7.3 intermittent knocking and fuel pressure.

Martyn

Supporting Sponsor, Overland Certified OC0018
With 250k on my 7.3 I wasn’t surprised when I started hearing some knocking from the engine. At first I thought it was time to replace the injectors but something told me to investigate further. As it turned out a good choice as performing that work would not have solved the problem.

After analyzing the problem I found a trend, it didn’t happen when the engine was cold, the knocking was intermittent, not rhythmical, and I had a higher than usual idle speed.

Luck was on my side when I did a Google search and the first link I clicked on described my symptoms exactly “Cackling or Knocking Noise” due to low fuel pressure.

Operating fuel pressure for a 7.3 should be 60-65 psi and mine was 30-45psi time for a new electric fuel pump. Further reading about the importance of fuel pressure also indicated that it might be time for a new fuel pressure regulator as well.

With both parts replaced my 7.3 is running smoothly again.
 

Ozrockrat

Expedition Leader
Also check the fuel filters in the tank pickup. Preferably remove them all together and put in a 100 micron filter/water trap before the fuel pump. Hit me with a PM if google doesn’t show you what I am talking about.
 

Martyn

Supporting Sponsor, Overland Certified OC0018
Also check the fuel filters in the tank pickup. Preferably remove them all together and put in a 100 micron filter/water trap before the fuel pump. Hit me with a PM if google doesn't show you what I am talking about.

Will do
 

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