Replacing Engine Fuel Pump

[deek]

Originally Posted by JSD755

I am a new RV8 owner and this is my first post. I want to say thanks for all the valuable insight that is posted here, it has saved me a huge amount of frustration trying to reinvent the wheel. I recently had to replace the engine driven fuel pump (0 360). What a miserable job, poor access and a masterpiece of poor design.
I want to single out Kcameron for thanks for the tip on using waxed lacing cord to hold the drive shaft up while starting the hex bolts, it worked when all the other tricks failed. If you ever need to do this nasty job try this tip first and save time and hide on your arms.

Many thanks John Deaton

Unfortunately, I've had to do this nasty task twice; once on each LongEZ I've built. I use an old green cylinder base O-ring instead of the waxed lace as KCameron did - but essentially the same idea. The O-rings are manufactured out of really strong and stretchy rubber and you simply stretch it to fit on something higher on the accessory case, and then remove it at the last minute. Removing the left mag helps (especially in safety wiring) but then you've got extra work to do.

deek

[judoka5051]

Hey Gang,

Here's how I installed the fuel pump in 15 minutes (engine on the plane). First of all, my engine came with a plate over the hole, so the bolts were the wrong length. I decided to use studs instead of bolts to help guide the pump on. So, I put permatex on the studs and installed them, then slid the gasket into place. Now comes the 'trick' I read on this thread bout using waxed string but I don't have any so I used a piece of 20g wire tied into a loop. I hooked the end of the plunger rod then hooked the other end to a ball bungee and clamped it to the top of the engine under tension. Now I reached in the hole and pushed the rod up and it stayed put. With the studs, there was just enough tilt down to get the pump in (with the arm clear) and start the nuts. I tightened them some, leaving just enough room to cut the wire and pull it out. Then I tightened it the rest of the way. It took me longer to type this that to do the install! I read all the depressing stories and studied the advice, and used some of it to make the job easier, so thanks to those of you who posted previously. I hope this helps.

Lance

[Fred.Stucklen]

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.....

[Randy]

Fred,

I have had intermittent low fuel pressure warnings haunting me for months. In the process of chasing it down I have replaced all of my fuel system components, eliminating many restrictive fittings etc. I thought I had the problem solved when I replaced the Kavilco sending unit and then could not re produce the problem. Months later it is back again.

Mechanical pump experts tell me the pump cannot fail on an intermittent basis but your experience seems to indicate otherwise.

Did the new mechanical pump solve the issue for you?

Anybody else have experience with intermittent low fuel pressure due to faulty mechanical fuel pump?

Charting fuel pressure after the events shows the pressure would drop down to around 13 PSI from the normal 25 PSI. My engine has never run rough during these events but that may be because I was quick to turn on the electric backup when I get the warnings, (Dynon System).

I may install a backup mechanical gauge to have a way to verify the pressure is actually falling. Precision Aeromotive tells me that the engine may actually keep running OK in cruise conditions with the low fuel pressure I have experienced due to the way the servo adjusts to different pressures. This makes it difficult to verify the pressure reduction is real...

Randall in Sedona

RV7A, IO-375, WW RV200

[Kent Ashton]

Originally Posted by Randy

I have had intermittent low fuel pressure warnings haunting me for months.

From experience, low and erratic fuel pressure indications may be caused by ground loops. A ground loop comes from having the sender and the instrument grounded at different points. The small difference in ground potential between the two points will cause all kinds of spurious indications in a sensitive gauge. You might look at that.

[Sam Buchanan]

Mechanical pump experts tell me the pump cannot fail on an intermittent basis but your experience seems to indicate otherwise.

I had a low pressure mechanical pump (O-320, carb) that definitely failed on an intermittent basis. Engine would lose power and immediately regain it when the electric boost pump was turned on. This was in cool temps with 100LL.

[tc1234c]

Just replaced the mechanical fuel pump using the safety wire trick. It was quite easy to get the pump on and bolts installed. As suggested before I used a loop of safety wire connected to a bungee cord. After looping the safety wire around the plunger I hooked the bungee cord and created a tension. Pushing the plunger up and it stayed. The first time I installed the pump and had the bolts almost in before taking it out. Using the mirror and later my finger I confirmed that the plunger did not drop. It was just to verify for myself that it is working. Second time I pulled the safety wire out before it got pinched by the pump. I did not have to take mag or anything else out to safety the bolts. I did have to move around the engine to tighten the bolts.

It is raining and I have not run my engine yet so I can not report the outcome. My 1,800 hr fuel pump (O-320, carb) intermittently drop pressure to 0.1 psi. It also start leaking oil. Even after I tightened all screws it still leak a few drops (shown on my nose wheel pant) each time I fly.

Without reading the experiences from others on the forum I would not have known what to do. Now, I have a new fuel pump on the engine and my arms are not even scratched. It all because I read the forum!

[flyboy1963]

can I ask a newbie question? there are a few references in this thread that are about mechanical, low pressure, hi-pressure pumps....so bear with me.
My mechanical pump is about 120 hrs old, but 10 years of age.
the fuel flow was good when tested in the climb attitude, but the pressure on the van's gauge is often in the 1psi range, if the scale is to be believed. Never had an operational problem, so is it safe to assume all is well? volume being more important than pressure, in a carb?
also, I thought something was strange, as there was always a drop of oil on the pump lower case bolt heads. Apparently, not that unusual for a little to seep thru the studs? the gasket seems dry, as far as I can see.

[tc1234c]

I learned from this:

http://www.vansairforce.com/communit...ad.php?t=74719

[petehowell]

I replaced my pump over the weekend - wow what a diff a few years and a few tricks make. When Alex and I did this back in the day, there was swearing and blood. On Friday using bundling lace to hold the plunger up, and an unregistered, sawed-off, 5/16 ball-tipped hex driver, I had the pump on and safety wired in 35 min, and I stink at safety wiring anything.

Don't fear da pump!