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First engine start attempt

ltn6a

Active Member
Hi all

Looking for some wisdom from the forum.
Attempted first run of my IO-320-B1A in my RV6a
Following the lycoming start sequence ,fuel pump on ,full throttle and full mixture , I got 35psi fuel presss but no indicated fuel flow .
Pump off , mixture idle cut off and throttle 1/4 .
After various attempts managed the odd cylinder to fire but could not get it to run , checked plugs a bit damp but ok . Replaced upper with new plugs .
Still occasional cylinder would fire .
Started investigating the fuel system and with fuel pump on we have good flow right up to the Bendix injector body but regardless of mixture or throttle position no fuel flow / out put.
Pulled the inlet screen filter and it clean so looks as if the injector body is not working .
The engine was stripped and rebuilt about 10 years ago but nothing was done to the injector .

Any advice or suggestions before I pull the injector for a service/ bench test

Thanks

Mark
 
Hi Allen

Will do 5hat but current concern is that we can see no real fuel flow from the injector body out let that feeds the spider.

Mark
 
After the servo repair, but before you grind on the starter any more (and wipe away ALL lube on the cam), make sure you perform an injector flow test. This will exercise the fuel system and verify the integrity of all components. Assuming you have good spark, it should fire and run.
 
Last edited:
Thanks Michael

I will do a search as I don?t recall seeing this in the lycoming operators manual

Mark
 
Purge the air out of the lines by disconnecting the fuel supply line and the fuel divider and running the electric boost pump until you have a solid air free stream of fuel. Make sure you do this safely and run the fuel into a bucket.
 
Hi David

We get good fuel flow to the servo body but no real flow from it .
Exercised the throttle and mixture with fuel pump running no change.
Pulled the servo. Body filter but that was clear

Mark
 
No Airflow No Fuel Flow

I am not sure this will help but will share my experience with my Airflow Performance throttle body/injection.

Summary is you will not get much fuel flow if there is no metered airflow in the system.

When I did my fuel flow check I disconnected the fuel line at the spider valve and flipped the fuel pump switch to find it trickling out of the hose, not a solid stream. Switched tanks, no joy. I then disconnected the line going into the throttle body, and like you, had full flow. Researched a bit (and confirmed with a call to Don) that there will be very little fuel flow because the system is not seeing the airflow across the venturi to know it should be pumping more gas. One way to test this is flow compressed air in the venturi and see if the FF increases with the electric fuel pump on.

Point is I guess it may or may not be the TB.

Hope that helps.

E
 
Hi all

Looking for some wisdom from the forum.
Attempted first run of my IO-320-B1A in my RV6a
Following the lycoming start sequence ,fuel pump on ,full throttle and full mixture , I got 35psi fuel presss but no indicated fuel flow .
Pump off , mixture idle cut off and throttle 1/4 .
After various attempts managed the odd cylinder to fire but could not get it to run , checked plugs a bit damp but ok . Replaced upper with new plugs .
Still occasional cylinder would fire .
Started investigating the fuel system and with fuel pump on we have good flow right up to the Bendix injector body but regardless of mixture or throttle position no fuel flow / out put.
Pulled the inlet screen filter and it clean so looks as if the injector body is not working .
The engine was stripped and rebuilt about 10 years ago but nothing was done to the injector .

Any advice or suggestions before I pull the injector for a service/ bench test

Thanks

Mark


Are you pressurising your oil system before the first start. Starting a new/overhauled engine with zero oil pressure is very bad for the engine. This is not the reason for your failure to start but I just thought I'd throw it in there.
You might like to get an Aircraft Maintenance Engineer to help you. They have the equipment to pressurise your oil system and they can also probably sort out your start problem in 5 minutes.
 
Mark
Check the fuel spider/distributor, I had the piston stick on mine after siting many years..... Also on another brand new engine in cold weather (bi metal with differential expansion rates).....

Peter
 
Just a wild thing to check, not academic either.

No air, no combustion.

Check your MAP, if you open the throttle WOT and hit the starter - - MAP should stay near 29", if it drops, then no air.

As me how I know . . . I left a full gasket over the servo hole during many fitting iterations to keep stuff out of the sump. SOMEHOW it was forgotten, I had to remove the servo and cut a hole. My MAP dropped to 10" with WOT on start. It would pop after it got oxygen from plug removal, but not start.

After cutting the hole . . BAM . . . instant start.
 
Thanks to all

I now have a few things to check at the weekend .
It?s great to get all this support and in put will let you all know what transpires.

Mark
 
I?ve heard of this situation. May sound obvious, but make certain that there isn?t an unnoticed piece of speed tape over the air inlet. Hard to see when mounting throttle body from the side. Can cause at least a weeks worth of frustration and make one so obsessed with the problem that they abandon all other endeavors such as a step-daughter?s college graduation trying to diagnose. Won?t divulge how I know this.

JRF
 
It runs 👍

Hi All

Thanks for all the in put ,today she ran well so forward we go . Here?s what the problem was
Firstly the Bendix injector had not been inhibited by the previous owner correctly this led to fuel varnish blocking the throttle/mixture on the injector body hence the no fuel flow ,all cleaned up good flow but still not running .
Secondly
Had a great hour with Ray Harper in the UK and a 1:2:1 lesson on mag timing as the previous attempt we just couldn?t get the synchroniser box to make sense.
Had another go from scratch today and the engine fired and run on the first attempt
So one again thanks to all those that took the time to comment and a huge thanks to Ray Harper

Mark
 
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