shop. He had to rebuild it. It got hot, scored a piston and cracked the back head. He put new cylinder kits in, rod and mains and a reman. back head, and the owner wanted new injectors also. He has it running and it runs awful. It just seems like it is getting way to much fuel. The injector rebuild shop gave him a new set of injectors (rebuilt) He checked with the injector shop and a cummins shop to make sure he is installing the injectors correctly and he is and the truck still runs terrible. It fills his shop with smoke and raw fuel.

He was wondering if something could be wrong with the fuel rail going through the back head or if something could be missing like a check ball in the new head allowing to much fuel to come in???

He is a good mechanic but he is stumped, so he called me to see if I could get online and find something out.

I have probably said a few things that don't make since. But the problem is way to much fuel. Any thoughts before he pulls out the rest of his hair.

thanks Mike
 

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The cpl 1210 is a stc timed injector.This means it has tappets in the injectors that advance the timing with oil pressure.It needs 50 or above of oil pressure to advance at idle or in a low power setting to clear the white smoke. If not it will be in a retarded mode and will smoke and miss when cold.A common thing i have found is oil pump sucking air at the oil pump pick up tube. Start and look at the oil leaking at the rockers and over head for air in the oil. Some times guys will forget to put the gasket in the top connection on the oil pump pick up tube or leave the bolts loose at the oil pan at the oil tube connection to the pan.Also not knowing how to set the injectors can be a problem.I like to add a update which is a oil pressure sensor kit to the stc circuit which helps bring the oil pressure up higher at cold idle but lets it go back to 40 psi when warm.
 

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If the engine has STC then when you assemble it, before you put on the rocker box's, what I do is fill the wish bones with ATF, and that way if there is a leak you can find it and fix it. That includes new injectors, if they leak replace them.
To stop the smoking, just have him park it away from vehicles and bakeries and put a stick on the throttle for 1/2 hour at 1500 RPM and above.
 

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Discussion Starter #4
Thank you guys for the replys

I called my buddy first thing this morning. He decide over night and after I read him your post that it is a oil pressure problem.

When the truck came in it had 50 lbs oil pressure at idle even with all the problems it had. After he rebuilt it he said it took awhile to build up oil pressure when he first started it (he is pretty worried about this) And when he runs it now it doesn't get past 20 psi. Which means like you guys said the injectors are not getting the proper oil pressure. He went out in his shop right after I called and he is going to look for the leaks you guys mentioned.

My buddy has been doing this all his life and is good at what he does but he has not worked on many trucks with the STC injectors. He is worried that it might of spun a bearing causing the low oil pressure.

When it is running, missing and smoking he says the oil pressure is low enough that the oil pressure warning light is faintly coming on. 20 psi or less.

He said he used good assembly lube on the crank but that doesn't last forever

Thanks again for your help

I will let you know what he finds out
Mike
 

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Those engines do have a problem, with the oil pump, It will spin on the drive shaft. They will walk forward, and disconnect from the PS pump.
What I would do is check the pressure with the compucheck fitting on the right side, If it is low, then remove the oil pick up off the pump and with a bar try and turn the oil pump gears if you can then, that is the problem.
Just a thought!
 

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Before you do any thing go under the front of the engine and look up at the oil pump. There is a 5/16 bolt holding the pressure regulator valve and spring in the pump. Remove this and dont loose the spring. Clean and put back in and check. This is a common thing on a cummins after over haul. Some dirt has goten in the valve and locked it open. It happens to the cleanest guys working on trucks.If it has spung a rod brg you would not need some one to tell you.
 

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Discussion Starter #7
I went over to my buddys shop yesterday and he was just buttoning up the oil pan again after looking at all the rods and mains. They were all good, so we took the oil pump off and sure enough there was a piece of probably the scored piston holding the relief valves plunger open. A little diamond shapped piece of metal about 1/16" across.

I must off left the house just before theakerstwo posted about just pulling the plunger out instead of taking the entire pump off.

We had to go get gaskets, so he is putting it back together today.

I will post the good news after he has it all back together. I am just the middle man here but I would like to say for my buddy that he really appreciated the info.

Thanks Mike
 

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Discussion Starter #8
Well He put the oil pump back on. Turned the key, it smoked for about a second oil pressure shot up to 50psi and the truck purred like a kitten, no smoke and smooth!!

Thanks Again for the help

Mike
 
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