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In the past year I have had three instances where the engine ran rough and I beleived it to be the fuel pump. In November of 2016 on a trip to Plymouth, MA, while over southern CT, the engine ran very rough for a few seconds. All cylinder EGT's dropped during this time. I quickly switched tanks and turned on the electric fuel pump before I could run any diagnostics. By that time, the issue resolved itself. Two weeks ago on my trip up to NY, the same issue occurred - nearly 11 months after the first incident. Finally, the other day I was on a trip up to Massachusetts and after I leveled off at 7,500', my fuel pressure dropped to 16psi. I switched the electric fuel pump on and the pressure returned to the mid-to-high 20's. After I switched the electric fuel pump off, the pressure once again dipped to the mid-teens. After three instances of what I believe to be fuel pressure related engine issues under the mechanical fuel pump, it was time to swap it out. Removing the old fuel pump was relatively easy. Two allen key bolts and disconnect the plumbing. The old pump was a Tempest. I am replacing it with a Genuine new Lycoming, and installing the cooling shroud.  Installing the new fuel pump proved to be a VERY difficult job. How can is be so touch with only two bolts? Well, there is a plunger which pushed down on the fuel pump arm. Under gravity the plunger wants to naturally fall since it is held up against the cam it actuates against due to the spring pressure of the arm of the fuel pump. So I needed some way to keep the plunger up while I installed the fuel pump. Some digging on the internet resulted in finding some genius who uses some 0.020 safety wire around the plunger and tensioned to keep the plunger in the up position.  It's tough to see in this pic, but you can barely make out the plunger. The safety wire with a little tension on it keeps the plunger in the up position.  Access to the two allen head bolts totally sucks. So little room to work. I bought a set of allen-key sockets from Lowes which worked perfectly.  They even have a "wobble" head allowing you to angle in to the bolts.  In addition to there being nearly ZERO room to work, you also can't see what you're doing. It finally dawned on me to punch a mirror near the firewall to give me some visibility.  Sp the safety wire trick worked great to install the fuel pump and tighten the bolts. The real fun started when it came to safety wire these two bolts together.  It honestly took me 4 hours to install one safety wire. Access sucks. Visibility sucks. This job SUCKS! Update 6/11/24 I ended up removing the cooling shroud because replacing the fuel pump and adding the cooling shroud didn't fix my intermittent low fuel pressure indication. Neither did replacing the pressure sensor. I removed the shroud because it interfered too much with properly tightening the fittings, reduced visibility to inspect the fuel pump, and didn't provide any benefits from what I can see. Also, to make your life really easy remove the left mag to give much better access to the fuel pump!  I decided to install a fuel pump shroud to further lower my fuel temperature. Only good things could come from this. I needed to install a new blast tube into the shroud so I punched a hole near the oil cooler.  And then used some red RTV to hold in place the new blast tube.  Before I went on a test flight, I emailed uAvionix with my issues with the FAA ADS-B Compliance Report failures due to an incorrect SIL. They recommended I change the "GPS Certification Level" from "C" to "A or B". This seemed to do the trick!  All passes!   
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Last Modified: October 5, 2024 |