My Low Fuel Pressure Fix, 0-360

[guccidude1]

I found that not all low pressure fuel pumps are the same about a month ago. On the go from a low approach, my engine started running very rough and losing power. I pulled up and, while turning into the downwind, went through engine failure EPs. Changing tanks and turning on the boost pump solved the problem. Troubleshooting the problem after landing, I determined that my mechanical fuel pump had failed. This fuel pump was the Lycoming pump with the laminated arm, not on the SB for replacement. I ordered a newTempest AF 15472 channel arm model and installed it and it did not work. No pumping action whatsoever. Removing the pump and reinstalling, I did determined that the pump would pump residual fuel halfway across the hangar by hand actuation. But there was enough slack in the lever that, approximately .75". My fuel pump push rod extension was approximately the same, therefore the push rod extension maxed out before the pump lever began its pumping action. I called Tempest and explained my problem and the teck rep suggested I replace the channel lever pump, the new model, with a laminated lever pump, a discontinued model but still available as a rebuild only. See part 2.

 

[guccidude1]

My Low Fuel Pressure Fix, 0-360, part 2

I replaced the new Tempest with a rebuilt 40295 pump. after installation it worked perfectly. Here is where it gets unsettling.Since new, my Dynon 180 fuel pressure had been low, less than 1 psi in all phases of flight, even down to .4-.5 psi on occasion. I followed the discussions on this forum that indicated that it was probably a sender calibration problem. I accepted that. Like others, I had high EGT(1450) and Cyl temp readings(430) on takeoff, so I developed the technique of climbing at 110 KIAS, 500' leveloff and let the cyl temps cool to 390 then contiuing to climb on reduced power. In cruise the cyl temps were 395 +/- 10 all cyls at 2500 rpm at 10500' lean to ROP to peak. With the new fuel pump, my fuel pressure is now 2.3 on full power takeoff, EGT 1340, Cyl temp 380. 345 +/- 10 for all cyls in cruise at 2500 rpm at 10500'. I think my original fuel pump was only partially pumping for the last 5 years and the pressure sender was correct. I was starving the engine for fuel on max power settings. If you have low fuel pressure readings, you might want to investigate a little further. Dan

 

[mspenc45]

Low, but not all the time!

I just purchased my RV-8 with an O-360 A1A experimental from Mattituck. I noticed in my first cross country in her that my fuel pressure dropped to 2PSI in climb and cruise and hit the chatter pump which immediately raised it to about 4PSI. When I turned off the chatter pump, the pressure would fall back down until later in the flight when it began to stay at 4PSI. I have flown her around local the last few flights with very little fuel and no problem. Today I filler her up and I am back to needing the chatter pump on to maintain 4PSI. I run about the same CHTs as what Dan states. Wondering why this might be happening when tanks are full?