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engine driven fuel pump gone bad?
I took off this morning to escape a cold Georgia day for the Florida keys.
Start up check. Warm up check. Taxi to fuel, check. Run up, check Take off all normal and green. Boost pump off 1000 feet, fuel pressure normal. Out of 5K for 9K, fuel throttle, 2700 RPM, I noticed the fuel pressure drops down to 12.8 PSI and starts floating between that and 13 PSI. Boost pump on, PSI back up to 25 PSI. Level off everything running normal. Shut boost pump off, fuel pressure drops to 18 psi and is varies one or two psi. Switched tanks with same results. Pump back on, back to the hanger. Before shutting down I did a static run up to fuel power. With boost pump on 25 PSI, when switched off it drops down and varies around 18-20 psi. Total time 180 hours. I think the pump is failing but its not old so checking to see if I should check other things before pulling it. |
Below is a recent thread, it pertains to a carbed engine but may make for interesting reading:
http://vansairforce.com/community/sh...highlight=pump Final solution was a new pump. |
Mine has done the same thing since day one, although usually a bit higher (more like 7000'): Nose up, full throttle/full RPM, and mixture FULL RICH. Solution is to lean a bit (needs it anyway), and/or go to cruise climb (MP top of green arc/2500 RPM): fuel pressure comes back up above minimum red line.
I have no idea why it does this. |
I?m guessing you fitted the fuel system per the Van?s plans - specifically the fuel selector valve, the filter, the fuel pump, the red cube flow sensor then through the firewall to the engine driven fuel pump. Is this correct?
Carl |
I know there has been some issues with the cube being installed before the mechanical fuel pump. My cube is between the Bendix Servo and the spider. I looked over the data log back at the house. All my previous flights fuel pressure were a solid 24-25 psi. Two years of flying no issue at all. It was the same today at start up. The log shows that it slowly began to drop right after shutting the boost pump off and really dropped between 5 to 7K feet. With a ground run the pressure drops from 25 to 18-19 psi when the boost pump is shut off. Hit the boost pump with the engine off and it pressured right up to 25 psi. So the sensor is working properly. Figure I just got a fuel pump that was a lemon.
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Yes, stock plans. I have the newer (circa 2008) fuel selector valve, mounted a little lower than the original. You thinking some vapor forming? I haven't noticed any temperature dependence.
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What was your fuel temp? I had a similar issue with ground OAT over 100 and the fuel heat soaked. Problem was worse at high flow during climb and went gradually away after on cruise at above 15 K and much lower temps.
I now leave the fuel pump on until established on cruise when the OAT is above 80 F and fuel is heat soaked. |
OAT at my airport was 45 degrees. CHTs under 400.
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If your fuel pressure gets to 12PSI the engine will stumble quite a lot. Perhaps you have a sender issue.
It is normal to run the boost pump in climb and in hot weather for a bit after TOC, especially if the plane has sat in the sun and the fuel is warmer. If the engine never missed a beat, and you have not commented on that (unless I missed it) then my first suggestion is the sender is faulting at lower pressures, but reading OK with the boost pump on. |
Togaflyer
Your comment “So the sensor is working properly.” maybe it’s working properly at one end of the range ? Is it a VDO type or something else like the Kavlico used in the Dynon systems ? If it is the VDO I’d bet it’s at fault :) hopefully it’s that simple & therefore cheap to fix. |
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