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Fuel Pump problem

pilotmansam

Active Member
Looking for an opinion / help. I am a new RV-6A owner - non-builder. So far have about 35 hours on the plane. 0-320 standard carb standard mags set-up. Last week-end I flew in a "missing man" formation for an amazing vet (another story). Anyway we were at low altitude for maybe 45 minutes waiting for the word to do the pass. Had the aux fuel pump on all the time (Facet automotive type). Later flew to another airport for gas. Upon takeoff engine almost quit during roll when throttle was full open. Also thought I smelled something hot! :eek: Shut it down, but could find nothing obviously wrong. Did another run-up with aux pump on and it almost quit again. Aux pump off, all seems OK. Is there any way one of these pumps could fail is such a way?
 
The Facet pump is a continuous duty pump so it should not hurt anything to run it all the time.

These pumps are dirt cheap so if there is any question at all about if it is good or bad, replace it.

The heat soak after prolonged low and slow flight and then a refueling is just about the worse case for an RV engine. Do you have an EMS system to monitor temps?

Sounds to me like you experienced the fuel flashing to vapor in the lines, gascolator, carb or similar. Typically though, the boost pump helps this situation but it might have been causing vapor lock.

How good are the baffles? Do you have a blast tube on the engine fuel pump? Do you have a blast tube on the gascolator? How well protected are your fuel lines from exhaust heat?

Please do a fuel flow test on the ground and do not fly again until you find the smoking gun. I also suggest you find someone local that is knowledgeable with RV's and have them take a look.
 
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I agree totally with Brantel, here's what I would do before I fly it again:

1) Replace the pump.
2) Clean all fuel filters.
3) Check Fuel flow at Carb with electric pump
4) Check all fuel line fittings and B nuts are tight.
 
Float valve in the carb? Sinking float? Flaky float valves can sometimes be overpowered by excess fuel pressure. The symptom would be running too rich as the bowl fills up & begins to flood the engine. Sinking float could cause the same symptom, & there are AD's on carbs for sinking floats.

If you can duplicate the symptom on the ground, check fuel pressure to see if it's stable & at its nominally higher level with boost on. If it drops with boost on, bad boost pump (though that one is hard to imagine, unless it's hanging up internally somehow). If it's higher with boost on, I'd suspect the float valve or float itself in the carb.

Charlie
 
I had a similar problem back in January. My issue ended up being I was running winter grade auto gas on a warm January day. The engine was running fine until I applied full power after a brief shut down. The engine died just as if I had pulled the mixture control. Since then I have been running nothing but 100ll and the issue has not showed back up.
 
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