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Engine Driven Fuel pump failure scenarios?

C

crabandy

Well Known Member
O-360-A1F6D
Approximately 4 hours ago I
Had a 0 PSI annunciation for fuel pressure about a minute after swapping tanks to my MoGas tank. Turned on boot pump and swapped to 100LL tank and landed with no issues. I landed, turned off the boost pump and engine pump held pressure fine on the taxi in. Flew .5 home no issues, I concluded maybe winterblend mogas wi the the warmer temps was my issue.

Another couple hours flying and it happened again, 100LL in both tanks. 20 minutes after takeoff I got the 0 PSI Fuel Pressure. Boost pump on and swapped tanks brought the PSI back to normal. After 5 minutes I turned the boost pump off and Fuel Pressure was back to 0 within a minute. Landed and turned the boost pump off, it held fuel pressure on the entire taxi in

Engine ran fine without a stumble, but it was only a couple seconds from 0PSI annunciation to the boost pump on.

I’m used to fuel pumps on cars failing and staying failed, anything else to look for besides the fuel pump?
 
I have seen/had a loose fitting in the fuel system that would occasionally suck air but amazingly did not seep fuel (may have been above the fuel tank level). This caused all manor of unusual fuel flow and fuel pressure indications but did not actually show or feel , to the pilot, reductions in power (perhaps because actions of turning on the boost/aux pump, happened before a power change or interruption could occur).
 
At 0 psi was your engine producing appropriate power for your MP setting and fuel flow? Could you have a bad fuel pressure sensor?

I’ve seen 0 PSI readings on fuel pumps that were operating normally. Typically on aggressive full power climbs in winter

FWIW, I just replaced my fuel pump because it had been weeping oil and I got tired of cleaning up its mess. PSI output was fine.
 
Kyle Boatright said:
I've had a failure that exhibited the symptoms you had. A replacement pump made the issue go away.
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Same here (O-320 carb). You didn't tell us how old or how many hours on the pump but if it has 650 hours on it I would put a failing pump at the top of my list. I think resolving the issue with the boost pump makes it unlikely you have a fuel line problem.
 
Ive had a couple of failures as you describe...once it was the engine-driven fuel pump, once it was the red cube.
 
Thinking about the pump internals. Keep in mind I have a high pressure FI pump. The only failure I can think of would be a leaking diaphragm. This would cause the pump to leak out the small drain to prevent fuel from dumping in the crankcase. I had that failure. I don't know how a pump can fail with out it leaking out the drain. If the pump were to lock up and not pump it would break the arm. Do you have any fuel coming out the drain tube?
I got lucky and noticed mine dripping while refueling. Otherwise I would not have caught it other than a little larger than normal fuel burn as it dumped overboard.
 
When my low pressure pump failed the diaphragm was fine. I suspect a check valve got tired and failed to maintain pressure.
 
Sam Buchanan said:
Same here (O-320 carb). You didn't tell us how old or how many hours on the pump but if it has 650 hours on it I would put a failing pump at the top of my list. I think resolving the issue with the boost pump makes it unlikely you have a fuel line problem.
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Almost 700 hours……
 
Out of curiosity was there still fuel flow indicated? I suspect the answer is yes because the engine didn't quit.

Next time it happens (PSI - 0), don't do anything, just fly it until something else happens, namely the engine quits. If/when it does, you know it's a janky fuel pump problem. If the engine never quits with 0 PSI and FF still indicating "normal" then you probably have a failing pressure transducer.
 
bjdecker said:
Out of curiosity was there still fuel flow indicated? I suspect the answer is yes because the engine didn't quit.

Next time it happens (PSI - 0), don't do anything, just fly it until something else happens, namely the engine quits. If/when it does, you know it's a janky fuel pump problem. If the engine never quits with 0 PSI and FF still indicating "normal" then you probably have a failing pressure transducer.
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I got low fuel pressure readings with the electric pump off and in a climb. The electric pump restored pressure. In level flight the mechanical pump would maintain pressure, same in a descent attitude. But (minor change in head pressure, whatever), the mechanical pump wouldn't hold pressure in a climb. A new pump fixed things. Probably very close to 700 hours and 10 years in service.
 
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