What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Mechanical fuel pump removal

erich weaver

erich weaver

Well Known Member
I want to remove the mechanical fuel pump off my lycoming-clone engine so that I can add a heat shroud to it. I havent removed one before - it looks straight forward, but is there anything to watch out for, like any parts that fall out or go flying off if you arent careful? I screwed myself once before removing something that I had no experience with and hope to avoid similar consequences here.

thanks

erich
 
Good that you asked if unfamiliar in that there is a definite potential with the mechanical fuel pump installation to damage the pump. There is specific instruction from the manufacturer on my engine (ECI) which is applicable to any lycoming or clone that the rod which transmits the force from the engine lobe to the pump arm must be fully retracted when installing the pump or the pump can be misaligned when installing, damaging the pump and causing it to malfunction. Basically, the push rod goes to the side and does not actuate the pump. You can probably go to the ECI site and get the warning instructions. Not very difficult to overcome knowing the possibility, but difficult to correct the damage.
 
Maybe this helps visualize

Below is a picture from my engine build of the inside of the accessory case looking up from the bottom of the case. That pin on the left side of the case is the rod someone else mentioned. It rides on an eccentric above it you cannot see to make it move up and down and actuate the pump. Make sure its is retracted (in the up position) or it puts a lot of pressure on the pump arm - whether installing or removing. Good luck.

IMG_1355.jpg
 
rwhittier said:
Make sure its is retracted (in the up position) or it puts a lot of pressure on the pump arm - whether installing or removing.
Click to expand...

I'm not aware of a way to tell whether the pin is up or down before removal, but but it definitely needs to be up for installation. Even when in the up position it will tend to sag back down under gravity so I found I had to push it up and quickly insert the pump lever to hold it up. You might feel a little bit like the proverbial one-armed paper hanger getting it positioned with the gasket and screws in place, but it really wasn't that big a deal when all was said and done. I found it handy to cut a 1/2" piece of 5/16 (?) hex stock from an allen wrench. That allows you to use a ratchet and flex socket instead of an allen wrench on the screws.
 
Checked with Bart at Aerosport power about this as well. His tips:

- Use a hex wrench with a ball on the end so it doesnt have to be exactly square to the bolt;

- May need to have one of the bolts part way on/off to remove/install the other bolt

- There is a potential to get oil leaks from the fuel pump after reinstallation. Therefore, (1) use a new gasket with sealant when reinstalling; proper size gasket should be available from any autoparts store; and (2) use a liquid teflon product on the two installation bolt threads.

- push the rod up before re-installation, as previously discussed

He didnt seem to think this was all that big a deal, but of course he's done it a few times before, and most of those were probably with engines on the stand!

We'll see how it goes.

erich
 
wondering if this will work?

I also have a fuel pump heat shroud that I was planning to put on my engine. I haven't even checked to see how the thing is attached, but it is apparent from the posts that it is attached by the fuel pump bolts.
After reading some of the posts it looks like a bear of a job removing & re-installing the pump. (for the novice anyway) I've looked at the arrangement of the pump on my engine and have an idea that may work.
I'm wondering if the shroud was cut in half (red line in picture) and then installing each half by removing one bolt at a time. Two splice pieces could be made (blue lines) and nutplated on to the shrouds. (All done before actually sawing the shroud in half.)
Does anyone have an idea if this would work? Would one bolt hold the pump in place while each half was being attached? Thoughts anyone?

http://i488.photobucket.com/albums/rr244/S7A_abi/Heat_Shroud.jpg
 
I accidentally busted one of the fittings on my fuel pump a few months ago, so it had to be replaced. While I had it off the engine, I figured I might as well install a pump cooling shroud when I went to put it back on. Well, after struggling with it for hours, I eventually gave up and put the shroud on the shelf. I think I could probably get it all on there if the engine was on a stand, but trying to do it with the engine on the airplane just drive me crazy.

An earlier post mentioned the use of sealant on the bolt threads... argh, why didn't I think of that! It took me lots of tries to get the safety wire just right, too. I did use a new gasket and fuel lube, but now I'm wondering if I need to pull the thing off again and put some permatex on the bolts...? :confused:

mcb
 
Update:

Reinstalled my p-mags after getting the recent update and decided to tackle the fuel pump heat shroudl, which requires removal of the fuel pump.

Getting it off is straight forward - betting it back on, uhhhh.... not so much. Man o man, what a chore. Per previous posts, the fuel pump body interferes with the socket head bolts so that you cant just line up the bolts with the threaded hole in the accessory case - you have to shove them half way through the holes in the flange on the pump first (past the point of interference), then position the whole pump up against the accessory case and hope for the best. You cant even see the bolt or the hole its supposed to go in on the far side of the pump. Throw in the extra hassle of the loose heat shroud around the pump and it quickly becomes an excercise in frustration.

Also, I dont know who is making the heat shrouds (I got this one through ACS), but they might want to actually install one of their products. NONE of the holes they put in the sides to accomodate the various fuel line fittings were correctly placed. I had to hack out all of them. I would have preferred to have gotten it with no holes at all so I could have put them in myself - in the right place. The shroud also interferes slightly with the mounting bracket for prop governor, whose position cannot easily be changed.

Baed on the earlier posts, I was concerned that the arm on the pump wouldnt be postiioined correctly under the little rod inside the acccessy case that goes up and down. I turned the prop until I could push the rod up, but it slid back down in just a second or two once I took my fingure off of it, so there was absolutely no way to get the pump mounted in that time. What I did figure out however is that if you can get the pump properly positioned against the accessory case, and be fortunate enough to get the bolts lined up just right so that they screw in with the allen wrench, then the arm has taken care of itself. I dont think its possible to have the pump perfectly positioned against the accessory case and the arm not be correctly positioned.

Well, tried and tried and tried again to get the pump with heat shroud installed and succeeded only in partially stripping the threads on the accessory case holes. Fixed that with a tap, and tried again over and over and over. No real recipy for success - the stars were finally in perfect alignment and it just happened. TIme to quit for the day.

But wait - the fun has just begun. Want a real challenge? Try doing the safety wire on that socket head bolt on the far side fo the fuel pump - you know - the one that you cant see. I saved that for the next day. I used a mirror, and a hemostat to hold and thread the wire through the hole, then a pair of real small vise grips to snare the end of the wire and pull it through.

It took me three hours to get that safety wire done. The good news is that I am now also fully qualified as a neurosurgeon.

Well, sorry for the rant. Just want to warn you if want that heat shroud, well, you better REALLY want it.

erich
 
Erich, well, now you've joined the "replaced the #$%^& fuel pump with the engine in place" club. It was the second most frustrating mechanical repair I've ever done on any vehicle. You described the problem exactly. Next time I'll just put the airplane in a refrigerator (or wait until winter), so that the little plunger will stay up. I tried grease, etc., but basically just kept trying until the thing went in. The good news is that it hopefully will be a rare event - the bad news is even if it happened again soon, there is no way to exactly remember the sequence to make it work!
 
The ball driver allen wrenches are helpful. GM fuel pumps also had a pushrod driven off a cam. Try a dab of grease on it to keep it from sliding down.

Roberta
 
robertahegy said:
GM fuel pumps also had a pushrod driven off a cam.

Roberta
Click to expand...

The early small block Chevy engines had a bolt hole (originally for the motor mount) that intersected the push rod bore. A long bolt installed finger tight would hold the rod in position. Later side mount engines kept the same hole, just used a bolt to seal the hole against oil leaks. Not sure of the new generation engines.

I wonder if there is such a bolt hole, or other provision, in the Lyc????
 
Mike S said:
The early small block Chevy engines had a bolt hole (originally for the motor mount) that intersected the push rod bore. A long bolt installed finger tight would hold the rod in position. Later side mount engines kept the same hole, just used a bolt to seal the hole against oil leaks. Not sure of the new generation engines.

I wonder if there is such a bolt hole, or other provision, in the Lyc????
Click to expand...

Sorry to say that there is no such bolt hole in your Lyc's.

Here's a picture of the accessory case.
 
Hi All.
I'm having a little trouble removing the fuel pump and was looking for some pointers. In the OH manual is says just back out the hex screws, it's that easy. In reality what is happening is that when I back the two hex screws out, the bottom of the pump moves outward, but the top stays in place, kind of like the plunger arm is being physically held in by something at the back of the accessory case. Does anyone know what I should be doing to get this thing out correctly? My engine is brand new and only just out of the packaging, so I haven't turned the crank or anything. The pump is coming off because of SB621B.
Thanks.
Tom.
 
turn the prop...

the plunger that runs off of the engine is pushing down on the lever arm... rotate the prop to bring the cam around for the plunger to back off and it will come right off.


tgmillso said:
Hi All.
I'm having a little trouble removing the fuel pump and was looking for some pointers. In the OH manual is says just back out the hex screws, it's that easy. In reality what is happening is that when I back the two hex screws out, the bottom of the pump moves outward, but the top stays in place, kind of like the plunger arm is being physically held in by something at the back of the accessory case. Does anyone know what I should be doing to get this thing out correctly? My engine is brand new and only just out of the packaging, so I haven't turned the crank or anything. The pump is coming off because of SB621B.
Thanks.
Tom.
Click to expand...
 
Thanks Stephen. I hadn't drained the preservation oil out of the cylinders yet, but I guess now I'm going to have to.
Thanks for your prompt response.
Tom.
 
You must log in or register to reply here.
Back
Top