Priming the C12

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JonM934

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I accidentally let some air into my fuel line and now the truck will not start. I think I found the priming pump but I do not know where the bleed screw is. Can anyone help me out with step by step instructions for priming the C12 with photos? Or if you have the MK23 repair manual I would love that!
 

MAdams

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I changed both my fuel filters(pre filled them before install) and my truck fired right up. There should be plenty of good info on the internet about priming a C12. They're a popular engine
 

JonM934

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I searched the internet but it seems these engines are not exactly like the civilian models. The youtube videos show engines that I see look close but it is not the same as my engine.
 

snowtrac nome

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the fuel system is a common rail style so you just pump the primer and the air will return to the tank through the return line, you can also crank it to force fuel through, it is self bleeding but its hard on the starter.
 

JonM934

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snowtrac nome, I agree with what you are saying. The problem is the pressure regulator will not allow fuel to pass until it has built up a lot of pressure. I tried to use the prime pump and I even backed out the regulator bolt to bypass it but the fuel is not flowing. It might be that the prime pump seals are shot. On the internet I see that is a common issue.

I also tried cranking and I cranked for a long time, pausing every 30 seconds as the manual says to. But still no luck.

I have found a mobile diesel mechanic that is an expert in Cat engines and he is going to stop by tomorrow. While he is here, I will ask him some other questions that I have.
 

snowtrac nome

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I've never messed with the c 12 engines bit the c-9 s I messed with I have blead them that way. The excavators all had an electric pump on them to bleed them. if I had to I would likely crack a line where the fuel enters the head , once you have fuel to the gear pump it will push through about anything
 

JonM934

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The mobile mechanic stopped by and we could not get the truck going. There was air getting into the line somewhere. It must be the water separator but we could not figure it out. He did tell me a lot of interesting things about the truck. One thing he pointed out to me was the Ether assist to get the truck started when it is cold. I always wondered my the truck was so easy to start when it is so fricking cold outside. Now I know why. I guess I need to replace the Ether can once in a while.
 

JonM934

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I got my truck started and I can drive it again!!

So I found a lot of instructions on the internet and even in the MK23 reference manual that is in the upload section. Most of it was wrong. I needed to take bits and pieces from many sources to finally figure out the proper way to prime this machine. I will make a video about it because it is complex.
 
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