[Joseph Signorino]

Joseph Signorino on October 23, 2020 at 5:36 pm #20277

Hi Steve and Brandon,

We are still chasing the issue. This is taking quite some time. Started off with all fuel injectors being clean and testing to be in spec on flow bench. Did not think that really had anything to do with it but the rubber air injection hoses were all very brittle and in need of replacement so it was apart anyway. No change.
Next sent out fuel servo, it was rebuilt, I was told they found a problem but I have not received details yet. plane was reassembled and tested. Same problem.
A few items of note:
1- The problem and even the effect of the electric pump has been inconsistent. I did not realize this at first but after repeated ground run ups I found results were not repeatable.
2- I would intermittently start having fuel drip out of the drain on the air tube tube leading from the turbo to the fuel injector input (sorry its been a busy week and my manuals are in my hanger so I do not remember the proper name). This happened at idle or after the engine was shut down.

After further investigation there are 3 lines that attach to the cast intake tube and technically 4 places the fuel could be originating.
1- It could be draining out of the fuel servo. This was dry, no fuel draining from this area.
2- Two of the lines feed the air injection lines to the fuel injectors. No fuel was draining out of these lines.
3- The last line is a vent hose from the fuel pump. Bingo… The fuel was draining out of this line. If I turn on the boost pump it really flows out. So not my Mechanical pump is at the shop waiting to be looked at. I do not anticipate getting it back until late next week.

I am hopeful based on the intermittent symptoms that this will solve the problem. It adds up that fuel draining directly into the intake tube would cause inconsistent issues. I will report back when things are back together, hopefully in a week or so.

Joe

[Brandon Dorsett]

Brandon Dorsett on October 23, 2020 at 10:51 am #20274

Sir,

My understanding was the gauge was downstream of all pumps but I too will look again at the service manual. Thank you in advance for your time.

Of note. The fuel pressure on the gauge is the same with the electric pump as with the mechanical pump. About 27psi at idle. When the electric pump is turned off there is a slight increase in pressure as the mechanical pump picks up the fuel flow but the flow itself drops about 0.5 gph when compared to the electric pump flow; pressure is steady at 27psi. That is when the motor lugs, is rough and does not want to run unless I turn the electric pump back on. Idle mixture has been adjusted by my mechanic and no visible leaks are present. The shop that has the pump now could not find any flow issues on the bench but they are opening it up today to take a closer look. Maybe there is debris the electric pump can push flow past but not the mechanical pump? I do not have much experience with these specific components.

This pump had a cavity drain leak repaired approx. 18 hours ago (6 weeks ago). This happened to me once in flight but did not re-appear until recently on deck.

R/,

Brandon

[STEVE]

STEVE on October 23, 2020 at 9:49 am #20273

Hi Brandon;
I’m looking at the service manual and parts manual to try to determine if there’s a check valve(s) in the system that might have failed or has a bit of debris between the ball and seat which would prevent the engine driven pump from building pressure, but I don’t see that.
What is confusing to me is that one drawing of the fuel system in the service manual shows fuel flowing from the tanks to the selector then through the electric pump to the engine driven pump, then through the fuel flow/fuel pressure gauge into the engine.
I find it hard to believe that Piper routes all the fuel flow back into the cabin and through a gauge before it flows to the engine and suspect that drawing is incorrect.
I’m reaching out to some other experts for an answer.
I’ll post when I get helpful advice.
Steve

[Brandon Dorsett]

Brandon Dorsett on October 23, 2020 at 8:47 am #20270

Similar issue. Mechanical Fuel pump is at the shop now but they aren’t finding any issues. Engine works great on boost pump but wants to quit on the mechanical pump alone. Any resolution?

R/,

Brandon

[STEVE]

STEVE on August 23, 2020 at 6:35 am #20125

Hi Joseph,
Thanks for the update.
I suggest you ask your mechanic to adjust the idle speed and idle mixture in accordance with the engine service manual.
If this hesitation is a recent anomaly, was there any maintenance performed on the engine immediately prior to the start of the problem?
For instance, had it just come out of an annual, or other type of maintenance? Were the spark plugs changed??
The main reason I’m want the idle mix and speed set is because these adjustments, esp. the idle mixture do need to be adjusted about twice a year to compensate for differences in air temperatures, etc.
Please keep me in the loop on what you find.
Thanks,
Steve

[Joseph Signorino]

Joseph Signorino on August 22, 2020 at 6:00 pm #20124

Thanks Steve, engine has 800ish hours and had all cylinders reworked, valve guides, etc a few hundred hours ago. I tried a few things today and I can still experience this after a 1.5 hr flight.

[STEVE]

STEVE on August 18, 2020 at 9:13 am #20119

I suspect the reason your engine hesitated after you idled full rich and fuel pump on was that the plugs were slightly carbonned up.
The other thing sort of sounds like what’s known as “morning sickness,” which is slang for a sticking valve.
How many hours on this engine??
I have attached two Word files that break this down.
Let me know what you find.
Steve

Attachments:

• Lycvalvereamingropetrick.pdf
• LycomingandStickingValves.pdf

[Joseph Signorino]

Joseph Signorino on August 17, 2020 at 6:00 pm #20116

I am new to using the forum so hopefully this is the correct approach. I have a 78 Turbo Lance with a TIO540S1AD. I have noticed a few times (very intermittent) over the last months after starting the engine and preparing to taxi when I slowly apply taxi power the engine may not respond normally (hesitation or loss of RPM and then recover). Typically this would be with the electric fuel pump off and mixture leaned. Yesterday I had taxied to the runway, did a run-up and all checked well. There was some inbound traffic and I had to wait for several minuets, fuel pump was on and mixture was full rich, I started to add power to taxi on to the RW and the engine died like running out of fuel. After a restart and another run up everything seemed fine. Normally I would not leave full rich at 1000 rpm for that long. Any thoughts? Mechanical fuel pump?