Fuel Injector Problems

[David Pfeffer]

Hey Gang,
Still working on wrapping up this PA-30 restoration. It's going on 8 months. These last 2 have been driving me nuts with the engines. Finally getting the final couple issues sorted out in Ops checks.

My problem:
Fuel Injectors on the L/H engine keep clogging with a greenish goop.

1. I've cleaned the injectors 3 times now in only about an hours worth of ground Ops.
2. After ~5 full power high speed taxis, the left engine will start to either miss fire, or indicate high MP and high fuel flow. The injectors are visibly "gooed up" with a green viscous liquid- no dirt/debris. Clean the injectors, and the engine runs perfect for another few hi-powered runs.
3. My hunch is the green is a mix of the blue dye in the 100LL combined with a dark viscous fluid. My first thought is it was the oil from the air filter- but that should never actual make its way to the injectors (only the air side of the fuel servo).

Pictures of the injectors are attached. Anyone seen this before? Dirt/debris is one thing, but I can't figure out where on earth this goop would be coming from. It's gotta be a mix of 100LL bubbling back after shutdown with something else..

Thanks!
David

[md11flyer]

David,
Check the fuel servo screen. If it also has green goo then you need to run the fuel boost pump with the fuel line disconnected to the fuel servo and see what comes out. Was their preservation oil in the fuel cells during the restoration?
Anything in the fuel strainer screens?
If everything comes out clean then you need to disconnect the fuel injectors lines at the injectors and put some mason jars under the lines and run the fuel pump with the mixture rich and full throttle. Fill the jars and see what is in them. Keep filling the jars until the fuel is clean without the green goop.
Only then install the cleaned fuel injectors and recheck the fuel screen in the fuel servo.
( that green goop is most likely remnants of evaporated fuel the same goopy stuff you see when you have a fuel leak in a fuel cell )

Let us know what you find.
Gary

[N3322G]

Agree with Gary.

[David Pfeffer]

Gary, Pat,
Appreciate the input! I was on my way to the filters today. Results: Pulled the fuel servo and fuel selector screens- both perfectly clean. Pulled the spider apart- clean as well. Reassembled and pumped fuel through the system with the boost pump. Collected ~8 ounces of fuel from each line at the injectors (with the injectors disconnected). No green goop. I finally saw a little bit of dirt settle after I combined the fuel into one jug for the lawn mower, but no green goop, clean filters, and very little dirt (though I realize it only takes a little). Interesting nonetheless. I didn't re-run the engine. I'm working on a stubborn oil pressure/prop governor problem in parallel, but will run it again tomorrow.

I clearly need to run it some more on the ground and monitor. It's possible it's worked itself through, but I doubt it. I ultrasonically clean the injectors in Hoppe's #8, then blow them out when done. I wonder if any leftover Hoppe's solvent is combining with the 100LL to make the green color? I may have to try cleaning them again in Acetone if they clog up again.

I'm still open to ideas!!

In other fun news, my prop is auto feathering on me (same engine). The engine is 400 SMOH in 2006. Bench tested my governor immediately. Had excessive internal leakage. Purchased a freshly overhauled governor and slapped it on- same problem. Hot oil at 1000 rpm or less = auto feather. The prop checked out good- no oil in the hub that would indicate internal leakage. When I got this plane, this engine's oil pressure was at 110 PSI at max power, 20 psi over max MM limit. I readjusted down to 90psi. It clicked that the prop started acting up when I did that. Bumped the oil pressure back up to 110 psi and no more prop issues. Someone has clearly gone through this before and bandaged it. The governor needs 40 psi to operate. My oil pressure at the accessory case (measured by external gauge) must be 50 psi with hot oil to keep the prop from feathering at idle. So I either have a blockage in the oil gallery on the accessory case starving the governor, a clogged oil line to the prop, or my leak rate past my forward main (engine) bearing is too much. This could get ugly. Nervously waiting on getting off work tomorrow to go run the tests. I'm praying for a clogged line! I don't want to split my case for an out of tolerance bearing!! If you haven't seen it yet, Lycoming at least has a Service Letter for performing a leak test on the bearing on-aircraft. Basically a simple compression test at 40 psi. Must leak between 6-35 psi to be acceptable. Anything less and the bearing has excessive clearance (but is at least getting good oil). Anything more and the fwd bearing has likely shifted and is being starved of oil. I'll report back on both problems tomorrow! Either one starves the prop of oil. I've never personally seen this happen, but found research from others where it had.

[David Pfeffer]

Well, by the grace of God, my forward main (saddle) bearing passed the leak check. I ended up right at 18/40 psi (almost right in the middle of the 6psi-35psi limits). That was a BIG relief.

Stopped the prop from auto-feathering at idle and have a healthy engine. Long story short, here's the lessons learned:

1. Our PA-30 props are unique in the fact that they're feathering props without counterweights (fairly obvious). Every prop shop tech expert I discussed the issue of auto-feathering with immediately asked me "Does this happen to be on a PA-30?" The combination of the high nitrogen charge and internal feathering spring create FAR more force for the governor to work against than in any other application were the Hartzell F-6-3A governor is used.

2. The permissible internal leak rate inside the F-6-3A at overhaul is 15 qt/hr. My governor was leaking at 25 qt/hr (a contributing factor, but not THE problem). I installed a freshly overhauled governor and still had the same problem. What I found (and confirmed with other prop shops) is the governor really can't leak more than 10 qt/hr with the PA-30's prop and still avoid problems. The internal leak rate should be kept on file for the overhaul, so the shop you use should have the information if you give them your work order and S/N of the unit.

3. I exasperated the problem by adjusting my oil pressure down a little from when I had received the engine (indicating high on the a/c gauges, but within limits with external gauge). I adjusted it down to 70 psi @ 2000 rpm with hot oil using my external calibrated gauge. That's fully within the PA-30 Maint. Manual limits, but was too low to enable even an overhauled governor to supply the prop with adequate oil pressure to keep it from feathering at idle once the oil heated up.

Solution:
I bumped my oil pressure up to 90 psi at 2000 rpm with hot oil (max Maint. Manual limit- but a little higher really wouldn't be an issue anyhow if you knew the governor was the only problem). This allowed the oil pressure at the governor to remain at 55 psi at 1000 rpm with hot oil. Problem solved.

Gotchas:
The forward main bearing was my biggest scare. If you experience feathering issues at idle, I'd look into the problem I had above, but you'd also need to consider (1) Oil blockages in the oil gallery, (2) oil blockages in the hose from the governor to the case, (3) Oil leakage past the forward crank bearing, (4) oil leakage into the prop hub (though it should be obviously spitting out the blade seals in that case). If you ever are concerned about oil leakage past the forward main bearing, a leak test can be performed per Lycoming Service Instruction No. 1462A.

Hope this helps someone in the future! Was a PITA for a few days for me!

[N3322G]

Thanks for sharing - hope I never have to go there - hope you get aloft soon.