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starting a 1971 cummings short cam

Posted By edshiffman Monday, March 28, 2022 11:01 AM
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edshiffman
 Posted Monday, March 28, 2022 11:01 AM
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Last Active: Monday, March 28, 2022 10:57 AM
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My cummings was running at the start of fire season last year. When I got back after 8 weeks it fired once and died. Since then I have rebuilt the fuel pump, replaced all the steel fuel lines, changed both filters and turned the screw on the fuel pump to bypass the shut off cellunoid. It fires on ether but will not start. I had a mechanic run the rack last year. Do I need to deal with bleeding air on this common rail set up? I am out of ideas.
jimfols
 Posted Monday, March 28, 2022 3:03 PM
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A lot of things were done but no time frame is given.

Did you fill the new pump with fuel?

Why were the fuel lines changed?

Is the fuel feed line connected to the bottom fitting on the head?

Don't know when your fire season is but 8 weeks seems like a short time for no start.

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Jim
eshiffman
 Posted Tuesday, April 19, 2022 10:53 AM
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I changed the lines into the head because I wanted to bleed any air in there and the nuts were rounded off so I could not remove them. I have fuel to the pump, 120 psi cranking it and using ether and fuel runs out of the lines into the head. I have used the screw to bypass the switch on the pump and with fuel leaking from the loosened line, I know it is getting up there. I disconnected the Jake switch also to be sure that was not the problem.
eshiffman
 Posted Tuesday, April 19, 2022 10:56 AM
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Our fire season last year was about 4 months and I went out in February for a fire near Bishop where I live. It popped once when I started it up but died and will not start. Runs fine on starting fluid. I also disconnected the decompression lever and manually made sure that is closed.
jimfols
 Posted Tuesday, April 19, 2022 2:03 PM
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Thanks for answering my questions.

The fuel runs through the injector all the time. This is why the system does not have to be bled. The injector takes what it needs from the fuel flowing through it.
If it is building 120 PSI cranking there is a restriction.
Judging by the fact that it runs on starting fluid, I would say the injector screens are plugged.

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Jim
eshiffman
 Posted Wednesday, April 20, 2022 4:34 AM
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Thanks, I will take a look at them
eshiffman
 Posted Thursday, April 21, 2022 10:58 AM
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I took the input line off from the head but there was no screen in there. How do I access the injector screen(s)?
jimfols
 Posted Thursday, April 21, 2022 12:34 PM
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The screens are in the injectors.

Please watch this video:

https://www.youtube.com/watch?v=KzuwdxEJfQA&t=265s

The injectors start at 23:00

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Jim
eshiffman
 Posted Friday, April 22, 2022 5:06 AM
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Thanks, great video. I am an old school gas engine guy and wonder if I should try to find someone who can work on this old engine.
I am guessing I access the injectors via the valve covers and will need to remove the tappets to be able to extract the injectors. Fuel lines will need to be removed to access the screens. Tappets will need adjustment on reassembly. Got the repair manual for this engine but it excludes the section on the fuel system and references a bulletin from Cummings.
Do I need to find an older mechanic for this or will any diesel mechanic know how to do this?
jimfols
 Posted Friday, April 22, 2022 1:15 PM
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It's not rocket surgery but it would be wise to find someone who has done it before.

Before that I think it would be wise to have someone diagnose the problem.

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Jim

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