2003 f350 7.3 cylinder compression help? - Ford Powerstroke Diesel Forum
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Old 11-07-2007, 09:16 AM
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2003 f350 7.3 cylinder compression help?

I'm in the process of buying a 2003 f350 7.3 diesel and needed some info on the cylinder compressions. I searched around, and found that supposedly, the "stock" cylinder compression should be around 425psi, and that a dusted cylinder would be more in the 200psi range?

After doing the compression test on the 2003 truck, the numbers were cylinder1 415psi, cylinder2 425psi, cylinder3 425psi, cylinder4 440psi, cylinder5 410psi, cylinder6 400psi, cylinder7 425psi, and cylinder8 375psi. I'm a noob at diesel engines, but using the normal gas engine compression rule of no more than 20% difference in compression across cylinders, this engine looks pretty good. However, I also am a little leery about cylinder 8 since the rest of the cylinders seem to be all up in the same tight range.

My question is, what is the cross over from good compression to bad compression in the 7.3? I thought I remember hearing numbers around 350psi for a cylinder is pushing it, then I read other numbers that say down in the 200psi range is considered a dusted cylinder. No one has a specific number to state. Can anybody help me out?
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Old 11-07-2007, 04:24 PM
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Those sound like pretty good numbers to me. You might check and see what the condition of the compressor wheel in the turbo is. If it shows some wear, then most likely dust got through the stock air box and into the engine. Honestly i wouldnt be to scared of buying that truck, sounds like the engine is in pretty good shape.
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Old 11-07-2007, 04:27 PM
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Hold on

Scuffy and i were just discussing this today as a matter of fact. I learned from him that 360 or less will cause a skip. All of them look ok except #8. I am used to seeing #5 go first but we have seen a run of engines lately with #8 issues.
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