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Replaced Fuel Pump Now Higher Pressure. Help!

Geico266

Well Known Member
Thanks for looking. I need some expert advice.

I replaced my old LW-15472 engine driven pump with a Lycoming #62-B26931. The pressure was 24 PSI, now it's 31 PSI.

IO-540 with a Precision Airmotive FI system.

Are there 3 difference pressure for pumps? I thought there was just a high & low PSI engine driven pump.

Any help or clarification deeply appreciated.
 
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I don't know what the spec's are for that pump series, but guess it may be 25-30. Many see pressures around 26-28 at times, especially when new. It definately won't hurt a bendix style servo, as they can handle a range of about 14-50+ PSI. The pressure is maintained via a small bypass disc and spring. Easy to see how the manufacturer needs a range to deal with tolerances.

The pump on my 540 gave closer to 27 when new and after several hours now gives a consistent 24.

Larry
 
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I don't know what the spec's are for that pump series, but guess it may be 25-30. Many see pressures around 26-28 at times, especially when new. It definately won't hurt a bendix style servo, as they can handle a range of about 14-50+ PSI. The pressure is maintained via a small bypass disc and spring. Easy to see how the manufacturer needs a range to deal with tolerances.

The pump on my 540 gave closer to 27 when new and after several hours now gives a consistent 24.

Larry

You are right on!
I just screwed up by paying $200 more for a new pump when I could have had a rebuilt Tempest. Live and learn.

My FP symptoms were the pressure was slowly degrading from 24 PSI to around 20-21. It was 13 years old and had 1100 hours. Time to replace it.

Thanks!
 
The pressure is maintained via a small bypass disc and spring.

No bypass in an engine driven diaphragm pump.

The pressure was 24 PSI, now it's 31 PSI.

In general, Bendix style systems specify pressure between 20 and 50 psig, and will operate from 15 to 80.

Here's a little song I wrote
You might want to sing it note for note
Don't worry, be happy
In every life we have some trouble
But when you worry you make it double
Don't worry, be happy

Bobby McFerrin
 
Might not be an issue. For a lot of the common IO-540s used in RV-10s (eg C4B5, D4A5, etc) the max pressure to inlet of the fuel pump is 35psi and to the inlet of the fuel injector is 45psi.
 
Might not be an issue. For a lot of the common IO-540s used in RV-10s (eg C4B5, D4A5, etc) the max pressure to inlet of the fuel pump is 35psi and to the inlet of the fuel injector is 45psi.

assuming you mean inlet of the servo and not fuel pump. That may be lycoming's spec, but they don't make the servo. Don from AFP (one of the most knowledgeable out there on the Bendix servo) says well in excess of 50 PSI is fine.

Larry
 
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assuming you mean inlet of the servo and not fuel pump. That may be lycoming's spec, but they don't make the servo. Don from AFP (one of the most knowledgeable out there on the Bendix servo) says well in excess of 50 PSI is fine.

Larry

Okayyy—I think you misunderstood my post. My point is the specs out of the operating manual (the way I posted it is the way the manual words it) indicates that a higher mech pump output psi is probably a non-issue. What you posted supports that supposition.
 
I called around nd several said it would be fine. Buttoned it up and flew it. Rock solid at 27-30 PSI. Just never saw that high of pressure before.

Thank you one and all for responding! :D
 
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