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Engine Fuel Pump Failure

Fuel Pump Autopsy

I cant say I found anything outwardly wrong with it and given the intermittent nature of the problem, I am not surprised. Nor would I ever profess to have ANY idea of what I was looking for other than something obvious.

More hours on the new pump with the same observation; the pressure is a steady 10psi above where it was before the swap without any wavering.

Here are pictures of the inside of the fuel pump.

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Thanks for doing the autopsy! One more thing you ought to do is take apart the check valves. You'll need to grind away the stakes helping hold the valves in place. I suspect your low pressure problem is due to check valve internal leakage.

Heinrich
 
One data point

I read this tread with interest. My pump had 1200 hours on it when it started having fluctuations just like others observed. The pressure would start and 24 psi and drop to as low as 20 psi. I had the warning set to come on at 21 psi so it kept getting my attention!

I checked the hoses and electrical connections and all was well. Being like minded with Walt, I replaced the pump. The only difference now is the fluctuations begin at 25 psi, one psi higher than the old pump!

My guess is the new pump's additional psi is due to it having 1200 less hours on it. I was hoping you gents would have solved this mystery for me, but I guess I'll have to keep looking.

Anybody interested in a slightly used .... ERR.... well tested Lycoming fuel pump that puts out 24 psi?
 
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Another data point

Like Danny I was getting the fluctuations in the exact same range. I installed a Tempest pump and now see 27.7 psi or more!

I dare say that I found the smoking gun and I am thrilled with the results!

Danny, which pump did you buy? Did you get a Tempest?

Anyone interested in buying a slightly even less used pump with 700 hours on it?

:cool: CJ
 
Like Danny I was getting the fluctuations in the exact same range. I installed a Tempest pump and now see 27.7 psi or more!

I dare say that I found the smoking gun and I am thrilled with the results!

Danny, which pump did you buy? Did you get a Tempest?

Anyone interested in buying a slightly even less used pump with 700 hours on it?

:cool: CJ

I replaced the original Lycoming pump with a Tempest. Today's flight the Tempest was putting out 27 psi and only deviated lower by 3 psi. I'm happy now.
 
I replaced the original Lycoming pump with a Tempest. Today's flight the Tempest was putting out 27 psi and only deviated lower by 3 psi. I'm happy now.

Great - now cover up the fuel pressure gauge and don't look at it anymore! Given the number of people who've posted similar fluctuations, I'd say the fluctuations are not completely unexpected. I've had the drops into the mid or lower teens show up from time to time for 16 years, two different pumps. Engine has never coughed. Current pump is a Tempest, but it is 10 years old so I might swap it out.
 
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