fuel delivery problems
 

My mission to get my GP Mustang 40 of the ground hit a snag today when I tried to run the engine for the first time. The engine needed a lot of priming even right after it had just ran. While the engine would start and run with the needle valve cranked out 4-5 clicks at any throttle setting besides idle seemed to me like it was fuel starved. I am also losing some unburned fuel from where my Pitts Muffler and the cylinder head meet which will need to be sealed with some red RTV. Either my low-end needle is WAY off ( I have not messed with the factory setting) or more likely it is the location of my fueler I have mounted it on the bottom of my plane to hide it. The fuels line are running down to it form the tank about 3" and then back up to the carb about the same distance. My thought was although it would need to be primmed once started that this set-up would work just fine, but maybe not. There is enough room to mount the fueler on the right side of the firewall between the 2 cowel mounting blocks. But I was wanting to get some advice from some of you guys before I stared un-doing stuff. I am using a Du-bro #205 fueler and at SuperTigre .51 with a Slimline Pitts Muffler.

RE: fuel delivery problems
 

The location of the fueler is not a problem. The fueler itself may be bad, but assuming it is working OK, you can mount it about anywhere. I have had bad luck with fuelers, so I tend to avoid them. As a diagnostic, try bypassing the fueler and go directly from the tank clunk thru the stopper and then to the carburetor. Sometimes the fuelers develop air leaks which can really be annoying. Don't worry about the muffler / cyklinder head fit just now. This will cause some exhaust leak, but will not affect the engine running or harm it in any way.

This engine should start with the main NV opened 2.5 turns from fully closed. Any more open than that does not do much. Try again with the main NV open 2.5 turns or even less.

RE: fuel delivery problems
 

Hi!
You would be better off without that fueler...it's much better to run the fuel line direct to the carb and have a third line hanging down under the cowl to which you fill the tank. The second line is also hanging down undre the cowl and this is the overflow line. These lines are closed with a short 3mm screw as soon you have fueled the tank. Much simpler!

Regards!
Jan K
Sweden

RE: fuel delivery problems
 

Thanks I was thinking of by passing it which should only take a few minutes I'll try that tomoowrw. DMcQuinn, you are about 10 minutes away from me in Chesterfield MO ( I am in Ofallon MO) What club do you fly at? Years a ago I flew at the Prop Nut's and the old McDonnell Douglas field I now fly at the Spirit's field.

RE: fuel delivery problems
 

Daryl, I think that Pitts style muffler could be the culprit. I've had to plug one exhaust outlet before to create enough back-pressure to pressurize the fuel tank. If you can temporarily plug one outlet, I think your troubles will go away.

RE: fuel delivery problems
 

TimC is right, Daryl that muffler has got far, far to much outlet area to develop any positive pressure to aid in fuel delivery. Poorly matched Pitts type mufflers are a major cause in poor fuel delivery and eratic needling problems. You would be much better off with a stock muffler or at least completely plug one of those holes.

John

RE: fuel delivery problems
 

Daryl,

I have a horizontal-mount G51 w/Slimline Pitts in my GP P-51D.

I have two suggestions. 1) Never assume a Super Tigre low end needle is set correctly from the factory and 2), never trust a fueler valve.

You might want to check your low end initial setting as described in the Super Tigre engine support forum here on RCU.

I have always preferred to use a third line and a "fuel dot" set-up for fueling. Lately, I've been skipping the fuel dot and just leaving the fill tubing where it can be tucked in somewhere and plugging it with a screw or fancy fuel line plug.

Sometimes I rig up some kind of a holder for the excess tubing to snap into or hook behind to keep it hidden and secure.

Good flying,
desmobob

RE: fuel delivery problems
 

Daryl - I fly at Buder Park in Fenton. I'm heading there now...

RE: fuel delivery problems
 

If your high speed needle valve is only backed out 4 or 5 click's... then the engine is too lean which would confirm your suspicion of being fuel starved. A good base setting to start with is 2 1/2 to 3 turns out from the fully seated position. Running an engine lean (especially a new one) is needless to say....not good. Hopefully, no damage was done.

RE: fuel delivery problems
 

Problem solved guys, thanks for your help. I ditched the the fuel filler and just went with 3 lines, I also removed the carburetor and reset the spray bar and low end needle per the instructions on RCU's ST support page and instructions turned out to be wrong. First off they recommend that the spray bar (with the carburetor and looking at it from the bottom side) should be pointing straight down the barrel this leaves the intake nipple about parallel to the ground (if the engine is upright) my personal experience from racing 40 star 40's with ST .40 motors and advice from others is that the intake nipple should be pointing at the first bolt hole on the engine that is where I had set it originally and where I left it at. I Set the low end needle per ST instructions which was to turn it to where it was 1/2 way into the spray bar slot. When I tried to run the motor today the low end was so far off that the engine would barley start and would not stay running the low end needle was way to lean and needed turned out about 1.75 turns. All these adjustments took about 2 tanks of fuel but now the engine is happily turning a 11 x6 propeller at 12,000 rpm and that is with it running a couple of clicks rich. It is all ready to fly as soon as the next good day comes around the weather was perfect here today in St. Louis the forcast for tomorrow as luck would have it is cloudy cold and windy.

DMcquinn, I have a buddy who flies out at Budder park he keeps wanting me to come out there but I have not done it yet.

Countryboy, I miss-typed in my first post I meant 4-5 turns, suprised nobody else caught that :)