Replacing Engine Fuel Pump

[RV7A Flyer]

I assume there's no Lycoming SI for how to replace the pump (which I am thinking I may have to do...been seeing increasing deviations in fuel pressure, with the occasional drop over a few seconds to ~14-15 PSI and then back up, over about 8-10 seconds).

I'll probably add the cooling shroud, although I have a blast tube aimed at it now.

But, my real question here...what sort of sealant is recommended, if any, for the gasket and/or the bolts?

 

[catmandu]

Another thank you for all the tips!

I had suspicions about the low pressure mechanical fuel pump on my carbed O-320 that is 40 years and 1300 hours old. No indication in the logs it had ever been replaced. So I got a new replacement and blocked off a full day. I used a full length ball end hex tool, Hylomar M to seal the gasket, teflon thread sealant on the bolts, fuel lube on the fittings. Made sure the cam was in the proper position, installed the inboard bolt one turn, and was able to tilt the lever arm on the pump under the cam driven piston, no securing tricks required. Then I installed the outboard bolt one turn, and confirmed proper installation by mating the pump to the case easily by hand. Torqued and safety wired the bolts. Full power ground run, no leaking oil or fuel. Two leisurely hours.

What to do with the rest of the day?

 

[krw5927]

I used a full length ball end hex tool, Hylomar M to seal the gasket, teflon tape on the bolts, fuel lube on the fittings.
What to do with the rest of the day?

The holes for these bolts go completely through to the interior of the accessory case. Teflon tape in general has been discussed a lot on here and generally concluded to be a huge no-no on aircraft. Any danger here of strings of the tape breaking off and doing harm in the oil system or any accessories?

 

[catmandu]

The holes for these bolts go completely through to the interior of the accessory case. Teflon tape in general has been discussed a lot on here and generally concluded to be a huge no-no on aircraft. Any danger here of strings of the tape breaking off and doing harm in the oil system or any accessories?

Nice catch, thanks for watching out for me. My fingers got ahead of my brain, tape was not used, I edited my post

 

[Jab]

Hi all

I have an O320 in a RV4 and had a fuel pressure drop in a full power climb, which caused the engine to lose power until I turned the electric pump on and went back to the airport. The engine would run ok at lower power settings but not at full power.

Pulled the pump off and found two hard ?granules? of some crumbly substance which were obstructing the diaphragms, holding them open. One granule in each diaphragm. Weird! After thoroughly cleaning the pump and gascolator I reinstalled it.

I had not found this thread so I had to figure this out myself and surprisingly, it worked quite well. I put the bolts through the housing and held the pump in place, ensuring the arm was in the correct position. I found if I tilted the pump clockwise, I could get the left bolt in easily and tightened it up, only enough to keep the flange faces aligned but the pump could still be rotated. I then pushed up on the right side, rotating the pump against the spring pressure on the arm to get the right side bolt hole to line up. It took a couple of tries to get the threads to take but once they did it was easy. Did a run up and had a firm 5 psi, leak checked everything and then did a test flight over the airport. Great fuel pressure at low power but at full power it would drop to about 1 psi, no faltering of the engine though.

However, after reading the threads here, I am concerned about what I did. If overhaul kits are no longer sold because a jig is needed to set the diaphragm pressure, there is no guarantee that my reassembly was correct. I plan to replace the fuel pump anyway since it?s old but it would be nice to fly until I get the new one. I would welcome your opinions.

Merry Christmas,
Gary

 

[Sam Buchanan]

Ground your plane until the pump is replaced. Aircraft Spruce can put a pump in your hands a couple of days after Christmas.

 

[YellowJacket RV9]

Hi all

I have an O320 in a RV4 and had a fuel pressure drop in a full power climb, which caused the engine to lose power until I turned the electric pump on and went back to the airport. The engine would run ok at lower power settings but not at full power.

Pulled the pump off and found two hard ?granules? of some crumbly substance which were obstructing the diaphragms, holding them open. One granule in each diaphragm. Weird! After thoroughly cleaning the pump and gascolator I reinstalled it.

I had not found this thread so I had to figure this out myself and surprisingly, it worked quite well. I put the bolts through the housing and held the pump in place, ensuring the arm was in the correct position. I found if I tilted the pump clockwise, I could get the left bolt in easily and tightened it up, only enough to keep the flange faces aligned but the pump could still be rotated. I then pushed up on the right side, rotating the pump against the spring pressure on the arm to get the right side bolt hole to line up. It took a couple of tries to get the threads to take but once they did it was easy. Did a run up and had a firm 5 psi, leak checked everything and then did a test flight over the airport. Great fuel pressure at low power but at full power it would drop to about 1 psi, no faltering of the engine though.

However, after reading the threads here, I am concerned about what I did. If overhaul kits are no longer sold because a jig is needed to set the diaphragm pressure, there is no guarantee that my reassembly was correct. I plan to replace the fuel pump anyway since it?s old but it would be nice to fly until I get the new one. I would welcome your opinions.

Merry Christmas,
Gary

For those times where you'd rather not wait or pay shipping, try calling Aeromech @ KLAL, http://aeromech-inc.com/ - they seem to stock a lot of stuff and several times I have made a 5 minute flight over there to buy an odd size bolt or some other small part. I'd recommend you not fly until replacing the fuel pump, but it's still a pretty quick drive from Tampa.

Chris

 

[skyking902001]

After a flight last week, I noticed a drip from the fuel pump overflow. It appeared to have leaked enough to leave a small streak on the lower fuselage, although I never had any indication of a fuel pressure fluctuation. After reading this thread, I could hardly wait to replace the pump (NOT). I picked up a new pump at Air Power in Arlington. I removed the cowling and set about removing the old pump. Access is rather limited, so I removed the scat tubing for the cabin heat and removed the lower line from the oil cooler. I removed the pump overflow tube and the fuel lines from the pump. I zip tied all of these lines to various places on the engine mount--this helped free up some space. I cut the safety wire and removed the bolts. I found that a ball end hex tool was the only way I could get on the bolts. So, old pump off, then cleaned off the old gasket material from the engine with a scraper and some disc brake cleaner. At this point, I called it a day. The next day, I ran some string around the rod that operates the arm on the pump and clamped the free ends to the plate where my GPS antenna is mounted. I held my finger on the rod and slowly rotated the prop until the rod was fully retracted. Looks like the string will hold it in place. I used the old pump as a test to determine how best to position it for the installation. After I was satisfied I had found an acceptable method, I proceeded with the new pump. I coated a new gasket with permatex #2 and stuck it on the pump. I also coated the bolt threads with permatex thread sealer. I inserted the pump and rotated it about 30 degrees counter clockwise. This allowed the arm to fit under the plunger and the inboard bolt to engage. I gave it about 3 turns. For the outboard bolt, the pump has to be rotated clockwise to line up the bolt hole. This was the difficult part because the plunger rod must slightly depress the arm on the pump--and that arm has one stout spring! After several tries, I got the bolt started. I pushed the pump flush against the engine to ensure the arm was under the push rod, then tightened up the bolts until there was less than a 1/4" gap between the pump and engine. I pulled the string out and finished tightening the bolts. The safety wire wasn't much fun either, but I got it done. Re-attached all lines. Ready to test run and check for leaks, but now it's raining--will do it tomorrow. I spent about 4 hours on this project--I stand in awe of the gents that did this fun task in 15 minutes and 35 minutes. Thanks to all for the tips found on this thread!

 

[JonJay]

Good job. I think a few hours invested well. Future ones will go a bit quicker but hopefully you won't have to find out!

 

[revenson]

Good ideas in this thread!
This was my second time installing the fuel pump. First time I needed to remove a pump cooling shroud that had a broken installation tab.

This time I called Tempest to confirm there aren't any new ones without the dreaded housing interference issue. Of course, no company has gone thru the pain of a new design and faa pma process.

This time I used his suggestion to be confident the pump arm is installed correctly...that is, remove the left mag, then one can see the pin. Rotate prop to up position, temporarily secure the pin in up position from inside the mag opening, and proceed to wrestle the pump and those **** hex bolts.

Worked much better this time after shortening a 5/16" hex wrench, but most importantly, I'm confident of the positioning.

 

[Hartstoc]

Is it just me, or are these engine mounted fuel pumps a real PITA to install? I have rotated the engine until the plunger is as far up as it goes. I can get the pump in all the way, as long as it is tilted a little bit. So far, so good. The problem arises when I try to get the socket head cap screw started. Because of interference between the screw head and the pump casting, I'm not able to get it properly aligned for starting the threads. The only way to get alignment of the screw is to pull back the fuel pump a little, which causes the lever to pop up above the plunger. AARRGG.

Any tricks would be appreciated. I have glued the gasket to the pump, so that "trick" is already used.

Thanks!

Mine was mounted with cap screws with allen-wrench socket- heads, and they are drilled for safety wire. I?ve permanently removed my engine driven pump so no longer need them and would be happy to mail them to you unless you have solved the problem by now. Just have to make sure I can get shorter bolts that will work to secure the cover I?m bolting onto the mount pad.- Otis

 

[scsmith]

This is a great thread - we need to keep it alive for those that come after us.

I still have not won this battle yet. I went out and tried the grease trick with the stickiest grease I could find. No joy. Doesn't help that it is 95F here. Maybe if it were colder.

Anyway, the waxed string/safety wire trick is brilliant. I will do that tomorrow.

It would make life much easier to shorten the screws, BUT the amount of thread engagement into the case would be potentially inadequate. It might be fine to take 3/16" off the screws, but it might not. I won't do it.

Knowing that you can see in through the left mag hole is encouraging. It means I have to re-time my Light Speed hall sensor afterward, but that is a small price to pay to be SURE the lever is properly engaged on the plunger.

 

[N184DA]

Having that left mag removed also allows you to route the string through the mag access, rather than slipping it between the pump and flange.

The way I did it was to basically tie the string off at one of the engine mount tubes, nice and tight, through the mag hole. Left it that way until the pump was in and the bolts were tight.

And you are correct, having the mag out is a small price to pay for knowing that the pump arm/pin are seated correctly.
And as an added bonus, makes the safety wire a little easier to install.

 

[scsmith]

Having that left mag removed also allows you to route the string through the mag access, rather than slipping it between the pump and flange.

The way I did it was to basically tie the string off at one of the engine mount tubes, nice and tight, through the mag hole. Left it that way until the pump was in and the bolts were tight.

And you are correct, having the mag out is a small price to pay for knowing that the pump arm/pin are seated correctly.
And as an added bonus, makes the safety wire a little easier to install.

Another time when I wish the forum had a 'like' button. Thanks.

 

[digidocs]

I talked to Tempest about installing the pump and they claim that you can actually reach in the L mag hole and hold the plunger up with your hand (where it contacts the camshaft). Not verified, but a good source...

 

[N184DA]

That is true,,
But I found I needed both hands to manipulate the pump, to orient the holes,, and to start the bolts that do not align when the pump is square on the mounting flange.

 

[scsmith]

I talked to Tempest about installing the pump and they claim that you can actually reach in the L mag hole and hold the plunger up with your hand (where it contacts the camshaft). Not verified, but a good source...

A great tip for those three-armed mechanics.

 

[WAustin]

Engine Fuel Pump Replacement Hints

Hi All

This was sent to members of our chapter of the Sports Aircraft Association of Australia (SAAA). I didnt go through all seven pages of replies, so maybe this has already been posted.

Link is to another forum that has hints on replacing the engine driven fuel pump.

Here it is: https://www.matronics.com/forums/viewtopic.php?t=16775207

Hope that helps someone.

Cheers

Wayne

 

[BruceW]

Used the safety wire trick for keeping the plunger up. Got it on the second try. Really had to tension the wire to keep the plunger up.
Great use of this forum.
Thanks to all.

 

[gasman]

Better off to use regular string instead of wire. String has way more drag and will hold the plunger in place with far less pressure.

 

[scsmith]

Better off to use regular string instead of wire. String has way more drag and will hold the plunger in place with far less pressure.

It turned out that the opposite was true for me. I tried dental floss first. No amount of force would hold the plunger up. Then I switched to safety wire and it worked quite easily.

 

[Captain Avgas]

It turned out that the opposite was true for me. I tried dental floss first. No amount of force would hold the plunger up. Then I switched to safety wire and it worked quite easily.

How many times did you go around the plunger with he dental floss....and was it a very broad ribbon dental floss. I would think that waxed electrical cord wrapped around a few times would do the trick and intuitively you'd think it would have more friction that safety wire.

 

[scsmith]

How many times did you go around the plunger with he dental floss....and was it a very broad ribbon dental floss. I would think that waxed electrical cord wrapped around a few times would do the trick and intuitively you'd think it would have more friction that safety wire.

I didn't try to wrap all the way around in either case. You are probably right that a full wrap would grip fine. I just put a half wrap on it with both tails coming up to a engine mount tube.

 

[Fred.Stucklen]

Fuel pump bolt oil leak

I have to thank all those whom did this job and posting their problems and results on this list. It helped me to easily do this repair.

I have an IO-360 on and RV-7A. I was seeing intermittent low pressure warnings, with the fuel pressures dipping randomly below 20 PSI (normal is 25-30 psi). Ground test resulting in fuel flows of 30 GPH using the AUX pump, so it wasn't a restriction. Running the engine at lower RPM's and leaned appeared to lessen the issue, but didn't completely eliminate it. Also, when fuel pressures dropped, with the engine leaned way back (two PMAGs allows this) RPMs would fall off with low fuel pressure, indicating it wasn't a sensor error, but a real low fuel pressure (and injector flow) issue.

So I ordered a new pump and a shroud and installed them today. Removing the old pump required me to remove the left P-MAG and some other hoses that were restricting access to the pump. The shroud from Spruce did not have to be modified as long as all the fittings were put onto the pump while it was on the bench.

I tried using the grease trick to hold the actuator in the UP position, but, in the Florida heat, it didn't work out. Instead I looped .020 safety wire around the actuator and had a helper put tension on it after pushing the actuator into the UP position. After installing a new gasket with a sealant onto the accessory case, I was able to insert the pump into position and, by hand, get both cap screws started, and turned then further in with a 5/16" ball Allen wrench. Before snugging up the cap screws the .020" safety wire was pulled out. The cap screw safety wiring job was tricky, but given the access with the left P-MAG removed, went smoothly. Then all the fuel lines were again connected.

To test the pump functionality, I removed the lower four spark plugs and turned the engine over with the starter, resulting in 29-32 PSI fuel pressure indications. I then reinstalled and timed the left P-MAG, and connected the other hoses I had disconnected. There were no oil leaks after running the engine...

I did not use a sealant on the cap screws, so will be looking for any oil leaks in that area.

I hope this write up helps others too.....

I've had an oil leak around the mechanical fuel pump since I replaced it a while back. I found out recently that the mounting bolts were supposed to be sealed, which I didn't do back then. So today, I removed the left P-Mag, Fuel hoses to the mechanical pump, and a couple of oil cooler hoses that were in the way, then the mechanical fuel pump (again). It was dripping oil from what looked like seepage from the mounting bolts. The oil was dripping into the area of the front nose gear mounting area, then down the front gear leg fairing and onto the front wheel pant, making it VERY noticeable!

With the left P-Mag out, it was easy to get the fuel pump plunger lifted up (with the prop set approapiately) by using a string in the left Mag hole. I removed the pump, cleaned it and the accessory case (so I could easily see any new oil leaks). I reinstalled the gasket, then re-mounted the fuel pump, but this time with Teflon paste on the bolt treads.

I'm still n the process of getting everything else back together again, and resetting the P-Mag timing. I'm hoping to test run the engine tomorrow....

 

[- Poindexter -]

Changing the mechanical fuel pump by yourself
(mechanical fuel pump failure circumstance listed at the end of this post)

I found this thread very helpful in changing my mechanical fuel pump. Read all the other posts above.
I also found this video very helpful:

Here are some more helpful tips.

Engine is an ECI 0-360 A1A. 800 hours. I installed a new Tempest AF-15472 pump (which comes with gasket).
Total time to change pump: ~6 hours.
Removed all associated pump connections and also removed oil line to oil cooler since it was in the way.
I did NOT remove any Mag's. Note that you need to completely remove the safety wire from both allen screws as the wire passes through the allen slot (so you will only be partial in getting a tool in). A mirror helps.
I had to cut a 5/16 allen wrench since the inboard screw was difficult to reach. I used a 5/16 socket to get leverage on the allen wrench. And, the round allen head is important as it allows flexible access.


Take photos of the pump and attachment orientation for later re-installation.
Take your time removing items and work back/forth on removing the (2) allen heads.
Once the pump is removed, clean the pump area, and stick your finger inside of the engine, where the pump is attached.
You will feel a rod, hanging down. Rotate the prop so you get the hanging rod in the uppermost position.
Take some long safety wire, make a "U" and lasso the hanging rod. Pull both safety wires firm and secure upwards. Push the rod up so it is out of the way (safety wire holding it in place).

Use sealants on gaskets and bolts as mentioned in other posts (Permatex #2, Permatex gasket sealer). Angle the pump in, below the rod. Install allen bolts, alternate screwing in both at the same time. It is very important NOT to force these bolts in. If you do, you are not aligned properly. I was not aligned (2) times and had to start over.
Tighten the pump down and with ~1/8-1/4" left, remove the safety wire. I found this difficult as there was a lot of tension on the safety wire. Torque as required. Install safety wire (see methodology in other posts). Install hoses, etc. torquing as appropriate. I hand spun the prop twice to make sure everything was smooth.

First engine start was easy as I put the boost pump on for 5 seconds. Two pumps of the throttle and it started up. Ran it for a couple minutes, and shut-off to inspect any leaks. Put it all together and did a couple laps around the pattern. Woo-hoo, a steady 4.6 PSI! Success.

Mechanical pump failure
800 hour RV7a, 0-360 A1A engine. 10 year old with the last (3) years of my ownership, putting on 600 hours.
In my case, I was going for a scenic spin out of Telluride, CO. Runway is at 9,000'. Took off, climbed 1,000' AGL and turned the boost pump off. The fuel PSI (normally around 2.6-2.8 PSI) dropped, and kept going to zero. I was briefly warned by my G3X and the engine started to quit. I quickly turned the boost pump on and regained fuel pressure. Climbed to 14,500' and needed to have the boost pump on, otherwise the pressure would drop. Once the climbing was done and the plane was leaned and level, the fuel pressure (with no boost pump on) would hold 2.3-2.8 PSI. Fluctuating up/down.

Couple days later I flew back to California, using the boost pump on climb-out. Level, it maintained 2.2-3.1 PSI, fluctuating up and down. Then, after crossing the Sierra, it jump and stayed at 5.3 PSI. After changing the pump out, the pressure is now holding at 4.6 PSI. Good luck.