fuel divider problem? (spider)

[ArtVandelay]

My GAMI spread is terrible, over 1.0gph difference, 1&2 lean well before 3&4.  This makes me think I have a problem with the spider.  Anyone know what they look like inside? I'm thinking it might be worth while to open it and clean it.  I have GAMI injectors.

[RobertGary1]

First guess would be to clean and maybe flow test the injectors. Flow testing isn’t hard. Just need some baby food jars.  The flow test will answer your question about the divider. 

-Robert

Edited May 4, 2018 by RobertGary1

[RobertGary1]

Flow testing divider. 

-Robert

[ArtVandelay]

1 minute ago, RobertGary1 said:

First guess would be to clean and maybe flow test the injectors. Flow testing isn’t hard. Just need some baby food jars.  The flow test will answer your question about the divider.

I don't have a baby

Since 1&2 are perfectly matched and 3&4 are perfectly match I was thinking it's not the injectors ( I will double check they are in the correct positions).

Do you do the flow test with or without the injectors? I would think to test the flow divider you would have to remove the injectors?

[DonMuncy]

Are you saying that after the GAMIs were installed, you had a decent GAMI spread, and then something changed so the spread is not good.

If so, what was it that changed? After annual? etc.?

[RobertGary1]

1 hour ago, teejayevans said:

I don't have a baby

Since 1&2 are perfectly matched and 3&4 are perfectly match I was thinking it's not the injectors ( I will double check they are in the correct positions).

Do you do the flow test with or without the injectors? I would think to test the flow divider you would have to remove the injectors?

I bought baby food jars on Amazon.

I do the flow test with and without injectors. Its a pretty simple test to do once you have the top cowl off.

 

-Robert

[ArtVandelay]

2 hours ago, DonMuncy said:

Are you saying that after the GAMIs were installed, you had a decent GAMI spread, and then something changed so the spread is not good.

If so, what was it that changed? After annual? etc.?

It seems to just gotten progressively worst, it used to be 0.5 gph spread a few years ago.

[N201MKTurbo]

There is no magic in the divider. It doesn't control the flow to the injectors except at idle. You can take it apart without messing it up. It has a piston, diaphragm, spring, screw and two washers to support the diaphragm. One has a shoulder to hold the spring in place.  

[DonMuncy]

My theory is that injectors don't form varnish or anything else that would restrict fuel flow. But they can become blocked by various forms of debris. The first step (my opinion) would be to remove the injectors and check for blockage, blow out with air pressure, or if you are a purist, soak in Hoppes #9. Reinstall (careful to go back in same positions), and recheck GAMI spread.

There is always some chance that, along the way, they go put back in the wrong cylinders. A call to GAMI will tell you what markings on the injectors belong on which cylinder. Check when you take them out.

Then I would open up the spider, but it would seem to me to take a large chunk of something to stop up the spider.

The baby food jar test is a bit more trouble, but could perhaps tell you where to look for blockage.

[jetdriven]

Get a stainless steel harbor freight ultrasonic cleaner and soak those injectors in the unit wirh hoppes #9. Reinstal wirh clean hands and clean 1/2” extra deep socket 

[RobertGary1]

If they’re like the factory injectors 95% of the time you don’t need to remove them. Just remove the line and pull the core out and blow on it. Stick it back in. 

-Robert

[kmyfm20s]

Don't over look any potential intake leaks. 

[bradp]

And last but not least inspect your supply lines from the spider to the injector.  They are known to crack and there is an inspection AD.  I had one give way at a solder joint probably from years of the injectors coming off.

Folks have been successful with cleaning those lines with stubborn fuel imbalances not traceable to injectors.  The thought is that the sticky leftover blue junk can build up in the lines.  Unlikely spider unless a flap of diaphragm is stuck up.  So really probably not that - the spring diaphragm doesn’t engage until idle and shutdown anyway.   

Make sure that injectors have correct orientation. The little stamped A should face down.  Your AP will show you this but be careful not overtorque your injectors. Keep the flow restrictors matched with their injector.  

I like the cheap US cleaner method with Hoppe’s cleaner.  One of my previous shops used US cleaner with MEK and I thought that was an an explosion waiting to happen.  

The real starting place is the baby bottle test. . 

[Guest]

Lycoming SB1275C covers cleaning and installation of fuel injection nozzles.  Be sure that your 1/2” socket as clean as the nozzles, no sense cleaning the nozzles then getting dirt in them from the socket.

GAMI nozzles usually have cylinder number stamped on one of the hex flats.

Clarence

[jlunseth]

On 5/4/2018 at 7:50 PM, DonMuncy said:

My theory is that injectors don't form varnish or anything else that would restrict fuel flow. But they can become blocked by various forms of debris. The first step (my opinion) would be to remove the injectors and check for blockage, blow out with air pressure, or if you are a purist, soak in Hoppes #9. Reinstall (careful to go back in same positions), and recheck GAMI spread.

There is always some chance that, along the way, they go put back in the wrong cylinders. A call to GAMI will tell you what markings on the injectors belong on which cylinder. Check when you take them out.

Then I would open up the spider, but it would seem to me to take a large chunk of something to stop up the spider.

The baby food jar test is a bit more trouble, but could perhaps tell you where to look for blockage.

Don makes a really good point about swapped injectors.  They are supposed to be tagged so they won’t be swapped, but the tags can come off somewhere along the way.  All it takes is a mechanic replacing the injectors who does not understand what GAMIs are, or just forgets the way the cylinders are numbered, different for Lycs than Contis.

[MARZ]

On 5/5/2018 at 5:29 AM, M20Doc said:

Lycoming SB1275C covers cleaning and installation of fuel injection nozzles.  Be sure that your 1/2” socket as clean as the nozzles, no sense cleaning the nozzles then getting dirt in them from the socket.

GAMI nozzles usually have cylinder number stamped on one of the hex flats.

Clarence

And make sure you have a proper torque wrench.........

[Seth]

Make sure they go back in the same position.  A local field when I had an issue once put my GAMI fuel injectors back on the wrong locations (just put them back on not realizing each was set for each cylinder).  It was caught at my MSC when I mentioned it wasn't running as smoothly and that I had two cylinder running hot.  

We fixed this years ago.  GAMI's were on my aircraft when I purchased it in 2011.  However, moving fuel injectors around to different cylinders may cause changes in your GAMI spread, even if not GAMI injectors.

I had dirt twice in my fuel injectors on my previous aircraft, a 1967 F model, and also what looked like paint chips once.  This is part of why I installed a engine monitor upon purchase of my Missile in 2011.

 

-Seth