720 d fuel pressure

JL2510 · Jun 28, 2020

I just had my engine apart on my 720 diesel. I'm having a time getting the fuel system bled. It seems to be running on 2 cylinders now but im showing 0 fuel pressure at the filters. The transfer pump and return fitting were recently rebuilt.

Think I just need to bleed it more?

Is it possible maybe the return fitting has dirt in it, holding it open at that might not be letting it build pressure? Or is that not how it works?

wore out · Jun 28, 2020

Is it returning a significant amount of fuel? If returning fuel it is getting through adapter or relief valve without building pressure, if little or no return, the transfer pump may be weak.

I can't remember the exact details, but there was an "upgrade" kit available to a different pressure relief valve, raised fuel rail pressure, IIRC?

You mention having the transfer pump "rebuilt", what was done, new gear/shaft to seal it up? Really nothing else that could be done if the housing is worn?

JL2510 · Jun 28, 2020

The early 720s had lower fuel pressure and no return line to the tank. The later ones and the 730s had higher pressure and a return line. Mine is an early 720 but I upgraded everything to the new style, high pressure set up and sent my transfer pump to Renaissance Tractor for rebuilding. I forget now what he did but he said he was getting 45psi out of it. I'm showing nothing now though.

wore out · Jun 29, 2020

So, have you checked, is there a significant return flow coming out of the valve?

720 d fuel pressure

JL2510

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wore out

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JL2510

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wore out

Well-known Member

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