BruceMe
Well Known Member
For background... Rv-4, IO-320 CS prop.
OAT at 11,500' was 4-8c. Power was set at 56% 19.5"(WOT) 2300rpm, 6gph. 320-380 cht very LoP.
On the mechanical only the fuel pressure has always fluctuated. It was behaving "normal" for the first two hours repeating this pattern over and over... 24-26psi for a minute then 20-22psi for a minute then repeat. Eventually, the lows started dropping lower until it was alarming the g3x at less than 18psi. I know from experience if it gets below 15 the engine will falter. So I turned on the electric boost for the remainder of the flight. I had something similar happen on a 1hr flight three years ago and I replaced the mechanical fuel pump with a Tempest which is what failed on this flight.
In Atlanta, I replaced the Tempest with a Lycoming "high pressure" OEM pump. For those who don't own an RV-4, the fuel pump very tight against the firewall footwell bump (1/2"), you can't put the pump on straight, you have to start the bolt furthest away first, then pivot the arm around to pickup the plunger. This is a challenging maneuver in very tight quarters.
The new pump generated 30-34PSI, I learned through the buyer's comments in the Aircraft Spruce page, that this is known, they bumped up the pressure on their pumps. But I persisted on as the pressure was still in the green arc, more is better right?! On my test flight, full power was giving extremely high GPH (20gph vs 15 typical at full power) and I was having a really hard time controlling cylinder temps. They were racing way up to 430 very quickly... typically I can keep them under 405 by switching to LoP cruise climb at 800'. But switching to LoP brings them down relatively quickly. Not ideal, but I can get home. The cruise phase of the flight was very uneventful, but the mixture was much more sensitive than I'm used to, but I found a place where it ran very comfortably for the 4hrs home.
When I got home I inspected the failed fuel pump, the lever arm was bent (see photos) and the contact point from the cam-plunger was not centered, it's well off to one side. All this said... I "THINK" the crazy motions I have to make to install the pump leave it pulled to one side and bent. This lead to side-loads the pump can't handle in some way I don't yet understand.
Here is what I was planning to do:
- Replace the Lycoming pump with a new identical tempest
- Pull the engine off it's mounts (I need to replace the mounts anyway) and install the pump straight on
I wanted to know if anyone in this group has seen anything similar?
Should I get the laminated arm?
Thanks
-Bruce
OAT at 11,500' was 4-8c. Power was set at 56% 19.5"(WOT) 2300rpm, 6gph. 320-380 cht very LoP.
On the mechanical only the fuel pressure has always fluctuated. It was behaving "normal" for the first two hours repeating this pattern over and over... 24-26psi for a minute then 20-22psi for a minute then repeat. Eventually, the lows started dropping lower until it was alarming the g3x at less than 18psi. I know from experience if it gets below 15 the engine will falter. So I turned on the electric boost for the remainder of the flight. I had something similar happen on a 1hr flight three years ago and I replaced the mechanical fuel pump with a Tempest which is what failed on this flight.
In Atlanta, I replaced the Tempest with a Lycoming "high pressure" OEM pump. For those who don't own an RV-4, the fuel pump very tight against the firewall footwell bump (1/2"), you can't put the pump on straight, you have to start the bolt furthest away first, then pivot the arm around to pickup the plunger. This is a challenging maneuver in very tight quarters.
The new pump generated 30-34PSI, I learned through the buyer's comments in the Aircraft Spruce page, that this is known, they bumped up the pressure on their pumps. But I persisted on as the pressure was still in the green arc, more is better right?! On my test flight, full power was giving extremely high GPH (20gph vs 15 typical at full power) and I was having a really hard time controlling cylinder temps. They were racing way up to 430 very quickly... typically I can keep them under 405 by switching to LoP cruise climb at 800'. But switching to LoP brings them down relatively quickly. Not ideal, but I can get home. The cruise phase of the flight was very uneventful, but the mixture was much more sensitive than I'm used to, but I found a place where it ran very comfortably for the 4hrs home.
When I got home I inspected the failed fuel pump, the lever arm was bent (see photos) and the contact point from the cam-plunger was not centered, it's well off to one side. All this said... I "THINK" the crazy motions I have to make to install the pump leave it pulled to one side and bent. This lead to side-loads the pump can't handle in some way I don't yet understand.
Here is what I was planning to do:
- Replace the Lycoming pump with a new identical tempest
- Pull the engine off it's mounts (I need to replace the mounts anyway) and install the pump straight on
I wanted to know if anyone in this group has seen anything similar?
Should I get the laminated arm?
Thanks
-Bruce
. The filter caught most of it but on the first oil change the oil looked like liquid aluminum instead of engine oil. Yikes.