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Bluebeard

Active Member
I am planning to replace my mechanical fuel pump (RV6, O320E2A, carb), and have been searching the internet for a step by step guide (some friends having said this is tricky!).
This needs to be done with the engine and other accessories in place, so there is not a lot of room for two or three hands to get in there. There is not a lot of information in Lycoming's overhaul manual.

I understand there is a danger of bending the plunger if it is not seated correctly on the pump arm, I'm going to have to do this by feel. Is there some trick for keeping the plunger in its 'up' position while the pump lever is inserted?
 
It can be done on the airplane. I did the one on my O320 B2B about 3-years ago when I hit 2,200 hours.

Once the pump is off, use your finger to fill the plunger to make sure that it can be lifter up easy. IF it cannot, rotate the engine and try again. IF you can lift the plunger with no force, the pump should drop right in.

The hard part, is getting an allen wrench that will fit to take the old pump off and to install the new pump.

My old pump gasket was the only oil leak that I had on my engine. I used gasket compound on the new gasket when I installed it. No more oil leaks.

When safety wiring the allen screws, I used a small piece of tubing / hose over it where it touches the pump.

This post is an OVER VIEW of what you need to do and not detailed instructions.
 
pump

Regarding the accident report in the old thread, I could not get the report, just the FAA home page. I did read the report quite some time ago. Also have a friend that is familiar with the accident. IIRC the bottom line is two separate problems that led to fuel starvation. First the engine driven pump was installed with the lever alongside the pushrod. So no engine driven pump.If one makes a habit of shutting off the electric pump during runup to check the engine driven pump, this accident would not have happened.
Second problem is that electric pump was on a breaker/switch combination. These switches are most common on Beech Aircraft but are widely used. The story my friend told me is that when the breaker switch trips, there is no indication. The switch must be turned off, then on to reset the breaker. I had always assumed that the overload would trip the switch to the off position. In 47 years of flying Beech products no one has suggested otherwise, including some professional training providers. I have some new breaker/switches and will try to remember to test them.
The accident happened in an area that is a very hostile environment for emergency landings. I think the pilot did the best he could and it wasn't good enough.
 
This is not a bad job if you pay attention. Knowing that the fuel pump plunger rod can be installed to the side of the push tube in the engine is half the battle. Turn the engine until the rod in the engine is all the way up. It will likely stay up but if it doesn't don't worry about it. Now, when installing the pump angle the pump lever down so that as you install the pump the pump lever will line up with the end of the push rod in the engine. As the pump is moved closer to the engine rotate it towards it normal mounting geometry. Now start to install the mounting bolts. The pump will not be flush against the accessory housing when installing the mounting bolts and getting the bolts through the pump holes ,the gasket holes and started is the most difficult part of the job. Once both bolts are started, the pump will be able to rock easily against the push rod in the engine and a little bit side to side if the pump plunger is lined up properly with the push rod. As you tighten the bolts, the pump will be able to continue to rock, and the bolts should tighten up normally. If the pump can't rock or the bolts are very hard to tighten, the plunger is on the side of the push rod. It is really pretty easy to tell if the pump plunger is on the side once you know it can be installed improperly. The problem is most don't realize you can do it wrong and blindly put the pump on and tighten it up with out paying attention.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
fuel pump

Mahlon- Do you have any words of wisdom on tools. I know I have done this with a plain allen wrench. It seems to me an allen wrench for a 1/4' drive ratchet would be helpful and maybe one of the round knurled starter ratchets.
 
I made my own allen wrench by cutting the long piece of a long 90 degree one. That would enable me using it with a 1/4 drive socket and ratchet. I ground down the portion of the allen wrench that would rub on the pump housing and it worked great for a long time and still get a bit of use when i dust off the cob webs on my tool box. Of course I used something like that a lot more then someone that is doing this only once or twice in a lifetime.....;-).
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
Many thanks guys for all the replies. My plane is currently about 1000 miles from my home so I am packing up whatever tools I may need to do this job, to bring them with me.

I have ordered two new socket screws STD-1882 in case there is any trouble with the existing ones, but can someone tell me what size Allen key fits in these?

It seems need to have one prepared, probably one with a ball end if I can get my hands on one, so as to work at an angle around the pump body.
 
5/16
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at your own risk."
 
Now I have done the pump change "in the field", it was not at all the tricky issue some have encountered. I made up in advance a "waisted" 5/16 inch drive by cutting off about 3 inches of an Allen key and grinding down its centre part to clear the pump body. But a 5/16 ball-ended Allen key (or 8 mm) really would be just as good. The pump was inserted with the plunger as far up as it would go; apart from a wandering gasket, and the general inaccessibility of the screws, there was no problem.

The new pump gives lower pressures than the old one, 2-4 psi indicated rather than the old 6-7 psi. I wonder why this should be the case with the same part numbers; however the Lycoming manual recommends 3 psi, minimum 0.5, so I suppose it should be ok. I also replaced the electric pump and this too gives lower pressure and lower max flow than the old one.

But they seem to work ok.
 
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