6.4 PSD Fuel Pressure

Advice Needed
1

The truck had the head gaskets replaced and a new turbo installed about two years ago. However, over the last month, I have noticed it “surging” and lacking power at wide open throttle (WOT).

I used the Torque Pro app to monitor the fuel pressure. At WOT, the pressure starts around 23,000 psi, but when the power drops and the surging occurs, it falls to between 10,000 and 13,000 psi.

The mechanic suggested that the turbo might be dirty and needs cleaning due to infrequent use. However, I am starting to think the fuel pump might be failing. Does anyone have other insights?

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2

Does it still have the factory lift pump? It might be experiencing low supply pressure to the high-pressure fuel pump (HPFP).

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3

Indeed. factory original housing, pump, etc. At first, I believed there was a problem with the fuel pump. Is that even feasible?

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4

Yeah, the lift pump is faulty and could damage the high-pressure fuel pump (HPFP).

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5

Spread pins are a typical feature of harnesses. On 6.4’s, pumps don’t break down. Under the valve cover on the right side, install a new injector harness and fuel pressure sensor.

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6

I recommend changing the fuel filters as soon as possible to see if that resolves the issue. When I first got my 6.4, I experienced something similar. If you have changed them recently, it might be due to dirty fuel, so it would be a good idea to replace them again.

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7

I did change them last week. No noticeable change. Filters were not particularly dirty when I changed them.

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8

I would check the fuel pressure for the HFCM (low-pressure pump) before it reaches the fuel cooler. Make sure you are getting between 3-8 psi. You will need to disconnect the line and find a way to rig a gauge to it. I usually use a fuel pressure gauge from Harbor Freight.

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9

Its ability to idle and operate satisfactorily at low speeds suggests that it is receiving enough low pressure pump power, doesn’t it?

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10

The only way to know for sure is to measure it. Everything else is speculation. If you can rule out the HCFM, then you move up to the HPFP, FRP, etc…

If I can figure out how, I will send you the shop manual(s) on fuel system troubleshooting.

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11

Thank you. I am having a hard time believing the mechanic when they say, “turbo dirty,” especially since the boost is smooth and the fuel pressure is dropping.