charlesual

Any suggestions swapping out a mechanical fuel pump on my F?

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I recently noticed erratic fuel pressure at cruise and needed richer then normal setting to keep the engine running smoothly. (11.5 gph vs the usual 8.5 gph). It ran smooth leaned out when I turned the electric boost pump on. The fuel screens on the fuel selector and fuel servo were clean and vent tube unobstructed so I’m pretty sure my mechanical fuel pump is degraded or getting ready to fail. Looks kind of hard to get to it without removing the mags or fuel filter. (My IA says mags need to be removed to access and estimates an 8 hour job but hasn’t actually done one before) Any recommendations on removal and installation of new fuel pump?

Thanks mooneyspace.

 

 

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I replaced the one on my E, top &a bottom cowl was removed but left and right mags stayed in place. Don't remember it being all that hard to get to. I removed the old one, my IA rotated the engine slowly to get the plunger fully retracted to allow installation of the new pump, torqued and saftey wired the 2 bolts and reassembled. Not sure about the time frame start to finish but was less than 8 hrs

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There is no need to disturb the mags when removing the fuel pump. Moreover,  8hrs seems a bit ridiculous. I’m pretty sure it took under 8 hours for me to completely remove my engine. It may be beneficial to remove the top bolts that fasten the engine mount to the firewall so that the engine can be tilted forward a bit.

The fuel pump is secured by two allen bolts IIRC. It may also have a cover which presents its own challenges.

this is what your accessory case looks like with FP still attached.

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That is very helpful!! Thanks for responding. Gotta love mooneyspace.


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removing the top engine mount bolts and tilting the motor gives plenty of room to access the fuel pump. it is still a bear to work on but you do not have to remove anything else. make sure an engine hoist is hooked to the engine before removing the engine mount bolts from the firewall.

Brian

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Yes, I should have mentioned the hoist. Definitely need a hoist to tilt the engine.

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It looks to me like you're about 45 Mooney minutes away from N87 where there is a very reputable and experienced Mooney shop. I'll bet it would be worth the fuel to take it to someone who knows what they're doing and have done it not just once, but many times.

Call ahead, and get on the schedule. Have them order the parts ahead of time. Then fly in, get it done, and fly home.

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I was laughed at when I asked if the grumpy IA wanted to do it or maybe that was the starter.   One AP said you have to remove the left mag.   I sacrificed a 5/15 allen wrench to about 2" and then used a socket and ratchet to turn it.  Making sure the plunger is in the right spot.   I was slow doing it the first time ever and probably took 5 hours.   Much like changing a Chevy V8 pump.  Except it is on the back of the engine and under a mag.

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Wait you said GPH what is the PSI doing?  Leak down test?

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I’m glad you posted about this.  We are getting ready to change my pump too.  I have the mags off for inspection and I don’t want to go back after the pump.  May as well swap it out since I’m there.  

Spruce has overhauled tempest pumps but for $20 more you can get new lycoming pump and no core charge.

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Heads up.  There is a thread (or two) about the mechanical pumps.  There is an ongoing issue with the new pumps putting out pressure above Mooney redline.  Lycoming says it’s fine, but your IA may not.  I ended up reverting to the old Lycoming pump, others go with the tempest.  This is really frustrating for those caught off guard.  

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4 hours ago, takair said:

Heads up.  There is a thread (or two) about the mechanical pumps.  There is an ongoing issue with the new pumps putting out pressure above Mooney redline.  Lycoming says it’s fine, but your IA may not.  I ended up reverting to the old Lycoming pump, others go with the tempest.  This is really frustrating for those caught off guard.  

I went with the Lycoming pump, while not at redline it's pretty close

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  In my experience, pulling the left mag serves a dual purpose when replacing the mechanical fuel pump.  1) allows better access for removing and installing the hoses and the pump. 2) allows a visual verification through the magneto mount hole that the fuel pump actuator rod is riding in the right place prior to buttoning everything up.  If the 2 fuel mount bolts aren't tightened progressively and evenly, there's a possibility that the actuator rod will ride off of the plunger and if the engine is started like this other damage may occur.

 

Ron

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