JeffC Posted January 4, 2017 Report Posted January 4, 2017 Hey Guys, Just installed a 690 hour used engine on my 67E after the dreaded tappet/cam corrosion occurred on my 117 hour and 12 years SM engine. The previous owner had 2 airplanes and seldom flew this one. Now doing some test flying close to the airport but fuel pressure is always on the low side compared to my old engine. Electric pump brings pressure immediately to 29 psi. Pressure wanders between 21 and 16 psi. No change with altitude or mixture. No leaks. I'm keeping below 5500 ft to maintain 75% power for a few hours since this engine got new rings and a bottom overhaul before install. I've got my spare 117 hour fuel pump but it looks like a real PITA to change. I've got no hanger and it's -20C ish (-4F) so won't happen right away but was wondering what other accessories will have to be removed to access it? Or do I have to pull the engine again? I'm hoping once I remove my spin on oil filter I'll have access from above but I want to have some gaskets on hand in case I need to pull the oil filter adapter and/or the magneto. Looks like zero access from the sides. Has anyone here done this? Thanks.
Gary0747 Posted January 4, 2017 Report Posted January 4, 2017 Had low pressure on my 67F in the range you are seeing. Replaced the fuel pump at annual and the pressure now is a bit high at 29 psi. I had no leaks with the old pump but found some of the screws around the diaphragm had backed off. We were able to change the pump by pulling the left magneto and removing the oil filter and some oil hoses. What were the operational symptoms of your cam failure?
JeffC Posted January 4, 2017 Author Report Posted January 4, 2017 Thanks Gary, that sounds encouraging! About what I was hoping for. How long did you fly at low pressure? Mine hasn't changed in the few hours I've been doing engine break-in procedure. Most of the tappet faces looked like the surface of the moon. One cam lobe was starting to wear down but only slightly. Maybe 1/32". No noticeable operational symptoms. Noticed a coppery film on surface of oil during change. Found some metal flakes in the oil screen. Ran the engine for another 10 minutes and there was more metal in the screen. Not a lot but it's the first time I saw metal in any airplane engine screen so I was more concerned than the AME was at the time. Oil pressure was running at the bottom of the green arc or slightly below which I didn't like either. Believe that's 60 psi? The new engine has been running a solid 80 psi at 180F at 2500 rpm so far. And around 50 psi at 1000 rpm.
Yetti Posted January 4, 2017 Report Posted January 4, 2017 You may see the FP gauge hiccup as you climb to altitude say 5000 feet. To test on ground. Prime engine with elec pump. 6 seconds with mixture open. Close mixture. See if pressure holds. If not you might need to replace. Also fuel coming from one of three hoses near firewall It can be done without removing anything. There is a long thread about cooling shroud vs. no shroud. and where does the cooling line go.
Yetti Posted January 4, 2017 Report Posted January 4, 2017 You might have to do a modification to a 5/16 allen key
JeffC Posted January 4, 2017 Author Report Posted January 4, 2017 Thanks Yetti, I've checked that. Pressure drops to about 20 psi after a half hour. Can't detect any fuel leaking. Pressure runs at about 25 psi at idle but drops when flying.
Yetti Posted January 4, 2017 Report Posted January 4, 2017 Mine was more immediate. Like within a minute you would see it go down. You might want to check for clear vent lines on the tanks. also screen on the fuel servo. or the pump may just need replacing. Clean the fuel screen on the servo after replacing the pump
N6758N Posted January 4, 2017 Report Posted January 4, 2017 10 hours ago, Gary0747 said: Had low pressure on my 67F in the range you are seeing. Replaced the fuel pump at annual and the pressure now is a bit high at 29 psi. I had no leaks with the old pump but found some of the screws around the diaphragm had backed off. We were able to change the pump by pulling the left magneto and removing the oil filter and some oil hoses. What were the operational symptoms of your cam failure? As Gary0747 says, if you pull the left magneto and the oil filter, this should give you enough room to get to the fuel pump. It is still a PITA, be careful when you install the new pump to make sure the plunger inside the accessory case is seated on the pump arm.
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