Questions on installing fuel injector nozzles

scsmith · #1 07-02-2016, 04:23 PM

I have a couple of questions for the engine gurus before I dive in and clean my lycoming fuel injector nozzles.

First, installation torques.

The Lycoming service bulletin says to torque the nozzle body to 60 in-lbs, then continue to turn until the "A" on one wrenching flat is downward.
I have not found any torque specification on the 'b' nut for the fuel distribution line to the injector nozzle body. Recommendations?

Second, the thread on the nozzle body into the cylinder head appears to be a NPT pipe thread. A maintenance article I found from Kelly Aerospace recommends lightly oiling the threads prior to installation and torquing. !!BUT!! a pipe thread will leak if no thread sealant is used. Some people think that since a pipe thread is tapered, it seals when tight, but there is always a helical leak path around the root of the threads. I'm guessing its OK to just have that minute leakage?

Jesse · #2 07-02-2016, 04:30 PM

I have no idea what the torque is required to be, but I have seen those nuts break before, so don't overdo it. I would talk to Airflow Performance and see what he says.

Lenny Iszak · #3 07-02-2016, 04:37 PM

Torque specs from Precision Airmotive, see page 9.

http://www.precisionairmotive.com/Pu...s/25-020_c.pdf

Lenny

BobTurner · #4 07-02-2016, 04:50 PM

I see little reason to pull the injector body from the engine. With the fuel line removed, you can grab and remove the restrictor with the precision hole in its end. Put that in the cleaner bath. If you have flow-matched the restrictors make sure not to mix them up.

scsmith · #5 07-02-2016, 04:51 PM

Thanks Lenny.

Again they say nothing about thread sealant on the nozzles.

BobTurner · #6 07-02-2016, 05:06 PM

Quote:

Originally Posted by scsmith

Thanks Lenny.

Again they say nothing about thread sealant on the nozzles.

Think about how much air is moving thru the induction; and how little past the threads. Besides, I think the injectors themselves 'leak' some air in, to help atomize the droplets.

Larco · #7 07-02-2016, 05:18 PM

I believe there is a screen embedded in the injector body that should be cleaned. I use a gun cleaner with an ultrasonic machine annually. I have seen some pretty ugly screens and some stay fairly clean.

BillL · #8 07-02-2016, 05:45 PM

Quote:

Originally Posted by LARCO

I believe there is a screen embedded in the injector body that should be cleaned. I use a gun cleaner with an ultrasonic machine annually. I have seen some pretty ugly screens and some stay fairly clean.

A tip found somewhere recently - take your ultrasonic bath and partially fill with water, then put your parts and desired solvent/cleaner in a zip lock bag and put it in the water. I did this with some parts and it reduced the smell and limited contamination, cleaned the parts well.

JohnInReno · #9 07-02-2016, 05:56 PM

Quote:

Originally Posted by scsmith

The Lycoming service bulletin says to torque the nozzle body to 60 in-lbs, then continue to turn until the "A" on one wrenching flat is downward.

Since the "A" is down and hidden when properly installed, I marked my injectors, "I", "II", "III", and "IIII" on the opposite side wrenching flat.

DanH · #10 07-02-2016, 07:46 PM

Hi Steve. Ordinary anti-seize on the NPT threads, 40 to 60 inch lbs. Tighten to 40, then turn until "A" is down, tolerance one flat, and not more than 60.

B nut is 20-25 in lbs, or finger snug plus one half flat with a wrench.

Like John, I mark the bodies with one, two, three, and four punch marks on the flat opposite the "A", first time they come out of the engine. Makes it easy to reinstall them with the "A" down.