Fuel PSI?

[Mike Schmidt]

I’m doing some low power troubleshooting and was wondering what the fuel pressure should be at the on-engine filter (6bta)?  I’m going to install a gauge there and it would be helpful to know how to go about this (e.g., what is the target PSI and what RPMs should I be measuring)?

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[Mike Schmidt]

Ok, thank you – I’ll check this next.  

Also, what do you think about the small bubbles in the squeeze bulb hose line?  Seems to me that the Racor introducing air would be unlikely, so I’m guessing these bubbles are not the likely culprit…

[Tony Athens]

Install a liquid filled 0-50 PSI -ish gauge on the on-engine fuel filter–If you maintain over 15PSI at all times on the outlet side of the fuel filter, then getting fuel is not the issue. Use a long fuel hose with at least one loop (Add some engine oil into the hose) to the gauge to eliminate pulsations….

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[Mike Schmidt]

Well, I’m at a complete loss here.  My 330 6BTA engine is only hitting 2400WOT with typical white smoke (nothing crazy), where it was previously hitting 2850 with the boat similarly loaded.  I went through Tony’s “low power troubleshooting” and mostly everything checks out (exceptions here is where I really need help!).

1. Throttle and fuel solenoid control linkage checks out
2. Racor AND on-engine fuel filters replaced
3. Added a fuel vacuum gauge after filter change and levels our fine (~3Hg)
4. Checked for air leak in fuel line from tank to Racor (added section of clear hose to check for bubbles).  No bubbles seen here
5. Checked for air leak between Racor and engine (to see if Racor was introducing air).  I checked this by installing the squeeze bulb priming system which included a clear hose bypass to the squeeze bulb.  NOTE that I did see some bubbles in this line, but after researching the issue it seem that it might be normal/acceptable to see some bubbles due to low pressures created in the fuel due to flow through fittings.  
6. No fuel leaks are appearing at the combo block or connections at the engine
7. I wanted to install a pressure gauge at the on-engine filter but I didn’t have the right adapter to take out the port plug (frustrating)!  I’ll get this done, but I don’t even know what PSI to look for so any help here would be appreciated.
8. Strobed tack and is accurate

After all this there is no improvement.  What do you all think – especially regarding #5 and #7?  If air in the fuel line is not an issue and the PSI checks out, then what’s the problem???

Also, not sure if this is relevant, but I did add the fuel cooler bypass shortly before this issue presented itself.  I don’t know if the engine every operated correctly after this mod because I think I just tooled around at ~1300RPM a few trips out over the course of a few months, then then once I opened up to WOT I noticed the problem.  When running slow there are not symptoms.

 

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